So, a little progress.
The H pattern gearbox works really nicely, with a very smooth and positive action, with decent weight to the side to side movement and good front to rear action. I decided to replace the aluminium detent plates with PTFE sheet, and that really improved the smoothness, resulting in a less gritty movement, although the more slippery PTFE needed me to double up on the detent balls.
I eneded up using asymmetrical springs on the side to side shock absorbers, this gave me a bias to the 3rd/4th gear plane as you would get in a real gearbox, and I boosted it with a small detent ball to ensure it returns to the same position each time.
I am toying with the idea of adding a front to rear damper to see if that makes a nicer weight to that plane, will try it and see.
I have never been able to get the G25 to correctly limit the travel of the wheel in rFactor (worked in other games) so I decided to take the opportunity to add a selectable rotation limiter to the extension shaft. This will give me 180, 360 or 720 degrees at the turn of a rotary switch.
First up was to make the G25 adapter with the driving gear and the universal joint to couple to the extension shaft
I have to make an adapter to sit under the motor housing to hold it at the 25 degrees necessary to reduce the angular movement to a minimum, and I have also to sink the motor unit down so that the axis is as low as practicable
The driving gear meshes with a gear with 2 more teeth, so by putting stop blocks on the driven gear coincident with the correct teeth and at different pitches, I can use a rotating plate with cams to push pins into engagement and so limit, depending on which pin is engaged. The rotating stop plate will use microswitches to make the plate stop in the right position automatically.
I suspect both the stop pins and the blocks on the gear will end up being made from metal as I don't think that the ABS will be strong enough over time, but the gear was made 30mm wide to ensure that has enough strength to cope.
Next step is to evolve the attachment of these units to the frame