we’ve just been having problems trying to get things working - we tried collars on the axle - axle is too big and so much pain in the arse this year ( we dont have a machine shop this year 
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anyone can offer any help or pics? it’d be much appreciated
too big? what do you mean? the diameter is too big or the length is too long?
I’m really not sure what you’re asking here.
To help you better, you might want to post a picture of the issue. If the shaft is too big, if you can find someone who has a lathe, then you are in business. A picture would really help us to give you a suggestion.
ivey
Assuming you mean driven wheels:
There’s 2 basic ways of mounting drive wheels:
You mount the sprocket to the wheel and leave the bearings in the wheel. Then use bushings to space and center the wheel where you want for chain alignment. This assumes you have a coupling or bolt pattern in the wheel hub that matches your sprocket. Then spacers to hold the sprocket out off the wheel.
You take the bearings out of the wheel hub and put a bushing in their place, that hub/bushing is either pinned or keyed to the shaft. Then you either set screw, key or pin your sprocket to that same shaft. Then 3rd you put bearings in the frame to allow the axle to spin.
Chain tension:
Option 1 allows you to slide the wheel back and forth if you make a slot in your frame. So you pull the wheel tight and then tighten the axle.
Option 2 would either require you to slide the drive/motor side to tension the chain or you’ll have to add a chain tensioner. This is because your axle bearings are going to be locked in place. Although you’ll see a lot of teams use pillow block bearings that can be slid for/aft to tension the chain.
Otherwise if your just mounting a free axle, use a bolt/locknut/washer combo.
the axle diameters are too big - at least for the collars
If it’s just slightly too large, chuck up the shafts in a drill press/drill and use some emory cloth to sand them down. Sometimes the edges of the face of a shaft can have burrs on them that interfere with sliding a collar/gear/sprocket on.
Are you using the FRC bolt together frame or one of you own design. If you are using the prefab base then you are using the 3/8" x 5" bolt as an axle. You can make spacers out of steel tubing that has an inside diameter of 3/8" or find a suitable solid, drill a 3/8" diameter hole through the length of the solid and then cut to length. I bet you can find the right size pipe (3/8" inside dia. please) at a hardware store and cure your problems.
You should be looking at Chassis%20&%20Drivetrain%20Assembly%20Instructions.pdf on the IFI website or have a hard copy in your hand.
where’s the chassis assembly instructions? - like, a link? or anythign? ( per request of our team leader)
All the documents including assembly instructions can be found on the Innovation First Kitbot site at http://www.ifirobotics.com/kitbot.shtml.