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View Full Version : Been given control of a cool project



RB211
06-15-2010, 08:02 PM
I cannot predict what life will throw at me, best I just ride the wave and appreciate things.

Let me post some images to wet your appetite...

http://www.flightschoolreview.net/images/front.jpg

and

http://www.flightschoolreview.net/images/twindrive.jpg


It is a twin drive with counter rotating propellers, powered via belt reduction to two Mazda 13B rotary engines. This will be going in the nose of a Cessna 185.

I have been given authority to make changes where I see fit, and engineer certain aspects. I am making all the drawings in Solid Works. Final engineering review will take place with a professional engineer.
I also will be building it. He has a Smithy 3 in 1 1340 in his hangar with all the basic machine tooling that I will get to use! Ahhh get to make chips again!!!!

Got tons more work ahead of me, exciting!

John Stevenson
06-15-2010, 08:07 PM
General question?
Who certifies something like that ?

.

RB211
06-15-2010, 08:10 PM
General question?
Who certifies something like that ?

.

The FAA has outlined a very lengthy and costly procedure for doing it. I do not know the exact details as it does not apply to this. This airplane is an experimental. :)

Dr Stan
06-15-2010, 08:43 PM
For a minute there I thought it was a new design for a BOP.

Your Old Dog
06-15-2010, 09:14 PM
Gee I thought you were recently out of work? If so, great job of landing on your feet! Good luck on your project.

RB211
06-15-2010, 10:50 PM
Gee I thought you were recently out of work? If so, great job of landing on your feet! Good luck on your project.

The guy I am working for, his hangar is next to where we park our airplanes from my old job. You know the saying, one thing leads to the next!

saltmine
06-16-2010, 12:05 AM
Ah, I see, one engine faces forward, and the other faces to the rear. They drive two propellers through two common shafts, one inside the other.
Throughout avation history counter-rotating props have been tried repeatedly, and abandoned...mostly due to third order harmonics in the drive system. Using two rotaries for power is certainly not the most economical set-up. Mazda engines aren't noted for fuel economy or long service life.

Good luck with the project. Keep us posted.

RB211
06-16-2010, 12:08 AM
Ah, I see, one engine faces forward, and the other faces to the rear. They drive two propellers through two common shafts, one inside the other.
Throughout avation history counter-rotating props have been tried repeatedly, and abandoned...mostly due to third order harmonics in the drive system. Using two rotaries for power is certainly not the most economical set-up. Mazda engines aren't noted for fuel economy or long service life.

Good luck with the project. Keep us posted.

We are looking at TBO's of 3500 hours, much better than a lycombing. Harmonics are an issue we've been discussing.

lakeside53
06-16-2010, 12:10 AM
If it works, nice.. no P-factor.

The Artful Bodger
06-16-2010, 12:15 AM
Throughout avation history counter-rotating props have been tried repeatedly, and abandoned...

Various aircraft types have enjoyed long service life with contra-rotating props. Others have used counter-rotating props but that is not what this adaptation appears to be.

RB211
06-16-2010, 12:41 AM
Various aircraft types have enjoyed long service life with contra-rotating props. Others have used counter-rotating props but that is not what this adaptation appears to be.

Contra-rotating, thank you.

A.K. Boomer
06-16-2010, 12:50 AM
General question?
Who certifies something like that ?

.


Smithy.............

RB211
06-16-2010, 01:36 AM
Smithy.............
All the important stuff will be farmed out to local CNC houses. Know of any good ones in the East Bay area of California?

Jim Shaper
06-16-2010, 01:52 AM
You're barking up the wrong tree.


Having quite a bit of internal knowledge about the 1.3L wankel (like I pulled 140hp per litre at the wheels from one without boost on low compression rotors while still running 5 points rich), I can tell you with certainty that what you want to do is build a bigger wankel.

2L wankels (3 rotor) are capable of 800hp under boost (lifespan is directly related to ignition timing as blown apex seals due to detonation mean the rotor housings are trashed and that means you're asking for trouble in this application). I'm assuming you want to use two NA engines piggy backed through some kind of clutch, when you could save all that trouble by devising a longer multi-piece eccentric shaft (which are commercially available for higher rpm applications anyway) and simply add more rotors to the primary power plant while supplementing them with center bearings (which the production 1.3L has always lacked). The remaining element is just an appropriate intake manifold and a custom header which are also less than overtly difficult (but runner length can't be too short or you'll lose any semblance of torque).

With bearings between all the rotors in their respective intermediate housings, you're looking at an engine that can reliably run at over 12,000rpm without much trouble.

oldtiffie
06-16-2010, 01:58 AM
You are very fortunate to get that job but I daresay that the owner went to a lot of trouble to pick his man for the job.

That is no small compliment as regards your skill, personality and reliability and ability to take on projects and work your way through them.

You must be well regarded - and that doesn't come without good reason.

Congratulations.

I had the best part of three years on an OZ aircraft carrier that was out-fitted with Fairey Gannet aircraft with contra-rotating propellers. They could operte or cruise on one engine if needed - especially "on patrol" as it was quite a lot more economical as regards fuel (AV-CAT).

http://en.wikipedia.org/wiki/Fairey_Gannet

http://www.google.com.au/#hl=en&source=hp&q=gannet+aircraft&aq=0&aqi=g1&aql=&oq=gannet+aircra&gs_rfai=&fp=97556ce57ce57d56

One of my jobs was the stabilised landing lights and mirrors - on sponsons out-board of the flight deck. I used to service and provide the anti-submarine torpedoes for the Gannets as well as the rocket and bomb lifts. I also had all the guns (17 x 40/60 Bofors) and the small arms and sonar (very simple). So I had a lot of work and time on and out-board of the flight deck and saw a lot of those Gannets. Their stall speed was incredibly slow - as was their take-off speed (no steam catapult needed if necessary). They could land-on without arrestor wires if necessary.

RB211
06-16-2010, 03:05 AM
You're barking up the wrong tree.


Having quite a bit of internal knowledge about the 1.3L wankel (like I pulled 140hp per litre at the wheels from one without boost on low compression rotors while still running 5 points rich), I can tell you with certainty that what you want to do is build a bigger wankel.

2L wankels (3 rotor) are capable of 800hp under boost (lifespan is directly related to ignition timing as blown apex seals due to detonation mean the rotor housings are trashed and that means you're asking for trouble in this application). I'm assuming you want to use two NA engines piggy backed through some kind of clutch, when you could save all that trouble by devising a longer multi-piece eccentric shaft (which are commercially available for higher rpm applications anyway) and simply add more rotors to the primary power plant while supplementing them with center bearings (which the production 1.3L has always lacked). The remaining element is just an appropriate intake manifold and a custom header which are also less than overtly difficult (but runner length can't be too short or you'll lose any semblance of torque).

With bearings between all the rotors in their respective intermediate housings, you're looking at an engine that can reliably run at over 12,000rpm without much trouble.

There is no doubt that adding a 3rd or more rotors and P porting would give gobs more horsepower and make for a greatly simplified power package. The gentleman that I am working for wants the reliability of a twin without the VMC issues of a standard twin. This build is also far cheaper than rebuilding the Lycombing.

The Artful Bodger
06-16-2010, 03:10 AM
With bearings between all the rotors in their respective intermediate housings, you're looking at an engine that can reliably run at over 12,000rpm without much trouble.

12,000rpm? I think that would need to be geared down for this application and any great increase in power over the original (Continental?) engine would start to need an unacceptably large diameter propeller. Contra rotation helps towards the big prop problem and if you have to gear down one motor it is likely quite easy to gear down two.

I am not saying they are barking up the right tree but I can see significant incentives to take that route.

RB211
06-16-2010, 03:32 AM
12,000rpm? I think that would need to be geared down for this application and any great increase in power over the original (Continental?) engine would start to need an unacceptably large diameter propeller. Contra rotation helps towards the big prop problem and if you have to gear down one motor it is likely quite easy to gear down two.

I am not saying they are barking up the right tree but I can see significant incentives to take that route.

Others have implemented the mazda rotaries into their airplanes. All of them are reduction drive. It is a shame, we have two sets of pulleys for very wide cog belts that are rated at 700 hp that we cannot use. For using two seperate engines on the same engine mount, we have to use rubber isolators for each motor and those things do not tolerate any mis-alignment. We have to use V-belts since they can tolerate it. Problem with V belts is that the pulleys need to be much larger in diameter for enough surface area to grip the belts to transmit the hp. Go too small in diameter, the belts slip. Gear drives in these applications do not fair very well, reliability becomes an issue. Just ask Thielert and Diamond...

Harmonic drives I will look into and see if it is possible to sneak one inside the driven pulleys to reduce the diameters of the pulleys.

RB211
06-16-2010, 03:40 AM
You are very fortunate to get that job but I daresay that the owner went to a lot of trouble to pick his man for the job.

That is no small compliment as regards your skill, personality and reliability and ability to take on projects and work your way through them.

You must be well regarded - and that doesn't come without good reason.

Congratulations.

I had the best part of three years on an OZ aircraft carrier that was out-fitted with Fairey Gannet aircraft with contra-rotating propellers. They could operte or cruise on one engine if needed - especially "on patrol" as it was quite a lot more economical as regards fuel (AV-CAT).

http://en.wikipedia.org/wiki/Fairey_Gannet

http://www.google.com.au/#hl=en&source=hp&q=gannet+aircraft&aq=0&aqi=g1&aql=&oq=gannet+aircra&gs_rfai=&fp=97556ce57ce57d56

One of my jobs was the stabilised landing lights and mirrors - on sponsons out-board of the flight deck. I used to service and provide the anti-submarine torpedoes for the Gannets as well as the rocket and bomb lifts. I also had all the guns (17 x 40/60 Bofors) and the small arms and sonar (very simple). So I had a lot of work and time on and out-board of the flight deck and saw a lot of those Gannets. Their stall speed was incredibly slow - as was their take-off speed (no steam catapult needed if necessary). They could land-on without arrestor wires if necessary.

I was upfront and told him that I thought the project was over my head. I think that convinced him even more I was the right person for the job, haha.

Those are cool airplanes, I wonder what they sounded like?

Jim Shaper
06-16-2010, 03:46 AM
Wankels have next to no torque even in proper operating form. My porting (very large street port, but not so much as to kill the rpm band) ended up with a 30 more lb/ft than anyone else had ever seen on an NA (and many turbos for that matter), but it also came on higher in the rpms than your prop will want to be spinning (5900rpm IIRC). I don't see how you could use the wankel without some form of gear reduction as it'll barely pull its own weight without some revs.

You're also going to want to run a stand alone engine management system or revert to carbs. The mazda ecu fought me to no end and eventually caused me to part out the car rather than sink another grand into it, and that was at sea level. 200hp at the crank is still pretty remarkable for nothing but a few hours with a carefully placed burr, but I know I could've hit that at the wheels had I been able to fool it into letting me lean it out more. I was gaining 5-7 hp with every half point of fuel I was taking out until I hit the wall with the computer refusing to go leaner.

I also lost my dyno sheets or I'd show you how abysmal the power band is on these in the lower revs. I never did a before run, but I'm sure there's probably something on the web somewhere. Stock is only 140hp at the crank on the S4. Standard redline is 8K on the older engines. The newer ones out of the rx8's is 10K and those have even less torque down low (unless it was a perception from gearing, since I could stomp all over one with my `86).

Having said all that, I still want another wankel, but I don't want another rx7. I've learned a few more tricks in the past 8 years and I'd love to see what I could do now - I just wouldn't waste my time with a chassis that can't take it.

At any rate, have fun. Working on experimental planes sure beats what I've been doing lately. :)

The Artful Bodger
06-16-2010, 04:21 AM
Gear drives in these applications do not fair very well, reliability becomes an issue. .

Sorry about my loose terminology but by 'gearing' I meant to include belt systems.

Circlip
06-16-2010, 04:25 AM
Ultimate economical Contra-rotating prop design was "10,000 rivets flying in close formation" and comparatively only recently retired Avro Shakleton.

Years ago "Norton" were toting their wankel engine and supplying to drone manufacturers. Two of them fitted to bikes had quite a good success rate in racing circles. Bit unnerving though seeing bright red exhaust pipe glowing under the seat.

Regards Ian.

Jim Shaper
06-16-2010, 05:02 AM
http://i6.photobucket.com/albums/y242/FishyJim/Flames-Copyright-tag.gif

Red exhaust pipe is nothing... This was prior to porting it (bone stock). I could only manage about a third the flame length once I got it breathing right. :o I have to admit, there's nothing quite like knowing you're melting the jackass' bumper who was tailgating you before the red light. :D

4" tip diameter for perspective. Those flames were about 3' long.

jugs
06-16-2010, 08:29 AM
I thought they were supposed to be internal combustion engines :D
john
:)

Circlip
06-16-2010, 09:14 AM
there's nothing quite like knowing you're melting the jackass' bumper who was tailgating you before the red light.

Or the ass of the rider. :rolleyes: Changing down had its moments - no braking effect with a vankel.

Regards Ian.

fasto
06-16-2010, 10:21 AM
Hey RB211, named after a famous aero engine yourself!

If you're going to be dismissive of existing aero engines, you should probably be a little more accurate:
Lycoming (no 'b') make aero engines, but not for Cessna 185 airplanes.
The Cessna 185 comes with a Continental IO-520 engine. Upgrades to IO-550 are readily available.
IO-520 is 310 HP for takeoff (5 minutes @ 2700 RPM), 285 continuous HP. In the C-185 seaplane, it's uprated even more to 2800 RPM for takeoff but I can't remember the HP rating there.
IO-550 conversions are rated 350 to 385 HP for takeoff, 310 or so continuous. Depends upon the particular STC involved. I flew a 385/310 HP C-185 some years ago, it seemed like flying a fighter plane in takeoff performance compared to my Archer (which is no slouch either). 40 GPH of fuel at takeoff power is a little rich for me, though.
Conversions to turboprop are also available I believe, I saw one at an airfield in New York with a very oddly shaped cowling covering a PT-6A.

Various attempts to power airplanes with auto engines have met with generally limited success. Even the much vaunted Theilert engines, based on Mercedes 4 cylinder diesels, had very limited life - around 500 hours TBO. Duty cycle is the killer. Airplanes don't coast or go downhill very much. The engines operate at high power settings continuously, often at 75% power, sometimes 85% power. Auto engines run around 15% power in a typical car driving cycle.

I'm sure that you and the airplane owner have taken all this into consideration, and I hope you'll keep us informed on the project. Twin engine centerline thrust, eh? Have to dust off that C-336/C-337 rating!

Years ago I saw the framework of an airplane at Oshkosh. It was a reno racer that had been used in the early 80's if I recall. It, too, was powered by 2 Wankel engines, in this case three rotors with dual turbos. There was one in front of the cockpit and one behind. I believe it had contra-rotating props in front. It had very complex cooling and fuel systems, and was quite beautifully made. The owner was trying to restore it. I don't know what happened with it.

RB211
06-16-2010, 02:10 PM
Hey RB211, named after a famous aero engine yourself!

If you're going to be dismissive of existing aero engines, you should probably be a little more accurate:
Lycoming (no 'b') make aero engines, but not for Cessna 185 airplanes.
The Cessna 185 comes with a Continental IO-520 engine. Upgrades to IO-550 are readily available.
IO-520 is 310 HP for takeoff (5 minutes @ 2700 RPM), 285 continuous HP. In the C-185 seaplane, it's uprated even more to 2800 RPM for takeoff but I can't remember the HP rating there.
IO-550 conversions are rated 350 to 385 HP for takeoff, 310 or so continuous. Depends upon the particular STC involved. I flew a 385/310 HP C-185 some years ago, it seemed like flying a fighter plane in takeoff performance compared to my Archer (which is no slouch either). 40 GPH of fuel at takeoff power is a little rich for me, though.
Conversions to turboprop are also available I believe, I saw one at an airfield in New York with a very oddly shaped cowling covering a PT-6A.

Various attempts to power airplanes with auto engines have met with generally limited success. Even the much vaunted Theilert engines, based on Mercedes 4 cylinder diesels, had very limited life - around 500 hours TBO. Duty cycle is the killer. Airplanes don't coast or go downhill very much. The engines operate at high power settings continuously, often at 75% power, sometimes 85% power. Auto engines run around 15% power in a typical car driving cycle.

I'm sure that you and the airplane owner have taken all this into consideration, and I hope you'll keep us informed on the project. Twin engine centerline thrust, eh? Have to dust off that C-336/C-337 rating!

Years ago I saw the framework of an airplane at Oshkosh. It was a reno racer that had been used in the early 80's if I recall. It, too, was powered by 2 Wankel engines, in this case three rotors with dual turbos. There was one in front of the cockpit and one behind. I believe it had contra-rotating props in front. It had very complex cooling and fuel systems, and was quite beautifully made. The owner was trying to restore it. I don't know what happened with it.

His airplane is actually a kit plane that is nearly identical to the C185. I do not remember who offered the kit. I actually have to drive down to Visalia to pick up his old lycoming.

I used to fly for Flight Express out of Oakland. All the 210's were upgraded with the Continental IO550's. I was flying nearly empty and enjoyed the takeoff performance. I am not being dismissive, just doing as the owner wants. This project was started 11 years ago, the engines have been collecting dust for years, as are all the other parts. Already have the props, carbs, oil coolers, and radiators. Yes, two of everything...

Been some discussion that perhaps we will change the ratios for 6500rpm continuous rather than 7500rpm. As you say though, the power band comes alive at higher rpm's and I am just wondering in case of a go-around, how the engines will respond. Granted, we will have around 400 total hp, which is a lot more than a stock 185.

Jim Shaper
06-16-2010, 02:53 PM
Which wankels are you using in this project? The older ones or the new ones out of the rx8?

RB211
06-16-2010, 07:35 PM
Which wankels are you using in this project? The older ones or the new ones out of the rx8?

13B's, brand new, never ran. They are of the later variety. They are the rx 7 engines.

winchman
06-16-2010, 08:12 PM
These aren't going to be variable-pitch props, are they? Will there be any means of feathering or freewheeling the prop when an engine dies?

What happens when one engine dies, and the stopped propellor impedes the flow of the one that's still turning? Seems like there would be some pretty high cyclical loads as the moving blades pass the stationary blades.

Will both props have the same pitch? Seems like the rear prop would have to have a higher pitch for best efficiency when both are turning, but it will be VERY inefficient when the front prop stops.

RB211
06-16-2010, 08:35 PM
These aren't going to be variable-pitch props, are they? Will there be any means of feathering or freewheeling the prop when an engine dies?

What happens when one engine dies, and the stopped propellor impedes the flow of the one that's still turning? Seems like there would be some pretty high cyclical loads as the moving blades pass the stationary blades.

Will both props have the same pitch? Seems like the rear prop would have to have a higher pitch for best efficiency when both are turning, but it will be VERY inefficient when the front prop stops.

We are using IVO props, the front prop will have variable pitch, the rear one will be added at a later date. The IVO props adjust pitch via an electric motor, and the blades actually warp to change pitch.

The props will not stop spinning if you lose an engine, there is way too much aerodynamic forces on the blades for them to stop windmilling. Even on a C172, you almost have to stall the airplane in flight to get the prop to stop windmilling. Don't ask how I know this...

boslab
06-16-2010, 09:51 PM
Think it through, every project i get sucked into bites my arse, i just ordered 2 spectrometers, 2 milling machines [robodrill] and 2 aBB 1200 Robots, i think my arse is in a sling [$2000000], your only as good as your last mistake
mark

legendboy
06-17-2010, 02:06 AM
building this is one thing

tuning it is a whole nother ball game

(don't think nother is a word after typing it)

Jim Shaper
06-17-2010, 02:08 PM
Those engines won't last long at that high of rpm without an intermediate housing bearing on the eccentric shaft.

The weight of the rotors start flexing it enough to scrape the side housings above 7K. You're talking about the engine living at that rpm, and that means you're going to have ugly problems in short order.

Look into how they did the bearing modification and tear those engines down and fix it. The engine is basically held together with bolts and o-rings, so you don't need but a couple gaskets (intake and exhaust) if you take it apart.