Was thinking about the drive last night. Why do you even need the shaft collars that are on the inside upto the bearing. Why not remove them and just install a steel/aluminum sleeve on the shaft in its space. The sprocket hubs are keyed and grub screwed in place on the axle to the width of the 2 attachment chains so if you made 2 sleeves the same size 1 on each side they would centre it all and make it a fixed width as they would be hard up to the centre of the bearing. Blue part is the sleeve in the drawing. What you think?
Just had a look in my photos folder and Mike Senna didn't use any collars on the original track system. He had the wheel hubs mounted on the axles all the way up to the bearings. I'm guessing he used shaft collars on his new track system like I'm building because he didn't have a lathe and was easier for him.
I was thinking why not just make the blue part (The steel sleeve) Make it part of the hub that way there is 1 less part to worry about.
Orange = Key, Pink = sprocket hub, grey = axle, green = bearing, black is the idle wheel arm/bearing holder. Hub is also grub screwed 1 onto the key and one 90 degrees from the key.
Doing it this way would be a matter of undoing 2 grub screws on the hub that has the sprocket on it to remove it from the axle and then the axle would come out the other side of the bearings with the other hub/sprocket still attached. Would need to remove the tracks 1st but that's just a matter of removing 2 chain connecting links.
If I used shaft collars I will have to remove the hub 1st then the shaft collar too remove the axle out the other side.