Interesting new BMW 1800

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AdrianS

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BMW have announced the
R18.


It's an 1800 cc air/oil cooled flat twin.
With pushrods.

91 hp @ 4750 rpm, 111 lb.ft from 2000 to 4000 rpm.

So thats 84.5 hp at 4000 rpm, 74 hp at 3500.

It will cost the earth, but at what weight would it be a viable candidate?

Edit: added image
 
Last edited:

Vigilant1

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So thats 84.5 hp at 4000 rpm, 74 hp at 3500.

It will cost the earth, but at what weight would it be a viable candidate?
Well, if we just need 75 HP, we know we can have it easily and cheaply at 3400 RPM in a smoother 4cyl flat engine (VW derivative) for about 160 lbs (with starter, electrical system, dual ignition, prop hub, proven prop bearing, etc). That's a starting point for comparison.
 

AdrianS

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The weight should be similar or less : same capacity, shorter crank, only 2 pistons/rods, etc.
The reality may well be different.

How long before the first wrecked one turns up in a scrapyard?
 

Vigilant1

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The weight should be similar or less : same capacity, shorter crank, only 2 pistons/rods, etc.
The reality may well be different.

How long before the first wrecked one turns up in a scrapyard?
Those slab-sided BMW cases always look massive, but apparently they don't weigh a lot (based on the R1100 etc weights).
Wrecked ones? It seems BMW motors are usually easier to get in Europe than here.
The torque pulses at some RPMs can be a challenge from these twins. Some PSRUs do work.
 

AdrianS

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Unless there's a built-in reduction we can use, I was assuming it would be direct drive from the flywheel end.
One downside would be that the exhausts would be away from the prop blast.

As far as availability, this thing is apparently positioned as a Harley-style cruiser, so they should get to the states. And you know someone is going to say "watch this" on their brand new bike...
 

Tornado Flyer

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I tried a BMW 1150 with a Hirth gearbox. Ground runs revealed tons of power but in less than an hour the rubber doughnut to the gearbox disintegrated and I abandoned the idea. It was rock steady smooth until I put on the three-blade warp Drive prop and then the power pulses felt like they would pull the plane apart.
 

Air Trikes

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I tried a BMW 1150 with a Hirth gearbox. Ground runs revealed tons of power but in less than an hour the rubber doughnut to the gearbox disintegrated and I abandoned the idea. It was rock steady smooth until I put on the three-blade warp Drive prop and then the power pulses felt like they would pull the plane apart.
This problem is well known and has been solved years ago. Decision - centrifugal clutch. Your propeller choice is also not the best, Warp is too heavy. We sell these conversion kits and converted engines. More info Air Trikes: Engines and Conversion Kits.
 

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galapoola

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Is anyone running these direct drive with an add-on case for a thrust bearing?
I'm thinking about what they do with Corvair installs.
Those setups under stress the engine at lower RPM so perfect for aircraft reliability.
 

addicted2climbing

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This problem is well known and has been solved years ago. Decision - centrifugal clutch. Your propeller choice is also not the best, Warp is too heavy. We sell these conversion kits and converted engines. More info Air Trikes: Engines and Conversion Kits.
Just had a look at your site. Your BMW setup looks great. A bit too big for the airplanes I am considering, but curious if you ever made a gearbox for the Briggs Twins? Ace has them in India, but Canada is a whole lot closer...

Ever try one on a Half VW?

Marc
 
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