BMW R1200 motorcycle engine

Hi,
I know the received wisdom on auto conversions is that they are probably more trouble (and expense) than they are worth, and that one would probably be better off buying a regular aircraft engine and have done with it. But I have just come across the BMW R1200 engine, and I think this changes the rules somewhat.

As far as I can tell, the major obstacles standing the the path of any would-be auto (or bike) conversion wanna-be, are the difficulties of:

• finding a suitable gearbox
• Ensuring sufficient cooling in very tight cowl spaces
• sorting out the engine mount
• Beefing up the innards to withstand the extra operating stresses aircraft use puts on engines
• fiddling with the ignition (dual ignition almost mandatory)
• getting the computer to work without some of the sensors feeding info back to the CPU (most car sensors are not required for flight, and their absense confuses the CPU

It is probably no coincidence that the VW conversions are so popular in aircraft. They have no complicated CPU's to worry about, require no gearbox, are air cooled. Add to that a very simple basic design, and voila - a very suitable candidate for aircraft conversion.

But the modern generation of BMW motorcycle engines offer the home builder a great deal:

• Air cooled
• No complicated sensors to work around
• EFI
• Dual ignition
• Bolt-on gearboxes available (Rotax or Autoflight)
• No need to alter the innards at all.
• Over 100hp without modification

Guys who have converted the older R100 to aircraft use make no engine modifications at all - except possibly (and optionally) to polish the ports and fit an extra spark plug per cylinder. They fly them as-is.

The latest generation of BMW engines already come with dual ignition and EFI. Bolt on either the Rotax-C gearbox or the excellent Autoflight box, and you're about ready to go.

Weight? The R100 stripped of the unnecessary bits and with the gearbox already in place weighs in at 74kg. The Aerovee (VW conversion by Sonex) weighs 76kg and only produces 80hp.

Reliability? The BMW engine is virtually unbreakable.

Cost? One can buy a late model BMW motorcycle in great condition here in Auckland for about $8k NZD (about $5k USD). Add a couple of grand for the PSRU, and it is a pretty sweet deal.

Duncan

Doesn't the R1200 have an integrated transmission?

Hi,
Possibly. I only started my enquiries yesterday by visiting the local BMW dealer. I could have the model wrong. Maybe he was talking about one of the others. I'll have to return to find the actual model I'm after. But the principle is the same. Thanks for the feedback.

Duncan

I haven't seen any modern motorcycle engines (haven't looked that hard, though) without an integrated transmission. When I figured this out, I stopped considering motorcycle conversions.

Hi,
A quick call to my local BMW dealer reveals that all boxer engine BMW's have separate gearboxes. He strongly recommends the R1200 series, because they are a lot lighter than the earlier engines, all have EFI, all have dual ignition, and produce upwards of 100hp unmodified.

So it seems I got my story right, after all. That's a good sign.

These are lovely engines, BTW. A joy to behold. I am really looking at them with a very favourable eye...

Regards,
Duncan

Hey Guys! this thread is of great interest to me as i think it is the begining of a shift in home built powerplants. I have had some good conversations with the following company regarding electronic engine management on engines that are parted from their origional prisons!

Race Tech Engineering
1007g 55 Ave Ne
Calgary AB, T2E 6W1
Phone #: 403-274-0154
Key contact: Ross Farnham , Owner

See some info below that may make an even stronger argument for the BMW and Suzuki engines (no suzuki conversions yet!):

YouTube Links worth watching!

BMW
YouTube - Schmidtler Trike BMW Trike Enduro
http://www.zenithair.com/zodiac/607/bmw1.jpg

Suzuki
YouTube - Radical SR8 - Nurburgring Nordschleife
YouTube - V8 caterham

Some discussion on leaving the engine internals alone - but helping them with a torque limiting drive coupling would be useful. does anyone have experience with these on aircraft (to limit low RPM torque wich destroys non-aero crankshafts).?

Where does the R1200 make peak power? Around 9k rpm or so? Just a bit fast for use in a ducted (or unducted) fan without a reduction, too bad...

I should think the reduction would be a good thing - enabeling you to match peak output with peak prop/fan efficiency??? also increasing crank longevity. reduction is not a bad thing!

Hi,
It seems to depend on which variant of the R1200 engine one gets hold of. But max RPM is in the region of 7250 to 7500.

Matched to a suitablly geared PSRU this sort of engine RPM would translate very nicely to prop speeds. Best of all, BMW conversions have been done hundreds of times (in Europe) and some helpful fellow has even published a how-to on the web where most of the answers to questions you or I might have when converting a BMW engine have already been answered.

The link is here:
R100

The instructions assume an R100 motor, but the principles are unchanged no matter which BMW engine one manages to find.

Duncan

Anyone looked into a Honda Goldwing engine? I think latter models produce 118BHP. Or is that one with an integrated tranny?

There have been a few attempts at incorporating a Goldwing, some good, some less so, but to the best of my knowledge none have been put into any form of production or distribution, most likely because the Goldwing engine is relatively expensive, and that's before the aircraft related mods.

The Honda GL engines are heavy and watercooled...

The BMW is light and hybrid air/oil cooled...it is a fantastic engine...and extremely torquey...I have considered it for several designs... It also can be made to make HUGE power with the right bits...

Dave

One consideration maybe the 80/85 Hp Jabiru engine
I have used one for 9 years here are my observations
The engine has undergone many changes and the latest change is to hydraulic lifters but that brought with it some other problems , and it means everyone is not interested in the older simple non lifter motors so they are traded back to the factory for around $ 5000 Australian
They do need work and it needs to be somewhere after engine number 700 because thats when they changed the heads and used steel conrods . The heads need work done and some mods to the rocker and ignition rotor lubrication , but if you are prepared to live with adjusting the valves at each oil service they offer some benefits
Direct drive but need wooden props
Simple strong bearing systems designed for loading at the crankshaft end
No special tools needed for repair or rebuild
You can get parts easily
Oil cooling is straightforward
Built dual ignition but needs careful attention
Some mods to the flywheel / crank connection
Torque curve at 3000 rpm will give about 70 - 75 Hp true
Air cooled although thats not as simple as it seems maybe one of the biggest challenges to get cooling right and uniform - some specialised cowling work .
I think they need about another $2000 Aus to get them working properly but you end up with a known quantity but they do need a complete strip down and rebuild/ check total roughly $7000 Aus

A decent gearbox for automotive rebuild is $2000 and the adapter plates , ignition systems etc makes the final price / time too high IMHO.
I am going to use my existing ( flying ) motor in my single seat project because its a known quantity , reducing the design , testing to only the airframe .
Flyoz

Take Off
Air Trikes: Engines and Conversion Kits. scroll down
Polmotor-aviation no idea here
BMW Engine
http://groups.yahoo.com/group/moto-air/ search for a guy named Kuba Mysluk

good luck, nice engine

Kevin

Hi,
The problem with the Jab engine is that it is already used, requires work of a technical nature to be done, and still isn't that cheap. I would love to have a Jabiru engine - I think they are great. But like so many things in the aircraft world, are priced beyone the pocket of mere mortals.

The BMW R1200 on the other hand, can be used AS IS directly from a bike. Even a very low milage bike is pretty cheap. Add on about $1500 for a redrive and bolt in onto the plane. That's it.

Here are some pictures of the complete engine, including redrive ready to bolt into an airframe. Check out the last pic. How neat/clean is THAT...

Regards,
Duncan