Team MedBots

[Max]

Probably true! We do have a small cnc milling machine which hopefully they will get going soon so that could be an option. The reason to go for the beetle motor is should have a lot more power so I can get some decent speed and should accelerate quickly. Also they only cost a couple of quid so I think it's worth trying to get one to have a play about with to see what can/can't be done.

[Max]

From looking on FRA forums apparently there is only a single stage reduction of around 5:1, I was expecting 2 4:1 stages giving 16:1. This means I can just complety remove the gearbox and drive the wheel directly off the motor (hopefully). It will probably draw quite large current for an antweight so may need a large battery but hopefully should be able to get it all in weight.

[Rapidrory]

The motors are 40g each... though make sure you get the ones with the plastic end cap rather than the metal endcap as they have more power... It may be worth having a look round to see if you can find any without gearboxes; they'll likely be a fair bit cheaper...

[Max]

40g should definitely be workable even with a 3s battery. Easier said than done finding the bare motor, eBay and AliExpress aren't coming up with much that is suitable, mostly it is smaller motors around 30g and only 6v which I fear will lack enough power.

Can anyone who has bought beetle motors from AliExpress remember which seller they used, if I know which ones sell good motors I can contact them directly to see if they episode be prepared to sell the bare motor.

But as usual I am impatient and would rather get one off a roboteer in the UK so I can get playing.

[Max]

Here is a test vid using a 9v block battery directly connected to a speed 400 motor:
http://youtu.be/TPPD3i9vUeA

It's fairly disappointing! It may be that the block battery cannot deliver the current but I think the motor just lacks the torque required as it is a high rpm motor (18000rpm no load). The beetle motors should be around 4800rpm so will hopefully have the lower speed and higher grunt needed to move the robot.

[Max]

Turns out it was the battery! Hooked up a 2s lips and the result was insane, it had enough power to spin but was way too fast and out of control and the wheel just flew off!
http://youtu.be/EkyPpkz-ki8
Perhaps with some speed control it would work a bit better but I think a slower motor would probably be better.

[Max]

Here is what I have been working on so far:
http://youtu.be/0JrpqfPtPyg
It's just using ordinary ant weight gear motors as I had them laying around. You can see it translating all be it incredibly slowly and the direction isn't very consistent as it struggles to keep track of which way is forward but that should be fixable by changing a few parameters in the program.

Hopefully with faster motors it will translate better and look a bit more threatening!

[Max]

10:1 HPs arrived from Harry today so replaced two of the three motors with them and was initially disappointed with the speed, it was faster but not fast enough to do any damage but then I remove the wheel from the one remaining slow motor and then it went crazy fast! In the first test the receiver which was just hanging out the top came uplugged and flew away, this meant it just kept going at full speed with no way to control it so trying to stop that was fun!

But after a short while a problem emerged with one of the motors, I started the motor and it had lots of power and spun the robot then after about 5 seconds it would start screaming and come to a stop, when you pick up the robot the wheel starts spinning again but can be stopped really easily. Then when you turn off the motor and then bring the power back on again it works and has lots of power again!
Any ideas what's happening?

[joey_picus]

Is it possible you're drawing too much current after a while from friction during translating or even just from centrifugal/petal force? From experience with those 10:1s it doesn't take too much to stall them on 2 cells.

[Rapidrory]

Sounds more like dodgy bearings to me..