18V motors in 12V drill gearboxes

On a scale of one to ten, exactly how bad an idea would this be?

Recently invested in some 85A BotBitz ESCs (finally!) and I'm wanting to get my entire system running to 6s LiPos so I only need one battery for the lot, naturally running 12V motors at nearly double that isn't the best idea, so I was looking at getting some 18V motors and replacing the 12v ones with those (specifically, these motors http://www.gimsonrobotics.co.uk/HRS5...r_12V-18V.html)

Would this work, and if so how many amps would this sort of setup draw during standard operation (from a battery point of view)? Thanks in advance!

It depends quite a bit on how rough you are with it when driving. A 12v motor and an 18v drill motor perform essentially identically at their nominal voltages; the 18v motor may have slightly superior torque. However running any overvolted motor into a drill gearbox is asking for trouble. We ran 12v motors at 5s in Tormenta 2, and we were killing gearboxes and thus frying motors left and right. To try and fight this we moved to 18v motors at 5s, we figured the lack of overvolting would reduce the kick of the motors and so reduce some of the stresses on the gearboxes. That uh... didn't go to plan. We were killing just as many as before. Not entirely sure how/why.

I think there's the simple underlying issue that, drill gearboxes, as they are, aren't good enough. You must replace all gears with metal ones (can be bought at gimson), and I'd recommend trying to keep a feather finger on the throttle if you don't want the carrier pins, on the second stage of the gearbox, to come loose and jam the gearbox. The latter failure is what plagues T2. There are other failure points too.

Basically, you can use them, but they will require lots of maintenance unless you're very kind to them. That's our experience. I would not recommend overvolting any motor combination with these gearboxes, as the additional torque produced by an overvolted motor makes preventing the gearbox insides from eating themselves all the harder.

There are ways you can toughen that second stage carrier plate/output shaft combo, and thus make overvolting a possibility. A straightforward solution has yet to arise, though, as far as I know.

tldr; I'd avoid the overvolting if possible, drive with care and you *should* be fine.

As for amp draws, the 18v motors at 5s in T2 pull about 1-1.5ah in a fight. That's four of them, mind.

I see... may have two batteries in the machine then - got a brushless motor turning what should be a 5.5-6 kg disc (this one http://www.hobbyking.com/hobbyking/s...0KV_2665W.html) though whether that works is another thing entirely! Would like to have it all running at 6s to just save on weight a bit, but if it'll kill the gearboxes, definitely not worth it. Should I just stick with the 4s and 12v motors then to aid reliability? (or even move down to a 3s?)

3s = 12v, give or take a volt. You'll be safest running at nominal voltage for the motors.

You could look into 24v 550 motors. Believe gimson sell them but several people using them at the champs had issues with the 24v models.

Ahh, I get it now! I'll have a look at those too, I had heard a while back about the odd issue with them, I'll not be using drill motors for much longer (rather hoping I can get that brushless drive sorted to be honest!) but it's just for now and possibly the champs too. 3S it is then, thanks! :)