4 Tetrix Motors Destroyed?

[UrizenII]

Based on other posts I've seen here, I'm noticing a recurring pattern of Tetrix motors being burned out/broken quite frequently. It seems that that the motors cannot withstand any sort of shock; we have broken a total of 4 motors during testing due to what we suspect is the transmission being jammed because of an impact (minibot freewheeling back down the pole and hitting the base). How many other teams are having problems with these incredibly fragile Tetrix motors? If these motors are so easy to break, why is FIRST making us use them? Shouldn't we be able to use something a little more durable?

[whosdadog]

Yeah, we've shattered 3 gearboxes already. We've got 6 on order, but I hope we don't need to use all of them. The same small gear has broken in all 3 gear boxes.

[Dan 1038]

We have had a few issues of smoking the motors at stall, but a 10A fuse appears to have fixed that... Concerning the free fall shock breaking the motors, I highly recommend that you consider shunting the motors when you hit the top, this will significantly slow the fall. Simply add a switch, like a 3 way light switch (SPDT), which can switch the + of the motors from the + of the battery to the - leg of the motors when it hits the top. That way, the motors act as generators for themselves, which should create enough drag to keep the minibot intact when it lands. It works!

[UrizenII]

Originally Posted by Dan 1038

We have had a few issues of smoking the motors at stall, but a 10A fuse appears to have fixed that... Concerning the free fall shock breaking the motors, I highly recommend that you consider shunting the motors when you hit the top, this will significantly slow the fall. Simply add a switch, like a 3 way light switch (SPDT), which can switch the + of the motors from the + of the battery to the - leg of the motors when it hits the top. That way, the motors act as generators for themselves, which should create enough drag to keep the minibot intact when it lands. It works!

I'm not sure about the fuses, as we have the motors connected directly to the battery. Does the motor have an internal fuse (sorry, I don't know much about the motors themselves)? As far as the "shunting" goes, I'm not sure I completely understand, as I know very little about electrical stuff like that. However, we do have a switch that gets flipped when the minibot hits the top of the pole that turns the motors off, so they are simply spinning freely on the way down. We cushion the fall with knotted surgical tubing attached to an aluminum L-bracket bumper. The design works well, except for the fact that we keep breaking the transmissions in the motors, which causes the gears to lock and burn out both motors (we have 2-motor rear wheel drive). We are having difficulty figuring out how to slow the descent; right now, we have a sort of ratchet system that locks the unpowered front wheels on the way down, which does make a significant difference, but it is still not enough.

[JB987]

Originally Posted by whosdadog

Yeah, we've shattered 3 gearboxes already. We've got 6 on order, but I hope we don't need to use all of them. The same small gear has broken in all 3 gear boxes.

Any chance you overtightened the motor mount? It doesn't take much to over compress the gearbox housing. Especially small clearance between the last 40:10 gear nearest the shaft.

[Mark Sheridan]

We switched to a 10 amp fuse with great success but I think shock from falling from the pole has damaged one internally. Since then we have been using all the memory foam we had from shipping and last year's arena pieces to cushion the fall.

[Nickle]

We have also gone through four motors. We found that using lower amp fuses helps (such as 5s and 7.5s) and we repaired one of our motors, although it is not competition legal, by mounting and external resistor to it.

[Joe Ross]

Originally Posted by Nickle

We have also gone through four motors. We found that using lower amp fuses helps (such as 5s and 7.5s) and we repaired one of our motors, although it is not competition legal, by mounting and external resistor to it.

You should read team update 11 (released yesterday).

[2403_Andrew]

Our team has also broken 4 motors (3 by our Minibot Lead stalling them, one in a soldering incident ), but we think we fixed the stalling. We're using a switch to shut off the motors at the top of the post. The last broken motors were just the result of the switches being set wrong. Another 60 dollars down the drain.