drive

how would i add a bearing to a wheel and the axle

between the two? Bore the wheel out and press it in (needle roller probably best for this)

Rotating axle, you need to make a bulkhead either side with a bearing pressed into it, can use needle roller however ball bearings are probably better.

If I'm making a 2 wheel drive wedge should I have 2 wheels or 4 wheels

Well considering you say it's a 2-wheel drive wedge, I'm guessing two wheels would be the logical choice :P

I think he may mean doubling up the wheels, having 2 lots of wheels on the same axle to have 4 wheels worth of traction but 2WD manouverability. If you can get away with it in the weight and design of your robot, then do it, but it won't make a huge difference if you can't.

Ahh, I follow now :)
Yeah, the extra surface area may improve traction and as such, pushing power. But remember that there is only 13.6kg of weight pushing that onto the floor, which isn't a lot in the grand scheme of things, so the increase won't be huge.

But as David says, if you've got the weight and space for it, may as well do it.

Is it possible that he means having idle wheels? 2 drive and 2 freewheeling (lol)? If that's the case then the two that aren't driven will be more inhibiting than useful I think. It would make turning quite difficult unless they're very close to the drive wheels. Instead of wheels you could have small casters or even just smoothed bolt heads would do fine.

If it's for 2 wheels on one axle for drive, then I can see why it would be beneficial but - for the pros - is the same weight spread over more surface better than spread over less surface? If more weight is on a single wheel will that be better than two wheels with the same weight? I can't get my head around it! I think that makes sense? Or maybe it does just not on this scale, you'd need to have 16 wheels before more surface area is less good. :lol:

Edit: in fact now that I think about it, by that logic tracks would have less grip than wheels which is not true. Just scratch what I said! :uhoh:

I was thinking of 2 drive wheels and 2 idle wheels :oops: but what I was hoping to do is that in the future I turn it into a 4 wheel drive bot with the same frame but at the moment my motors and batteries are too heavy for a 4 wheel drive bot and I don't really have enough money (should of added it with the question, sorry)

what batties you using?? should be more than about 2kg max for batts with 2 drills being 1.5kg ish

I am using drill batteries but the motors are ridiculously heavy