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Breaking some laws....of physics


Hey Hack'n and Claude;

Yeah....I beveled the ends of both mating tubes real well, plus, the inserted central portion of tubing is slightly larger in diameter, giving me more 'meat' to weld to. Of course, that ended up making the ends of the struts have a fairly neat taper down to the bolt.

I ground off the upper portion of the welds, and ran another pass or two, just to make sure penetration and thickness of the weld was at least as thick as the parent material. The taper, built in because of differing diameters allowed me to lay the build-up to an even higher level, while still maintaining a smooth overall appearance (although, I'll have to add a little Bondo here and there, where the inevitable little pockmark or two appears). But since I'll paint the struts anyway, that's just a plus in my book.

I've spent quite a bit of time in Hannigan's showroom and shop, crawling over and under, around and in and out of his installations, and I feel pretty good about mine to this point. With just the two front connections and the upper rear connection made, I can raise and drop the sidecar frame and bike two or three feet, and nothing shakes, twists or offers any kind of reaction save just plain solid....

Still and all, I've got my fingers crossed; that cantilever bit is still hard for me to get used to.

Later Guys! and thanks....


I think you're concerned unnecessarily about the sidecar being "cantelevered" out on one side of the bike. Well, yes it sticks out on one side, but properly triangulated braces will keep everything under control. I don't really think of the sidecar as "cantelevered".
The concerns that have been expressed are where connectors, axles, swing arms, etc. are cantelevered (supported only on one end). Your sidecar braces aren't cantelevered, assuming both ends are attached. And I like having both sides of the bike frame tied together. Those welds in the strut tubes are basically resisting push-pull forces, not bending forces. I've had similar tubes butt welded, and also made up connector tubes by inserting the threaded ends into a slightly larger diameter tube for the middle part. In that case, brass brazing can be almost as strong as welding, since brass is almost the same tensile strength as mild steel. Obviously, brazing wouldn't be advised for tubes butted together. When making up struts, a larger diameter tube is stronger and more resistant to bending than a smaller diameter tube, even if the larger tube has a thinner wall.
On a related subject: when visiting "professional" sidecar shops, be aware that they must operate within the "time is money" frame of reference. So, even if it might be possible to fabricate a special clamp/strut/connector that would be stronger or more slip-proof, it makes economical sense to use standard adjustable fittings that are applicable to a wide variety of machines. The owner/builder has the luxury of spending hours with the cutoff saw, drill press, welder, dremel grinder, primer, etc. to produce a part that (if done correctly) is stronger and more reliable.
What I find most amazing is that almost all of the professionals I've met seem to believe that their system is better than the others', yet everyone has a different system. I continue to believe that it would--in the long run--be helpful to have a sidecar "engineering" book that would suggest appropriate techniques, dimensions, etc. I've gathered considerable information from here and there, but received no encouragement from the industry to produce such a document. One of these days I'll do it, and you can expect the fur to fly. But a "sidecar assembly" book would certainly answer a lot of questions for the enthusiast.


Okay, between the several of you folks, I'm pretty much convinced. My background includes several stints as civil engineer on larger, taller and even unusual buildings (8 story Sheraton Hotel, huge Paper Mill, etc.), and we simply had to pay careful attention to any kind of overhang or cantilever. Its hard to get above your raising, isn't it?

Talking to David Hannigan the other day, he informed me that the sidecar isn't nearly so mysterious and difficult as many people make it seem. In fact, he said, he's had lots of very satisfied customers attending sidecar seminars at various rallys and so forth, who when leaving the seminar said they'd never realized it was all so tough; that if they'd heard the seminar beforehand, they'd never have considered buying a sidecar after all.

When I think about it, looking back at many of the sidecar set-ups I've seen, the differences seem not so much to be related to strength of the system overall, as in the varying degrees of elegance of construction seen in those set-ups.

So I expect you're right....ask ten different sidecar fabricators/installers, and you'll like get nearly as many different approaches, all of them equally adequate for the task at hand.

On the other hand, certain things, forces and so forth, must remain the same from sidecar to sidecar....and that's where the potential book you mention would be most helpful. To tell you the truth, I've spent many hours on various websites and links; and until I stumbled upon this forum had many more questions than answers. Its good to finally get some of those questions answered so completely.

Thanks again Sir!