Swing arm stays angled from frame

[SaMoSteps]

I bought a two-wheel drive motorcycle with a totaled frame, and just for kicks I'm planning to build a scooter utilizing only the front engine (and fork assembly).
To be sure, this is only a "scooter" for tooling around the neighborhood --not meant for high(er) speeds--, and a project to keep me off the couch and watching football.
It appears that ALL swing arm design uses diverging lines for the stays from the rear axle toward the front pivot. In other words: the width between dropouts for the axle is wider than at the point where the cross member joins the two stays (around the tire).
Since this is a wacky sort of thing, I was thinking to reverse that custom and have the pivot points at the frame wider than the width between the axle drop outs.
Question: anyone see or know of any problems for trying this?
The approximate measurements will be 3.5" between the drop outs and 5" at the frame (cross member of the swing arms stays).

Big thanx in advance!

(see attachment for drawing)

 

[BrianPetersen]

Link is to your local hard drive ... that ain't gonna work!

But I gather that you want to have the swingarm outside of the frame pivot rather than inside. As far as the geometry is concerned, it makes no difference which way it's done.

 

[SaMoSteps]

Gotcha... I thought the pic would be inserted into the email. I figured it out.

Okay, so, as I thought it doesn't matter for frame geometry. But the two says must NOT be parallel, right?

Thanx!

-G

 

[MikeHalloran]

There is no reason the swingarm arms should, or should not, be parallel.


Mike Halloran
Pembroke Pines, FL, USA

 

[SaMoSteps]

Oh. Hmmmm.... I thought it was a strength thing.

 

[Timelord]

Please tell us more about the 2 wheel drive motorcycle. The only one on the market to my knowledge is the Rokon (), but you mentioned a "front engine" and the Rokon only has one motor. I curious exactly what you have.

TIA,

Timelord

 

[MikeHalloran]

I thought it was a strength thing.

It is. You signed on as a mechanical engineer, so figuring out the effect of geometry on strength should be no big deal. ... or maybe you need to find an engineer friend to help you.

At least, don't go crazy trying to make the new parts lighter than the ones you're replacing.

In fact, since the frame was totaled, maybe you should study some other bikes with frames that are not totaled.


I'm also curious about what you bought, exactly.


Mike Halloran
Pembroke Pines, FL, USA

 

[SaMoSteps]

Funny you should ask! I was very curious about this thing so I started looking into it.

I never did see the rear half of the bike--apparently, it was run over by a tractor and tossed away. I guess that's part of the reason I got this thing for 50 clams. This is the front half of a Solex bicycle. Apparently, another weekend mechanical-fixiter-hobbyist-junkie-dude like me had two of these and combined them: he attached another front motor on the rear, rigged the throttle to act simultaneously, and from his description it was just as good as the tractor getting from one side of the farm to the other--sun shining or rain falling. So, I guess it wasn't a "true" two wheel drive motorcycle after all. If I can wrangle some pics from the old guy I will surely post them!

 

[SaMoSteps]

Hey, Mike,
I didn't know what to do to sign on to simply get a question answered... didn't mean to mislead.
The frame is from scratch. I don't have the frame from this "bike". The project, really, is just to keep my welder from collecting dust. I could easily mount this on an existing bike frame, but what fun is that??
I'm going to use 1/2x1" tubular steel for the frame and swing arm. Pretty easy (and strong) stuff. I've done something similar in the past but this time I'm going to make it full suspension. I weigh 200 lbs., and the thing won't go faster than 20mph, so lightness isn't really a major concern. It's going to be to simply tool around the streets and make all the neighborhood kids jealous as heck.