Need help with spinning weapon

[CallumMcM]

Hello

I am brand new to roboteering, a few friends and myself are designing a horizontal bar spinner featherweight robot and need alot of help with what motor to use, the dimensions of the bar and also how the motor would connect with the bar and spin it whilst also sticking on a budget of around £150-200 for the weapon

Thanks very much

[R9000]

Hey. Never made a spinner but I've seen lots, so take what I say with a pinch of salt. You'll want a brushless motor for your spinner, something with a high kv rating if you're going for massive RPM on the bar. Probably an outrunner like a helidrive or equivalent. Have a search to see what I mean, but make sure you check all your stats before you buy anything. As far as connecting the motor to the bar, every spinner I've seen uses a belt, usually with teeth, and pulleys that lower the speed of the motor a little (small one on the motor shaft, larger one on the weapon). I assume this is so that they slip under shock, and don't just strip like gear teeth. Remember you'll also need some way to adjust belt tension. As for the balancing and dimensions, I don't know enough to help with that. :P

[CallumMcM]

Thanks alot Will have a search now but what I was pondering is how I could drive a horizontal bar spinner from the centre with belts

[R9000]

Is your spinner somehow in the centre of your robot? I don't quite understand what you're asking.

[CallumMcM]

It will be very similar in concept to this picture I found on the internet, Having the spinner mounted in pretty much the same wayfiasco.jpg

[CallumMcM]

I was wondering if the belt method is the most effective or if there is any other way to do it

[R9000]

Considering it's the most common, I'd assume so, though of course that's not always the case. The only other methods I can think of are a gear train or connecting the disc directly to the motor, which both risk damaging your gears and your motor on impact. Belts on the other hand, are cheap-ish, easy to replace (you can even 3D print them) and can cover a decent distance, as shown in the picture there. You can see on top, the little idler wheel that acts as a belt tensioner.

[john_frizell]

Belts are good, they help protect the motor from shock damage when the spinning bar hits something. Don't forget that spinners are very dangerous to their owners, particularly when you are testing them. Before you do your first test spin think about what will happen if the bar comes off or breaks at full speed.