Beetle Spinner Weapon Braking

Dear all, Please be kind I’m looking at my first build.
I’ve been looking at the rules about spinner weapons.
I’ve seen in the rules for BBB the spinner should stop within 30 seconds of being switched off.
Generally will the magnetic resistance in the driving motor (brushless) be enough for this, or is some sort of fail safe breaking system normally used?
I’m also a bit confused with the weight limit for the weapon, 10% of Bot weight, so 150g maximum for a beetle bot? Does this rule apply at BBB events?

Hi John,

Welcome to combat robotics, it’s a wild ride.

As far as spinner braking goes, I don’t even bother with braking on my ESCs - the friction in a belt or gear system is usually enough to stop a weapon from the sort of RPMs the UK tip speed rules limit us to.

There isn’t any rule on weapon weight in the UK beetle scene that I know of. Most UK events run rules similar to the BBB ones, these can be found here: BBB: Build Guides & Rules

I would recommend against building a spinner for your first bot, they can be incredibly dangerous - you basically end up building a power tool from scratch, and one that has way more ability to go out of control and wound you without a proper testing setup. I’d really recommend having a look at doing a control bot, something like a lifter or grabber. Craig’s Snappy is a fantastic example:

Best of luck with your building journey

1 Like

Hi Henry, Thank you for your advice on the slow down. I think your right, certainly a pushing bot would be a good start. my two kids are driving the specifications :- ) .
Hoping to be ready by Feb event, but May seems more likely.


Something tells me you read the FRA rules, which annoyingly are pretty archaic as while technically our governing body it still kind of holds on to the time when there were only 3 relevant events (2 of which identical in terms of ruleset) that needed governing.

Hi Harry, Yes indeed I’ve been looking at the FRA rules. My feeling at the moment is I’ll stick to that 10% rule to avoid arguments. (Spinner weapon 10% or under robot weight) Cheers, John. Or have an Aluminium and Steel version to swap out.

Genuinely, I wouldn’t bother at this class at all. To my knowledge this has never been enforced for any beetle event. 150g is very much on the low low end for any kind of rotating mass and that’s about half what most the “big” spinners weigh.

Keep an eye on your tip speed and your failsafing and locking bars as these are all essential!

I cannot fully recommend a spinner for a first off but depending on your background and how much you’re willing to try things out and compromise it’s totally possible.

Even if you can’t get done for February please come and watch and shake some hands! The social side is great and there is no substitute for talking shop with people and getting some hands on experience.

1 Like

Yep happy to say the 10% thing is an outdated FRA thing - we have no such rule in UK beetles but everything else Harry says is absolutely essential - 250mph tip speed max, failsafing and locking bars.
Looking forward to seeing progress on the design and build!!

Hi Craig, thanks for clarifying this.
Thank you, looking forward to some progress as well :slight_smile: