Major mechanical problems....

[Tom Bottiglieri]

well how are youu driving? are you sure there is not too much friction on the wheels? does the main drive shaft drive freely when it is off the ground? what type of wheels/treads are you using?

[quickie25]

We dont have any problems whatsoever as long as the bot is off of the ground. We are using the standard wheelchair wheels in the back and caster in the front. Our bot weoghts about 75-80 pounds. We are also assuming that the motors are encountering either friction/resistance from somewhere and that is what is overloading the circuit.

One question that we do have is:

Are the CIM motors as good as the drill motors? We seem to get much more power out of the CIMs that we did the drills, but that all depends on the gearbox, of course. We plan to continue with the CIMs as long as we can track down the fuse problem.

Thanks

Team 1380

[Ryan Albright]

the cims are reliable they have been our drivetrain motors for the past 3 years, but the drills our also good well really depends how much torque and speed you want

[Tom Bottiglieri]

are you running the CIM's into the drill motor gearbox?! This will give a speed that is insanely high and far less torque

[Rickertsen2]

can you give a more exact description of your drivetrain? What gear ratios do you have? What are you using to acheive these gear ratios? Is there any misalignment anywhere? Your explanation is a little confusing?

Oh and btw to answer your question about drills vs. chips, they both have their place. The drills are i believe slightly more powerful than the chips. The drills have a much higher free speed and a much lower torque output. The chips have much higher torque and much lower speed. The CIMs are much more reliable and durable than the drills.

[quickie25]

I do apologize for my lack of knowledge in the subject area, but as I mentioned we are a rookie team and are unexpereinced in these areas. We are using the standard gear boxes, the large gear amd the small gear and thats it. The lasgre gear is in on the output shaft and the smaller gear is on the wheel shaft. All of these came in our kit. We havent riiged any special gearings or customizations.

Thanks

[Ben Piecuch]

Originally Posted by quickie25

The lasgre gear is in on the output shaft and the smaller gear is on the wheel shaft. All of these came in our kit. We havent riiged any special gearings or customizations.

Thanks

Since there were no drawings of the Kit drivetrain this year, it's easy to have problems with the drive. I think your problem lies in your gears. You want to reduce the output speed of your motors using those 90 degree gears. But you've increased the speed by putting the larger gear on the drive, and the smaller gear on the wheel. Reverse the two gears (smaller on the drive, bigger on the wheel) and your problems should be solved. Hope this helps!

BEN

[Matt Leese]

Motors draw a lot of current because they are put under a high load. By pushing the motor's beyond 40 amps just by putting more stress on the motors, it would appear that there is too much load in your drive system. You may have some parts which are not able to move as freely as they would like to. You also may have problems with parts of your drive train being misaligned. Any of these issues can cause the motors to draw too much current.

As for my suggestion in solving the problem: put the robot up on blocks and run the drive train. Stress it. Watch how the drive train reacts. See if anything doesn't align. See if anything hits anything else. That will help you diagnose the problem.

Matt

[Peter Matteson]

We had a similar problem with our drill drive motors last year. The root cause turned out to be current draw. We discovered this when we borrowed a portable ammeter from our electrical lab at work. The solution was to simply lower our gear ratio. The down side was that we could no longer use the drills in high gear for a high speed.

[KenWittlief]

Originally Posted by Ben Piecuch

Since there were no drawings of the Kit drivetrain this year, it's easy to have problems with the drive. I think your problem lies in your gears. You want to reduce the output speed of your motors using those 90 degree gears. But you've increased the speed by putting the larger gear on the drive, and the smaller gear on the wheel. Reverse the two gears (smaller on the drive, bigger on the wheel) and your problems should be solved. Hope this helps!

BEN

YES YES YES!!!!

what Ben said!

you assembled the transmission backwards - the small gear MUST be on the motor shaft and the large gear on the wheel shaft

man! your wheels must be spinning a couple thousand RPMs when you have them off the floor!

also, it would be better to get the original drill motors and white gearheads in there instead - they are geard down lower than the Chips - and the FIRST transmission was designed for them.

If your motors were destroyed you can buy replacements, you can even buy complete Bosch drills at the hardware store and put them in tonight - it will cost you more, but dropdead date is only 3 days away.

[spyder_man]

are you guys running 2 cim's? and if you are are you running both motors through one fuse?, because that will definately cause them to blow under any load, the only other thing you could do is to de-sensitize the joystick signal with programming, but don't ask me how to do this, i don't do the programming for our bot.

[Kevin Sevcik]

Another thought. If the drivetrain was working ok with the drills, why don't you try testing the drills outside the robot and such? If you think it's a problem with the motors themselves, there are several atlanta teams. try to get in touch with them and borrow their drills if they're not using them.

If you're using the gears (they have diagonal teeth) with the CIMs, then they aren't being geared down enough to work. The CIMs look like they're designed to work using the sprockets, chains, and 6" wheels. If you want to use the CIMs you'll have to completely change out your drive system.

[quickie25]

We dont necessaryilt think of it as being the motors themeselves because the bot runs fine off of the ground with either motor. We were just trying to problem solve with the CIMs and we thought that we were well ont he way, untilwe put the bot back on the ground.

[Kevin Sevcik]

next chance you get, run the motors with the bot off the ground. if you can stop the wheel from turning with one hand, then it's not putting out enough torque

[quickie25]

We just tried that and we blew the fuse again. The whole things runs like mad until its put under stress. Based on the past posts, I think that we have a serious problem. We are going to dissasemble our gearboxes and check the driveshaft opening through the frame for any friction that may be occurring. If that doesnt solve the problem then we may drop the current drivedtrain altogether and create a direct drive system with sprockets and chains.

Thanks for the suggestions..any further ones please feel free to post,

Thanks,

Team 1380