What teams have desgined a 6 wheel drive system?

[Rich Kressly]

Originally Posted by JVN

Momentum is one explanation but...
I watched them (From a standstill) win pushing matches against teams they shouldn't have! It was incredible...

John, on a purely non-scientific note, one needs to watch very closely to see how 25 gets that "little extra" in a pushing match. In the past two years, for part of (nearly) every pushing match they are in they are actually not moving at all. Once they are in a desired position they stand still with almost no exertion on the motors or battery at all. As to how they get that done, you'll have to ask 25, but I do know, that at the end of a match they generally have happier and cooler drive motors than most opponents not to mention more left in the battery.

[SpaceOsc]

Originally Posted by JVN

Momentum is one explanation but...
I watched them (From a standstill) win pushing matches against teams they shouldn't have! It was incredible...

against who or what matches? so i can see it on soap (Very interested in this machine)

New 6wd Question : IF the Robot Keeps Teterring on The Center Wheels then doesn't the Center Of Turning Keep Changing From a Point in the Middle of the 4 wheels Touching the ground, then another center when the other two wheels make contact and the previous two rise off the ground?



2nd New 6wd Question: i Noticed Several teams who executed a 6wd, didn't use all 6 wheels of one type (8' 12' 6' 3' there were all over the place, 233 comes to mind) How does this effect the 6wd?


3rd New 6wd Question: Also Noticed like in the previous Question that some teams went out of there way to have a lower traction wheel in the middle, why and how important is it?


-Osc-

i Like the 2003 25 Bot Alot more , flew an like eagle and look cool too (Threatening)

[Bharat Nain]

Originally Posted by JVN

PS - Your gearbox isn't any more over-powered than the rest of ours! 2 Drills + 2 Chips = 1552W = 2.08 Hp. How you guys manage to gear it so fast, yet still push so hard is beyond me. Up here on 229, we're genuinely convinced you guys are defying physics somehow. Are you sure you don't have 2 extra drills tucked inside that thing somewhere?

yeah we have 4 drill and 4 chips, can't believe it took someone so long to figure that out on CD. just kidding...

Wanna know a big secret? Yes, we are powerful and all that, but in a pushing match, we use BRAKES(used very less this year, but in last years game it was the thing). I am just starting to learn more about drive trains, torque etc etc from you guys, so maybe I can figure out how on earth we're so fast and powerful at the same time. I think I will ask one of our tradesmen...
-Bharat

[Wayne C.]

Originally Posted by JVN

Wayne,
First off, I'd like to say I'm a huge fan of your team's machines. You guys are great.

The amazing turning ability of your machines is DEFINITELY linked to your "wide" wheel configuration. It's all physics (you can see it in Chris Hibner's whitepaper, I linked in my previous post).

I disagree with you on one point:
I would argue that your 6WD configuration isn't helping you get more traction. For the most part, surface area isn't a factor in tractive force. (F = mu x N) <-- No "A"

For our applications (rubber on carpet) these are NOT perfect surfaces, and cannot be expressed perfectly with the above equation. They are intertwining meshes. This would help explain getting "more" traction using 6WD.

However, I would argue that you're not getting very much more.
Is there any chance you'd be willing to help with a little experiment?
It is for the mutual sharing of knowledge to benefit the entire communitty.

Wayne, do a straight up pull test with one of your robots. Record some values for it's maximum linear force. THEN, have one of your kids remove the 2 middle wheels from your drive modules (put them on top of the robot somewhere, so the normal force doesn't change). Now try the pull test again.

I hypothesize that your second test will be within 10 lbs of the first test (if not closer).

If you participate in this little experiment, I know I'd be (along with many others) very interested in the results.

Thanks,
John

PS - Your gearbox isn't any more over-powered than the rest of ours! 2 Drills + 2 Chips = 1552W = 2.08 Hp. How you guys manage to gear it so fast, yet still push so hard is beyond me. Up here on 229, we're genuinely convinced you guys are defying physics somehow. Are you sure you don't have 2 extra drills tucked inside that thing somewhere?

John- you're probably right on the physics of it all. One thing that I do notice is that the rubber of the tires is quite soft and wears quickly- possibly just enough to naturally create the surface needed. In any case it works. And when the wheels get some pressure pushing back on them they probably flatten a little and grab better. I'm not sure I want to test it however although all this discussion gave me an idea about recycling some of the old tires we have layiing in the shop.

As for experiments- it IS more fun to just have the machine throw Big Mike around.......

WC

[Wayne C.]

Originally Posted by Rich Kressly

John, on a purely non-scientific note, one needs to watch very closely to see how 25 gets that "little extra" in a pushing match. In the past two years, for part of (nearly) every pushing match they are in they are actually not moving at all. Once they are in a desired position they stand still with almost no exertion on the motors or battery at all. As to how they get that done, you'll have to ask 25, but I do know, that at the end of a match they generally have happier and cooler drive motors than most opponents not to mention more left in the battery.

Of course now every robot in the world is going to try to shove us around- thanks Rich !!!

As Bharat posted- we use brakes. At the flip of a switch we can lock up the entire drive train. It is very simple. Of course knowing when to use the brake is the key and that's what the drive team works out. Since we have six, wide wheel surfaces in contact with the ground I believe we get a little edge on robots with normal wheels.

And no, we dont defy the laws of physics but we do have a genius tech guy on the team named Mike Lubniewski who devotes a lot of time to thinking about improving the drives each year. (hence Bharat's avatar)

WC

[Bharat Nain]

Originally Posted by Wayne C.

John- you're probably right on the physics of it all. One thing that I do notice is that the rubber of the tires is quite soft and wears quickly- possibly just enough to naturally create the surface needed. In any case it works. And when the wheels get some pressure pushing back on them they probably flatten a little and grab better. I'm not sure I want to test it however although all this discussion gave me an idea about recycling some of the old tires we have layiing in the shop.

As for experiments- it IS more fun to just have the machine throw Big Mike around.......

WC

And its probably the only thing that can throw him around...

As for the wheels, the custom made Skyway wheels with diamond cuts on them makes them stick to the carpet like crazy(traction). Then, Straight-cut spur gears along with needle and ball bearings ensure all the motor torque gets to the wheels with minimal parasitic loss...

Thats the explanation I got from our tradesmen.

[gavinb900]

My team is thinking about 6 wheels. Has anyone experienced any problems with it? Does it go straight when its supposed to? Is turning smooth? Those are our main concerns right now. Thanks.
-gavin-

[Ali Ahmed]

6-wheel drive is probably the best way to go. It will drive straight if your chains and everything is tensioned properly. The only problem with driving straight is in the gearbox of the Drill motors. But thats only in the gearbox and is easily fixable. For turning the best to do that is to lower the middle set of wheels so that when you turning you are basically turning on those two set of wheels. We haven't had any sort of problem with our 6-wheel drive systems yet.

[RogerR]

Originally Posted by ali_rockon22

...The only problem with driving straight is in the gearbox of the Drill motors. But thats only in the gearbox and is easily fixable...

if you're talking about the directional bias that the drills have (i.e., they spin slower in reverse), its actually built into the drill motors themselves.

[Rich Kressly]

Originally Posted by Wayne C.

Of course now every robot in the world is going to try to shove us around- thanks Rich !!! WC

I thought that was already true ... oops

[artic_raven]

Originally Posted by Alex469

I know my team built a 6-wheel drive in 2002, but this was before my time and I don't know too much about it. The only pictures I could find on CD were here and here, but they probably won't help too much.
_Alex

is the bot still in tact or what?
if it is it would help me immensely if you could get a few pics of the motors and the way that it was all put together. if this is at all possible please help me out!!! thanks!

[DangerDanger!]

294 has been working on a prototype 6-wheel drive.