Re: how does one go about making a 6 wheel config drivetrain?
 

6WD is heavier than 4WD, typically, but that doesn't mean that it needs to be heavy. This season, our drivetrain is 35 lbs. with electronics -- lighter than most 4WD systems. It's not as powerful as some, but that wasn't important to us.

Re: how does one go about making a 6 wheel config drivetrain?
 

A couple things I saw on this thread I want to comment on the distance the wheel should be spaced down is not a set distance it depends on what kind of wheels and traction material you are using. For instance wedge top tends to compress, so 1/8 may not be enough if you are using wedge top material in particular. Also the thoughts on 25 vs. 35 chain, this all depends on what kind of fabrication/machining facilities you have. I will now tell you why this matters. #25 chain requires more precise alignment then #35 because of the size difference. However #25 is much lighter and will save you weight to do other things with. #25 chain is plenty strong we used it in the drive last year for the first time and only broke it once and that was in a pushing match against 233 at a off season in Tampa and 233 broke there #25 chain as well. Just my thoughts on how to make an effective 6 wd base. I have been involved in two 6wd designs on 1251's 06 and 07 robots both won regional events these comments are things I learned on both those robots.

Re: how does one go about making a 6 wheel config drivetrain?
 

Yep... this year, team 45 is also using a 6wd without a dropped wheel in the center. All 6 axles are on the same plane, and all 6 wheels are 2008 Kit Wheels. The middle two wheels have been lathed down a bit and then a traction wheel tread has been riveted on. This makes the middle wheel about 3/16"-1/4" larger in diameter, compared to the outer wheels.

(edit...

Oh... by the way... team 45's 6wd uses only 3 different custom fabricated parts this year (not including bumper mounts). All of these parts can be made with a band saw and drill press. Stop by the pit in Atlanta and the kids will give you a tour.

... close edit)

Andy B.

Re: how does one go about making a 6 wheel config drivetrain?
 

So you just added tread right over the flat gum surface? Interesting... Too simple to be true it seems.

How did it work out?

Re: how does one go about making a 6 wheel config drivetrain?
 

This year we used a six wheel dive based off the KOP frame and wheels. It works great an is still easy to drive even if one chain is lost. There are two chains on each side one each chain goes from the transmission to the center wheel and then one chain goes to the front and the other to the rear. This keeps the center wheel powered even if one chain fails. I've found that as long as the center wheel remains powered the robot can still be driven effectively.

Re: how does one go about making a 6 wheel config drivetrain?
 

The feeling you are getting is partially substantiated. The problem with that solution is the middle wheel has slightly larger diameter, but rotate at the same speed as the outer wheels, so they are bound to scrub a little because the middle wheels move slightly faster than your outer wheels.

6WD drivetrains are designed to rock back and forth a lot, and this should eliminate any and all issues you might have with this. If you are pushing the carpet into itself, you will just rock some more. Additionally, the change in diameter will only change the circumference by a slight amount, (~5-10%). I am sure any effects are completely negligible.

I should note that we did the exact same thing. We were having troubles turning at Portland (heavy bot, only 1/8" lowered, carpet), so we screwed on tread to our colsons at SVR, and we turn much better, although we rock back and forth a lot now.

Re: how does one go about making a 6 wheel config drivetrain?
 

Also if at all possible try to direct drive the center wheels. We did that for the first time this year and it makes things so much simpler. Then you only need 4 chains so the only extra weight over a 4 wheel drive design is the weight of 2 wheels and sprockets which is probably 1.5 lbs. We have always gone with the center wheel lowered 1/8" with both kit wheels and colsons and have never had a problem.

Re: how does one go about making a 6 wheel config drivetrain?
 

There are a lot of teams I know of that uses 4x4 aluminum box tubing for their chassis. Back in 2007, I talked to Karthik and he directed me to Taylor. They were gracious enough to share close pictures of their chassis. Personally, I love 6wd and in my designs I use an 1/8th inch drop. Below are few pictures that may help you.

http://www.chiefdelphi.com/media/photos/27523 ... that's 1114's 2007 chassis
http://www.chiefdelphi.com/media/photos/29996 ... that's 1345's 2008 chassis
http://www.chiefdelphi.com/media/photos/26373 ... that's 1345's 2007 chassis

1114 makes their own plates and puts the transmission inside the box tubing. It's very neat. If you have any questions, I would suggest getting in touch with Karthik and I am sure he will be more than happy to share their designs. Also, if I can be any help, you are more than welcome to send me a pm. Good luck.

Re: how does one go about making a 6 wheel config drivetrain?
 

This year we did six wheel drive with a unique twist. We originally tried four wheel drive, but wanted a tighter turning radius.

We didn't like the tippy drive with the center wheel lowered so we used omni wheels on the front and back with all wheels at the same height.

On the kitbot frame we drove the middle and back wheels with the toughbox gearboxes. Then we slaved the front wheels to the middle ones (so the middle wheels had two sprockets - one on each side.)

Picture:
6WD Pic


We were happy with the results and seemed to have quite a bit of power.

Re: how does one go about making a 6 wheel config drivetrain?
 

Our team has attempted six wheel drive systems for the last two years. We did extensive prototyping work in both 2007 and 2008 to develop six wheel drive systems. And guess what... we ran into the SAME problems in both 2007 and 2008, too much traction and difficulty turning.

We solved these problems the same way both years; removing two of the traction wheels are replacing them with omnis. We noticed HUGE increases in performance when we replaced the wheels. Our robots were much more nimble with only four traction wheels.

At the Portland regional this year it occured to me that powering the omni's was a waste of time. I mean, how much traction are you gonna get out of an omni wheel anyways? So we removed the chains from our omni wheels. Do you know what happened? Nothing. Except we lost about a pound of weight.

So here is my challenge to teams using omnis this year: take off the chains and see what happens. You may be surprised to find that there will be no change in preformance.

What I've learned amounts to this:

-4 WD* Is the best configuration for a game with no obsticles. 4 WD is more controlable than 2 WD and is significantly simpler than 6 WD.

-6 WD Is only neccessary when there are obsticles to climb over. Fewer wheels and you'll increase the risk of bottoming-out.

*With the wheels oriented in a square NOT a rectangle.

Re: how does one go about making a 6 wheel config drivetrain?
 

Hello guys!

I'm 17 years old, and robotics is a big interest of mine.

Recently, I built a 6 wheels drivetrain chassie with a 1/8" center wheels drop.

the chassie looks like this one (the only defferance is that i'm using 2 motors in each side with one gearbox, two motors that goes to the same gearbox):


my problem is that i'm not a programmer, so i can't drive it. i wish someone can provide me a good code, which is Appropriate for 2 joystick drive so i can try it (one joystick for the right wheels and the other for the lefts).
please provide me the best code that you can, because i know nothing about programming and i can't amend the code.

in addition, i'll be very thankful if some one can provide me with a geartooth sensors code for this drivetrain (2 geartooth sensors, one for each gear).

thank you alot! :)

Re: how does one go about making a 6 wheel config drivetrain?
 

I've found that adding two wheels is as simple as it sounds: add two wheels and two more lengths of chain (though this year we didn't even need to add more chains, just make them longer). 6wd is not more complicated than 4wd, it's just a little more work. We've used 6wd with 1/8" center drop for the last two years without any problem, and we've found it to be very maneuverable. Our chassis this year could be made with hand tools, and only took a few days to assemble.

http://www.chiefdelphi.com/media/photos/30068
http://www.chiefdelphi.com/media/photos/26813