Hi. I’m working on a design for a small rail based camera dolly. The dolly holds only the camera on a small carriage running along two parallel 42mm aluminium poles supported on scaffolding brackets. It differs from the normal dolly of this type in that it has as simple set of gears and a fly wheel inside to generate inertia and make the camera moves more fluid. The basic structure is three vertical, parallel sheets of aluminium with three shafts running between them. One carrying the flywheel, one carrying gears and the last the axel of the two front wheels. I need to keep it as quiet as possible so I’m using nylon helical gears and polyurethane wheels. The shafts are mounted in bearings where they pass through the aluminium panels. This is the first time I’ve built something like this so I thought I’d try to find somewhere to try and ask some advice about what I’m doing. The things that concern me are quite simple but I just can’t find out how I should go about them. Fixing the bearings in the panels. The only way I’ve found of mounting the bearings so far is folk freezing the bearings and heating the panels then pressing the bearings in and when it cools they should be fixed in the panel tight. Is this a good idea, I don’t like the idea of heating aluminium, is there a better way of going about this? The other thing is that if the axel passes through the two panels supported in the bearings how do I prevent the axel sliding out of place. I thought of putting collars onto the shaft either side of the bearings but I don’t want any friction with the collars rubbing against the panel creating drag and noise. So I thought of putting spacers between the collar and the bearings so they grip only the central part of the bearing but now I’m concerned that pressure from the side on the bearings, if the wheels get a knocked from the side for example during transport, that this might damage them, are they designed for the kind of thing? The shaft at the moment is 12mm and the panels 10mm but this can be changed if it would solve the problem. Anyhow I can’t help thinking that this is a very common situation and there must be some standard way of going about it. I could sandwich the bearings between two sheets with recesses milled into them but I’d like to find a more simple solution. But I’ve not managed to find it anywhere so I thought I’d come here and ask if anyone could help, or if I could just be pointed in the direction of somewhere I could learn this stuff. Thanks, N.