Saturday, 8 October 2016

The XS Triple Sidecar - Building a subframe

... that ticks all the right boxes for me. (And that's quite a few!)

Ordered by personal importance
  1. Provide a sturdy set of mounting points to attach the sidecar to
  2. Prevent the frame from punctual overloads by distributing the stress as evenly as possible
  3. Retain the usability of the XS'es kickstart (even though it's only a backup, but still nice to have, especially in Winter)
  4. Not obstructing any place that has to be accessible for routine maintenance (daily driver...)
  5. Easily installable and removable, with all the bolts the same size and nicely reachable
My first step was to have a very close look at the frame and come up with a concept on how to realise both subframes so they could meet those requirements best.

 Then I had a look around and tried to find a shop that would provide the necessary mounting hardware, which directly affected the diameter of the tube to be used for building a properly strong subframe.

The next trip lead directly to my local metal-supplier and saw me buying quite a length of various tubings. The main bit of the subframe has been built from 25x3 tubing, plus the odd bit of tubing, where the inner diameter matches the parts of the frame, where it is supposed to be attached.

I started off with the front subframe, because you have to start somewhere and I expected it to be the more simple one to be honest. It's a relatively simple construction, which wraps around the right corner of the engine and connects both downtubes.

Not really that much to it, right? Well the rear subframe put up a bit more of a fight and left me scratching my head for several days. Mainly because I wanted to link both rear downtubes down from the shock mounts as high up as possible, as that's where the frame on my old XS 750 sidecar cracked more than once and also include as much of the swingarm pivot area to give the subframe the much needed strength.

Now that's the rear subframe all tacked up, but in order to give it a bit more strength more needed to be done. Most importantly all the tack welds had to be welded and dressed up and in the picture above the lower sidecar mount is held on with three tacks, once I found the right spot, but that was (of course) not the proper way to do it. After all most of the forces, when cornerning go into the rear mounts...

Ball cut off.

 Drilled a hole for the threaded bar to go through.

 And welded in from both sides, so it's not going anywhere anymore.

 Cooling the ball with a wet rag - check out the blueing underneath.

 And there you have the finished product.

The fact that this fine piece of subframe has taken me two weeks has a) strained my motivation quite a bit and b) is the reason behind the lacking updates on the blog recently.

The next posts will deal with the sidecar brake and axle.



  1. We've all suffered from "strained motivation" at one time or another, I know exactly what you mean. Good work and you got there in the end!

    1. Cheers! Yup, the subframe put up a good fight and I honestly underestimated the amount of resulting headscratching to make it fit just right.

  2. We've all suffered from "strained motivation" at one time or another, I know exactly what you mean. Good work and you got there in the end!