ALTERNATIVE AVIATION ENGINE

[Flooi]

Can someone advise...........

Rotax 4 stroke is designed around motorcycle engine technology. Has anyone ever tried
to fly with a superbike engine? (Not the old boxer BMW engines)

Firstly: they are highly reliable. Many superbikes are still around from the 80's and most of them
have been ridden hard from time to time.

Secondly: Power to weight ratio is unbeatable.

Thirdly. It can be fitted with it's gearbox which is small and light; so one can select the
permanent drive to fit the most efficient prop.

I am not a technical expert, so can the informed please advise!

Thank you!

Moegvirrotaxpryse

[Tailspin]

I have heared of a Yamaha Virago motor being used

[Morph]

I would say they are too highly reving. Most aircraft engines are required to run constantly at 75% of their peak rpm. On a superbike the peak is around 12 to 13000 rpm, therefore 75% is around 9000rpm. Most aircraft engines peak at around 6000rpm and cruise at 5000to 5500. I am not sure if a bike motor is capable of sustaining that sort of RPM constantly and at what fuel consumption, I suspect very high

The prop-tip must never exceed the speed of sound and this typically results in a prop rpm of 2300 rpm. You would need a gearbox with a ratio of about 1:5.21 to bring the tip speed down.

An aircraft also has to be able to operate at sea-level all the way up to 12000feet in one flight without any adjustment to the engine. Again, is a bike engine capable in handling a takeoff at 200ft and 30minutes later cruising at 8000ft, If fuel injected this should not be a problem.

V-Twin engines and Beemer Boxer motors have been used in the past, with the beemer being the only successful one. They are typically lower revving, and with some tweaking on the mapping of the ignition and fuel injection, capable of being very successful.

Lastly, superbike motors require a lot of maintenance and 20 to 30,000 km is sometimes considered a lifetime. This equates to 200 to 300 hours in a plane, very low. On a 4-stroke we expect a rebuild time of 1500 hours, or 150,000km. Very few bike motors are that reliable.

[Mogas]

Further to all said, most bike motors have the gearboxes integral with the crankcase casting. Ideally we need the crankcase separate so that we can make a plan for an "aviation" gearbox. This is one of the main reasons that the BMW boxer engine is a good candidate, the road gearbox bolts off.

[Flooi]

See, I knew there were intelligent people out there. Thank you Morph, Tailspin & Mogas!

An interesting option: What about the Nissan 1400 engine? What says the informed about this?
Here is a guy on the East Rand with a Nissan 1400 (stock standard) powered gyro.
He swears by it for reliability.

Surely there must be options besides VW. With the slumping Rand, Rotax 4 stroke has become
a VERY costly way to go.

[Morph]

Car engines are a different story, except for weight

Subaru engines are extensively used in Gyro's, especially the RAF. VW motors are also used to a great degree. Both of these engines are flat boxer style engines which fit into the nose of an aircraft better.

As far and car engines go look for 2 main things, 1. weight, 2. fuel injection if possible. A rotax 912 4-stroke 100HP motor weighs about 70 to 75Kg full installation. A VW will be closer to 100KG. Add to that the weight of the aircraft at say 230Kg. Now you only have currently a max of 450 kg to play with, which has to include pilot, pax, luggage and fuel. A rotax installation leaves 145kg and a VW installation leaves 110kg to play with. Not much. If you can get 100Hp from a car engine at a lighter or the same weight great. Heavier not.

There has been a lot of talk about using Smart Car turbo diesels. Waiting to see a tried and tested installation.

[Boet]

The ONLY alternative engine I am looking at is this one......Properly tested by Vliegvark and his dad. Lots of power, reliable, light and simple enough. And the price does not break the bank. Shortly to be installed in the new BB Safari......

[bosbok]

Now that`s what I would call a serious alternative to Rotax motors ! I`m interested.

[grostek]

Hi Boet,

Any idea of cost at this stage?

Kind regards,

Gunter Rostek

[Boet]

It depends what you pay for the engine. The gearbox is slightly expensive @ +_ 20k. Gearbox comes with a centrifical clutch. The prop stands still while your engine is warming up. The clutch double as a "slipper" in case of a foggapie. Vliegvark and his Dad is looking at having the gearbox manufactured locally to keep the price in check.

[Flooi]

Boet, Baie interessant! Dit lyk soos 'n tipe R BMW enjin.
Gaan dit nie ook baie kos nie; aangesien dit van Duitsland
ingevoer moet word?

Groete!

[German]

Hierdie centrifical clutch moet net nie begin "slipper" as jy vlieg nie!

[Rudix]

I like this option a LOT

A few photos of BMW installations in Zodiac 601's









Boet, waar kan mens daai ratkas koop ? Ek strip sommer my 1200 GS

Vlieg veilig,
Rudi

[grostek]

Hi All,

Dit some scratching around on the net and found the following.

http://www.takeoff-ul.de/

Click on "products"

Then click on "englisch engine description"

and for prices click on " Preise Prices Prix Precios - engine.pdf "

These are 2007 prices so would contact them for current prices if you need to know more.

Some general BMW and other engine info here

http://www.loginet.nl/europa/euroengi.htm

Here for a builder of a Cherry using a BMW

http://www.spang-air.de/index.html

Happy reading.

Gunter Rostek.

[Tailspin]

I am also very very interested in the BMW motor route
Maybe looking at putting this into a trike i have lined up on the horison