Joe Johnson Please Read....

[archiver]

Posted by Brian at 2/6/2001 7:33 AM EST


Student on team #56, Robbe Xtreme, from Bound Brook High School and Ethicon Inc..



Joe,
Every year my team has produced a drivetrain that has had a problem, the problem is that when we are driving(not that long of a period) maybe 5 minutes oneof the motors cut out and like if you wiggle the joystick it will come back, can you think of any reason why this would be, any help or advice would be appreciated...

Brian

[archiver]

Posted by control guy at 2/6/2001 7:50 AM EST


Student on team #250 from HVCC.


In Reply to: Joe Johnson Please Read....
Posted by Brian on 2/6/2001 7:33 AM EST:



Are you guys sure you're not tripping the breakers?

[archiver]

Posted by Matt Leese at 2/6/2001 9:31 AM EST


Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Rochester Institute of Technology.


In Reply to: Joe Johnson Please Read....
Posted by Brian on 2/6/2001 7:33 AM EST:



I know it's already been suggested that you're tripping your braekers but that (and other causes of the motors dieing) are usually the result of a mechanical failure somewhere. First of all, make sure that you have a usable gearing ratio on the driver train. If you get this a lot you may have to change the gearing ratio you use (you'll want to gear down MORE if it trips a lot). Also, you'll want to make sure that (assuming you're using sprockets and chain) that the entire drive train is inline and you aren't putting sideloads on the motor. In all likely hood you'd want the drill motor shaft supported on both sides of its sprocket (again, assuming you used sprockets and chain) and the wheel to be supported on both sides of its shaft. Most likely you've got a mechanical problem on your hands so it's best to treat it that way.

Matt who doesn't even claim to know nearly as much as Joe J but decided to give it a shot anyway

[archiver]

Posted by Anton Abaya at 2/6/2001 12:08 PM EST


Coach on team #419, Rambots, from UMass Boston / BC High and NONE AT THE MOMENT! .


In Reply to: Joe Johnson Please Read....
Posted by Brian on 2/6/2001 7:33 AM EST:



those LEDs can be lifesavers for small problems. are they blinking anything?

questions:

1. is the battery weak? the control sys should say this? if it's weak, then your motors will have intermittent failures as they try to get power.

2. circuit breakers tripping? a quick test for this is to change the circuit breakers for the ones that are connected to the motors as soon as they die.

3. wiggling the joystick? i dont think it would have anything to do with the problem except that when u wiggle it, the robot JERKS and fixes something in place. My guess is that you do not have the wires to your fuse panel properly touching the terminals (the screws DO NOT conduct electricity). that or you might have a lose connection somewhere (speed controllers? motors? fuse panels?)

4. if it's a problem with the your gear ratios, i would expect the motors to be extremely HOT HOT HOT as well after 5 mins. if they are, then maybe it is a mechanical problem.

5. does ur control sys lose power? do the speed controllers lose power? are all the wires crimped nicely? are you tethered? are you transmitting? are your joysticks working? go through these questions one by one and i'm pretty sure you'll find a solution. (gulp)

good luck.

Anton 'JoeJWannabe' Abaya
"Any other opinions?" -JoeJ

[archiver]

Posted by Ryan at 2/6/2001 12:13 PM EST


Student on team #30, Fury, from High Technology High School and CelWave.


In Reply to: Joe Johnson Please Read....
Posted by Brian on 2/6/2001 7:33 AM EST:



: Joe,
: Every year my team has produced a drivetrain that has had a problem, the problem is that when we are driving(not that long of a period) maybe 5 minutes oneof the motors cut out and like if you wiggle the joystick it will come back. :

Hey,
My team has experienced the same problem, assuming you are using the BOSCH drill motors for your drive system. Two major faults with using these motors lies in how they are supposed to be layed out within the drill and how you lay them out on the robot. The first problem, is that although the motors appear to be "in" and attached to one another, if one side should slide out it causes the motor to disengage from the gear housing. My team uses 1/8" lexan as spacers underneath the motor to keep it inline. A second problem is the high/low shifter on the gear housing. When operating for over about 2 minutes it moves enough to slip in between the high/low gear. It is then unable to move and the motor spins but nothing else does. For this my team either uses a zip tie to hold it in one gear, or we use this year secret weapon... Hope this helps.
-Rc

[archiver]

Posted by Al Skierkiewicz at 2/6/2001 1:35 PM EST


Engineer on team #111, Wildstang, from Wheeling High & Rolling Meadows High and Motorola.


In Reply to: Joe Johnson Please Read....
Posted by Brian on 2/6/2001 7:33 AM EST:



Brian,
"Need more input!!!" Johnie 5
Let your robot talk to you, look for missing lights, hot wires, missing rotating light, etc.(see post about battery change) Missing LED on speed controllers are almost guarantee of breaker resetting. (although this usually occurs rapidly, not a few seconds) No rotating light and the robot interface is rebooting. Hot wires usually an indication of bad crimp/high resistance connection, replace or recrimp. (solder preferred) If robot says all is ok then suspect speed changer and use a couple of tie wraps tied real tight to keep it from jumping out of gear. (Raul taught me this one.) The other posts tell what to do if tripping breakers (see correct gear ratios) low battery, or drive train mechanical. If you still are having problems at a regional ask for help. We would be happy to come over and trouble shoot, sometimes it is not one of these things and we always look for a chance to learn something. Good Luck,
Al

[archiver]

Posted by Ken Leung at 2/6/2001 2:06 PM EST


Student on team #192, Gunn Robotics Team, from Henry M. Gunn Senior High School.


In Reply to: Joe Johnson Please Read....
Posted by Brian on 2/6/2001 7:33 AM EST:



Are you sure the motor is really not moving? Is it not moving because there are no power to it or is it not moving because the motor is locked some where?

The reason I ask those questions is because we've been experiencing a similar problem with the same symptoms for the past year. And we figured out the root of the problem are the no-back pins. Well, last year we kept those pins in to hold our robot from sliding down the ramp, and the whole one-side drive train lockup thing started.

It turns out because of the drill motors are mounted so that one side of spinning forward and the other spinning backward, there is an inconsistency between the two motor in starting up. It's either that little timing difference or because the driver engage one side of the drive train a little faster than the other.

So what happened is whenever one side of drive train starts first, the other side got "pushed" by the ground and got locked in by the no-back pins. Just the same way you can't spin the chuck of hand drills when they are off. So the robot will start doing "donuts" on the field... And the driver always have to wiggle it to get it unlocked, while there is no telling what exact moves of wiggling will get it unlocked.

Now, I am not sure if you took those out already. But if not, they are likely to be the source of problem. Why don't you test the drive train out by lifting the robot off the ground and test it without load? Or even take the gearbox out and see if the motors are free spinning and if they will cut out just by themselves...