Van's Air Force
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MPS, Maxwell Propulsion
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There was a discussion on one of the Sube forums about the hp claims made by MPS. It is impossible that this engine can make 205hp at the 4500 rpm they listed. This represents a BMEP of 227 psi.
I suspect they are still using the dyno from the old NSI days which used to give a lot of suspect data. They countered by saying it was recently recalibrated. Hmmm... It might be possible to make 205 hp at 5500-6000 rpm.
Some flight test data (third party) on a Glastar fitted with the MPS package does seem to show comparable performance in cruise to an O-360, suggesting that it may produce around 180hp. Cruise numbers and fuel flows were very good.
One of my friends will be fitting a MPS 2.6 in his 7A shortly. This has already flown with another Sube package so we can compare to that and known Lycoming performance to verify the claims. If it has the goods, MPS sales will certainly pick up.
I suspect they are still using the dyno from the old NSI days which used to give a lot of suspect data. They countered by saying it was recently recalibrated. Hmmm... It might be possible to make 205 hp at 5500-6000 rpm.
Some flight test data (third party) on a Glastar fitted with the MPS package does seem to show comparable performance in cruise to an O-360, suggesting that it may produce around 180hp. Cruise numbers and fuel flows were very good.
One of my friends will be fitting a MPS 2.6 in his 7A shortly. This has already flown with another Sube package so we can compare to that and known Lycoming performance to verify the claims. If it has the goods, MPS sales will certainly pick up.
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I just looked at their site - they are only advertising 165hp now. That seems more reasonable since my non-turbo 2000 Subaru (car) is rated at 140hp.
As for Subaru engines in general, my aircraft is one row over from a fellow who went through 5 (as I heard it - don't shoot me if I'm off by one) such engines before he gave up. Does that mean they haven't figured it out yet? I don't know, and I'm too chicken to try it myself.
As for Subaru engines in general, my aircraft is one row over from a fellow who went through 5 (as I heard it - don't shoot me if I'm off by one) such engines before he gave up. Does that mean they haven't figured it out yet? I don't know, and I'm too chicken to try it myself.
I just looked at their site - they are only advertising 165hp now. That seems more reasonable since my non-turbo 2000 Subaru (car) is rated at 140hp.
As for Subaru engines in general, my aircraft is one row over from a fellow who went through 5 (as I heard it - don't shoot me if I'm off by one) such engines before he gave up. Does that mean they haven't figured it out yet? I don't know, and I'm too chicken to try it myself.
This fellow, have these all been MPS engines or were some NSI?I am the one planning to try a version of this engine on my 7A. After having many problems associated with the supercharger at first, and then a turbocharger setup, I am attracted to the simplicity of the setup and the fact that it will allow me to shed between 40 and 45 lbs from my firewall forward weight.
I think MPS made an error in stating the 205 HP at 4500. It will probably make more than 200 HP at it's take off RPMs of around 5,000, but not down at normal cruise RPMs. I live not far from the MPS shop and have grown to trust that they can build up a quality engine for me. I was and remain pretty skeptical of any one messing around with the insides of an engine I plan to fly behind. I believe MPS is indeed a different company with a very different business model than what it was in the past. I am giving them a chance, but with the old "trust but verify" approach.
The demonstrator did record impressive performance numbers on the trip to and from OSH, and based on those numbers, I think this engine has some great potential to be relatively light Sube RV engine package. No, probably not as light as a Lycoming package.
My engine will be Sube EJ25 based with a billet stroker crankshaft, balanced and blueprinted, stock rods, custom pistons with a compression ratio of 10.4 to 1. The MPS demo plane is running WRX heads, mine will use the dual cam STI heads that should help a little more with the horsepower as they are known to breathe better.
For me this is a natural follow on experiment in trying to get performance as good or better than I could get with a Lyc. but with a smooth running liquid cooled Sube engine. I had great performance with the Turbo STI, but it did suffer some in the reliability area, mostly caused from my own inexperience in turbo installations. I will still have to have a turbo STI again one day. I have tasted what it is like to have control of MAP and will probably not be satisfied until I have it available to me again. It is so fun to be able to keep the power up at high altitudes. I think I am adicted to the experience.
I have been through a tremendous amount of trials in my quest to accomplish the above stated goal. To be honest I have been ready to give it up a few times and put a Lyc. in it and just get in some enjoyable flying hours instead of continuous experimentation, it gets old after a while seeing other RVs rack up the flying hours while I work on mine. I am stoked about this new approach though. The installation may not meet Van's definition of "lighten and simplicate", but from where I have been, that is indeed the direction in which I am heading.
Perhaps in a few months I will be able to report in with some new performance numbers and weights, and hopefully start racking up the flight hours without problems.
Randy C
I think MPS made an error in stating the 205 HP at 4500. It will probably make more than 200 HP at it's take off RPMs of around 5,000, but not down at normal cruise RPMs. I live not far from the MPS shop and have grown to trust that they can build up a quality engine for me. I was and remain pretty skeptical of any one messing around with the insides of an engine I plan to fly behind. I believe MPS is indeed a different company with a very different business model than what it was in the past. I am giving them a chance, but with the old "trust but verify" approach.
The demonstrator did record impressive performance numbers on the trip to and from OSH, and based on those numbers, I think this engine has some great potential to be relatively light Sube RV engine package. No, probably not as light as a Lycoming package.
My engine will be Sube EJ25 based with a billet stroker crankshaft, balanced and blueprinted, stock rods, custom pistons with a compression ratio of 10.4 to 1. The MPS demo plane is running WRX heads, mine will use the dual cam STI heads that should help a little more with the horsepower as they are known to breathe better.
For me this is a natural follow on experiment in trying to get performance as good or better than I could get with a Lyc. but with a smooth running liquid cooled Sube engine. I had great performance with the Turbo STI, but it did suffer some in the reliability area, mostly caused from my own inexperience in turbo installations. I will still have to have a turbo STI again one day. I have tasted what it is like to have control of MAP and will probably not be satisfied until I have it available to me again. It is so fun to be able to keep the power up at high altitudes. I think I am adicted to the experience.
I have been through a tremendous amount of trials in my quest to accomplish the above stated goal. To be honest I have been ready to give it up a few times and put a Lyc. in it and just get in some enjoyable flying hours instead of continuous experimentation, it gets old after a while seeing other RVs rack up the flying hours while I work on mine. I am stoked about this new approach though. The installation may not meet Van's definition of "lighten and simplicate", but from where I have been, that is indeed the direction in which I am heading
.Perhaps in a few months I will be able to report in with some new performance numbers and weights, and hopefully start racking up the flight hours without problems.
Randy C
I believe they were early Eggenfellners, but cannot swear to that. I'm sure things are better today, but also sure that I'm not convinced.
Lack of adequate flight testing has come back to haunt many engine vendors. MPS has been stating that they don't want to follow that old path as it can only lead to business failure eventually. I hope lessons learned from the past will be applied and that they will offer reliable, comparably priced FF packages with comparable performance to the Lycoming setups. In 3-5 years, perhaps we'll be able to answer that one.
We'll be looking eagerly at Randy's numbers soon!
A word of advice to MPS- if you want to succeed in this market, post real data and have it vetted by a third party. People are very jaded in this market and rightfully so. I'm thinking, do the Van's fly off thing. This will remove any performance doubts and help sales along without much advertising. The rest will come through solid engineering, transparency if there are problems and good customer service.
L.Adamson
Well Known Member
Not that much better....
A friend of ours has had countless problems with his six cylinder Subie installation, which involves mostly cooling problems with his RV8. He has now spent far more, than a Lyc would have been; and has only got 19 hrs in the last year. Mostly on the ground!
His test pilot at least got some more time in it the other day, without boiling over (after a lot more modifications), but you can still smell the hot antifreeze. Performance isn't as good as a Lyc either. Perhaps it has to loosen up some.
But never the less; a Eggenfeller Sube engine isn't near the advance for aircraft, that one might get from reading the Eggenfeller website. Between cooling problems, less performance, and required upgrades such as swapping $4500 gear boxes........... I'm surprised he hasn't junked it already!
They need a muffler too! The engine runs at an annoyingly high pitch in anything but taxi speeds. It's now become a joke..........that airport residents are going to sign a petition for noise control...
Bottom line............. I wouldn't recommend one to anybody.
L.Adamson ---- RV6A (flying)
They need a muffler too! The engine runs at an annoyingly high pitch in anything but taxi speeds. It's now become a joke..........that airport residents are going to sign a petition for noise control...
Bottom line............. I wouldn't recommend one to anybody.
L.Adamson ---- RV6A (flying)
I agree about the noise. The atmo Subes are raunchy sounding things even with the two types of mufflers tried to date. Someone needs to do some serious testing on a real muffler system. You reach the pain threshold at about 4500 rpm without headphones with the Egg sixes. Quite unpleasant.
Any auto engine conversion should include proper stainless mufflers or a turbo which makes everything sound proper.
Randy is used to that nice mellow, quiet turbo note now. We'll see what he thinks of the MPS 2.6 atmo note.
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Hello folks,
Last week I heard there was a discussion regarding Maxwell Propulsion Systems on this site, so I decided it was time to join the group and with luck, present some of the issues from the MPS perspective.
205+ HP 2.6 L Stroker
Just before the Arlington Show, we put a high performance engine package on N787MX, the MPS Sportsman that we use as our testbed. It has 298 hours since June 26, 2008. The first 240 were flown with the normally aspirated 165 hp system. The package was built using the following components:
The engine was blueprinted and balanced prior to installation, however it was not run on the MPS engine dyno. As a result the hp ratings are not fully verified. Having said that, the data from our return flight from Oshkosh to Arlington are shown below. In comparing these to the numbers published in the recent Kitplanes IO 360 and IO 390 Sportsman flyoff the numbers compare favorably with the 390, advertised as 210 hp. (Data from Captain William Graves, retired Continental Airline Pilot.) I will try to post the complete table later, but here is data from the final leg from Bozemen to Arlington:
Performance -BZN TO AWO
Initial Climb -700 fpm
Fuel Burn - 12.1 gph
MAP - 24?
RPM - 5250 rpm
Average Climb - 500 fpm
Speed - 100 kts
Fuel Burn - 10.9
MAP - 24?
RPM - 4700 rpm
Cruise Altitude - 8500 ft
TAS - 138-143 kts
RPM - 4700
Fuel Burn - 8.1 gph
MAP - 21?
STATUTE MPG - 16.5 mpg
MUFFLERS
I can't say that our straight pipes with baffles are up for best sound of the year, but I will try to get some video with sound posted on YouTube of our current muffler package so you can evaluate for yourself. Better yet, we are developing a 4 into 2 tuned exhaust. I am expecting that will be a huge improvement in both sound and increased hp! Short of a turbo that should be pretty nice. A welder is due here this week and when the mockup is complete, we will get if off again to Aircrafters Exhause.
MPS Testing and Analysis
Excellent point. I totally agree. In addition to the flight testing noted above, and, in contrast to other engine vendors, we test all of our products on the ground and in the air.
Our propeller and PSRU were subjected to the equivalent of the FAA certification test required for certified engines. The testing protocol used was that included in the FAA regulation 33-2A.
We also performed vibration analysis of our PSRU that was recently published in Contact! Issue 97.
Dominic Acia, has written an article that describes the engine blueprinting and balancing that is part of our build/assembly process, and the rationale behind it. Of note is that the most likely cause of the unfortunate customer who had 4 or 5 engine failures with his Eggenfellner engines is that the Subaru factory clearances are inadequate to support the engines when they are run at high rpms for long periods of time. The article was published in the GlaStar-Sportsman Flyer last January and Marc Cook of Kitplanes tells me that it is scheduled for the November issue of that magazine.
MPS Dynamometer
Again, you are correct, and I totally understand your concern over the highly suspect data. (You probably don't know the half of it!) So, while it is certainly hard to prove a negative...I can say that getting two SuperFlow Dyno technicians out to Arlington to replace the circuit boards, recalibrate, and install the software upgrades and train the MPS technicians put quite a hole in my checking acount balance! I am unlikely to forget that experience!
Confidence Building
My thanks to Randy for his kind words and confidence in MPS. While I have some RV customers, I would certainly enjoy the opportunity to help others fly behind a Subaru, be it a complete MPS package, a builder-designed system, or an upgrade to another package. I believe the Subaru is an excellent option for the experimental aircraft, it is unfortunate that converting it to a safe, reliable package has been so long in coming, that said, I believe that the products that MPS is has tested and flown meet these criteria ...I am happy to say that having flown behind the MPS package for upwards of 120 hours this year alone, I have complete confidence that it is just about everything that I want...yeah, yeah, yeah, OK, More speed would be nice!
Best Regards,
Gwen Maxwell
Maxwell Propulsion Systems, Inc.
19132 59th Drive NE
Arlington, WA 98223
Phone: 360.474.8118
Fax: 360.474.8299
www.maxwellpropulsion.com
Last week I heard there was a discussion regarding Maxwell Propulsion Systems on this site, so I decided it was time to join the group and with luck, present some of the issues from the MPS perspective.
205+ HP 2.6 L Stroker
Just before the Arlington Show, we put a high performance engine package on N787MX, the MPS Sportsman that we use as our testbed. It has 298 hours since June 26, 2008. The first 240 were flown with the normally aspirated 165 hp system. The package was built using the following components:
- Subaru EJ257 STi Block w/ 2.5 SOHC
- Normally Aspirated 2.6 L Stroker
- Custom Camshafts
- Modified/Polished 10 mm oil pump
- J E Forged Pistons
- K-1 83 mm Billet Crankshaft
- K-1 4340 Forged Rods
- ACL Race Bearings
The engine was blueprinted and balanced prior to installation, however it was not run on the MPS engine dyno. As a result the hp ratings are not fully verified. Having said that, the data from our return flight from Oshkosh to Arlington are shown below. In comparing these to the numbers published in the recent Kitplanes IO 360 and IO 390 Sportsman flyoff the numbers compare favorably with the 390, advertised as 210 hp. (Data from Captain William Graves, retired Continental Airline Pilot.) I will try to post the complete table later, but here is data from the final leg from Bozemen to Arlington:
Performance -BZN TO AWO
Initial Climb -700 fpm
Fuel Burn - 12.1 gph
MAP - 24?
RPM - 5250 rpm
Average Climb - 500 fpm
Speed - 100 kts
Fuel Burn - 10.9
MAP - 24?
RPM - 4700 rpm
Cruise Altitude - 8500 ft
TAS - 138-143 kts
RPM - 4700
Fuel Burn - 8.1 gph
MAP - 21?
STATUTE MPG - 16.5 mpg
MUFFLERS
I can't say that our straight pipes with baffles are up for best sound of the year, but I will try to get some video with sound posted on YouTube of our current muffler package so you can evaluate for yourself. Better yet, we are developing a 4 into 2 tuned exhaust. I am expecting that will be a huge improvement in both sound and increased hp! Short of a turbo that should be pretty nice. A welder is due here this week and when the mockup is complete, we will get if off again to Aircrafters Exhause.
MPS Testing and Analysis
Excellent point. I totally agree. In addition to the flight testing noted above, and, in contrast to other engine vendors, we test all of our products on the ground and in the air.
Our propeller and PSRU were subjected to the equivalent of the FAA certification test required for certified engines. The testing protocol used was that included in the FAA regulation 33-2A.
We also performed vibration analysis of our PSRU that was recently published in Contact! Issue 97.
Dominic Acia, has written an article that describes the engine blueprinting and balancing that is part of our build/assembly process, and the rationale behind it. Of note is that the most likely cause of the unfortunate customer who had 4 or 5 engine failures with his Eggenfellner engines is that the Subaru factory clearances are inadequate to support the engines when they are run at high rpms for long periods of time. The article was published in the GlaStar-Sportsman Flyer last January and Marc Cook of Kitplanes tells me that it is scheduled for the November issue of that magazine.
MPS Dynamometer
Again, you are correct, and I totally understand your concern over the highly suspect data. (You probably don't know the half of it!) So, while it is certainly hard to prove a negative...I can say that getting two SuperFlow Dyno technicians out to Arlington to replace the circuit boards, recalibrate, and install the software upgrades and train the MPS technicians put quite a hole in my checking acount balance! I am unlikely to forget that experience!
Confidence Building
My thanks to Randy for his kind words and confidence in MPS. While I have some RV customers, I would certainly enjoy the opportunity to help others fly behind a Subaru, be it a complete MPS package, a builder-designed system, or an upgrade to another package. I believe the Subaru is an excellent option for the experimental aircraft, it is unfortunate that converting it to a safe, reliable package has been so long in coming, that said, I believe that the products that MPS is has tested and flown meet these criteria ...I am happy to say that having flown behind the MPS package for upwards of 120 hours this year alone, I have complete confidence that it is just about everything that I want...yeah, yeah, yeah, OK, More speed would be nice!
Best Regards,
Gwen Maxwell
Maxwell Propulsion Systems, Inc.
19132 59th Drive NE
Arlington, WA 98223
Phone: 360.474.8118
Fax: 360.474.8299
www.maxwellpropulsion.com
Welcome aboard Gwen.
You will not find a more skeptical bunch here when it comes to alternative engines! It can be like a cat on a hot tin roof here at times...
I really welcome the fact that you want to do things right and distance yourselves from what others vendors have done in the past in this field. I truly hope MPS can deliver the goods and give builders a viable alternative to the mighty Lycosaurus.
That being said, you will find some smart people here who are not convinced easily and will call you on any questionable claims or data. Don't take it personally, RVers are very friendly at heart. Really.
I studied the Glastar data a couple weeks ago with Randy and found it compared more closely with the 180hp Lycoming data he sent along than the 210hp version. Of course RV people want to compare what the MPS package will do against a 180hp Lycoming RV where we have thousands of data points, that being the most popular engine fitted here. Can we impose on you to urge Randy to do a fly off at Van's (open invitation to alternative engine vendors/ users I understand) to get an impartial comparison against their factory demonstrators? This is probably the only way you'll sway this bunch of Lycoming die hards here on VAF. If the package can do the job, the good press will do wonders for your company's image and sales.
I do understand that Randy will probably only have your engine, not drive, prop and cooling system. Perhaps another 7/7A customer could be convinced running your whole FF package?
You will not find a more skeptical bunch here when it comes to alternative engines! It can be like a cat on a hot tin roof here at times...
I really welcome the fact that you want to do things right and distance yourselves from what others vendors have done in the past in this field. I truly hope MPS can deliver the goods and give builders a viable alternative to the mighty Lycosaurus.
That being said, you will find some smart people here who are not convinced easily and will call you on any questionable claims or data. Don't take it personally, RVers are very friendly at heart. Really.
I studied the Glastar data a couple weeks ago with Randy and found it compared more closely with the 180hp Lycoming data he sent along than the 210hp version. Of course RV people want to compare what the MPS package will do against a 180hp Lycoming RV where we have thousands of data points, that being the most popular engine fitted here. Can we impose on you to urge Randy to do a fly off at Van's (open invitation to alternative engine vendors/ users I understand) to get an impartial comparison against their factory demonstrators? This is probably the only way you'll sway this bunch of Lycoming die hards here on VAF.
If the package can do the job, the good press will do wonders for your company's image and sales.I do understand that Randy will probably only have your engine, not drive, prop and cooling system. Perhaps another 7/7A customer could be convinced running your whole FF package?
Thanks for the nice welcome, Ross. I certainly welcome questions and comments...it is how we learn, grow and make our products better.
I would love Maxwell Propulsion to be enormously successful, but that can only happen with honesty and fairness to its customers as well as potential customers. In the absence of those two qualities, all else is for naught.
I have already talked with Randy about doing the RV challenge and he is very happy to do so. He should be getting his engine from us by the end of the month, all the parts are ordered and either here or on the way, but not sure what his timeline is for getting it installed, tested and flying. I flew with him earlier this summer with his Turbo version, so it will be pretty interesting to see what happens with the 205 hp.
You are right that Randy will only have the long block, so a full firewall forward customer that is ready or nearly ready to fly is something that I would love to find...any takers out there? If so, give me a call. We have full FWF packages for RV6, 7, and 9s available and would be very interested in discussing opportunities.
Agree that the data posted earlier are probably closer to a 180 - 190 hp Lyc, but then again we were not trying to get max climb performance numbers. In fact, it was only when we were sipping our libations Monday after Oshkosh that I bugged Bill to write down the performance data from our return.
On a related note, Ephraim (my actual test pilot) is planning to collect formal test data at 4000 and 8000 foot altitudes in order to establish baseline performance parameters with the current setup. Then, as we develop new products...exhaust, cooling, EMS/ECU...we will have a comparison. Hum, can you tell that I like data!
Looking forward to some lively discussions...mind you I am a retired statistician...not an engineer so some of the technical questions may be deferred to either Craig or Dominic.
Gwen
BTW, as a newbie to the site, I am wondering if there is a way to post attachments on this site. I have some info posted on the Maxwell Propulsion group site ([email protected]) but thought it might be nice to get it posted here as well. I confess that I am a complete website novice...a major reason our site does not get updated too often...but clearly I need to take some website for dummies courses!
I would love Maxwell Propulsion to be enormously successful, but that can only happen with honesty and fairness to its customers as well as potential customers. In the absence of those two qualities, all else is for naught.
I have already talked with Randy about doing the RV challenge and he is very happy to do so. He should be getting his engine from us by the end of the month, all the parts are ordered and either here or on the way, but not sure what his timeline is for getting it installed, tested and flying. I flew with him earlier this summer with his Turbo version, so it will be pretty interesting to see what happens with the 205 hp.
You are right that Randy will only have the long block, so a full firewall forward customer that is ready or nearly ready to fly is something that I would love to find...any takers out there? If so, give me a call. We have full FWF packages for RV6, 7, and 9s available and would be very interested in discussing opportunities.
Agree that the data posted earlier are probably closer to a 180 - 190 hp Lyc, but then again we were not trying to get max climb performance numbers. In fact, it was only when we were sipping our libations Monday after Oshkosh that I bugged Bill to write down the performance data from our return.
On a related note, Ephraim (my actual test pilot) is planning to collect formal test data at 4000 and 8000 foot altitudes in order to establish baseline performance parameters with the current setup. Then, as we develop new products...exhaust, cooling, EMS/ECU...we will have a comparison. Hum, can you tell that I like data!
Looking forward to some lively discussions...mind you I am a retired statistician...not an engineer so some of the technical questions may be deferred to either Craig or Dominic.
Gwen
BTW, as a newbie to the site, I am wondering if there is a way to post attachments on this site. I have some info posted on the Maxwell Propulsion group site ([email protected]) but thought it might be nice to get it posted here as well. I confess that I am a complete website novice...a major reason our site does not get updated too often...but clearly I need to take some website for dummies courses!
Refreshing attitude Gwen and the fact that you fly and test what you produce says volumes too along with your willingness to to do the Van's test.
I'm a turbo guy so I don't expect the atmo 2.6 to come anywhere close to what Randy's 2.5 turbo did for speed at altitude. It would be huge just to be able to match an O-360 overall in weight, climb, speed and fuel burn. Of course if you could exceed those figures, the Lyco boys will sit up and take notice at least even if they never buy a package. I must say they were a little silent after Randy posted the turbo speeds here- grumble, grumble...
VAF is a THE best way to get info out to the RV world which is huge in comparison to the Glastar world. I would add for Doug's benefit that ads here are optional and so are donations but one or the other is always appreciated when it comes to vendors I'm sure. Doug is a great guy with the best experimental aircraft forum anywhere. We luv him so much we helped buy him a new airplane kit! How's that for family?
People here really are interested in alternative engines whether they admit it or not- the viewing numbers are huge on some of these engine threads- either that or the epic battles have a ton of entertainment value!
We all look forward to learning more about MPS. It's always nice to have some of the top people from a vendor here to answer questions directly about products that RV builders use.
Can't wait to see Randy's numbers.
I'm a turbo guy so I don't expect the atmo 2.6 to come anywhere close to what Randy's 2.5 turbo did for speed at altitude. It would be huge just to be able to match an O-360 overall in weight, climb, speed and fuel burn. Of course if you could exceed those figures, the Lyco boys will sit up and take notice at least even if they never buy a package. I must say they were a little silent after Randy posted the turbo speeds here- grumble, grumble...
VAF is a THE best way to get info out to the RV world which is huge in comparison to the Glastar world. I would add for Doug's benefit that ads here are optional and so are donations but one or the other is always appreciated when it comes to vendors I'm sure. Doug is a great guy with the best experimental aircraft forum anywhere. We luv him so much we helped buy him a new airplane kit! How's that for family?
People here really are interested in alternative engines whether they admit it or not- the viewing numbers are huge on some of these engine threads- either that or the epic battles have a ton of entertainment value!
We all look forward to learning more about MPS. It's always nice to have some of the top people from a vendor here to answer questions directly about products that RV builders use.
Can't wait to see Randy's numbers.
I think Ross is somewhat right, but it's only part of the story. Indeed everyone was impressed with the numbers, but if you can't do it for 500 or a 1000 hours than it's of less value when trying to compare to traditional engines (IMHO)....I guess for me what still causes a bit of pause is when Randy himself made the following quote just a few days ago:
"I had great performance with the Turbo STI, but it did suffer some in the reliability area.....I have been through a tremendous amount of trials in my quest to accomplish the above stated goal. To be honest I have been ready to give it up a few times and put a Lyc. in it and just get in some enjoyable flying hours instead of continuous experimentation, it gets old after a while seeing other RVs rack up the flying hours while I work on mine...."
Indeed the numbers were impressive, but now the engine is being removed for a different solution. Obviously the entire package when taken in totality (performance vs. reliability vs. weight, etc..) still has some room for improvement on this particular install or the engine probably wouldn't get removed and replaced with something else. It's fine to do a fly-off with Van's and I encourage that, but I'd like to see the same fly-off done at 250 hrs, 500 hrs and 1000 hrs with NO modification or changes done to the engine within that time-frame other than usual maintenance. When that happens I'll really sit up and take note as I'll bet others will too! I'm encouraged that Randy is doing the legwork, but just posting speed numbers alone without a bit of "the whole story" is of limited value in the long run.
To the the MPS folks, I'd say data like this when only taken in part is what gets a lot of the "community" suspicious. For so long so many alternative suppliers and fliers are quick to post numbers that on the surface are extremely attractive. When they fail to post is the "rest of the story"...this is where people start getting doubtful. In order to build a good reputation, take a look at people like the Pmag/Emag folks. Not only do they discuss the good things, but they also are open and willing to discuss their struggles. This has only worked to better their reputation as a top notch company. If MPS can do the same (that is be entirely open and honest - with all aspects of the products) I think you'll find the RV community to be very encouraging of your business and products.
Again I don't have a horse in the race and I'm not personally for or against alternative engines. I hope MPS is able to figure the entire formula out (that being performance/reliability/weight) and am eagerly waiting to see such data accumulated. Competition, technical improvements and alternatives in aviation are all good things. I don't have the motivation, knowledge or willingness to go through what Randy and Ross do, so I appreciate their efforts to do so.
As Ross said, we all await the new numbers from Randy, but as much I await the hours getting accumulated with the same performance.
Cheers,
Stein
"I had great performance with the Turbo STI, but it did suffer some in the reliability area.....I have been through a tremendous amount of trials in my quest to accomplish the above stated goal. To be honest I have been ready to give it up a few times and put a Lyc. in it and just get in some enjoyable flying hours instead of continuous experimentation, it gets old after a while seeing other RVs rack up the flying hours while I work on mine...."
Indeed the numbers were impressive, but now the engine is being removed for a different solution. Obviously the entire package when taken in totality (performance vs. reliability vs. weight, etc..) still has some room for improvement on this particular install or the engine probably wouldn't get removed and replaced with something else. It's fine to do a fly-off with Van's and I encourage that, but I'd like to see the same fly-off done at 250 hrs, 500 hrs and 1000 hrs with NO modification or changes done to the engine within that time-frame other than usual maintenance. When that happens I'll really sit up and take note as I'll bet others will too! I'm encouraged that Randy is doing the legwork, but just posting speed numbers alone without a bit of "the whole story" is of limited value in the long run.
To the the MPS folks, I'd say data like this when only taken in part is what gets a lot of the "community" suspicious. For so long so many alternative suppliers and fliers are quick to post numbers that on the surface are extremely attractive. When they fail to post is the "rest of the story"...this is where people start getting doubtful. In order to build a good reputation, take a look at people like the Pmag/Emag folks. Not only do they discuss the good things, but they also are open and willing to discuss their struggles. This has only worked to better their reputation as a top notch company. If MPS can do the same (that is be entirely open and honest - with all aspects of the products) I think you'll find the RV community to be very encouraging of your business and products.
Again I don't have a horse in the race and I'm not personally for or against alternative engines. I hope MPS is able to figure the entire formula out (that being performance/reliability/weight) and am eagerly waiting to see such data accumulated. Competition, technical improvements and alternatives in aviation are all good things. I don't have the motivation, knowledge or willingness to go through what Randy and Ross do, so I appreciate their efforts to do so.
As Ross said, we all await the new numbers from Randy, but as much I await the hours getting accumulated with the same performance.
Cheers,
Stein
All true Stein which is why I mentioned the 3-5 year wait and see period for reliability over many users on the introduction post. The numbers don't mean much if the TBO is less than 1000 hours.
As Randy stated, many of the problems he encountered were due to things he did not recommended with the turbocharger. A few too many forced landings will change your mind on this whole engine thing...
This forum can make or break your business depending on how you use it and treat people.
As Randy stated, many of the problems he encountered were due to things he did not recommended with the turbocharger. A few too many forced landings will change your mind on this whole engine thing...
This forum can make or break your business depending on how you use it and treat people.
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Actually, if the engine performed better than a Lyc but with only a 1,000 hr TBO, I'd be ok with replacing a $3,000 engine.
The real issues seems to be variability. Some folks do just fine with these engines for a long time, others not so much.
Options such as Gemini and Adept Airmotive which purport to be designed from the ground up as aircraft engines sound very attractive; but then you begin to notice things like the web site not being updated in a year, etc.
To my way of thinking we need a real order-of-magnitude change to make it worth switching to an alternative engine - all of the energy spent trying to wring a few more ponies out of an essentially similar-performance package is, IMHO, flying time lost.
But to each their own - that's why it's "Experimental!"
The real issues seems to be variability. Some folks do just fine with these engines for a long time, others not so much.
Options such as Gemini and Adept Airmotive which purport to be designed from the ground up as aircraft engines sound very attractive; but then you begin to notice things like the web site not being updated in a year, etc.
To my way of thinking we need a real order-of-magnitude change to make it worth switching to an alternative engine - all of the energy spent trying to wring a few more ponies out of an essentially similar-performance package is, IMHO, flying time lost.
But to each their own - that's why it's "Experimental!"
Actually, if the engine performed better than a Lyc but with only a 1,000 hr TBO, I'd be ok with replacing a $3,000 engine.
The real issues seems to be variability. Some folks do just fine with these engines for a long time, others not so much.
Options such as Gemini and Adept Airmotive which purport to be designed from the ground up as aircraft engines sound very attractive; but then you begin to notice things like the web site not being updated in a year, etc.
To my way of thinking we need a real order-of-magnitude change to make it worth switching to an alternative engine - all of the energy spent trying to wring a few more ponies out of an essentially similar-performance package is, IMHO, flying time lost.
But to each their own - that's why it's "Experimental!"
I think the same way as far as TBO if the basic engines are so much less money than a Lycoming. 1000 hours is about 10 years flying for a large majority of RV pilots.
David-aviator
Well Known Member
Vendor Observation
A vendor I regularly see at OSH is Sam James. I've been to his workshop sessions a couple times and he is always a joy to watch and listen to.
A salient comment at his work shop this year - never make claims to the RV crowd you can not back up. They will prove you wrong very quickly, if you are.
That being said, a vendor does not have a chance at long term success without demonstrating in a convincing manner that his product is worth the money. That is a key element in the success RV airplanes.
In the beginning the 2.5 Subby engine demonstration flights around the country were a smashing success. The orders came in so quickly, the EGG factory was overwhelmed. No such demonstration effort was undertaken with the STI or H6 engines. The notion that the experimental drive of some builders will carry a business forward without adequate testing and demonstration of the product IS OVER. Too many people have taken a serious financial bath with the later engines. When customers are asked to bear the cost of development miscues as occurred with these engines, the charm and excitement of the effort unravels quickly. When the vendor of what was initially such a popular item does not bother to fly the current product to OSH, the show is over. Demonstrating the product can not be replaced with pictures and words. Relying on customers to do the demonstration part gets old quickly. Customers were invited to show their airplanes at the display booth at OSH, but not one had the gumption to do it. What's in it for them?
That's not to say some very talented builders can not take the product and bring it up to a level of safety and reliability they find acceptable, but that never should be a part of selling that product. Most customers need a product that is beyond the beta test mode to make the effort work overall.
There also needs to be a customer screening process where money is not the ONLY qualifying item on the table. The Dan Lloyd tragedy is plenty of evidence such a screening process is appropriate. Such a notion, obviously, is easier said than done. Money talks in this country and always has.
A vendor I regularly see at OSH is Sam James. I've been to his workshop sessions a couple times and he is always a joy to watch and listen to.
A salient comment at his work shop this year - never make claims to the RV crowd you can not back up. They will prove you wrong very quickly, if you are.
That being said, a vendor does not have a chance at long term success without demonstrating in a convincing manner that his product is worth the money. That is a key element in the success RV airplanes.
In the beginning the 2.5 Subby engine demonstration flights around the country were a smashing success. The orders came in so quickly, the EGG factory was overwhelmed. No such demonstration effort was undertaken with the STI or H6 engines. The notion that the experimental drive of some builders will carry a business forward without adequate testing and demonstration of the product IS OVER. Too many people have taken a serious financial bath with the later engines. When customers are asked to bear the cost of development miscues as occurred with these engines, the charm and excitement of the effort unravels quickly. When the vendor of what was initially such a popular item does not bother to fly the current product to OSH, the show is over. Demonstrating the product can not be replaced with pictures and words. Relying on customers to do the demonstration part gets old quickly. Customers were invited to show their airplanes at the display booth at OSH, but not one had the gumption to do it. What's in it for them?
That's not to say some very talented builders can not take the product and bring it up to a level of safety and reliability they find acceptable, but that never should be a part of selling that product. Most customers need a product that is beyond the beta test mode to make the effort work overall.
There also needs to be a customer screening process where money is not the ONLY qualifying item on the table. The Dan Lloyd tragedy is plenty of evidence such a screening process is appropriate. Such a notion, obviously, is easier said than done. Money talks in this country and always has.
Very good thoughts as usual David. All engine vendors need a factory demonstrator that they fly regularly and continually, building up flight time ahead of all customers, take to air shows and fly ins etc. This does so much for client confidence and sales- plus it is a tax write off in most cases. There is simply no reason not to do this.
Gwen, I have a question on gearboxes, some time ago it appeared that you might be offering the Autoflight gearboxes from NZ as well as your own design. What is the story on that and what is the current offering?
Gwen, I have a question on gearboxes, some time ago it appeared that you might be offering the Autoflight gearboxes from NZ as well as your own design. What is the story on that and what is the current offering?
All:
Agree....that is what we are doing. With nearly 300 flight hours in approximately 13 months we have done the equivalent of 3 years flying for the average experimental pilot. Of course it would be great to have multiple aircraft all flying with different hp packages, but I am afraid the economics of that are not in my budget. So, after one year and 240 hrs on the 165 hp NA we decided that due diligence was satisfied for the engine component. The new 205 hp system however uses all of the accessories including the prop and PSRU that were used on the 140 hr ground testing and the 240 flight test hours. (Well that is not totally true, the alternator failed on our way to Oshkosh, so we had to visit the local Napa store and get a new one.)
Regarding the Autoflight PSRU. Ross, you are correct MPS is a distributor for the entire Autoflight line of PSRUs. For the most part we sell the lower hp rated products for the EJ engines where weight is often an issue. I also have a couple of EA81 customers. I keep trying to get Neil to get me some promotional material, but he must have even more computer issues than I! At least my major failing is the web site...but I promise to try to get some refreshing info up there soon.
I can post my MS Word document in a separate post later today. It is what was sent to Pat Panzera.
Gwen
Agree....that is what we are doing. With nearly 300 flight hours in approximately 13 months we have done the equivalent of 3 years flying for the average experimental pilot. Of course it would be great to have multiple aircraft all flying with different hp packages, but I am afraid the economics of that are not in my budget. So, after one year and 240 hrs on the 165 hp NA we decided that due diligence was satisfied for the engine component. The new 205 hp system however uses all of the accessories including the prop and PSRU that were used on the 140 hr ground testing and the 240 flight test hours. (Well that is not totally true, the alternator failed on our way to Oshkosh, so we had to visit the local Napa store and get a new one.)
Regarding the Autoflight PSRU. Ross, you are correct MPS is a distributor for the entire Autoflight line of PSRUs. For the most part we sell the lower hp rated products for the EJ engines where weight is often an issue. I also have a couple of EA81 customers. I keep trying to get Neil to get me some promotional material, but he must have even more computer issues than I! At least my major failing is the web site...but I promise to try to get some refreshing info up there soon.
I can post my MS Word document in a separate post later today. It is what was sent to Pat Panzera.
Gwen
I get some people contacting me who'd like more info on the Autoflight PSRUs. Can I send them to you in future? Many are interested in the 200hp versions and there is precious little info on the larger 300 hp model which one of my clients has in Alaska on a Bearhawk. They'd like to deal with someone in North America besides RAM.
MPS Vibration Analysis Part 1 of 2
Here is the text of the Vibration analysis MPS did on our new PSRU. I would note that the PSRU now has approximately 440 hours on the gear set. Our bore scope inspection prior to Oshkosh showed normal wear pattern and no metal in the gear oil.
Apologies in advance...the photos may or may not come through. I will try to get the pdf of the actual article posted on the website this week...just as soon as I learn how to do it!
VIBRATION STUDY OF THE MPS MX1 SUBARU CONVERSION PACKAGE
By Lawrence D. Kerr and Gwen Maxwell
INTRODUCTION AND BACKGROUND
The vibration dampening system between a piston engine and a propeller speed reduction unit (PSRU) must be designed to minimize the potentially damaging effects of the torsional vibrations produced by piston engines on the gears and shafts. Since the early days of converting automotive engines to experimental aircraft use, a variety of PSRU designs have been developed to provide torsional vibration dampening between the engine and PSRU. These include gears, belt drives, clutches and other gear reduction systems.
The subject of torsional vibration continues to be surrounded by mysticism. One myth is that any level of torsional vibration will inevitably lead to a catastrophic failure of the prop shaft, the gear set, or other flight critical components. In truth, as long as the level of vibration is kept below the fatigue strength of each system component, there will not be a failure due to torsional vibration. It is the responsibility of the engineer/designer to incorporate appropriate safety factors into the design, and then to test the finished product, to ensure the level of reliability one expects in an aircraft. Despite the fact that many designs have experienced mechanical or structural failures, there has been remarkably little scientific testing and analysis done on the effects of engine vibration on the PSRU.
MAXWELL PROPULSION SYSTEMS ENGINE AND PSRU
In fall 2006 Maxwell Propulsion Systems, Inc. (MPS) made the decision to develop a new geared PSRU. The MPS goal was to bring into the experimental aviation marketplace a scientifically-designed and tested system that would address the critical issues of fatigue and failure resulting from torsional vibration. The design requirements included a projected TBO of at least 1500 hours. While the heart of an automotive conversion for aircraft use is the PSRU, MPS also believes in building quality from the start. All MPS engine packages are based on a Subaru EJ25 STI Turbo block and the stock EJ25 normally aspirated heads. The short block is disassembled, then balanced and blueprinted. The Subaru long block is then coupled with a dual ignition system, custom throttle body, exhaust, cooling, and mounting system.
DEVELOPMENT AND DESIGN CHALLENGES
Guided by preliminary market research, the initial MPS PSRU development proceeded along two parallel paths to address the design and testing objectives. The first approach tested used an automotive-style racing clutch to engage and disengage the PSRU. We chose the Tilton 5.5? rally clutch assembly coupled with the Tilton disc pack and hydraulic release bearing. MPS assembled a complete firewall forward system on a mockup of a GlaStar cockpit/firewall then mounted this to the flatbed trailer shown in Figure 1. This package was ground tested between July and September 2007. The test results demonstrated that an automotive clutch could effectively minimize the damaging effects of torsional vibration. However, designing an effective process to engage and disengage the clutch would require cumbersome activators that were not pilot-friendly.
Given these results, MPS immediately moved to incorporate a one-piece elastomeric coupler from Lord Corporation into the design. An initial consultation with Lord indicated this could be a very cost effective solution, with few modifications required to fit into the design envelope. Unfortunately, initial testing of a prototype unit showed it was not effective at keeping torsional vibration below the desired level. Construction of a more sophisticated unit that allowed testing of elastomeric bushings of a number of different durometer ratings showed little improvement. A parallel investigation suggested by Hugh Evans into the engine attachment frame design produced some minor improvements, and convinced us it was not the root of the problem.
We returned to David Kalivoda at Lord Corporation for more extensive consulting using their proprietary simulation software for coupling design. Feeding estimates for the mass elastic properties of all the mechanical components into the simulation, and optimizing wherever possible gave us our next design iteration. We were able to use off-the-shelf elastomeric bushings housed by a metal plate at a much larger bolt circle diameter to produce the torsional characteristics desired.
Construction of a prototype unit, and some initial testing gave us encouraging results. We then followed up with a validation of the entire package as regards its torsional vibration. A key component of the validation procedure of the MX1 engine package included performing a vibration test similar to the one reported in Issue #90 of Contact! Magazine, ?A Vibration Study of a Mazda 13B Installation in a Van?s RV6A?, by Steve Boese. The primary purpose of the test was to assure that the torsional coupler between the engine and the gear box was working as designed. In addition, we also wanted to ensure there were no outstanding mechanical resonances that would adversely affect the longevity of the gearbox or engine package. The results of the tests on that final design are described below. These results demonstrated that all observed vibrations fell well below the maximum tolerable level. After approximately 140 hours of ground testing and 190 hours of flight testing in N787MX, MPS believes that their PSRU meets both their design expectations as well as the practical requirements for their Subaru automotive conversion.
Here is the text of the Vibration analysis MPS did on our new PSRU. I would note that the PSRU now has approximately 440 hours on the gear set. Our bore scope inspection prior to Oshkosh showed normal wear pattern and no metal in the gear oil.
Apologies in advance...the photos may or may not come through. I will try to get the pdf of the actual article posted on the website this week...just as soon as I learn how to do it!
VIBRATION STUDY OF THE MPS MX1 SUBARU CONVERSION PACKAGE
By Lawrence D. Kerr and Gwen Maxwell
INTRODUCTION AND BACKGROUND
The vibration dampening system between a piston engine and a propeller speed reduction unit (PSRU) must be designed to minimize the potentially damaging effects of the torsional vibrations produced by piston engines on the gears and shafts. Since the early days of converting automotive engines to experimental aircraft use, a variety of PSRU designs have been developed to provide torsional vibration dampening between the engine and PSRU. These include gears, belt drives, clutches and other gear reduction systems.
The subject of torsional vibration continues to be surrounded by mysticism. One myth is that any level of torsional vibration will inevitably lead to a catastrophic failure of the prop shaft, the gear set, or other flight critical components. In truth, as long as the level of vibration is kept below the fatigue strength of each system component, there will not be a failure due to torsional vibration. It is the responsibility of the engineer/designer to incorporate appropriate safety factors into the design, and then to test the finished product, to ensure the level of reliability one expects in an aircraft. Despite the fact that many designs have experienced mechanical or structural failures, there has been remarkably little scientific testing and analysis done on the effects of engine vibration on the PSRU.
MAXWELL PROPULSION SYSTEMS ENGINE AND PSRU
In fall 2006 Maxwell Propulsion Systems, Inc. (MPS) made the decision to develop a new geared PSRU. The MPS goal was to bring into the experimental aviation marketplace a scientifically-designed and tested system that would address the critical issues of fatigue and failure resulting from torsional vibration. The design requirements included a projected TBO of at least 1500 hours. While the heart of an automotive conversion for aircraft use is the PSRU, MPS also believes in building quality from the start. All MPS engine packages are based on a Subaru EJ25 STI Turbo block and the stock EJ25 normally aspirated heads. The short block is disassembled, then balanced and blueprinted. The Subaru long block is then coupled with a dual ignition system, custom throttle body, exhaust, cooling, and mounting system.
DEVELOPMENT AND DESIGN CHALLENGES
Guided by preliminary market research, the initial MPS PSRU development proceeded along two parallel paths to address the design and testing objectives. The first approach tested used an automotive-style racing clutch to engage and disengage the PSRU. We chose the Tilton 5.5? rally clutch assembly coupled with the Tilton disc pack and hydraulic release bearing. MPS assembled a complete firewall forward system on a mockup of a GlaStar cockpit/firewall then mounted this to the flatbed trailer shown in Figure 1. This package was ground tested between July and September 2007. The test results demonstrated that an automotive clutch could effectively minimize the damaging effects of torsional vibration. However, designing an effective process to engage and disengage the clutch would require cumbersome activators that were not pilot-friendly.
Given these results, MPS immediately moved to incorporate a one-piece elastomeric coupler from Lord Corporation into the design. An initial consultation with Lord indicated this could be a very cost effective solution, with few modifications required to fit into the design envelope. Unfortunately, initial testing of a prototype unit showed it was not effective at keeping torsional vibration below the desired level. Construction of a more sophisticated unit that allowed testing of elastomeric bushings of a number of different durometer ratings showed little improvement. A parallel investigation suggested by Hugh Evans into the engine attachment frame design produced some minor improvements, and convinced us it was not the root of the problem.
We returned to David Kalivoda at Lord Corporation for more extensive consulting using their proprietary simulation software for coupling design. Feeding estimates for the mass elastic properties of all the mechanical components into the simulation, and optimizing wherever possible gave us our next design iteration. We were able to use off-the-shelf elastomeric bushings housed by a metal plate at a much larger bolt circle diameter to produce the torsional characteristics desired.
Construction of a prototype unit, and some initial testing gave us encouraging results. We then followed up with a validation of the entire package as regards its torsional vibration. A key component of the validation procedure of the MX1 engine package included performing a vibration test similar to the one reported in Issue #90 of Contact! Magazine, ?A Vibration Study of a Mazda 13B Installation in a Van?s RV6A?, by Steve Boese. The primary purpose of the test was to assure that the torsional coupler between the engine and the gear box was working as designed. In addition, we also wanted to ensure there were no outstanding mechanical resonances that would adversely affect the longevity of the gearbox or engine package. The results of the tests on that final design are described below. These results demonstrated that all observed vibrations fell well below the maximum tolerable level. After approximately 140 hours of ground testing and 190 hours of flight testing in N787MX, MPS believes that their PSRU meets both their design expectations as well as the practical requirements for their Subaru automotive conversion.
MPS Vibration Analysis Part 2 of 2
TEST CELL SETUP
The engine package, with its attachment frame, was bolted to a test stand consisting of the cabin structure of a Glastar kit plane, complete with firewall and a simplified instrument panel. Instruments included a tachometer, manifold pressure, engine oil temp, engine coolant temp, gear box temp, and exhaust gas temperatures from each cylinder. As seen in Figure 2 , controls included the ignition and throttle.
The cabin structure was bolted securely to a small trailer, allowing extended engine testing to take place on the far side of Arlington, WA airport, in an area designated by the airport authority for this purpose.
DATA COLLECTION AND SOFTWARE
The accelerometer used was the same as the one used by Steve Boese, a Freescale Semiconductor, Inc. evaluation kit, part number KIT3109MMA7260QE, with a mounting fabricated by our machine shop. The accelerometer has three axes, and a selectable range, from +/-1.5g to +/- 6g maximum.
We did not use a sensor on the propeller, since the propeller turns more slowly than the engine, due to the gear box, and we were primarily interested in engine-coupled vibrations. We did however use a tach signal from the ignition controller when required.
Data were collected from the accelerometer using a National Instruments USB-6009 Data Aquisition device (http://www.machinevisiononline.org/buyers_guide/newproducts/details.cfm?id=770). We also used the National Instruments Signal View software that came with the device, on a Lenovo ThinkPad T61p, to process the data. Signal View is sophisticated enough to provide accelerometer voltage vs. frequency graphs out of the box, but not quite customizable enough to imbed calibration data for the accelerometer, and provide g level readings directly. Working backward from the maximum vibration levels permitted by http://www.azimadli.com/images/severitychart.jpg, and the calibration data for the accelerometer, we calculated max voltage level at each frequency to remain within the acceptable and tolerable ranges for reciprocating engines.
RUNNING THE TEST
The engine was started on the test stand, and run at medium idle until temperatures and pressures were within the operating range. We had decided to test for vibration levels every 200 RPM from 3200 RPM to 5400 RPM. Throttle and prop pitch were adjusted for a typical engine output at each RPM, and a ten second sample of the vibration level recorded from the accelerometer. Between readings the engine RPM was returned to idle. Excluding warm-up, sampling and recording the data required approximately an hour run time.
PROCESSED DATA
Critical vibration frequencies are usually the first and second order, or 1X and 2X the engine RPM. Levels for these were read from the accelerometer data, along with the highest peak that was NOT a first or second order vibration. The data from every sample are shown in Table 1. Figures 3 demonstrates that the first and second order vibration levels are well below the maximum tolerable level. Figures 4 through 7 graphically displays the test run data for rpms of 3200, 4000, 4800, and 5400 respectively.
Figure 3 ? Vibration Tolerance Level Results
PSRU INSPECTIONS
In addition to the vibration analysis conducted on the MX1 PSRU, we also conducted a detailed examination of the PSRU during a complete tear-down following 75 hours of ground testing (See Figure 8 and Figure 9) as well as a visual inspection through a bore scope after approximately 120 hours. Both of these inspections revealed no wear beyond a normal break-in polish on either the pinion or driven gears. Bearings were still within nominal limits at 75 hours, and the torsional coupling components were in original condition.
CONCLUSIONS
We are pleased that the test results demonstrated vibration levels of the final MX1 system design were at acceptable levels, with only two minor excursions into the lower levels of the tolerable zone. The PSRU longevity continues to be evaluated, however initial inspections appear to corroborate that the design specifications for a 1500 hour TBO have been met and/or exceeded. As we continue to accrue actual flight hours on the first production PSRU now installed on N787MX, we continue to evaluate the system for evidence of gear wear. The total number of hours is nearly 350 (140 ground test and 190 flight test). We expect to do a complete tear-down inspection prior to AirVenture 2009 when the system should have approximately 400 hours logged.
We would like to acknowledge Mr. Steve Boese, his friend Doug Dempsey, and DLI Engineering for their willingness to share their knowledge and experience with the readers of Contact! Magazine. Our sincere appreciation also to the engineering staff at Lord Corporation and Mr. Hugh Evans for sharing their expertise.
TEST CELL SETUP
The engine package, with its attachment frame, was bolted to a test stand consisting of the cabin structure of a Glastar kit plane, complete with firewall and a simplified instrument panel. Instruments included a tachometer, manifold pressure, engine oil temp, engine coolant temp, gear box temp, and exhaust gas temperatures from each cylinder. As seen in Figure 2 , controls included the ignition and throttle.
The cabin structure was bolted securely to a small trailer, allowing extended engine testing to take place on the far side of Arlington, WA airport, in an area designated by the airport authority for this purpose.
DATA COLLECTION AND SOFTWARE
The accelerometer used was the same as the one used by Steve Boese, a Freescale Semiconductor, Inc. evaluation kit, part number KIT3109MMA7260QE, with a mounting fabricated by our machine shop. The accelerometer has three axes, and a selectable range, from +/-1.5g to +/- 6g maximum.
We did not use a sensor on the propeller, since the propeller turns more slowly than the engine, due to the gear box, and we were primarily interested in engine-coupled vibrations. We did however use a tach signal from the ignition controller when required.
Data were collected from the accelerometer using a National Instruments USB-6009 Data Aquisition device (http://www.machinevisiononline.org/buyers_guide/newproducts/details.cfm?id=770). We also used the National Instruments Signal View software that came with the device, on a Lenovo ThinkPad T61p, to process the data. Signal View is sophisticated enough to provide accelerometer voltage vs. frequency graphs out of the box, but not quite customizable enough to imbed calibration data for the accelerometer, and provide g level readings directly. Working backward from the maximum vibration levels permitted by http://www.azimadli.com/images/severitychart.jpg, and the calibration data for the accelerometer, we calculated max voltage level at each frequency to remain within the acceptable and tolerable ranges for reciprocating engines.
RUNNING THE TEST
The engine was started on the test stand, and run at medium idle until temperatures and pressures were within the operating range. We had decided to test for vibration levels every 200 RPM from 3200 RPM to 5400 RPM. Throttle and prop pitch were adjusted for a typical engine output at each RPM, and a ten second sample of the vibration level recorded from the accelerometer. Between readings the engine RPM was returned to idle. Excluding warm-up, sampling and recording the data required approximately an hour run time.
PROCESSED DATA
Critical vibration frequencies are usually the first and second order, or 1X and 2X the engine RPM. Levels for these were read from the accelerometer data, along with the highest peak that was NOT a first or second order vibration. The data from every sample are shown in Table 1. Figures 3 demonstrates that the first and second order vibration levels are well below the maximum tolerable level. Figures 4 through 7 graphically displays the test run data for rpms of 3200, 4000, 4800, and 5400 respectively.
Figure 3 ? Vibration Tolerance Level Results
PSRU INSPECTIONS
In addition to the vibration analysis conducted on the MX1 PSRU, we also conducted a detailed examination of the PSRU during a complete tear-down following 75 hours of ground testing (See Figure 8 and Figure 9) as well as a visual inspection through a bore scope after approximately 120 hours. Both of these inspections revealed no wear beyond a normal break-in polish on either the pinion or driven gears. Bearings were still within nominal limits at 75 hours, and the torsional coupling components were in original condition.
CONCLUSIONS
We are pleased that the test results demonstrated vibration levels of the final MX1 system design were at acceptable levels, with only two minor excursions into the lower levels of the tolerable zone. The PSRU longevity continues to be evaluated, however initial inspections appear to corroborate that the design specifications for a 1500 hour TBO have been met and/or exceeded. As we continue to accrue actual flight hours on the first production PSRU now installed on N787MX, we continue to evaluate the system for evidence of gear wear. The total number of hours is nearly 350 (140 ground test and 190 flight test). We expect to do a complete tear-down inspection prior to AirVenture 2009 when the system should have approximately 400 hours logged.
We would like to acknowledge Mr. Steve Boese, his friend Doug Dempsey, and DLI Engineering for their willingness to share their knowledge and experience with the readers of Contact! Magazine. Our sincere appreciation also to the engineering staff at Lord Corporation and Mr. Hugh Evans for sharing their expertise.
Just needs some resizing. Tip; photos and scanned documents post nicely here at about 600 pixels wide. One of our moderators can resize the above post if so inclined.
Received the two Contact articles you sent; thank you. I'd recommend you not publish your test method/results.
The Boese article (Contact #90) outlines an excellent method to survey the linear vibration of engine accessory components (radiators, alternators, etc). Put another way, it allows the user to determine if the natural frequency of a component on its mount is matched by an exciting frequency. If it is matched, the component will vibrate in a resonant manner and the mount will break sooner or later. The security of engine accessories is indeed very important to the reliability of an auto conversion, and Mr. Boese is to be complimented. However, he makes no attempt to determine the actual stress level of his component mountings and confirm they are below the knee in the S-N curve.
You've taken the Boese method and applied it to torsional vibration.
It is true that a resonant period will result in a block shake, thus a plot like Fig 3 is useful in determining the presence of resonant RPM ranges. Fig 3 shows two, one at 4200 and one at 4800 RPM. Their mere presence is not in itself reason for alarm. However, the method as presented offers no way to determine the actual stress applied to any rotating component when operating at these RPM settings. The "acceptable" and "maximum" values appear to be arbitrary, something akin to declaring a safe level of UV radiation based on a relative humidity chart.
In addition, the plot does not show the RPM range most likely to generate maximum stress. Propeller/engine drives incorporating a soft element have a first natural frequency typically found in the 25 to 50 hz area. Assuming a 4-stroke 4-cyl and translated to critical RPM , the most severe resonant period would be expected at less than 2000 engine RPM, probably between 750 and 1500 RPM. That data is not presented, but observe the downslope found at the far left of the chart (3200 RPM). Vibration levels are falling from some unknown higher level.
I do not wish to unnecessarily critical, and none of the above says the Maxwell system is unairworthy. I am suggesting the supplied document may be interpreted in a less than favorable light (an unintended consequence) when subjected to serious review. Please accept my sincere compliments for your efforts; alternative engine development really needs the serious measurement you've attempted.
Thanks for the comments an insight, Dan. Since you're "above my pay grade" I have passed the info onto our engineer for his thoughts/comments. May take a few days to get back to you.
Thinking back, I do recall from the testing process that while there is was a resonnance observed below the 3200 rpm level included in the article, it was outside the operating range and below the recommended engine idle speed. Thus, it was not considered a torsional vibration "risk" to the engine components. The intent of the article was to report the vibrations within the operating (flight) rpm ranges.
Also, as I read the Boese article, while the main focus of his testing was to address vibration levels in the accessory components that you mention, it also appears that he tested the vibration of the rotary engine/PSRU using the same test equipment. See quote from his article below:
Thanks again.
Gwen
Thinking back, I do recall from the testing process that while there is was a resonnance observed below the 3200 rpm level included in the article, it was outside the operating range and below the recommended engine idle speed. Thus, it was not considered a torsional vibration "risk" to the engine components. The intent of the article was to report the vibrations within the operating (flight) rpm ranges.
Also, as I read the Boese article, while the main focus of his testing was to address vibration levels in the accessory components that you mention, it also appears that he tested the vibration of the rotary engine/PSRU using the same test equipment. See quote from his article below:
Thanks again.
Gwen
Quote "Received the two Contact articles you sent; thank you. I'd recommend you not publish your test method/results."
Dan, I see much value in Gwens publishing of the test results. This to me is an indication that MPS is being open and honest about the testing that has been done, and, it exposes the results to people like yourself that apparently have a background in the subject and gives you an opportunity to provide feedback as you have done here on this forum.
Without your feedback in an open forum like this, those of us withtout your background might blindly accept the results.
I appreciate having trhe results and your feedback out in the open and I hope that Gwen can see the value of this also. If the testing is flawed in some way, it is good for us to learn about it.
I see this as a refreshing attitude to the secrecy so many vendors have shown in the past regarding testing or the lack thereof...
Randy C
Dan, I see much value in Gwens publishing of the test results. This to me is an indication that MPS is being open and honest about the testing that has been done, and, it exposes the results to people like yourself that apparently have a background in the subject and gives you an opportunity to provide feedback as you have done here on this forum.
Without your feedback in an open forum like this, those of us withtout your background might blindly accept the results.
I appreciate having trhe results and your feedback out in the open and I hope that Gwen can see the value of this also. If the testing is flawed in some way, it is good for us to learn about it.
I see this as a refreshing attitude to the secrecy so many vendors have shown in the past regarding testing or the lack thereof...
Randy C
I couldn't agree more. Any vendor that posts on this forum is taking a bit of a risk. There are some REALLY knowledgable people here who will not hesitate to point out errors. (also some who are quite critical just because they can and it's in their nature...that's another story ) Transparency is always worth it in the long run. So, Gwen and Dan and others..... keep up the work. Our lives may depend on it.
) Transparency is always worth it in the long run. So, Gwen and Dan and others..... keep up the work. Our lives may depend on it.Hum...To publish or not to publish is, as they say, a moot question. It is in print in Contact! 97 that was first distributed at AirVenture 2009.
Obviously the decision to publish "what we did and how we did it" does come with downsides. It opens one up to public critique...also known in the scientific world as "peer review." Since I lived in that world for more years than I would like to acknowledge, I actually welcome different ideas and viewpoints and, at least try to, learn from them.
Larry, our (now consulting) engineer is coming out to dinner tonight with the rest of the folks, so I will try to get his views on the various emails.
_______________
Dan,
Clearly you have the expertise, if you also have a testing protocol and equipment I would enjoy having a conversation about doing some additional testing.
My initial thought would be that if we were to conduct any additional tests we would use the PSRU that is currently on the Sportsman. With the 140 ground testing hours and flight hours it has approximately 450 hours. That is nearing 25% of the design-specified TBO. Note: MPS is currently advertising this as a 1500 hr TBO pending actually experience.
Thoughts?
________________
Gwen
Obviously the decision to publish "what we did and how we did it" does come with downsides. It opens one up to public critique...also known in the scientific world as "peer review." Since I lived in that world for more years than I would like to acknowledge, I actually welcome different ideas and viewpoints and, at least try to, learn from them.
Larry, our (now consulting) engineer is coming out to dinner tonight with the rest of the folks, so I will try to get his views on the various emails.
_______________
Dan,
Clearly you have the expertise, if you also have a testing protocol and equipment I would enjoy having a conversation about doing some additional testing.
My initial thought would be that if we were to conduct any additional tests we would use the PSRU that is currently on the Sportsman. With the 140 ground testing hours and flight hours it has approximately 450 hours. That is nearing 25% of the design-specified TBO. Note: MPS is currently advertising this as a 1500 hr TBO pending actually experience.
Thoughts?
________________
Gwen
Gwen, I've advocated what you're trying to do for a very long time. Yes, I've done torsional telemetry and I'll help where I can. Can't do it for you (other commitments, like a business and an RV project), but it would be fun to observe even from a distance. Click on my name above to send regular email.
Fair warning; this is one of those "fast, cheap, good, pick any two" projects.
BTW, here's an example of a commercial plug and play torsional telemetry transmitter:
http://www.binsfeld.com/videos/tt10kdemo.html
There are many other brands. They're used by everyone in vehicle development.
Postscript: Just for fun, this is the "master control console" (ha!) for vibratory torque measurement on the cheap, circa 1999. The stuff piled on the cardboard box is an old Wireless Data FM analog telemetry receiver coupled to an ancient BK o-scope and a Fluke true RMS multimeter. The recording media was a clipboard.
Not nearly as sexy as the new digital stuff feeding a laptop, but one of the goals was to prove it could be done cheaply....and it did. The result is a plot like you see below, vibratory shaft torque in ft-lbs for the whole operating range, which can be compared directly to the capacity of shafts, bearings, couplers, etc.
Go back to the SAE papers of the 1930's. You'll find P&W and Wright were measuring vibratory shaft twist by direct mechanical means. Same idea.
Fair warning; this is one of those "fast, cheap, good, pick any two" projects.
BTW, here's an example of a commercial plug and play torsional telemetry transmitter:
http://www.binsfeld.com/videos/tt10kdemo.html
There are many other brands. They're used by everyone in vehicle development.
Postscript: Just for fun, this is the "master control console" (ha!) for vibratory torque measurement on the cheap, circa 1999. The stuff piled on the cardboard box is an old Wireless Data FM analog telemetry receiver coupled to an ancient BK o-scope and a Fluke true RMS multimeter. The recording media was a clipboard.
Not nearly as sexy as the new digital stuff feeding a laptop, but one of the goals was to prove it could be done cheaply....and it did. The result is a plot like you see below, vibratory shaft torque in ft-lbs for the whole operating range, which can be compared directly to the capacity of shafts, bearings, couplers, etc.
Go back to the SAE papers of the 1930's. You'll find P&W and Wright were measuring vibratory shaft twist by direct mechanical means. Same idea.
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