Re: Help with drive train
 

First off...Woo for my first post!
Now that that's out of the way, I just thought I'd ask for any suggestions. Seems like my team (2nd year rookie) is having problems turning. I can go in a straight line though! lol. We're using the FIRST transmission with a sproket on the output shaft with a single chain which turns two wheels on each side. Essentially a cheesy 4wd. The sprokets for each wheel are keyed to the axle, as are the 12 inch pneumatic wheels. Our problem seems to be one that others have experienced in the past. Seems to me like we've got too much traction when trying to turn. I think we're going to try moving to a front-wheel, rear caster type setup. Hopefully that'll solve our problems. Any suggestions from you fine people out there? Personally I wanted to have a more sophisticated drive system, but the skill level of the team isn't quite where it needs to be for such a task. Any help would be greatly appreciated.

Re: Help with drive train
 

i have a question then i'll put my two cents in...are you using one sprocket to power both wheels?

Ok, for one I would never suggest using casters, especially the swiveling kind, my team used them in our first year (b4 i was there) and the robot could not manuever very well.

We used the 12" pneumatic wheels last year on our bot and also had trouble turning. with those wheels, you are usually about 6" off the ground so have a wide wheelbse to keep you stable when turning. Now, for a solution, our team bought zipties (like foot long ones) and put about 10-20 on each of the back wheels, and we were able to turn better, we still shook (?) when we turn but that is because we had a scissor lift that would go up and down as we turned. but anyway, try the zipties, they should work, if not post again!

here is a pic of our robot from last year, and be sure to poke around the website: http://montclairrobotics.org/view.php

just some thoughts

Re: Help with drive train
 

We used a center wheel design last year with the 12" wheels and it worked out very well. Here's some examples of last years prototype and the actual bot and in action .

The center wheel has a 6" pnuematic from Skyway and was offset by about 1/4" depending on air pressure. We are using a center wheel again this year because it makes turning so make easier on the drive system. However, one lesson learned from last year is that it is a lot of weight placed on that little 6" wheel, and very little on the 12" wheels. But last year we wanted to easily get up those steps - so it proved useful. I'm not sure how critical it is to use such large wheels in this year's competition. We're using 6" wheels this year. Good luck.

Re: Help with drive train
 

Just to clarify, yes, we're using one sproket to power two wheels. If you look at it from the side the chain makes a bit of a triangle shape. One sproket on top from the transmission, and the other two on each side sharing the axles for each wheel. Anyways I'll be sure to try the zip ties tomorrow when I get to school. I do remember seeing that tactic used last year now that I think about it. Seems like those 12" pneumatics have caused some problems for other people too. Oh well, robotics wouldn't be fun if it wasn't challenging.

Re: Help with drive train
 

The easiest solution would be to use the gearboxes that are supplied with the kit. They are superior to last year's worm drives *shudder*. The worm drives were made of a plastic housing, which cracked, and our team had to use enough oil on the gears to power a small city. The CIM motors are the most powerful, but you could buy some Bosch drill motors from last year, those worked beautifully.

Mike F.
Team 1279

Re: Help with drive train
 

NO, you can not buy some Bosch drill motor from last year. Please read rule <R20> and <R39>!!!

-dave

Re: Help with drive train
 

Are you guys using the right angle gearboxes from pre-2005 competitions?
Try using 4 CIM's with the FIRST supplied 2005 gearboxes, if you already are, increase the gear reduction (maybe a bigger sprocket on the drive wheels). You could also even shorten the wheel base. Consider the zip tie method as a last resort, don't just hop to some cheapo quick fix solution when you still have time to try and fix it appropriately.

Re: Help with drive train
 

Last Year we used 2 CIMs in the back with 12 inches pneumatic wheels. At first we had casters in the front, not only did they weight a lot but it didn't have very good handling, so we changed them for skits. They worked really good and although they werent the best thing for pushing they were a lot better for controling the robot. Just another idea... :D

woo we fixed it!
 

Well thanks for all the ideas. We actually fixed the problem last night. Now we've got amazing control. As the driver, I'm very pleased with the result. I've finally got the kind of control that we've been waiting for. Not only that, but now that that's done I've got at least two solid weeks of practice. Just goes to show what can be solved when you really attack a problem!