sidecar tuning

[RogerSB]

Considering that diagram, altering the length of the fork leg move the centre of the hub forwards or backwards in relation to the steering axis, and by my reckoning alters the degree of "Trail". So the length of the fork springs and consequent ride height could be a contributing factor.
  Am I right? Waddya reckon?
 Swarfy.

Made me think - so I played around with my drawing, amending it to show different fork lengths by making one with shorter slider and one with longer (click drawing to make bigger). Looking at it, to me it seems the only way to change the trail is by rake (like a chopper or with leading link forks).

Another point to consider is that BSA had sidecar use very much in mind because swing arm A10s and A7s had two rear sidecar mounting points built into the frame, one on the frame under the front of the dual seat and the other down by the rear footrest. They would have considered the trail to be ok or they wouldn't have done that.

Not that my last para will help the original poster who has an M20!.

Rog.

[Kickaha]

Looking at it, to me it seems the only way to change the trail is by rake (like a chopper or with leading link forks)

My experience with sidecars is confined to racing, we ran 3mm of toe in over 1 metre, 1/2 degree negative camber on the chair wheel and 1/2 degree positive camber on the bike, at very low speed like exiting the pits there was a slight wobble, at any other speed it was nonexistent, this was however a more modern outfit

The sidecar lead is also something to look at, where the chair wheel sits compared to the rear axle

You can also change trail by altering the position of the axle, various people have had different clamp on devices added to forks to do this, the other method offset fork clamps

http://blog.3wheelsbetter.uk/2023/02/sidecar-steering-wobble-trail-and.html

https://simplysidecars.co.uk/fittingguide.html

[RogerSB]

Thanks Kickaha, links to two good informative articles there. The 3wheelsbetter one I've not read before, but when reading through the simplysidecars article I realised it was where I'd copied some of my bits from.

In the mid 60s I fitted a Canterbury Double Adult to my A10 GF (the one in my pic) with the help of a friend who worked for Kings of Oxford, a well known m/c dealer in the UK. We fitted it in a cobbled lane behind my parents house and when finished my friend suggested I take it up the lane to try it. Off I went, in complete ignorance, and nearly hit the wall either side of the lane - we'd forgotten to firm up the handlebars by turning the steering damper down. So when I fitted the GP Manx to my current GF I had some idea of what to do . . . and what to expect. It took me (often with my wife's help) from Oct 19 to Jan 20 (just checked my notes) to get it to handle to my satisfaction. Adjust something and it affects something else, get all measurements spot on, as you think they should be, tweak all the bolts up really tight, check it again . . . and it's all changed  .

From standard, when riding solo, I've fitted 11 3/4” heavyweight sidecar springs, NJB 126 lbs/in rear shocks, 18T engine sprocket, new IWIS chains and Norton semi-western handlebars, that has 7” pullback and a 4.75” rise. Then I added indicators and LEDs so the dynamo could keep the battery charged. I didn't need to change the front tyre though.

I can now steer it in a straight line, with just fingertips, with confidence, but I rarely go above 55 mph. The main thing I find that makes me very aware of the sidecar is the heavy steering when turning tightly to right, such as going around a small mini roundabout, but turning left it's very light and easily turns in it's own length.

Rog,

[Brandis]

I made a steering damper.   It's a completely different ride.  Zero wobble., no matter what the sidecar toe-in is. Steady right through the gears.  Thanks for the damper suggestion.

[limeyrob]

When you look at the old drawings of how to set up a sidecar a big element is the road camber. The bike is shown sitting upright and the sidecar lent over down the camber.  This is from the days of British roads with a steep curve. We hardly see that anymore except on country lanes and a lot of roads are flat but with a slight slope to one side. So the first thing is to look at the roads you are likely to ride and set the lean out / in somewhere that is a reasonable compromise.  When i had an outfit we lived in a village and I had it set for the local roads, I went on a main road with no camber and the front tyre scrubbed the whole way.
The second piece of advice I found very helpful was to use the brake and throttle as your primary means of steering and only resort to heaving on the bars once you had done that.  I would use the analogy of an airplane: you climb and descend on the throttle not the elevator.  A sharp dab on the rear brake will turn you right quicker than the bars will

[RogerSB]

A sharp dab on the rear brake will turn you right quicker than the bars will

Too true, throttling down with a little touch on the bike's rear brake coupled with the sidecar's continuing forward momentum pulls the outfit around to the right nicely and opening the throttle accelerating the bike ahead of the sidecar takes it nicely around to the left.  That's why mini roundabouts with their small diameters tend to make a sidecar turning right more noticeable, as it requires you to slow down to almost a walking pace and then you have no choice but to open the throttle to get around it . . . and that's just the opposite to what is best.  Driving a sidecar requires a completely different technique to riding without.

For those not familiar with sidecars the above applies when driving on the left and a sidecar is attached on the left side. With a sidecar attached on the right the opposite applies.

Here's one to think about: When moving slowly and turning the handlebars left to full lock the sidecar wheel goes backwards. When I had my Canterbury double adult outfit I used to park it a narrow back lane at the back of my parents house, which was a cul-de-sac and I had to turn around 180 degrees to ride out. Turning around left it turned in its own length, bike wheels going forward, sidecar wheel going backwards . Demonstrates it very well.

Rog.