Light Aircraft Association

The April edition of "Light Aviation" reveals that Jim Cripps proposes to produce a home-built quasi-turbine diesel engine. Although a very interesting project, I think it may prove "a bridge too far". The quasi-turbine is said to be very smooth, but I understand that while it might work well as a pump, it has yet to prove itself as a viable motor.

To quote Wikipedia:
*it has far more moving parts than the Wankel engine
*it has never been shown to work as an internal combustion engine
*for all other possible uses there are many other designs that are more reliable and function more efficiently
http://en.wikipedia.org/wiki/Quasiturbine

I suggest that the Wankel would be a better engine. In the UK, the Staverton-based firm of MidWest once produced a successful twin rotor aero-engine. Unfortunately, MidWest are no more, and the rights to that design are now owned by Diamond in Austria. I understand that Diamond bought it in case engine suppliers such as Rotax or Thierlert should prove too expensive or unreliable. Despite such forethought, it seems that Diamond have no plans to continue production of the twin rotor engine (although I believe that they still produce the single rotor version for self-powered gliders).

At a PFA rally, MidWest showed that their engine (which runs on both Mogas and Avgas) could run as a "petrol-paraffin" engine; that is, starting on Mogas and switching to Avtur (Jet A1) once warm. (It would remain a spark ignition engine). I'm told that the engine proved unreliable using Avtur, (possibly because of poor main-bearings), but with further development, MidWest might have had a world-beater on their hands.

The MidWest engine was developed from the "Norton" engine developed at BSA by David Garside. MotorCycle News of 24 March reports that the newly reincarnated manufacturer Norton (which has just started to market its all-new Commando motorbike) has designed a new twin-rotor Wankel for racing. The original Norton engine was a nominal 588cc and could rev to 10,000rpm; and the new one is a nominal 695cc than can rev to 13,000 rpm, with bearings safe to 17,000 rpm. Norton says the original engine's bearings were not up to the job.

Fliers who might think that 13,000 rpm sounds too high should consider this: the "10,000rpm" MidWest engine was detuned to a max of 5,800, with a max continuous of 5,500rpm and a typical cruise of 5,000rpm. And it is only the camshaft-like twin-lobe mainshaft that spins so fast; the rotors spin at a third of that rate, so that in flight the rotors would turn at less than 2,000 rpm; and a gearbox of about 3:1 or even 4:1 would drive a slow-turning efficient prop.

A Wankel engine has these qualities: it is compact, light and has a high power to weight ratio; but the rotors are massive and need to be warm before the engine is given full power. So it has never been ideal for road motorbikes, where impatient riders would give it full throttle before it was ready for it; and the same applies to cars. But the Wankel is ideal for aircraft and for racing engines, where the operators are careful with the engine at warm up. In an aircraft, an engine allways be warm by the time the plane is ready for take off.

Norton's boss, Stuart Garner says he will explore applications for his new engine "outside of motorcycle racing", including military uses. This opens the door for a new petrol-paraffin Wankel engine for aviation use. Not a true diesel (i.e. not compression ignition, which requires a more massive and heavy "crankcase"); but still an engine that would be ideal for most fliers, even including Jim Cripps.

Well best of luck.

The Wankel is a bit like the Holy Grail - it really should exist!. In the real world however it has proven to be highly inefficient and prone to wear and unpredictable failure modes
Given that conventional recip engines have a huge track record and Wankels have a very limited track record (although first produced in the 1960s), it is hardly surprising that there are a few glitches to be ironed out.

Mid-West failed because they could not sort these issues. Diamond did not develop the engine because of those same issues - and this is the same company that did manage to develop their own diesel engine when Theilert went bust. That single fact should give you perspective - in around 9 months they managed to develop a certified diesel engine, but decide not to try and sort the underlying issues that a Wankel presents.............

There is a reason that Wankels are not generally in production - they are undeveloped and have a number of physical characteristics which do not make them ideal engines. Give it up and buy a Rotax!

Google uavenginesltd

I spoke last week to the people that Bill suggests. They have a fascinating range of engines but unfortunately will only supply the military. I couldn't see any way forward.

Mike Clark

gasax wrote:Wankels ... are undeveloped and have a number of physical characteristics which do not make them ideal engines. Give it up and buy a Rotax!

Some misunderstanding here! This thread is not about rotary vs pistons; it is about the optimum rotary engine for aircraft.
Obviously, any competent firm can get a piston engine up and running in a matter of months as all the technology is known.
But a diesel piston engine is heavy and vibrates, and that is why aviators still search for something better.

As you observed, Wankels have been up and running for over fifty years, whereas the rather complex quasiturbine is still an unknown quantity.
Although the quasiturbine is said to work well as a pump, I suspect that by-products of combustion would "gunge-up" its innards.

Any designer of a diesel piston aero-engine must note that Avtur lacks lubricant and is more like paraffin than road diesel;
but an engine that uses Avtur can be ignited by spark rather than by compression (not as efficient, but much lighter).

I suspect the truth behind MidWest's failure was that they spent so much time and money getting CAA certification.
Rotax took a more sensible course, namely producing engines for microlights and non-certified aircraft, making a fortune, and THEN getting CAA approval.
(I did hear that MidWest had a MarkII version that was a substantial improvement; but Diamond just weren't interested in taking it further).

The Rotax 912 is a brilliant engine, but very expensive, a little overweight and still lacking fuel injection. Rotax need some competition; come on Norton! Norton may be a minnow among motorcycle manufacturers, but they have a track record with Wankels; and building on their previous experience, I am confident their new high-output racing Wankel engine will succeed. Hopefully the Norton rotary engine could become the basis of a new British fuel-injected aeroengine that would be light, compact, smooth and powerful.

In race-bike tune, the Norton engine is expected to produce around 210bhp. Compared to the Midwest, the new engine has a larger volume, a higher rev limit and the benefit of research; and I estimate that, detuned for aviation, it could produce between 120 and 150bhp.

This estimate is based on: (i) the MidWest yielded 110bhp on the factory workbench with a water-cooled exhaust, but it produces more like 90bhp installed. (ii) The 695cc Norton is nearly 20% larger than the Mid-West. (iii) The Wankel's power/rpm "curve" is almost linear; there isn't the drop-off at high revs that reciprocating engines suffer. The Norton can spin at up to 13,000rpm (with an absolute maximum of 17.000), which compares well with the MidWest 5,800 (with a max of 10,000).
The arithmetic: 1.2 x 110 x 1.3 = 169bhp, so 120-150 is a conservative estimate. Another route is to say if the racing Norton will give 210bhp, then a detuned version will give less, according to taste and needs.

(The Midwest engine has peripheral ports. Although Mazda have shown that side-ports are more effective, the CAD-sketch of the new Norton seems to suggest that it has peripheral ports like the MidWest).

You probably won't find a bigger fan of aviation combustion engines, I have a library of books on Hooker and Fedden and a bit of an Olympus engine (compressor blade from a Concorde or a Vulcan), and a excellent 912ULS at the front of my aeroplane.

But COME ON, all combustion engines are SOOO 20th Century, even fancy non-reciprocating ones.

The future is electric, forget carrying around flammable liquids and burning it...

Instead, lets start a thread on electric motor development.

Or are motors fairly well sorted - and the real question be about electron storage or generation? (i.e. batteries or hydrogen fuel cells). Where are the regulators at on this subject in homebuilts?

Cheers

Simon C
~~~~~~
(my next car will be electric)

Major feature on alternative power systems coming up in the next couple of issues of LA.

Simon Clifton wrote:Instead, let's start a thread on electric motor development.

OK! I'll call it "alternative power systems".
http://www.lightaircraftassociation.co. ... 591fb45b93

Hi Guys 'n Gals,
It was great to see that my article had raised some interest I had thought that I might be losing my touch at stirring things up. Actually the QTD has not got much in common with the Wankel and my version will not have more parts, like I said in the article I like to keep things simple. The bottom line is that all the aircraft engines currently available are much, much too expensive for the normal wage earner. You can build a complete Jodel plane sans engine for circa two grand but when it comes to the engine you have to fork out mega bucks. No what is need is a cheap easily made engine. Yep it's a dream but like the song goes "If you don't have a dream ,how you going to make a dream come true". ie you have to give it a try or rather I do. Oh and yes I also have plans for an electric engine for planes probably to go into a SSDR. Bye the way I have found an engineering company who will do my machining for free and I have also been donated the bearing for zilch. I am also trying to get other parts donated. Got to watch those baubies!

Onwards and Upwards, Jim Cripps

Hi Guys 'n Gals,
Trevor has asked nay nagged me for an update on my progress on the Quasi Turbine Diesel. To date the castings have been complested in LM 25 alloy and heat treated to TF grade by two firms who have donated their services for free. Next I shall be getting the castings to the engineering company who are willing to do the machining for free and who will make the drive shaft etc. Once I get the machined parts back I will set to work making the pistons and other parts. I am aiming to be testing early next year so watch this space. I have also constructed a front fuel tank ro assist in the weight and balance regime as the engine will I expect be no heavier than 80lbs much lighter than current engines on the Jodel D18

Onwards and upwards, Jim

Rotary engines are used on the Watchkeeper UAV

http://en.wikipedia.org/wiki/Watchkeeper_WK450