Does anyone have any knowledge or experience with small, light, rotary engines for aviation?

Ridge Runner wrote:Does anyone have any knowledge or experience with small, light, rotary engines for aviation?

I assume you mean a Wankel-style non-reciprocating rotary?

Mazda RX-7?

It's a brilliant concept in my opinion, something I wish someone really smart would put some effort into.

This looks highly interesting as well.

I talked to these guys at oshcosh last year, seems interisting the only downfall I could see is they dont start cold verry well.
http://www.mistral-engines.com/Company/About-us

There are a lot of rotary companies around but few of them are active at promoting their products, to the point that one would wonder if they are still doing business. Those that sell FWF kits are asking $30k+

The best rotary company I've found is: http://www.rotaryaviation.com/ Tracy and Laura Crook are top-notch people and Tracy is a brilliant engineer. He has developed, extensively tested and operates his products on his RV-4. Last I checked he was building an RV-8 with a Renesis engine on the front.

They don't sell engines, but they have a very detailed book and DVD to show you how to take a used Mazda engine and rebuild it. It looks ridiculously easy especially if you've ever rebuilt a recip. They also supply rebuild kits.

Their most important products are three different types of gear boxes, an electronic engine controller (used with automotive injectors and plugs), and engine monitor. You can probably do a top-notch FWF installation for around $15k.

I've flown in his RV-4 and it was a blast.

The only down side to the rotary is the exhaust. The temps are hot enough to melt regular steel exhaust systems and they are loud. You need to use stainless components and some ear plugs.

I recommend you buy the book http://www.rotaryaviation.com/book.html Even if you don't build it yourself, all the mystery is taken out of it and practical engineering challenges are solved and explained. It's a good read.

Since you said small and light...

Look up the Rotron, a small go-kart racing rotary engine modified for aviation use by a company called Para-Jet. They make those powered parachute thing-a-ma-bobs. The Rotron is very small and light, I saw one at Copperstate. 25 and 40 HP versions. This has exceptional potential for small homebuilts, due to the benign failure mode of the Wankel design. http://www.parajet.com/index.php?id=28

BTW, on similar lines there is a movement starting in the homebuilt world to use the small Briggs and Stratton 23HP generator engines. There are two good, well engineered, viable airplanes now using that engine, the Colomban MC-30 Luciole in France and the SD-1 Minisport in Czech. Apparently these aircraft fly 100-120 mph on 1.5 gallons of car gas.
http://www.youtube.com/watch?v=ZKOrmETgMkM . The Briggs motors apparently have a reputation for being pretty bullet proof, and a NEW one is about $1500.

Flying on low power like that is very possible and really does work great with an efficient airframe, which is usually mutually exclusive with back country flying. Your useful load will also be you plus possibly your toothbrush. But you literally have a good chance at flying at 140 mph+ on a couple of gallons an hour if you are willing to fly a small, light, composite homebuilt.

The small core of the Wankel Rotary engine make them intriguing. Best torque and power come on at about 6000 rpm with a lot of heat rejection. Add the gear reduction drive, coolant radiator, oil cooler, turbo intercoolers and it gets large and heavy with no advantage of bsfc. The radiator drag is also huge. Its interesting that the Moller rotarys haven’t come along.

Check out; http://www.rotaryeng.net Alot of interesting information.

Dave

Thanks for the interesting links and info.

The Rotron engine looks interesting...except that it screams at 7800rpm. Maybe they will come out with a higher horsepower, lower rpm engine sometime.

I actually talked with the guy with the RV 6 with the rotary engine in it. He's very knowledgable. Most of his work is with Mazda RX7 mods, rebuilds et etc...not many Wankels around anymore. And it sounds like here in the US at least, everybody is pinching pennies, not willing to invest in any new technologies or making rotary technology better.

Seems only the Global Rotary Power people have an 80hp rotary, suitable for planes that would normally carry a 50hp to 100hp motor. I emailed them today for more information...It seems their small engine specialist is on vacation...for the winter.

Ridge Runner wrote:
The Rotron engine looks interesting...except that it screams at 7800rpm. Maybe they will come out with a higher horsepower, lower rpm engine sometime.

Remember that the "speed" of a rotary engine is only the speed of the "eccentric shaft" which is a lot less of an issue than a crankshaft. Meaning, 7800 RPM is likely not a dangerous speed for that size rotary engine. You don't have the reciprocating motion and massive parts flailing around that you would have in a piston engine. 7800 may be a perfectly safe and sane engine speed. We had small model airplane engines that turned 10,000 to 20,000 RPM with pistons and rods, and some 4-strokes with valve trains turning well over ten grand. It's all about the speed versus the mass, not just the speed. I also believe the Rotron engine has a reduction built in to the engine, allowing you to run a normal size prop for that power.

For grins and giggles, what kind of airplane are you considering a "small and light" rotary for?

Schleicher has been using Wankel engines to power their self-launch gliders since at least 1995. . . I have a 50 hp version in my ASH26E. The advantages are small form factor, so it fits in the relatively narrow fuselage, smooth almost vibration free operation, and enhanced reliability (as compared to 2-strokes used in most other self-launch gliders that try to shake themselves and anything attached to them apart). Downside is higher fuel consumption than a recip and a fair amount more waste heat to deal with. Exhaust is stainless, and I've seen the muffler glow a dull cherry red during a ground test.

The Wankel in the Schleichers is a single rotor version of the Norton Motorcycle two rotor Wankel from the fifties. Didn't work so well in bikes, so they certified it for aircraft. Diamond bought the rights to the engine a decade ago with the intent to use it in one of their aircraft models - - never happened. So it remains a nitch product for one of Diamond's subsidiaries. I think the cost of the engine is over $25K, so hardly practical for adaptation to an experimental aircraft.

For grins and giggles, what kind of airplane are you considering a "small and light" rotary for?

I'm looking for a 4 cycle alternative, between 65 and 80hp, that when fully equipped weighs in at no more than 110 lbs. Whatever engine I choose, it will be going onto a new, custom made Ridge Runner that is being built for me right now...should be finished in May. These parameters obviously exclude the Jabiru, 912, HKS 700E, as well as the Suzuki, VW and Geo metro conversions...so I just thought would investigate what rotary engines had to offer. 110 lbs may be unrealistic.

Look at the Simonini Victor 2 from Italy. BCP member dirtstrip has flown one of these, probably the only one here with hands-on experience. With the parameters you are looking at, an advanced, modern-era 2 stroke is where you're headed IMHO.

Probably no rotary engine that is a direct match for your needs, certainly nothing with any amount of success under its belt.

The HKS engine is about 60HP, 4 stroke, and fairly light. It may not make enough power for your requirement. One of the Geo Metro engines with Raven redrive may actually be in your target range, can't remember if it is 110 pounds or 150 pounds.

It would be a faily safe bet that if you want an engine with any amount of development and field experience behind it, making anywhere near 85HP and weighing 110 pounds installed, you're buying a one-way ticket to two-stroke-ville.

Thanx for the input, and the suggestion of the Simonini. I was not aware of their 92hp version, 114lbs fully outfitted. Except for it being 2-stroke, it fits the bill pretty good. I'm not looking to go fast, just to take off short and climb steep. I need a dependable engine that will swing a big prop (big for the Ridge Runner)...I'm considering something in the 72" to 74" 2-blade in-flight adjustable.

I've had very good performance from the Rota 503 I've got on my existing Ridge Runner, not a hint of a problem, not even a hiccup. But where I fly at (Philippines), and for the new plane, I would like an added degree of dependability of a 4 stroke. The HKS 700E (60hp) is a little light on hp, and it comes in at 121 lbs fully outfitted.

Still, I'll look into this Simonini some more. Another 4 stroke option, though a little heavy at 130 lbs fully outfitted, is the HKS 700T, 80hp turbo version. I'm not too sure I want 130lbs up front though.

There is a bearhawk on barnstormers with a rotary right now

In a routine Google search for "180hp aircraft engine," I found this article on the case for the Mazda 13b:

http://n4vy.rotaryroster.net/WhyMazda.html

Lots of good points. Unfortunately the same obstacle always fears its ugly head: The dearth of supported PSRU's on the market.