Drivetrain Issue
 

Hey all, we are competing at NYC regionals and our drivetrain is acting a little funny
when we try to drive straight, our robot swerves to the left
after the matches, our left motors are BURNING hot and our right motors are cold

any suggestions to what's wrong?
btw, we dont think the motors are fighting each other...at least on the left side

Re: Drivetrain Issue
 

Check your PWM's to the right side motors
Check polarity of the left side motors/right side
check for mechanical problems in the gearbox

Basically, do an entire "overhaul" on the gearboxes and see what is wrong, more then likely the polarity is reversed, or there is a big burr or something on a gear clogging the system up.

Re: Drivetrain Issue
 

We had a similar problem on Sat. @ MN. The first thing I would do is put the robot up on blocks (so it can't drive) then fire it up and push your sticks all the way forward so the Victors should be getting a full signal. Look at the LEDs on the Victors with the sticks still forward. They should all be green. If they aren't you have a problem with your code or PWMs. If they are all green then it is a mechanical problem or electrical problem with wiring other than the PWMs.

To check motor polarity you can unplug the PWMs from your Victors and plug in one at a time and run them full forward and see which way the wheels spin.

Re: Drivetrain Issue
 

It sounds to me like you may have an increased load on the left side of the drivetrain. I suspect one of the gearboxes is binding up.

Try to spin the right-side drive wheels by hand.
Now spin the left-side drive wheels by hand.

Is it significantly harder to spin the left wheels than the right? If so, try to find out why.

That is my best guess.

Good Luck!
John

Re: Drivetrain Issue
 

The aforementioned insights provided are probably your most likely bets, but also check to make sure that your burning hot motors have intact o-rings around the ends of their casings (places where the black painted portion of the CIM meets it's two cast endcaps).

Missing or damaged o-rings can allow fine particlates into the interior of your motor and degrate or destroy the brushes in your motor. From there, it's possible that you rmotor could be partially or completely shorted out.

-q

Re: Drivetrain Issue
 

Also, have your programmers check your code, a typo could be the cause of all of that.

Re: Drivetrain Issue
 

what kind of transmissions are you using. We had custom one and on one side the output shaft got bent and it added a lot of binding problems. If you using the kit of parts ones then check the pwms we had lot of problems with that.

Re: Drivetrain Issue
 

[quote=JVN;731180]It sounds to me like you may have an increased load on the left side of the drivetrain. I suspect one of the gearboxes is binding up.

Try to spin the right-side drive wheels by hand.
Now spin the left-side drive wheels by hand.

Is it significantly harder to spin the left wheels than the right? If so, try to find out why.

That is my best guess.

Good Luck!
John
Welcome BACK, My Friend.

Re: Drivetrain Issue
 

what kind of gearbox are you using? Check the motor polarities as well as for burrs in the gearbox on the left side.

-Vivek

Re: Drivetrain Issue
 

If it turns to the left, then the right side is going faster.

If the right side is going faster even though both sides are told to go the same speed, then the left side has more resistance.

If the left side has more resistance, then:

1. Check any chains for alignment and tension (not TOO much tension!)
2. Make sure there is grease in the gearboxes.
3. Listen to each side independently. If they sound different, there is a mechanical problem most likely in the gearbox (alignment or debris).
4. Make sure all electrical and mechanical connections are TIGHT!
5. Sanity check yourself by removing the motors and seeing if they seem to match in speed when not loaded.

Re: Drivetrain Issue
 

1726 experienced a similar problem during our early build season testing. A victor had burnt out forcing the remaining motor on that side not only to move the robot, but also to back drive the other motor. We discovered this when a student noticed that one motor was much hotter than the other. If both your motors are the same temperature then this is probably not the problem, but it's probably still worth checking.