The 77 and on column switch arrangement. Both stalks are mounted on a common plate and there is a plastic or Nylon cancelling collar that, with the steering wheel removed, is free to rotate with respect to both the switch assembly and the steering shaft. With the wheels in the straight-ahead position, the collar needs to be orientated as shown with the cut-outs top and bottom and the rib pointing at the indicator/turn stalk, i.e. pointing to the right on RHD cars and the left on LHD cars. When the steering wheel is fitted I assume there are protrusions on the wheel boss that engage with the cut-outs in the switch cancelling collar, so care must be taken to align these. With the wheel fitted the wheel, column shaft and cancelling collar rotate as an item. If the cancelling collar is aligned to the wrong side it will take a much larger movement of the steering wheel before cancelling will occur. And if the wheel should happen to be fitted in other than the straight-ahead position the cancelling will be unbalanced between the sides.
An original late model wheel showing the protrusions on the back that engage with the slots in the cancelling collar of the switch.
An example of an after-market wheel boss. In this case it has two holes that I can utilise for a linking piece that will also engage with the cut-outs in the switch cancelling collar. Another possibility is to use a rod in a through-hole (arrowed), and see if that engages with the slots in the switch.
The metal linking piece that will engage with the two holes in the steering wheel boss and the two cut-outs in the switch cancelling collar.
The linking piece slid over the steering shaft and engaged with the slots in the switch cancelling collar. In fact it was easier to fit the linking piece to the steering wheel first, then carefully slide it on to the steering column.
Barrie's 'gizmo' ...
... attached to his wheel.