Questions on Ross's EG33 Subie RV-10, Marcotte Drive

From another thread (LINK), I'm spinning off some questions to Ross on his RV-10 and RV-6A projects, primarily regarding the Marcotte drive:

rv6ejguy said:

I have designed things using the engineering data say on a bearing with a 3X fudge factor on top of that even and guess what? It doesn't last sometimes. Many times there are unknown variables that we don't uncover until we build and run/test a design for a while. The proof is indeed in the pudding as your post heading states.

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Ross I checked your site for RV-10 updates, http://sdsefi.com/aircraft.html

-How's the RV-10 with EG33 coming? (when's it going to fly)
-Why did you use a Marcotte PSRU and not a Gen III eggy on your RV-10?
-You have +200 hours with the Marcotte, on your RV-6A. How is it going, still happy? LINK

Searching on "Marcotte" some of your "one liners" came up. As a memory joggle and so you don't have to repeat, I list some of your comments on the Marcotte PSRU below:

Marcotte M-300 PSRU is 47 lbs

our Marcotte drive and gearbox oil always runs below coolant temp.

Offset drives like RFI, Marcotte, Auto Flight and EPI give these users other options.

I'm using the same Marcotte M-300 drive as the 6A has except a 1.93 ratio instead of 2.2.

I built a chip detector for my Marcotte. Gives me a bit of piece of mind to a slow failure at least.

Interestingly my Marcotte drive has never exceeded 90C on the oil even in the climb on a hot day.

I look for everything to be massively oversized and that is why I like most parts of the Marcotte box.

Drives that are fitted to a variety of different engines like the Marcotte that I use are more of an unknown quantity.

The Rotax, Ross, Marcotte, RWS, Egg, Crossflow and NSI drives have all had issues which have resulted in modified designs or operational changes.

The Marcotte drives I use are totally bulletproof and don't care if the prop drives the engine. They have massive Timken tapered roller bearings for the main shaft which is also massive.

....the sheer amount of time needed to collect data for multiple propellers and engines. It could never be afforded by companies like RWS or Marcotte which cater to several different engines fitted with dozens of different props.

The one thing I don't like about the Marcotte box is that they have one ball and one roller bearing bearing supporting the drive gear- a bit short on thrust load capability possibly. Twin tapered roller bearings support the cantilevered driven gear so that part is fine. Maybe the fact that everything is so massive in these boxes makes this a non-issue. We shall see.​

The bottom line is what is the best PSRU? Egg, Marcotte, EPI.......

One criticism of the Marcotte I noted was from 'DanH' about weight and harmonic vibration at one RPM (on the Subaru EJ22?). I gather you're happy with weight. I am not sure about the harmonic vibration issue. I see you recommend a "pinion" modification.

You mention other PSRU's: EPI, Ross, RWS, Egg, Crossflow, NSI and Warren. What are the viability or recommendations of these drives?

The Big question? When is the twin turbo RG33 RV-10 going to take flight? I see pics of a White Lightning with a EG33 with pics dated to 2000, has that flown yet? (I see it is registered as 111LG)

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Not related to PSRU's, about your SDS 4D or 4F Lycoming application - You say you can replace the carb with an automotive throttle body? What kind? I see you need to mod the intake tubes/runners to locate the injectors there, due to heat. How hard is that modification? Are those fittings included? What's the approx cost for a SDS injector ignition system for a 4 cyl Lyc?

As you can see from the latest update, the -10 is finally resting on its gear with engine and prop installed to fit the cowling and finish off some minor things like ducting, prop brush mount etc. I have no idea when it will fly. I'm very busy with work now and some new R&D projects. Making a living is job 1.

As I've said before, I prefer a drive with a prop shaft offset. This allows more space for the intake manifold and injectors without removing the stock water manifold on the Subaru. My philosophy is to have the best possible airflow through the engine to make max hp with the least amount of boost and heat. The drive on the -10 has a 1.5 inch offset. Jan's Gen 3 drive was not available at the time the engine mount and installation was designed and the EG33 engine simply would not fit with an inline drive due to injector placement on the heads.

I've had no problems with the M-300 on the 6A. It has never been removed from the engine since initially installed and it sounds the same as the first day. This made it the clear choice for the -10.

The pilot bearing mod was devised by Marcotte before I installed the engine. Another friend had helped them learn that the original bushing was not up to the task. This has been standard since circa 2003.

What is the best drive? Nobody knows.

I do like the thorough engineering and testing that EPI does to their products and I like their educational approach to all matters in the prop/engine/ PSRU unit. If I was building a V8 powered aircraft, it would have an EPI drive on it.

Tracy Crook has a lot of drives flying and is an engineer who has put a lot of thought and real world testing into them. Can't argue with that too much and he is a really nice guy. His company gets good marks from his customers. This is another non-offset drive so not so good for many piston engines.

NSI is thankfully gone and been replaced by MPS. They do have engineers on staff and I like the preliminary discussions and details on their new drive. I've had some minor dealings with them a couple years ago and even though they did not select our EMS, I don't hold that against them. Looks like they are on the right track now but they have a lot of wounds to heal left over from NSI days. I do find their hp claims somewhat unlikely. I have not checked lately on what rad setup they were supplying. I was never keen on the complicated NSI setup. I hope they will use something lighter and simpler.

Never a fan of the defunct Ross drives. They had issues with machining accuracy and a poor coupler design. Some users like Al Wick and others have made mods and appear to get decent life out of them now. Again no offset so this limits clean installations on many piston engines.

Crossflow has a poor rep with customer satisfaction overall and I have helped several of their customers get their engines flying. I have serious concerns about some technical aspects of their packages and QC. There have been a couple bad failures of their drive with low time but I don't know all the details. I'm assisting an EG33 turbo customer in Canada who will be watching his drive carefully. Crossflow must learn that to survive and prosper, you need to treat customers fairly, stay on schedule and take care of issues.

Bud Warren's drives seem to be holding up well so far and I like his innovative/unorthodox design. Keven Eldridge's NXT is having a Warren Drive fitted to an experimental 502 Chevy. While I don't think it will race at Reno in 2008, this may be the shape of things to come as the Lyconentals approach their thermal and mechanical strength limits. This will be a great testing ground for Bud's products and very public. That says volumes in my book and so does his own flight testing. I have friend close to this project so that will be interesting to watch. Bud needs more flight hours to solidify the products. That will come in a few more years.

Jan has more stuff flying than anybody and in my view it has been quite successful. While problems have cropped up, this is completely expected in this field on the available development budget. He is not offering rehashed hardware, it is better each year. Jan has the hours that nobody else has and this is VERY important.

Marcotte sells to many different engine types so it is likely too expensive to carry out TV testing on even 4-5 of the most popular engines his drives might be fitted to not to mention the many types of props as well. His drives are very strong but being generic and not part of a dedicated package, lack what a FF supplier can do with only one type of engine. They are good for the experimenter but you may have to tweak the coupler design to get the best results. Marcotte is renown for slow service so don't be in a rush to get one. My 6A setup is not as refined as say Jan's design either in appearance or smoothness and it would not be salable to the public as is but it does perform pretty well. I can tweak it for lower weight and drag in the future I think. Life is unknown at this point and I do have two bad TV spots at low rpm.

The White Lightning has never flown to my knowledge. There were too many people with their finger in the pie and several induction iterations were tried. Not sure where it all stands now.

On the Lycoming EMS front, we have supplied a small number of EMSs to DIYs and they have been pretty pleased with the results. We have supplied a number of Continental guys also including Mike Dacey for his Sport Class Questair Venture. To date these have all been well received. Another client is developing complete bolt on kits for Lycoming engines to start flight testing later this year. So there may be some other choices soon in this field. Ford 5L TBs are commonly used and sometimes revised manifolds. Most people are using our weld on injector holders to mount injectors to the stock induction tubes. Heat has not been a big issue but we stress careful design in this area. We are also partners in Rotax 912 EFI with a couple companies and there are some of these flying now with our EMSs including dozens of UAVs overseas.

Now you see why I can't get the RV10 done!

Thanks Ross what about your SDS for Lycs

Would you care to share the cost of the whole system and what is involved in the conversion (from a stock Carb set up)? What do you do for a throttle body?

We're not developing this kit, just supplying the ECU and sensors probably. It is being developed by another well known RV guy but I can't say much more at this time. I would expect it to be a fair amount less than FADECs currently being offered by other companies for experimentals. I would expect that a complete solution with new throttle body will be supplied.

Peculiar to Lycoming and Continental engines is the requirement to use very large injectors due to the large cylinder size. Since we don't prime any more, the injectors need to have high flow rates for cold starting. 440cc for O-200 or O-235 engines, 570cc for O-320s, 720cc for 360s, 520s, 540s and 550s.

For Reno Sport class engines where hp is closing in on 650-700hp as of last year, 850cc injectors are used along with very large 28V pumps and regulators. The fuel flow is pretty impressive on the twin turbo Contis. We were seeing a serious limitation on the factory mechanical injection to supply enough fuel to these engines at this power level from the data logs. DG burnt a few pistons due to this problem over the years and went to EFI last year but had serious PSRU problems. The Lycomings in the NXTs do not have this problem so far. Data logging and/or telemetry is a must now in this class to be competitive as the engines are pretty close to destruction. Manifold pressures over 60 inches will be the norm in 2008. The Thunder Mustang has always had a Motec EFI system.

I should mention a few more things about the Marcotte drives. They currently offer 4 models to my knowledge- 150, 200, 300 and 450 hp versions and a variety of ratios.

The internal helical gear has many advantages over spur gears. Bath oiling works well because centrifugal forces keeps the oil pinned to the ring gear rather than being flung off. Self contained oil can be hypoid type which is designed for gear sets. Engine oil is not the best for gears. This feature also eliminates external feed and drain lines from the engine. In the event of oil loss, the ring gear gets larger due to heat and clearances increase, reducing the chance of seizure. The helical gears and higher mesh ratio than spur gears make for a very quiet and strong part. There have been no seal issues like many other drives have had. I have been told that each box is designed to take 50% more torque than the rated value. The size of the components used would tend to back up that statement. This setup retains the same prop and engine rotation and being a single mesh design is quite efficient and generates little heat.

This is not to say that planetary or spur gears don't work well, just that the internal type gear set has some advantages. Being custom made and a ring type helical gear, it is rather expensive to manufacture however.

I'd also mention that the Crossflow and new RDM drives use straight cut internal designs.

The Marcotte can also run a hydraulic prop using an external pump if desired. Chevrolet and Subaru adapter castings are available and they may have others now.

OK 20 questions ... ha ha, well how much for ...

rv6ejguy said:

We're not developing this kit, just supplying the ECU and sensors probably. It is being developed by another well known RV guy but I can't say much more at this time.

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OK well how much $$$$ for the ECU, sensors and I guess injectors (or what ever you can or are willing to supply).

Can your say whot the well known RV guy is?

gmcjetpilot said:

OK well how much $$$$ for the ECU, sensors and I guess injectors (or what ever you can or are willing to supply).

Can your say whot the well known RV guy is?

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We sell a generic system to control 1 set of plugs and fuel for $1515. On top of this, you need bosses, injectors, pump, regulator etc. To DIY, you are looking at $2500-$3500 depending on the system and options. To do both sets of plugs and have twin pumps with new TB, the second figure is more likely. So it is not cheap compared to a carb or mechanical FI but a lot less than a certified FADEC. The traditional engine market for EFI is presently small compared to the the auto conversion market which is growing at the rate of around 25% per year for us now.

I can't name the guy yet who will offer the full kits due to our agreements. He wants everything in place and plenty of testing under his belt before release of the product. (wise choice)

Ross,
Can you share how it is that you know about the two TV ranges you refer to on your RV6 installation?

I have a feeling that it may be from feeling it? Or have you done some kind of strain or vibrational testing that shows it?

Randy C

Randy said:

Ross,
Can you share how it is that you know about the two TV ranges you refer to on your RV6 installation?

I have a feeling that it may be from feeling it? Or have you done some kind of strain or vibrational testing that shows it?

Randy C

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The 6A has never been instrumented so yes, I report these periods from simply feeling them- not very scientific. As I have said before, all PSRU systems have TV. It is the amplitude and where these are in the operating range that are the concerns.

Psru Types.

George,
Your question about which drive is better is much like the "which engine is best?" question. That is the question is open to dispute. Perhaps a better question is, "What PSRU is safe and durable." The answer to that is, several are.
Let's list the PSRU types so that people will know what we are talking about.
1) Marcotte; internal helical gear type. The drive gear has the teeth cut on the inside and the pinion is placed inside. Ross already mentioned the characteristics so I won't re-list. Small offset about 1-3/4 - 2 inches
1a) PowerSport; Also internal gear type, Spur gear (straight cut) otherwise very similar to the Marcotte. Both are around 45-50 pounds.
Positives: Strong, compact, Small offset which is usually a benefit. Gear drive which is totally proven. rotation is not reversed, for "normal" prop rotation.
Negitives Fairly heavy, strong coupling but requires lash which can cause TV problems. Requires an expensive internal ring gear be custom manufactured.

2) Eggenfellner; GenIII Helical gear external gear w/lay shaft. All external gearing. Egg uses a inline (no offset) crank to prop. power comes out of the Crankshaft, over to the layshaft, back to the propshaft.
Positives: Compact, External gear drive which is more available. Double reduction allows more ratio choices. Using the layshaft keeps the rotation the same for standard prop rotation. Most gears, bearings can be off the shelf, and therefore cheaper.
Negitives: Double reduction, wait wasn't that a positive? Yes but the additional gearset requires another mesh to be controlled making it harder to ensure equal lash in both gearsets. Layshaft requires case to be stronger to positively locate layshaft and bearings. Two gear lashes means more angular lash and TV control.

3) Planetary: Tracy Crooks and others. Typically requires a premade gearset be available for affordability. (Mistral uses a planetary, an excellent one of their own design, bring $$$) The planetary is possibly an excellent and lightweight design. The key being that there are several gear meshes. The planetary has both external and internal gears.
Positives: Compact, theroetically the strongest gearset because of multiple constant meshes. Several ratios available from a single gearset. Both reversed and standard rotations available.
Positives: Smallest package for a given horsepower. Gear drive, has limited self-centering capability. Many gearsets available from commercial automatic transmissions.
Negitives: Complex, highest parts count of all gear drives. All gears must be carefully made to have identical pitch diameters and lash. Always includes an internal gear which is expensive to make. Argueably most angular lash, though similar to the Egg layshaft approach.

This is a start, others include, chain drives, belt drives, fluid couplings, the list goes on. We must have a good background in engineering to design any of these drives. These are just a few types, I have listed these because they are now available from several suppliers. Most other drives are going to be built-to-order. EPI will build you any of these types, to order, including an external spur gear drive. Again bring $$$. These descriptions ignore how these drives are coupled to the engine. That coupling can be a source of more problems or solutions than the drive itself. Dan H has been pounding on thew need for TV issue. This is as important as the drive itself, do your homework! I'm stopping now to get back to work!
Bill Jepson

For those just entering the discussion

Rotary10-RV said:

George,
Your question about which drive is better is much like the "which engine is best?" question. That is the question is open to dispute. Perhaps a better question is, "What PSRU is safe and durable." The answer to that is, several are.
Let's list the PSRU types so that people will know what we are talking about.
1) Marcotte; internal helical gear type. The drive gear has the teeth cut on the inside and the pinion is placed inside. Ross already mentioned the characteristics so I won't re-list. Small offset about 1-3/4 - 2 inches
1a) PowerSport; Also internal gear type, Spur gear (straight cut) otherwise very similar to the Marcotte. Both are around 45-50 pounds.
Positives: Strong, compact, Small offset which is usually a benefit. Gear drive which is totally proven. rotation is not reversed, for "normal" prop rotation.
Negitives Fairly heavy, strong coupling but requires lash which can cause TV problems. Requires an expensive internal ring gear be custom manufactured.

2) Eggenfellner; GenIII Helical gear external gear w/lay shaft. All external gearing. Egg uses a inline (no offset) crank to prop. power comes out of the Crankshaft, over to the layshaft, back to the propshaft.
Positives: Compact, External gear drive which is more available. Double reduction allows more ratio choices. Using the layshaft keeps the rotation the same for standard prop rotation. Most gears, bearings can be off the shelf, and therefore cheaper.
Negitives: Double reduction, wait wasn't that a positive? Yes but the additional gearset requires another mesh to be controlled making it harder to ensure equal lash in both gearsets. Layshaft requires case to be stronger to positively locate layshaft and bearings. Two gear lashes means more angular lash and TV control.

3) Planetary: Tracy Crooks and others. Typically requires a premade gearset be available for affordability. (Mistral uses a planetary, an excellent one of their own design, bring $$$) The planetary is possibly an excellent and lightweight design. The key being that there are several gear meshes. The planetary has both external and internal gears.
Positives: Compact, theroetically the strongest gearset because of multiple constant meshes. Several ratios available from a single gearset. Both reversed and standard rotations available.
Positives: Smallest package for a given horsepower. Gear drive, has limited self-centering capability. Many gearsets available from commercial automatic transmissions.
Negitives: Complex, highest parts count of all gear drives. All gears must be carefully made to have identical pitch diameters and lash. Always includes an internal gear which is expensive to make. Argueably most angular lash, though similar to the Egg layshaft approach.

This is a start, others include, chain drives, belt drives, fluid couplings, the list goes on. We must have a good background in engineering to design any of these drives. These are just a few types, I have listed these because they are now available from several suppliers. Most other drives are going to be built-to-order. EPI will build you any of these types, to order, including an external spur gear drive. Again bring $$$. These descriptions ignore how these drives are coupled to the engine. That coupling can be a source of more problems or solutions than the drive itself. Dan H has been pounding on thew need for TV issue. This is as important as the drive itself, do your homework! I'm stopping now to get back to work!
Bill Jepson

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George, Ross,
I know this is old news but I wanted to post it for some of the guys that aren't familar with the drives we're talking about.
Bill

Thanks Bill, good summation on the different drive types.

Robinson's chain drive PSRU has been fairy reliable hasn't it?

TSwezey said:

Robinson's chain drive PSRU has been fairy reliable hasn't it?

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Todd,
They seem to have been putting the hours on it in the SeeBee. I didn't mention it in the summary because the discussion was on (I thought) the geared drives. I could be wrong. (As usual!) The Hi-Vo chain can be a very reliable drive. If you can think back to the Olds Toranado they ran a big block GM/Chevy using that drive to handle all the power continously. Proper engineering is the needed thing again. You can do a thing from scratch, or you can use drives available from a manufacturer with a proven track record. You need to have a good idea of the data and apply it carefully. Gershwinder produced a nice version. The owner is retiring and wants to sell now. The add is in the front of Contact! magazine. I have never seen the inside of the Robinson drive but it has been holding up on at least 1 example!
Bill Jepson