A VW for the 21st Century

MikeGodsell · Post by **MikeGodsell** » Fri Oct 09, 2009 6:24 pm

Sorry to go a bit off topic, but why develop yet another avgas/mogas engine?
The three cylinder 100 hp Gemini diesel engine weighs the same as my 80hp Limbach with even better fuel economy. Jet A 1 / Diesel fuel is available everywhere, and is inherently safer than petrol.
see: www.ppdgemini.com

Also the French homebuilders are way ahead with their car diesel conversions. see> http://delvion.free.fr

mcfadyeanda · Post by **mcfadyeanda** » Fri Oct 09, 2009 7:20 pm

And the Gemini will be priced against the Rotax 912S!

Brian Hope · Post by **Brian Hope** » Fri Oct 09, 2009 7:33 pm

Hi Mike, the idea of a competition is to develop an engine that is competitive with the 912 because the 912 is THE engine as far as most modern aircraft designers are concerned, so it is the obvious benchmark. It could well be that a diesel is the answer, because though it would probably struggle on engine weight, it could be argued that reduced fuel load to cover similar range should be taken into consideration.
It should be noted that as of this moment a competition is still at the ideas stage, so input is very welcome.

MikeGodsell · Post by **MikeGodsell** » Fri Oct 09, 2009 7:34 pm

Ah yes the price is indeed the main point. I was comparing the Gemini against the price of a new Limbach which is similar to a new 912. Sorry to butt in, will go and eat worms in the garden

mcfadyeanda · Post by **mcfadyeanda** » Fri Oct 09, 2009 7:37 pm

Bill McCarthy wrote:Whatever became of the Weslake engine - a 90hp two cylinder four stroke. I found details of its lauch at the Popham Microlight Trade Fair in an old "Today's Pilot" (July 2005) The price tag then was less than half that of the Rotax

I personally think that the concept of a two cylinder (4S) engine is flawed for c.80+HP.
It requires heavier mount (and whatever that attaches to as well), larger exhaust volume, heavier battery to crank it, much heavier gearbox if geared. The list goes on.

I speak from the experience of having had a 2-cylinder BMW RS1100 in a Europa (yes, it had a Permit and flew for 13 hours, long story). When that was sustituted for a 912S, the aircraft lost 60 lbs!
Note that Lycoming gave up on the idea of a 2-cylinder engine too.

By the way, whilst the BMW RS1200 is a nice engine in a motorbike (and is much improved on the RS1100) it's bizarre to think that Rotax actually make many of the BMW bike engines! But at about 70 times the rate of 912 production.

cardiffrob · Post by **cardiffrob** » Sat Oct 10, 2009 8:25 am

Scat just E-mailed to say that their unbreakable race cases are about 70lb each. How does that compare?

Bob F · Post by **Bob F** » Sat Oct 10, 2009 8:08 pm

Although being a Spam Canner I have watched this thread with interest. This post will add nothing to the thread except to show "what goes around comes around". Saw this in this week's Flight International:

100 years ago exactly a Mr Patrick Y. Alexander thought that "the aerial problem is being retarded by the want of a reliable motor suitable for aeroplane work".

He offered a prize of £1,000 for the first British aero motor of 20h.p. which could, if necessary, run for 24hrs continuously. It never said if it was collected!

Trevor Harvey · Post by **Trevor Harvey** » Wed Oct 14, 2009 9:13 pm

Bill McCarthy wrote:Anybody know if hydraulic motor drive has been tried. A small engine with direct drive to a hydraulic pump, then the output from that used to drive a prop through a hydraulic motor. There are some fancy hydraulic motors with swash plates that can be used to reverse the prop for "air braking" on landing. Some of these motors are only the size of a bean can and can chuck out a hefty bit of torque. Just thinking out loud - must go and investigate further !

Before I retired from a large company that built hydraulic motors, I did once design & build an experimental "turbine" motor 4" dia & applied 6 bar of compressed air to it which produced 8500 rpm.
I never got around to developing the thing further but I do believe it would produce enough torque & sensible rpm if run on hydraulics. My quaint idea at the time was to drive prop & rotor spin up on a gyroplane & also drive the mainwheels for road use, wishful thinking.
A system was tried (USA) to drive both wheels on a motor cycle, successful, but fluid cooling was a serious problem. On a fixed wing a/c this could produce an effective de-icing system.
The "bean can" variety was/is used on machine tools & are indeed very powerful.
Is there a case for an "outside the box think tank" here?
I think I shall dig that turbine thing out from under the bench & try something.

Nick Allen · Post by **Nick Allen** » Wed Oct 14, 2009 10:52 pm

A system was tried (USA) to drive both wheels on a motor cycle

Ohlins (Swedish motorbike shock absorber manufacturer) had/have a functioning system with a small hydraulic motor taking power to the front wheel.
http://www.ohlins.com/Checkpoint-Ohlins ... l-started/
It was reading about this a few years back that got me thinking about aviaton applications...

Trevor Harvey · Post by **Trevor Harvey** » Thu Oct 15, 2009 10:31 am

The reason I stopped dreaming about developing a system was when I discovered the certification "system/process".
Designing a perfectly suitable hydraulic drive for a/c would not be difficult.
My lawn tractor has a hydrostatic drive, a 3 blade cutter deck 54"wide. It can tow a heavy trailer full of horse manure & cut the grass at the same time. Powered by a very small 3cyl diesel.
Serious question. How does one build & test a device in an a/c to the point where it works without incurring the crippling cost of the legislation?
Then how much does it cost to get it certified?
The actual idea I think lends itself to all manner of aplications, How fast could a fan system be driven at? If a series of 4/6 fans were run in oposite directions in a venturi tube, how much thrust would it produce?
In this country it is more likely that the designer/inventor would be "certified" before the piece of engineering.

Bill McCarthy · Post by **Bill McCarthy** » Thu Oct 15, 2009 10:51 am

If you can keep the weight down (which is entirely possible), I suspect you can develop and demonstrate it free of any regulation or certification in the SSDR route. The added advantage of hydraulic drive is that the engine supplying the drive motor can be separated with the engine not necessarily bolted to the front behind the prop.

Nick Allen · Post by **Nick Allen** » Thu Oct 15, 2009 12:01 pm

The added advantage of hydraulic drive is that the engine supplying the drive motor can be separated with the engine not necessarily bolted to the front behind the prop.

That was precisely what I struck me as a major advantage: rather than contorting the front of an aircraft to accommodate the engine, the nose could be made much, much sleeker...

Trevor Harvey · Post by **Trevor Harvey** » Thu Oct 15, 2009 6:59 pm

Nick Allen wrote:
The added advantage of hydraulic drive is that the engine supplying the drive motor can be separated with the engine not necessarily bolted to the front behind the prop.
That was precisely what I struck me as a major advantage: rather than contorting the front of an aircraft to accommodate the engine, the nose could be made much, much sleeker...

We seem to be of like mind here. I had a thought that the engine could be used as a weight & balance trimming device attached through a suitable screw jack. Added weight of course but there may be some spare available to play with.
Point two. What would a twin prop single engine reduced size PBY Catalina lookalike be classed as? A twin or a single? One could boggle the mind of the regulators here.
SSDR sounds like a good start.

Trevor Lyons · Post by **Trevor Lyons** » Sun Nov 15, 2009 7:01 pm

Another existing engine that has already proved itself is the Hewland, originally developed for Richard Noble's ARV Super2. The Hewland is an inverted in-line 3-cylinder water-cooled 2-stroke engine with a mechanical reduction gearbox. Originally, it produced about 77bhp, but has since been developed to give over 90bhp.

Of course, everyone who has heard of the Hewland will say, "Oh yes, I remember, they had gearbox troubles, and the CAA grounded the aircraft!". True; but the problems were quickly sorted and there are many Hewland engines still giving good service 25 years later. One pilot regularly flew from Plymouth to Alderney in a Hewland ARV, so confident was he in the motor's reliability.

The Hewland was beautifully-made, light and compact; and being three-cylinder, was inherently smoother and more reliable than the more common 2-stroke twins. The Hewlands have an LAA mandatory life of only some 800 hours; but I'm told that they are virtually as good as new after this time. (It seems criminal to decommission engines that are still in good order. If it ain't broke, don't fix it!)

The good omens for the future are that the Hewland is a British design, the rights are still in British ownership, and the current owners are engineers who have been upgrading the engine over the years. Future proposals might include oil-injection, fuel-injection and further tuning for extra power.

The 3-cylinder Hewland was developed from a 2-cylinder go-kart engine; so once it were put back in production, there's no reason why a modular 5-cylinder 150bhp version should not follow in due course!

Rod1 · Post by **Rod1** » Sun Nov 15, 2009 7:54 pm

The problem you will have with a new engine is the overall cost of the solution v a second hand Rotax. A Rotax will go well past TBO and there is an 80hp one advertised in the mag for £2700. Most aircraft are designed round the Rotax, the mounts are cheap and approved, the props are cheap, and approved and the aircraft / engine / prop combination will be approved. Added to that is that the running costs of a Rotax are quite low, even if the engine is expensive new. To compete the new engine would almost certainly have to be mount compatible, or the work to adapt the installation would be beyond 99% of us.

Rod1