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Radial powered RV-8R V2.0

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Why are you changing engines?

Lots of us aren't on Facebook, by the way... VAF's Build section is also available.

Dave
 
Why are you changing engines?

Lots of us aren't on Facebook, by the way... VAF's Build section is also available.

Dave

The new engine is around 20 more hp from what I’ve seen with other builders. Also it is a simpler engine with no gear reduction. This was always in the back of my mind since i was running a heavier constant speed prop. As far as pictures of the installation goes, I’ll only be posting those on Facebook at this time. If others want to post the pictures on this forum then they are more than welcome to.
 
The new engine is around 20 more hp from what I’ve seen with other builders.

Interesting move. The Rotec R3600 is rated at 150 HP and the Verner 9S at 158 HP. It seems like a lot of trouble and expense changing out engines to gain a nominal 8 HP. Are you disappointed with the Rotec for other reasons?
 
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Interesting move. The Rotec R3600 is rated at 150 HP and the Verner 9S at 158 HP. It seems like a lot of trouble and expense changing out engines to gain a nominal 8 HP. Are you disappointed with the Rotec for other reasons?

The advertised HP on a Rotec is 150, in reality it's more like 135. The Verner is Dyno tested to 158 HP. Other than that I've had no other problems with the Rotec.
 
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I'm building an RV8 now, I'm putting a Lycoming in it. I always liked your airplane, this is whats great about Experimental airplanes. I"m following you on Facebook now.
 
Rotec R3600 vs. Verner 9S

I'm going to follow Brian on Facebook. Wouldn't want to miss out on this conversion. (I thought this was the way to go in the first place but I won't say I told you so!)


Rotec 3600

Designers Matthew & Paul Chernikeeff
Configuration Nine Cylinder Four Stroke
Capacity 3600 cc (220 ci)
Total Diameter 840 mm (33.1 ”)
Dry Weight 120 kg (265 lbs)
Propeller/ RPM Large 80” – 90” Diameter x 55”
Pitch @ 2,450 rpm
Ignition / Type Dual, electronic and magneto
Carburettor TBI-40-S / Bing Mixture Control
Lubrication Geared Oil Pressure and Scavenge Pump
Bore/ Stroke (3.15 ”) 80 mm x 80 mm
Heads Two Overhead Valves,
Push Rod Operated
Spark Plugs Two per Head (NGK DCPR8E)
Starter Electric Auto Type 12 Volt
Charging System 45 Amp Alternator
Fuel Consumption Avgas 100LL – 28 liters
(7.4 gallons) @ 75% Power
Rated Power 150 hp @ 2450 Prop RPM (Via 3:2 PSRU)







Verner 9S

Displacement 6094 cc / 372 cubic inch
Pistons 9
Cooled by Air
Bore 92 mm
Stroke 102 mm
Compression ratio 1:7,8
Maximum power 158 BHP (116 KW) @ 2400 RPM
Max. continuous power 136 BMP (100 kW) @ 2300 RPM
Torque 485 Nm @ 2000 RPM
Propeller rotation CCW, viewed from the front (tractor propeller)
Complete dry weight 108kg
Spark plugs Champion RN12YC, Denso Q20PR-U
Electric starter 12V / 1000W
Generator (Alternator) 12V / 336W
Lubrication Philips X/C Aviation SAE 25W60; Total 20W60
Fuel Motor petrol, octane number 95
Carburetor Marvel; S&S
Reduction drive None
Propeller hub ∅111,12 x 6 x 16 holes - M8 (3/8 24 UNF) SAE 1
Max propeller 220
Installation Back
Recommended TBO 1000 hours
Batteries 12V 24Ah

 
I'm going to follow Brian on Facebook. Wouldn't want to miss out on this conversion. (I thought this was the way to go in the first place but I won't say I told you so!


Actually saying "I told you so" wouldn't work to well as the Verner 9S wasn't in existence until I was already flying with the Rotec. The R-3600 was the only option at the time. Steve Wolf was the first 9S to fly on his Samson Mite. I was very critical of the Verner early on, and am still critical of a few items, but we are working through those things. One thing that I have learned from all of this is to be critical early, question everything, and never take things at face value. This will be a good conversion when done and I am very excited to be working with Verner and Scale birds on a safe installation.
 
Actually saying "I told you so" wouldn't work to well as the Verner 9S wasn't in existence until I was already flying with the Rotec. The R-3600 was the only option at the time. Steve Wolf was the first 9S to fly on his Samson Mite. I was very critical of the Verner early on, and am still critical of a few items, but we are working through those things. One thing that I have learned from all of this is to be critical early, question everything, and never take things at face value. This will be a good conversion when done and I am very excited to be working with Verner and Scale birds on a safe installation.

I was reading the specs on the 9S some time back and your RV8 radial came to mind. I didn't know the 9S was that new to the market. Big advantage being higher torque and no PRU. And the sound!
 
AWESOME!! I got the privilege to meet you and see your RV8 up close when we gave a talk at your local EAA chapter about flying to Cuba a few years ago. Seeing the quality of your work I know this will be a super upgrade. I can't wait to read about your progress.

:cool:

WithBrianKelly1stRadialEnginePoweredRV81.21.2016.jpg
 
This project rates up pretty high on the "cool factor". I was following the original engine pretty closely.

I'd ask how performance was affected with the larger frontal area, but I suppose there aren't many 135hp RV8s to compare against. Not that it needs to be the fastest when it's already the coolest RV8 around. :cool:
 
This project rates up pretty high on the "cool factor". I was following the original engine pretty closely.

I'd ask how performance was affected with the larger frontal area, but I suppose there aren't many 135hp RV8s to compare against. Not that it needs to be the fastest when it's already the coolest RV8 around. :cool:

I would get a constant cruise speed of 145 KIAS with the Rotec at 85% power. I'll have a little bit more drag with this installation, but am expecting a bit better in cruise and a much better climb rate. GT Propellers will have to make me a new blade to handle the new engine.
 
good stuff Flyboykelly

Was surprised of hearing so little about the coolest -8 on the planet. That explains :)
I'll sure be following your progress, but will not be able to comment or like any since I'm not a face bock :rolleyes:
Thanks for all the info, pretty interesting and exciting.

PS
The Verners have a pretty good reputation, was considering the smaller 3 cylinder for the Hummelbird... moved on since then...
 
Is the 158 HP @ 2400 a continuous rating?

Can you go to a higher rpm for more HP? Maybe a 5 minute rating......
 
If you pay for it, I'll do it :D. BTW I remember your talk at our EAA chapter. It was great meeting with you and hope to again some day.

It's a deal. Meet up that is, not the paying for a propeller part. Fly that beautiful piece of art up here to St. Augustine (KSGJ) and lunch/dinner is on me. ;)
 
Is the 158 HP @ 2400 a continuous rating?

Can you go to a higher rpm for more HP? Maybe a 5 minute rating......

I'm not going to mess with the manufactures ratings or limits. the 158@2400 rating is for take off power and is limited to 5 mins. 138hp is the continuous power output. Keep in mind that radial engines make a lot of torque at low RPMs
 
... the 158@2400 rating is for take off power and is limited to 5 mins. 138hp is the continuous power output. Keep in mind that radial engines make a lot of torque at low RPMs

Torque is a force. Power is the rate at which work is done.

Horsepower is torque x RPM divided by a constant (5252). More torque at less RPM is the same as less torque at more RPM. For example...

9S radial (346 lbs-ft x 2400)/5252 = 158 HP
O-320 (307 lbs-ft x 2700)/5252 = 158 HP

Either way, torque is just one component of a force-distance-time definition for power. Power makes airplanes go, in particular go up.
 
Torque tells you how far you'll move it.

Technically, no. Again, torque is only a force. Force x distance ("how far you'll move it") = work. Common terms would be Joules or ft-lbsf.

Let's not get too far afield here. Subject is a lovely radial RV-8. I was merely noting more torque at lower RPM is not in itself significant. Potentially, in some applications the lower RPM could allow a larger prop disk at the same tip speed (72"@2700 is the same as 81"@2400), and some advantage might be found. However, that route is limited by the RV-8's leg length.
 
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Round engine RV-8

View attachment 9300[/QUOTE]

Um.....could all those people in front of a (probably) really cool-looking airplane step just a little to the left (or right) so we can see the airplane.....? Asking for a friend...............:p

Is there a photograph somewhere that could posted that doesn't involve Facebook? Asking for another friend...........:eek:
 
Round engine RV-8.....and torque....

Perfect! Thank you for posting that! AWESOME-looking airplane!! Is that Midway Island in the background? ;)

Here's some practical experiences with torque:

When I converted my J-3 to higher HP (here in the land of No Air: field elevation 5200), I had a choice between a C-85-8 and a C-90-8. Having flown both I chose the C-90-8. The C-85 gets it's power from RPM; the C-90 from torque. The -85 is rated at 2575 RPM; the -90 at 2475. That doesn't seem like much difference but when you pull back to climb in a -85, the RPM starts to drop; pull back in a -90 and it seems to hang on to the RPM much better: torque? I can outclimb a PA-11 with a -85 in my J-3 with the -90 pulling back and climbing from cruise RPM.

I have been told by those who have flown all of them that the difference in the step-up from a C-65 to a C-85 is similar to going from a C-85 to C-90. No personal experience but I flew the J-3 with the C-65 for 1000 hours or so and putting a C-90 in :eek::eek:........hard to wipe THAT smile off of my face. :):):)
 
Better?


Um.....could all those people in front of a (probably) really cool-looking airplane step just a little to the left (or right) so we can see the airplane.....? Asking for a friend...............:p

Is there a photograph somewhere that could posted that doesn't involve Facebook? Asking for another friend...........:eek:[/QUOTE]


 
OH, yeah!

OH, yeah! Great air-to-air photograph! Love the gun port tape!. I still believe that is Midway Island in the background......!;)

Nice to see variations in our group of airplanes. This model is NOT going to be judged as a "ramp flea"!
 
Kentucky Lass

Brian, is Kentucky Lass paying homage to a WW2 airplane? I’ve looked and not found any so named. Two thumbs up for your craftsmanship.
 
While we're talking about hypothetical engines, lets put the S18 on a Rocket. The RV8 would fit the S14, two rows of 7 cylinders, a bit over 200hp will do quite well.
 
While we're talking about hypothetical engines, lets put the S18 on a Rocket. The RV8 would fit the S14, two rows of 7 cylinders, a bit over 200hp will do quite well.

It’s not as easy as it sounds. When they were developing two row Radial’s they had some harmonics going on that destroyed quite a few engines. They eventually got it figured out with dampening counterweights, but it took a lot of development. You are basically trying to get two engines to work together on a common shaft.
 
So I guess the 4-row is out of the question...........


On a 2-row, are the master connecting rods on opposite sides?

What about the masters on a 4-row?
 
It’s not as easy as it sounds. When they were developing two row Radial’s they had some harmonics going on that destroyed quite a few engines. They eventually got it figured out with dampening counterweights, but it took a lot of development. You are basically trying to get two engines to work together on a common shaft.

This is true! There is a technical paper that recounts the history of the R-2800 development, which boiled down to running it on a stand until the crank broke, then trying something else, repeat, until successful. It wasn't trial by error -- they did have good technical understanding, and direct measurements of the modes that were causing the problems. But it was still very iterative. There was huge pressure on the engineering team because the war was cranking up. It amounted to true heroism worthy of Congressional Medals of Honor. (I don't know what awards/recognition they did receive?)
 
This is true! There is a technical paper that recounts the history of the R-2800 development, which boiled down to running it on a stand until the crank broke, then trying something else, repeat, until successful. It wasn't trial by error -- they did have good technical understanding, and direct measurements of the modes that were causing the problems. But it was still very iterative. There was huge pressure on the engineering team because the war was cranking up. It amounted to true heroism worthy of Congressional Medals of Honor. (I don't know what awards/recognition they did receive?)

This is the exact report that I was thinking about. I'm glad to see others looking to the past to understand the future. This is the whole point of the radial RV. I get asked all the time "why a radial engine". This is why. I really wish that people would remember the past some times. I can't afford a warbird, but If I can honor the men and women in my own way, then so be it. It's the people behind the scenes that really won the war and advanced everything. Hats off to all of them.
 
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Many of the problems of radials stem from the use of master/link conrod arrangements because the link-rod big ends travel ellipsoidally rather than circular creating some wierd distortions to the conventional harmonic series that is a slider-crank mechanism.

In theory a radial engine can be perfectly balanced to the (n-1)th order but in practice it isn't.
 
For a 9 cyl single row, the primary contributors are the 4.5 and 9th orders. The 4.5 order tends to be below the practical running range, but the 9th can be problematical, as it tends to intersect with the system's first natural frequency given typical shaft sizes and propeller inertias. However, it can be controlled in various ways, including plain old component reinforcement.

Look at the harmonic torque contributions below, from an old textbook I found in the Air University library. The largest is the 4.5 firing order. The 9th is much smaller. Even so, the magic of resonance can turn it into a monster.

Ok, now couple two 9 cyls into a double row, and stagger the firing between rows. See the problem? The 9th becomes the really powerful order; there would be 9 firing events per revolution. If the shaft stiffness and prop inertias are similar to the single row, there will probably be an RPM at which it will resonate and break.

For example, see the Campbell diagram below. It's for the 9-cyl geared M14P and two direct drive variants. The range around 2000 RPM is not a happy place.
 

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Another nice illustration of an intersection of system F1 and the 9th order, at about 1600 RPM with a Wasp Jr, here noted via propeller stress measurements. A Campbell diagram like the one in the previous post might have predicted the resonant intersection.
 

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All of my experience around the R-985 (deHavilland Beaver), they are operated at 1900 to 2000rpm in cruise. This sounds like exactly why.

The neat stuff one learns on this site.

Now we just need to find a home built that can accept a R-985 AND someone willing to pay for 20 Canadian gallons per hour in cruise (23 "small" US gph).
 
All of my experience around the R-985 (deHavilland Beaver), they are operated at 1900 to 2000rpm in cruise. This sounds like exactly why.

Probably above the resonant intersection, as it would be with the Wasp Jr example.

The Russians, on the other hand, tend towards, um, stout. When doing the fixed pitch shaft for the M14, I tried to convince my Romanian counterpart to accept a shaft with reduced torsional stiffness, in order to lower the F1. Material stress would have still been quite a lot lower than found in an aerobatic Lycoming crank, but no, they would not hear of it. So, you see the F1 for the M14DH is somewhat higher than the M14P's. This was not a good thing, as it pushed the resonant intersection further toward the desired operating range. Worse, the intersection was further up the boost scale, and we had already increased the supercharger ratio (think bigger bangs). When run in the cell with a structurally inadequate test propeller, at the resonant intersection RPM it drove the prop into a vibratory mode severe enough to split a maple blade.

Side note...in this case, "structurally inadequate" meant the blade was a bit too flexible, but a big contributing factor was a bad glue line from the prop vendor. Resonance will expose the weak.

Now we just need to find a home built that can accept a R-985 AND someone willing to pay for 20 Canadian gallons per hour in cruise (23 "small" US gph).

Done: https://www.griffonaerospace.com/systems/lionheart/
 

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Look at the harmonic torque contributions below, from an old textbook I found in the Air University library.

OK Dan, I'll bite :D. It's not either of Liston's books "Aircraft Engine Design" or "Powerplants for Aircraft". So what's the title and the author?
 
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