Bouncing turns
 

We just had our first practice with our bot running and when we try to turn it it bounces out of control. :( It is four wheel drive and we used the wheels that came with the kit.
Is there anyway to stop it from bouncing and make it turn smooth?

Re: Bouncing turns
 

I am currently working with 406 and we had the same problem. In order to fix that problem we found that replacing the front tires with some that have a smooth surface will give you a nice smooth turn.

Re: Bouncing turns
 

Try increasing the tire pressure.

-Kevin

Re: Bouncing turns
 

A few weeks ago we had the same problem. It is caused by friction with the carpet. If you place the robot on a tile surface and drive it you will find that the bouncing does not occur. We were not able to find a way to negate this bouncing with the pnuematic tires, but rather went to a wheel with a low friction surface and it works great. If you have any other questions fell free to IM me on AIM: DavidButzin If I can't answer questions you have chances are I will be able to direct you to someone who can. Hope this is helpful!

Re: Bouncing turns
 

Last year we put casters on pneumatic cyclinder on back to lift the back wheels barely off the ground. This year we fully inflate the tires and just deal with it. There are several good solution to this including completely inflating tires and changing a set of tires so that they will slide sideways but still drive forward. Omni-wheels of sorts (not really, unless you can make them quick) But something that has less contact with the ground but still can grip forwards.

Re: Bouncing turns
 

It sounds like you're having the ever popular trouble with 4 wheel drive turning. Chris Hibner wrote a really good white paper to help solve this problem. If none of the quick tips here work, I'm sure some of the information in this white paper will help.

Re: Bouncing turns
 

That white paper doesn't appear to be available at the moment.

Re: Bouncing turns
 

This was a problem at the UTC scrimmage 716 was bouncing out of control they didn't have the problem as bad after taking most of the air pressure out of there tires. Increasing the pressure made it bounce higher. even though really hard to control it looks rather amusing :D

Re: Bouncing turns
 

just like he pointed out.... get more pressure on your tire... about 35 psi.

Re: Bouncing turns
 

there IS another option... shave down the wheels!! or mabye get some teflon and start wraping them... :D

Re: Bouncing turns
 

Yea, we noticed this problem back in week 2 durring our first trial run, we fixed it by putting casters on pnumatic cylinders. On carpet we are always in caster mode but when we climb or we are on the platform we are on awd mode.

Re: Bouncing turns
 

You can't very well shave down pneumatic wheels now can you?

Re: Bouncing turns
 

Well, at the DC Scrimmage last Saturday, I saw quite alot of bots w/ this problem...
Luckily ours wasnt one...
But anyway, the 12" pneumatics wheels seem to be used ALOT this year. Mainly, I would assume to climb the platform from the side, which based on last weekends results, isnt going to work quite as well as people would hope...
We personally stick with our 8x2" wheels, spaced out 26" wide (roughly)
I'm not too sure how to eliminate the issue. If you're not planning on going up the platform, try to get some smaller wheels with a little less traction. Or, you could make 2 big omni wheels for the front or back 2 tires of your bot using a bunch of smaller omnis.
I would make sure your tire pressure is full though. That was an issue with a few of the 12" 4x4 bots...

Re: Bouncing turns
 

someone posted earlier that they painted the back wheels with poly somthing or another. the robot will rotate around the front wheels because the back ones slip.


also with the tire pressure deflate the front ones and inflate the back ones. you want it to rotate around one wheel set and slide the other.

we just stuck some casters on the back that come up when we are climbing the platform

Re: Bouncing turns
 

Somoene actually suggested using a wax type substance like armor-all on the tires? Would that work, or be legal?

Re: Bouncing turns
 

yes, anything to reduce the friction

there is another post about this(by me) but it ended up in the pnuematics section sence i said pnuematic wheels HA!

http://www.chiefdelphi.com/forums/sh...ad.php?t=25061

Re: Bouncing turns
 

The Schmoebots had this problem as well. They solved it by simply removing the tires on one end and running on the rims. There's a little bit of slip from the different diameters, but it doesn't seem to cause any problems.

Re: Bouncing turns
 

Hmm. Well, I would think wax could be a bad idea, since it could(would?) rub off easily onto the carpet, something which FIRST would not like.

However, what does work, is wrapping some sort of material around the tires...

Re: Bouncing turns
 

we had this exact same problem last year. the cause was too much top weight and too much traction. we looked like we were convulsing while turning. we could never figure out how to stop it and just kind of lived with it. on the bright side...we never lost a pushing match. good luck!

Re: Bouncing turns
 

My team, 177, has perrenially had this issue we finally broke down and made omniwheels for the rear. Our experience shows that having lower friction in the rear wheels increases manueverabilty while retaining control compared to the fronts. Most teams who saw our bot at the UTC scrimmage can attest to it's speed and manueverabilty with these wheels. We were also never at a loss for traction.

Re: Bouncing turns
 

No you can not do this, once again a case of "if you don't know don't answer"

<R15> Lubricants may be used only to reduce friction within the robot. Lubricants shall not be allowed to contaminate the playing field surfaces, balls, or other robots.

You can use anything that will stay on your wheels, tape, paint, glue. But nothing that will rub off and contaminate the field.

Re: Bouncing turns
 

or make a wheel outa lexan or delrin ;)

Re: Bouncing turns
 

We did have this problem but after our first match we deflated our tires to the recommended 35psi(instead of 50psi), we still get some bounce but only in low gear.

Re: Bouncing turns
 

wax wont rub off. Though you would loose so much traction that you probably wouldnt be able to climb to the bar anymore.

Re: Bouncing turns
 

I assume everyone is talking about 4-wheel-based bots. I guess if you were surprised that it wouldn't turn well, the lesson is to think carefully before committing to a major design decision.

Our bot has only two wheels, midship, and plastic skids on the corners. It turns nicely in any radius we choose and turns on a dime.

And it can't climb the steps at all. Engineering is the art of making tradeoffs. We'll go for the bar from the side.

Has anyone built a bot with a rear-end differential and steered wheels like a car?

Re: Bouncing turns
 

Be nicer than that. You can use anything that will not rub off on the field. Armor-all when used right won't damage the playing field while making your tires a little slicker. I wouldn't reccomend it though. However tape may not be used. The only tape that is allowed is electrical tape as an electrical insulators. I don't want to be offensive about this but it is not good to post about someone else not knowing the answer and having incorrect statements in your own comments.

Re: Bouncing turns
 

It has been posted elsewhere but our team came up with it early on during the design stage once we realized that we might have some problems turning. Zip-ties on either the front or the rear wheels. On all four wheels is overkill, you may want to put them on the wheels farthest from the center of gravity of your robot in order to keep as much traction as possible.

Re: Bouncing turns
 

Tried armor-all like tire shine. It doesn't really help.

Re: Bouncing turns
 

we added a caster that helps us turn. it lifts the front two wheels off the ground andit turns much better

Re: Bouncing turns
 

We have struggled with this problem since we started 2 years ago.

Last year, we put zip ties, 1 every half inch or so, on the wheels at the lightest end which helped a lot.

This year, thanks to an idea that we got from Team 254 and Team 60 (which I understand originally came from Team 25), the problem is history.

The solution: 6 wheel drive with the middle wheels 3/16's of a inch lower than the other wheels. We turn on a dime and still have 6 wheel drive using chains. Basically our robot is rocking on the middle two wheels. We had to actually reduce the turning rate to make it more controllable.

Re: Bouncing turns
 

We fixed this problem with zip ties and pnumatic tubing. Check it out...

Re: Bouncing turns
 

We had the same problem. What we did to solve this problem was to wrap the tire with spiral rap that is typically used to bundle wires. It has worked well for us and still gives us lots of traction in the forward direction.

Re: Bouncing turns
 

thank you all for all the replies and ideas to help.....

we eventually tried the zip-tie idea, and it seems to help a bit (since we dont have the $$$ or time to make omni-wheels).... we can turn in place with minor bouncing, and turn along a radius with no bouncing.... we put the zip-ties on our front tires, as our bot is pretty well balanced betwen front and back, and it actually seems as if the zip-ties help us climb the step better.....

thanks again!

Re: Bouncing turns
 

wow. the almighty power of the zip tie.

Re: Bouncing turns
 

we tried to with a rotozip not too many weeks ago, long story short, when the shop smells funny, and you can see a black cloud of tire bits, laugh about it, because getting some disease never felt this fun....

but if you use zipe ties or pool vacuum hhose, you eliminate bouncing by allowing your robot to slide easily, and still not loose too much forward traction...