Saturday, May 27, 2017

Six mounts on my rig

So many projects on the go but something new comes my way and suddenly takes up all my attention even though it works just fine already...

Having taken the fairing off the Beemer R80 combo all the sidecar couplings are exposed to be tweaked. Since buying the bike I felt that there was a little bit too much flex between bike and sidecar. I'm not sure if some flex is a good thing in a combo or not but instinctively I feel it should be as rigid as possible. The naked look exposed a broken lower fixing at the front which I replaced with a new BMW frame mount from Watsonian I had that was kicking around the workshop from a previous project.That stiffened up the front a good bit but the rear still felt a little springy and the front could do better.

A few years back I picked up a cheap bucket full of sidecar fittings at a local auction. In the way of the compulsive hoarder I knew they would come in useful some day. As indeed they have. A rummage around yielded the fixings to add a fifth mount at the back, then I realised that I could even add an extra at the front too so why the hell not?

I felt that the rig steered slightly to the left and had a little too much love for the gutter so before adding the new mounts I gave it a spot more lean out and took it for a test ride. Improved but I don't really have a benchmark for what a really good combo rides like. This however feels pretty good to me. One negative result of taking the fairing off though is a weight bias off the front and to the rear which gives the front end a few low speed wobbles. Previously it didn't need any steering damper, now I reckon it could do with one. Sidecar mountings truly are a dark art!

Details on the extra mountings with the pictures below. The result is a truly rigidly mounted sidecar. No worries there. It handles pretty well but improving one thing has highlighted issues elsewhere. Those rear shockers are pretty dreadful, the sidecar one too. Funny how these projects grow!

Fairing-less she looks better but has less wind
protection and cruises a little slower too. Success
or fail? What price style?

And the other front quarter.

Extra rear mount added by drilling the frame just in front of
the rear shock mount, turning down a spacer to brace the mount
and stop the plate steel crushing on tightening and adding a
'sidecar spade'.

The top mount at the front originally fixed on
to the cross brace in front of the engine. I thought
that this resulted in a slightly too long mounting
bar and gave a parallelogram with the bottom mount
rather than a nice rigid triangle. So I moved the mount
across to the front downtube and cut about four
inches off the bar.

The front also gained an extra mount. This triangulates it all
up very nicely. It will all be painted later when I am confident
I've got the geometry correct.

And the extra rear mount. Again, needs tidying up. I had to put a
spacer on the spade as it conflicted with the pannier bracket
and shocker through bolt.

Like the Forth Bridge!

Rear view. I put the Craven panniers back on
whilst I was tinkering. Funnily enough I found that
they looked a bit small with the fairing fitted so
took them off. Without a fairing the proportion
returned so on they went again.

All her glory. Still a work in progress though...

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