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I'm not sure I see the good things that come from trying to transfer any decent loads from steel structure to the aluminum engine/tranny case. Somehow I would think that when you get to loads that are high enough to really make a difference, you will be damaging the aluminum. Dunno...

Kurt in S.A.

Kurt in S.A. wrote:I'm not sure I see the good things that come from trying to transfer any decent loads from steel structure to the aluminum engine/tranny case. Somehow I would think that when you get to loads that are high enough to really make a difference, you will be damaging the aluminum. Dunno...

Kurt in S.A.

I hadn't thought about that, but it's a good point. Engines that have been designed to be a stressed member of the frame (such as the Oilhead) have their mounting points designed for such stresses. I have no idea if the Airhead engine mounting points can handle such stresses, and I'm not sure anyone does know. I do know that I haven't seen any Airhead race frames that used the engine in that way. Vanzen has seen a lot more Airhead race bikes. He would probably have some useful input.

Interesting, there are very few pictures of the factory race bike frames without the bodywork, but I just stumbled onto these. The Butler and Smith race bike: Without it's skin, showing the highly modified frame, with no top engine mounts: And then this one, just labled a BMW R75/5 "Imola": Notice the similarity to the B&S bike:

But the brace from the gearbox to the spine have been used for years (did BMW use these?).
With my ideas around the rear of the frame - the forces are being directed to the crankcase - that's one big sturdy casting!

There have been lots of frame bracing threads over the years that seemed an awful lot of work for questionable gains.
Fabricating and welding of gussets, braces, tubing etc is the easy part. Knowing exactly where the flexes occur is the baseline.
I'm surprised that the ultimate add-on structural reinforcing kit for our frames hasn't been perfected by now, and become well known and readily available?

Nobody mentioned Tony Foale and his website:

http://www.tonyfoale.com/

Kurt in S.A.

I've been thinking a lot about vanzen while reading this thread. I hope he is well. I miss seeing pictures of his project.

That Imola is Imazing.

Major Softie wrote:That Imola is Imazing.

Sounds good too! Apparently this was the bike raced by Helmut Dahne in his signature red leathers: http://youtu.be/D5d6M44ZZv8

Here's a photo of a racebike with an interesting brace between the motor and frame.

I wonder if it transfers a lot of vibration to the handlebars, footpegs, and so forth. It looks like there are also some diagonal braces welded in the aft section of the main frame (see directly behind the aluminum brace).