How much of an aircraft engine is the boxer, anyway?

Steve Carlton · 04-04-2006, 06:39 PM

I see it mentioned now and then. So, what's the deal? Teach me stuff...

fiery · 04-04-2006, 06:57 PM

I fly light sport aircraft.

I have seen internet pics of the Oilhead boxer powered light aircraft. I am uncertain if the engine is authorised BMW conversion though.

wildduc · 04-04-2006, 06:58 PM

Check out this link: http://www.microlightsport.co.uk/Catalogue/bmwengine.htm

I think it looks better in the boxer configuration.

Steve Carlton · 04-04-2006, 07:09 PM

I'm talking about historically; the roots of our powerplant. How much does our motorcycle engine have in common with BMW's engines from the beginning through WWII?

repoe3 · 04-05-2006, 03:11 AM

Quote:

Originally posted by Steve Carlton
I'm talking about historically; the roots of our powerplant. How much does our motorcycle engine have in common with BMW's engines from the beginning through WWII?

BMW was in the business of aeroplane engines for many years. those aeroplane engines looked like that big pic in the post above...lots of cylinders postioned radially around the crank. well, this heritage is demonstrated in the blue and white and shape of the roundel for sky, clouds, and propeller blades.

so engine-wise, lop off all but the two opposing cylinders and you have the basic layout for the flat twin used on the bikes. this design has carried through in the 1920's to today.

feel smarter?

repoe3

repoe3 · 04-05-2006, 03:13 AM

obviously, they have evolved from 2 valves to 4 valves, valves and cams changed along the way. power is up from the original bikes...even though they broke and held many land speed records back in the day.

you dont have to look hard at an R69S next to an R1100S to see some striking similarities in the engine.

repoe3

RoundelRider · 04-05-2006, 03:37 AM

Heres a plane being built from our very own S engine!!!

http://www.spang-air.de/willkommen/B...mw_engine.html

Its cool to see how he has arranged things like the intake box, exhaust using a good bit of the factory parts! Heres a taste........youll have to click the linky to see more!

repoe3 · 04-05-2006, 04:11 AM

i think that engine did come from a pelican member.

repoe3

jweicht · 05:34 AM

Quote:

Originally posted by repoe3
so engine-wise, lop off all but the two opposing cylinders and you have the basic layout for the flat twin used on the bikes.

Well, kinda. Radial engines have odd number of cylinders, so no cylinders are actually 180 degrees out from each other. In the case of the engine shown it's a seven cylinder. All those pistons and con rods also share a common crankpin I believe. Someone correct me if I'm wrong - I've been a turbine engine guy my whole aviation career. Suck and blow, baby!

-EDIT- Actually, I just looked really close at the picture again - that's a stacked radial as you can see a second bank of cylinders behind the first. Some serious power coming out of that thing.

repoe3 · 04-05-2006, 05:40 AM

Quote:

Originally posted by jweicht
Well, kinda. Radial engines have odd number of cylinders, so no cylinders are actually 180 degrees out from each other. In the case of the engine shown it's a seven cylinder. All those pistons and con rods also share a common crankpin I believe. Someone correct me if I'm wrong - I've been a turbine engine guy my whole aviation career. Suck and blow, baby!

-EDIT- Actually, I just looked really close at the picture again - that's a stacked radial as you can see a second bank of cylinders behind the first. Some serious power coming out of that thing.

yeah, i noticed the odd number and stacked cylinders in the pic. but was generalizing for the purpose of brevity. its those types of details that had to be tweaked to make it work for a moto-engine.

either way, while they are opposed cylinders they are offset front to rear for obvious clearance issues with the crank. hence you lop off all but the opposing cylinders and there you go.

you could probably write a small essay on the actual differences in the engines, but all that said, every engine came from the first combustion engine design...where you stuck things might have made it unique, i.e. OHV, OHC, DOHC, vtec, vanos, hemi, etc. etc...but they are, basically, the same thing.

repoe3

repoe3 · 04-05-2006, 05:43 AM

take a look at the engine...i circled the two opposing cylinders...now remove all the rest and you ganin room to slide the rearward cylider forward a nudge and there you have it.

strip the prop gear stuff off, slap a getrag tranny and sachs clutch in there and off you go.

repoe3

Steve Carlton · 04-05-2006, 06:53 AM

The picture I posted was of the BMW 801, a 41.8 liter 14 cylinder radial. I was aware that BMW made aircraft engines and the story behind the roundel (also that the blue and white represented Bavaria's colors as well as or instead of the clouds and sky).

I was just curious how literally their motorcycle engine was an adaptation of an aircraft engine, and from what vintage.

racegun · 04-05-2006, 06:58 AM

the jugs on my 1974 r90/6 were made of the same material and by same ppl as airplane engines...it was a colaborated effort between BMW and another German company ...each contributed their own expertise. I read about it over 20 yrs ago.... so thats all i can remember. Barnes & Noble, has books ( or can order) very interesting to be sure. BUT YEA, the same qualities and enginnering prowess was used in the jugs of both. I would guess it carried over to other parts as well. BMW m/c engines are very over built & and understressed as were the airplane cousins

Trex · 04-05-2006, 07:55 AM

Let's not forget that regarding the roundel, blue and white are the colors of Bavaria.

As far as engine design moving from aircraft to motorcycles, I think it was a matter of a form follows function mentality. BMW knew how to make reliable aircraft engines and they understood the advantages of an air cooled engine. The transfer of that design was easy enough for a motocycle and there was the added bonus of a good dose of over engineering. Not just over engineering in design, but I imagine that materials used and methods of manufacturing were very advanced for a motorcycle at that time. That meant a motorcycle that, in a sense, was not measured by miles but hours of use. That engineering craft that was brought over to the BMW motocycles certainly allowed them to hold on to a great reputation for reliablity.

A quick run through Google should get a list of books and articles detailing the alliance between aircraft and motorcycle engineers in those early years.

Just as an aside, the sales side of high engineering always commands a premium. BMWs (cars or motos) were never cheap because they were never cheaply built. Take a look at the sea change that Mercedes went through in the early 90s. Up until around 1993, the engineers ran Mercedes and they defined their goals and built the car accordingly and you marked the car up from there to sell it. Then it all changed. The marketers were in charge. You set a price point and subtracted what went to the dealer and subtracted what went to the parent company and then you built the car to that wholesale price level.

Anyone notice the complaints the last few years about things not working properly on Benzes?

More importantly, are the engineers in charge at BMW? Anyone notice a new marketing strategy for BMW? Hey, anyone notice a new marketing strategy for the BMW MOA (read the new editors comments in the latest BMW ON)?

What a time we live in. Earlier today the exact time was 123456. And Nortons are coming back.

Perhaps, it is the best of all possible worlds.

1100prep · 04-05-2006, 08:12 AM

am not sure about the color but I think the roundel was made because when you see an airplanes propeller spin up to speed, that is the design you see, it looks like it starts to spin backward.

Steve Carlton · 04-05-2006, 08:29 AM

I think there's some doubt about the true origin of the roundel, with the propeller story being the predominant one.

I agree with you, Trex, on the Mercedes marque going downhill quality-wise. Their prices have become much more affordable, and the quality isn't there like it used to be. I hope the same isn't happening to BMW motorcycles. Were the older ones prone to such catastrophic failures as input shafts and ABS modules? I don't expect a BMW to be perfect, but it sure would be nice if the factory would stand behind failures that shouldn't take place, like Mercedes did with their turbodiesels with soot trap oxidizers.

Speaking of aircraft quality manufacturing; that's what I've heard about MV Agustas, with their history as an aircraft manufacturer, to this day with Agusta making helicopters.

Nevermore · 04-05-2006, 08:52 AM

Quote:

Originally posted by Steve Carlton
I'm talking about historically; the roots of our powerplant. How much does our motorcycle engine have in common with BMW's engines from the beginning through WWII?

Actually, there is a great show on The History Channel about the History of Motorcycles. (I didn't sleep at Holiday Inn, but I do watch TV

) the first half hour of the show featured the first BMW motorcycle. During WWI, BMW made airplane engines, but as a part of the Treaty of Versaille (sp?) BMW was specifically prohibited from building anything else for airplanes. The former aircraft engineers decided to design a motorcycle. It was radical for its day with an opposed twin cylinder engine and shaft drive! Sound familiar? Our bike hasn't changed in over 80 years.

Steve Carlton · 04-05-2006, 08:55 AM

And all along I was thinking the Treaty of Versailles was a bad thing...

Mark Estes · 04-05-2006, 08:55 AM

I don't know about that big stacked radial pictured above, but I've seen radial aircraft engines where the end of the crank is hard bolted to the firewall. The prop is fastened to the engine case and the whole bank of cylinders spins around the stationary crank. Maybe they're all like that, i don't know.

Nevermore · 04-05-2006, 08:56 AM

http://www.motorcyclecity.com/History/BMW/index.htm

Here's good link. BTW, I didn't even know they called it a boxer because the pistons looked like they were punching back and forth