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BMW motorcycle engine for a plane?

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Loco

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Aug 1, 2008
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over here.....
after looking and looking and getting scared of the engine prices...I have a question, has anybody used or heard of anyone using a BMW motorcycle engine ( 2 cylinders, opposed engine) on a ultralight/ small airplane?...Im window shopping for an engine in the 30 to 50 hp at 85 pounds of weight or less, I would love to get my grubby little hands on a Citroen C3V or a mosler engine, even a working 1/2 VW engine ( with oil pressure issues ironed out), but I have the big question mark about the BMW engine....it seems to be readily available at my local junk yard for cheap ( I would like to have the rocker cover in plain sight just for kicks).

my future project is a PIK-26, ( Im saving some cold cash for the blue prints).
 

Joe Kidd

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Apr 9, 2008
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Tennessee
Check out moto-air in the Yahoo Groups. Also in answer to your question yes it's been done, however you'll have to run a PSRU to make it work. Check out the files and pictures in the Yahoo group for ideals.
 

PTAirco

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Not uncommon in Europe. One British company offered these for a while with a Rotax C-type gearbox. Worked quite well, some are flying in Europas.
 

djschwartz

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Jun 21, 2008
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Portland, Oregon
There is a guy here at Lenhardt Airpark in Oregon with a Beemer on an LSA. It works, but like almost all of these low cost conversion attempts, it has taken him a long time and a lot of fiddling to get it working. It still isn't very reliable. The core engine is fine, the Beemer is a good basic design, but he has continual problems with other parts of the system. I'll try to get his name for you so you can talk to him directly.
 

Hugh Lorimer

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Feb 14, 2008
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298
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Stair, Ayrshire, Scotland.
after looking and looking and getting scared of the engine prices...I have a question, has anybody used or heard of anyone using a BMW motorcycle engine ( 2 cylinders, opposed engine) on a ultralight/ small airplane?...Im window shopping for an engine in the 30 to 50 hp at 85 pounds of weight or less, I would love to get my grubby little hands on a Citroen C3V or a mosler engine, even a working 1/2 VW engine ( with oil pressure issues ironed out), but I have the big question mark about the BMW engine....it seems to be readily available at my local junk yard for cheap ( I would like to have the rocker cover in plain sight just for kicks).

my future project is a PIK-26, ( Im saving some cold cash for the blue prints).
I used a BMW R100RS 1,000 cc boxer engine on my Iolaire, cheap, reliable loads of torque, electric start etc. onthe heavy side but fuel load can be cut down since, at constant revs., is frugal. Initially I modified the BMW 5 speed gearbox,stripped, locked in second gear and slugs to prevent backlash. I then made a centrifigual clutch `cos the engine does not like starting on props. when cold. Finally made a three vee belt pully system. A light ignition condenser, a light starter,a light flywheel, removing the casings etc. helps with weight. See www.hughlorimer.co.uk , engine and g/box cost me £350.

Hughie.
 

Loco

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Messages
36
Location
over here.....
interesting, just for sake of curiosity, what was the reduction ratio you used on the Iolaire?..I venture to say about 2.3 to 1?...Im curious....

PS that clutch looks quite interesting too...
 

Hugh Lorimer

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Feb 14, 2008
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Stair, Ayrshire, Scotland.
interesting, just for sake of curiosity, what was the reduction ratio you used on the Iolaire?..I venture to say about 2.3 to 1?...Im curious....

PS that clutch looks quite interesting too...

I first of all stripped the box completely and left only second gear sleeved in place, the ratio was 2.86:1. You need a hydraulic power press to remove layshaft gears, the box was spun on the casing spiggot to give a centreline thrustline. I put steel slugs into the dogs to prevent backlash which helped a lot when starting from cold. I limited the revs. to 4,000 and the s/s exhaust had a balance pipe with the exhaust tails biased in the direction of the prop. rotation, all very quiet and reliable.

Hughie.............
 

Hugh Lorimer

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Feb 14, 2008
Messages
298
Location
Stair, Ayrshire, Scotland.
interesting, just for sake of curiosity, what was the reduction ratio you used on the Iolaire?..I venture to say about 2.3 to 1?...Im curious....

PS that clutch looks quite interesting too...
The centrifigual clutch was made from a "mini" brake drum and a pair of brake shoes. The drum was lightened and a diaphragm made and mounted to mount the drive splines. The shoes were narrowed and pivoted on the lightened flywheel diaphragm, The connected levers have steel bob weights attached and the springs adjust along the lever length to adjust take up revs. I set the take up revs to 700 on the lathe using a strobe.

Hughie.............
 

pwood66889

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Feb 10, 2007
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Sopchoppy, Florida, USA
"There is a guy here at Lenhardt Airpark in Oregon with a Beemer on an LSA.
...
I'll try to get his name for you so you can talk to him directly."

That would be nice if you could. I have a chum at Lenhardt's.

Percy in NM, USA
 
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rtfm

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Jan 3, 2008
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Brisbane, Australia
Hi,
The use of the BMW motorcycle engines is well documented, and well proven. Although not common in the US, these engines fly in many aircraft in Europe and have a devoted following.

Of the available engines, the new generation (ie R1200 series) engines are far superior to earlier incarnations. Most importantly, the R1200 series have balanced chrank shafts, which almost entirely does away with the typical rocking vibration common to opposed twins. These new engines run from low to high revs with barely discernable vibration. Ideal for aircraft.

Secondly, one should go for the "S" variant of the R1200 if possible since these engines in stock form produce 122hp. Earlier engines produced far less, and were heavier, to boot.

I would also strongly recommend using as much of the original BMW parts as possible. For example, don't mess with anything unless absolutely vital. Keep the engine stock. Don't fiddle with the engine. If you want 122hp, then essentially you need to transplant the engine from the bike to your plane and go fly. There is no need to adjust anything, add anything or replace anything. If you can buy a relatively new engine, then that is (almost) all you need to do. IE There is little or no "conversion" to do.

One of the major reasons new "aircraft conversions" give so much trouble is that builders INSIST on trying to do things to the engines. The R1200 has fuel injection and dual plugs. Leave as-is.

There are four things you WILL have to do before you can go flying behind your BMW, however...


  1. You will need to fit a new exhaust. The BMW engine is mounted back-to-front in the plane (ie gearbox side forward. In the bike it is the other way round). This will require a new exhaust. However, a word of caution. Don't go fiddling with the exhaust trying to improve it. Keep the header pipes the same length. Lead the two pipes into a single pipe (just like on the bike). Keep the catalytic converter. Lead the exhaust into the stock muffler. You will end up with a quiet, efficient, manageable and above all, reliable exhaust system. So you lose a few HP because of the catalytic converter. Get over it. 122hp is plenty. So the exhaust is quite long, and relatively heavy. Big deal. There is no particular reason why the exhausts of aircraft need to be 6 inches long, poke out of the bottom of the cowling and roar loud enough to wake up every conservationist in the tri-county region. In my installation, I'll keep as much of the original exhaust as possible, and have the silencer also. It will exit the plane behind the cockpit.
  2. You will need to create your own air intake box. The one on the bike is custom designed to fit in the bike frame. Keep the same volume, but make your own.
  3. You will need to fit a PSRU. Here you have a number of choices. Because the BMW offers such a clean surface on which to mount the redrive, it is a relatively simple operation by anyone who knows what they are doing. The older BMW1100 engines accepted the Rotax C box, I believe. I prefer to go with one of Neil Hintz' Autoflight gearboxes. These are used world-wide in everything from trikes, to gyros to fixed wing. He has a universal mount drive which can easily be matched to the R1200. It is reliable, has an excellent reputation (no reported failures - ever - I believe) and is competitively priced.
  4. The above three "conversion" items are pretty easy, and should present minimal problems, since you are basically keeping sizes and lengths identical to the bike. The PSRU is a bolt-on option. But the fourth "modification" is more problematic. The R1200 is computer controlled. Problem is, the ECU expects a zillion inputs which are specific to the bike. They are out of place (or non-existant) on an aircraft. The only way round this is to fit an aftermarket ECU. Having said this, the task is far from being as daunting as it sounds. I am using a Link ECU. This is a Kiwi-designed unit, and widely used on aircraft here and in Australia. These units are (almost) self-tuning. But for the final tweaks and adjustments, any competent tuning shop can oblige. I intend to make my ECU map available for other users, so that even this part of getting your aircraft flying behind the R1200 will be a "bolt on" option.
Regards,
Duncan
 

rtfm

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Brisbane, Australia
Hi,
This is a matter for some speculation. However, apparently the old R1100 engine (which is heavier than the R1200) weighs in (including Rotax "C" gearbox) ready to fly at 172lbs.

Having said this, I have not actually seen proof of this (ie pictures of the complete engine on scales). But this is the figure being reported on some of the European sites. And before you ask - no, I don't have the sites bookmarked, sorry.

Regards,
Duncan
 

kuba_mysluk

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Jan 27, 2009
Messages
13
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Warsaw POLAND
Hi,

I aeroconverted ~40 BMWs (1100, 1150 and one 1200 R-series).
I probably can answer any questions, spent few hundreds hrs behind flying BMWs in different planes. Sources of PSRUs, typical problems, wireing conversion, vibration problems&solutions... maybe mine experiences (and mistakes too)maybe will be interesting for someone.

best regards for all homebuilders

Kuba
 

kuba_mysluk

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Aha, regarding Grimace's question:
The typical engine /PSRU dry weight is ~78kg (Im "metric" one).
In real installation with oil cooler and exhaust it can be about ~85kg

Regarding power... huh, well... as rule of thumb pls use ~15hp less than BMW claims for given version. We all have never used genuine airbox and exhaust, the real output in real installation are far less than advertised BMW power (no free meal, isnt it?)

But the great advantage is really flat torque curve. Nothing compared to typical carb engine. And it have a great low fuel economy far better than Rotax 912. The next issue is the price - in europe You can have engine/PSRU combination for 2500-3000EU depends of sources.
It is also VERY strong - we exchanged engine after 3500 hrs in flight school Zodiac CH601!!! Two times better than typical Rotax 912. (and pls remember - almost all BMS came from bike wreck yard with unknownt mileage)

IMHO - its the best replacement for Rotax 912 engine, I even dismounted one certyfied Walther and instal BMW instead...

K.
 

PTAirco

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Corona CA
I'm sure we would all like to see some pictures of your conversions, as well as hear your specific experiences.
 

rtfm

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Jan 3, 2008
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Brisbane, Australia
Regarding power... huh, well... as rule of thumb pls use ~15hp less than BMW claims for given version. We all have never used genuine airbox and exhaust, the real output in real installation are far less than advertised BMW power (no free meal, isnt it?)
Hi,
May I ask why you do not use the bike's airbox or exhaust? It seems to me that it might be problematic to use the bikes air box because of its shape, but if you used a similarly sized box of your own making, the results would be very similar? But as far as the exhaust is concerned:
Why not use it? Is it too long? Too heavy? Without a doubt, it certainly WORKS, so my thought was yes, use an identically sized exhaust. I will have to route the header pipes differently, of course, and run the rest of the exhaust differently, but I was planning on using an almost identical exhaust to what is used on the bike.

My reasoning was that if it works on the bike, it will work in a plane. Since the EFI is altitude compensating, all one should really need to worry about is adequate cooling?

Duncan (always-eager-to-learn) Meyer
 

kuba_mysluk

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Jan 27, 2009
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Warsaw POLAND
Hi
All bellow is regarding BMW R-series 1100 or 1150!!!

The genuine exhaust is too heavy and very unpractice to install, just look at its shape. Designed for bike, not symetrical..

About BMW exhaust... Funny, but no one aftermarket systems available as "tuned" part wasnt as good as genuine one. BMW did their home work well. Homebiulders using heavy BMWs usually weld "any" own exhaust system, rarely it was calculated for resonance waves causing some suction when both valves are open. Most of us just skip those few hp possible to gain here due to weight and dimensional problems.

Airboxes, well.. it isnt so easy. It depends from many factors, not volume only. Local resonances and effects of hipersonic waves mainly. Geniune airbox is just to high for any normal aplication, but I saw it used in trikes (when height isnt the problem) The problem with airboxes is strange: BMW injectors have one fuel shot per each revolution!!! It means: half of fuel dose is waiting one full engine revolution till inlet walve will be open. It causing loosing of some escaped air/fuel mix and generally give strange effects with improper designed "just airbox' Pls remember - typical EFI have especially "rear map" designed for correction all of dynamical fluid effects. We cant fix or set this "rear map" when "any" airbox will be used.
The common practice is skip it, and use sponge filters on throats instad.

Altitude compensation in BMWs... well.. its kind of myth. BMW (1100 and 1150) are using very simple Motronic 2.2 (for R1100, excluding 1100S) and Motronic 2.4 (for all 1150 and 1100S).
This system have no any air quantity metering, but just TPS (throttle position sensor) and lambda (o2) sensor. The best think You can do here with lambda is... disconnect it from the wireing.
I not want write too much about lambda theory, but it is for NO2 low emision mainly, not for proper air to fuel mix. EFI will set kind of "service mode" causing a bit bigger fuel consumption. (Aha - BMW doesnt using "wide" lambda, theirs work in very narrow band, more like switch than sensor). Second note: in typical automotive engines lambdas are working till 35-45% of RPMs. We usually flying near WOT or 85% of power... it is not working for us anyway

Mine personal craft is still flying without it at typical level few thousand feets. I had some problems with lambda, when it was connected: non-smooth idle when lambda wasnt tighten properly and worse rpm dropping in flight when lambda was broken. (You will really scared when your engine will drop and back about 1000rpm without any throttle movements)

best regards

Kuba

PS Duncan, pls let we discuss BMW issues in one thread.
 

kuba_mysluk

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Jan 27, 2009
Messages
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Location
Warsaw POLAND
-> PTAirco:
I'n newbie here, have no idea how and where put my photos. I will check it, but If you are interesting: pls subscribe Yahoo/moto-air group, and take a look in "photos" section. I put few photos few mine BMW installations. (ch601, ch701, Skylark, Tulak and as I remember one or two trikes)

best regards to You

Kuba
 
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