Big Dilemma..

We have a robot which is a four wheel drive… Motors are directly attached to all the four wheels. The motors have been modified to high speed gearing. The motors get cut off after just 30 seconds of run. We have figured out that it is the thermal breaker inside the motor which is kicking off. Already have tried external 3:1 gear ratio but still had the same problem. Is there a way to increase the speed of the robot??

Lift : Four 393 Motors, Geared for torque
Intake : Two 269 Motors
Base : Four high speed 393 motors

The speed is what is tripping your motors. They don’t have enough torque to make the robot move, so your motors just receive current trying to spin but don’t go anywhere. The result is that your motors overheat. Try using high strength and then gearing up for speed as able.

We have played all our competitions now with high strength gears but then the robot is very slow… Once we switched to high strength gears and then used an external 3:1 ratio, still same problem. What gear ratio do u think we should use?

Have you put bearings on? Friction can cause motors to overheat very quickly so it’s best to reduce as much friction as you can. I would also try a lower gear ratio for speed, 3:1 seems a little too high.

What gear ratio do u recommend we use? We have about a total of 20 pounds of robot weight

Also another problem could be a weight problem. The robot could simply be too heavy for that kind of speed ratio.:stuck_out_tongue:

1.6:1 at the most. 2:1 is going to give you problems.

20 lbs? Really? How did you get that heavy?

EDIT: You couldn’t get the internal gearing to run without dying? Loose some weight or go to 1:1. Your choice. You have to be able to drive the entire match.

Is 1:1.6 an external gear ratio??

20 lbs is a rough estimate, because we have heavily braced all mechanisms…

If your robot is already at a 1.6:1 drive with 4 motors and stalling, I suggest you try to lighten your robot, or take two motors from your lift and add them to the drivetrain. Otherwise, slow it down to 1:1. Better to have a slow reliable robot than a fast one that doesn’t last.

Maybe it could be, I guess. That’s the internal gearing for high speed on the motors, direct drive. It’s what most teams use.

Thats what is making the robot to cut off… Our lift is a 10- bar lift working at 1:5. Anything we could do to the lift?

Our scissor lift ended up being 19-1/2lbs. And we had to stick with high torque on the drive. Our solution was to build an 11-1/2lb 6bar lol.

You have a 10 bar? That fits inside the box? Seriously? How? Why?

I think I found part of your weight problem. Cut that down to a six bar, and loose 3-4 lbs.

If you can’t use the internal HS gearing, you need to loose weight. Reducing that lift is going to help, but it might not be enough. Can we see some pictures of your robot?

Rubber bands! If your not hanging use a lot of them. We used 4 high speed 393’s and 12 rubber bands per side.

10-bar??? I’d like to see that!

Where are you using steel and/or aluminum parts?

Our robot is 18x18x12. Perfectly fits. We have used lot of latex tubing on the lift. We have decided to take two wheels of the lift and change the lift gear ratio to 1:7. How do u think is it possible to distribute 393 motors among two front and two back wheels?

Our whole robot is made of aluminium. No steel anywhere

I’m going to give you the same advice I did earlier; Build a six bar. There’s just too much metal on your lift. Cutting it out is the easiest solution to your problem. The 10 bar is entirely unnecessary; unless this robot has a ton of features we’re missing that are contingent upon the height, you will never need more than a 6-bar for this game. In the case you needed the height, you should have a scissor lift because it’s less metal.

If, however, you’re set on powering a 10 bar arm on 2 motors (which prevents you from hanging), then I guess I would recommend chaining all of your wheels together using the 6 tooth sprockets. That’s the best way to put 6 motors on a 4 wheel drive.

You seem to have tried a lot of what we’ve told you. Are you willing to share pictures to see if you aren’t missing anything? Four high strength 393 motors should be able to move almost every robot imaginable, perhaps slowly, but almost certainly without burning out within 30 sec… I would bet that the answer is the same: cut weight or gear up for torque and sacrifice speed.

Another thing, where do you have your drive motors plugged into on the cortex? What ports?

Here is a picture of the side base plate, we can not use chains because then the chain is exposed to the bump when the robot tries to go over.
Base plate.jpg