Boring Brick

Adams got a point, it's just as costly to get the current one altered than to get a new one. You're better off getting the new one. If you want, I can mod the other one a a spare, up to you.

Thanks for the advice, having looked at the current one again I think modifying the bore to 8mm would weaken the boss too much anyway so it'll probably cost me less in the long run to just buy the one made for the motor

Just a quick question before i go ordering the sprocket, if i drilled a hole straight through the boss of the existing sprocket and drilled a hole through the shaft of the motor and used say an m4 bolt to hold it all together would that work or would it just be a waste of time?

Sounds like you're describing a cotterpin system. It would work in theory, but I'd worry a 4mm hole through would weaken it a lot. A much smaller hole for a pin of some sort, perhaps. You may find you can't drill the scooter motor shaft easily anyway, I imagine it's a decent, possibly heat treated steel that regular small drill bits might struggle to go through. Getting a designed-for-scooter-motors sprocket may be the path of least resistance.

Okay thanks Ellis, scooter sprocket it is

So after realising that i need a sprocket with a 'D' shaped hole and hastily cancelling my ebay order i'm back to square one, which at this point looks like i'll have to get ANOTHER custom job from technobots, only problem with that is that at this point my robot budget is blown for this month and although i do get paid 6 days before the champs it's going to be a very tight squeeze to get the axe running before, so my plan to have the axe fully tested and working weeks before has slightly backfired

Is this not an option? http://www.ebay.co.uk/itm/Electric-S...item27dfccef95

With a half-round needle file you could file out one of the flats in the bore to make it a D shape, or you can grind/file a second flat on the scooter motor shaft to make that fit the sprocket. Both will work.

if you've got a D shaft, is using a massive set screw an option?

Sam, is it the MY1016 scooter motor? If so, I've just taken delivery of a new one for Onyx that has the sprocket still attached. I don't use it (I weld a Technobots one on instead) so if it looks like it will fit, it's yours.

It has got 11 teeth though, not sure how that plays into your axe ratio. The scooter motor currently in Onyx also came with a sprocket that might have been 9-tooth (certainly was double-D). Can't remember if I held on to that one but I'll have a look tomorrow morning and let you know.

Here are a couple of pics of the 11-tooth sprocket:

Attachment 4406

Attachment 4407

Jamie that would be great, I'll have a look at the motor tomorrow and see which model it is, the 11 tooth would lower my axe ratio but I could always add a second stage with the sprocket that doesn't fit the motor