Wheels for drivetrain

[jon-s]

We currently are using mecanum wheels for our drivetrain but need more traction to climb onto the bridge. Our chassis is too stiff for the mecanum wheels to work properly, and limits us to 8in wheels. We also need to be able to make the change(s) in the practice day of competition.

We are considering changing to either the FIRST wheels (http://www.andymark.com/product-p/am-0420.htm) or the Plaction wheels (http://www.andymark.com/Plaction-s/103.htm). Which of these wheels do you guys recommend or would you suggest a different type of wheel?

[Brandon Holley]

What type of wheel orientation do you have? ie: How long is your wheel base from the front set of wheels to the back set?

If its longer than it is wide, you will probably want to use 2 different wheels to help you turn effectively. It could be pairing an omni-wheel with a high traction wheel, or even a delrin skid with a high traction wheel.

Bottom line, give us more information so we can help.

-Brando

[jon-s]

Our robot is wider than it is long (27 x 37). The distance between the centers of the wheels lengthwise is about 17-18 inches. The wheels are approx. 30 in apart, widthwise. The wheels are directly driven by the cims, with no chains connecting them - the wheels turn independently. Our chassis is a folded metal box with an open top. We're not sure we'll be trying to climb the barrier.

[Whateveryousay]

If you got enuogh torque on your drive motors (4 CIMs?)

These wheels are a solid choice, but be careful, although noted as 8 inches wheels, even fully inflated, they are only close to 7 3/4''

http://www.andymark.com/product-p/am-0970.htm

[jon-s]

the wheels do not have to be exactly 8 inches, but large deviances (6in or 4i wheels) won't work.

[Brandon Holley]

With a wide aspect drivetrain you should be able to use 4 high traction wheels as replacements.

I am concerned about what you stated about your gear reduction. Are the wheels actually directly driven by CIM motors right now? There is no gear reduction whatsoever???

-Brando

[MattC9]

So, there are a few more questions you need to ask you're self like, Do we want to go over the bump, ramp ect.? If yes go with the 8in AM plaction wheels (they give you a lot more grip) which are good for going on the ramps and getting grip over the bump.

Also it sounds like you have a long drive base so use omni's in the front, a 4WD is like a mullet "omni's in the front, plaction in the back" or vise versa, it's all about how you want the turn. Also pleas use the dual omis they tend to "bump" around less (you want to eliminate the space inbetween the rollers on the wheels).

[Cal578]

When you say the motors directly drive the wheels, do you mean there's no transmission in between? If so, I think you'll have trouble with a lack of torque, whether you stay with mecanums or change to any other type of wheel.

Also, a four wheel drive with high-traction wheels will have difficulty turning on carpet. I recommend using one pair of traction wheels (plaction, pneumatic, etc.) and one pair of slick wheels (eg. omni). Put the traction wheels in the back and slicks in the front, or the other way around. And if you don't have it already, I highly recommend some reduction between the motors and wheels; you'll need the torque.

[jspatz1]

With the aspect ratio you describe, you should be able to turn effectively with four traction wheels if you are geared for a speed less than 10 fps and perhaps as low as 5 fps (assuming you are single speed). If necessary, plan to increase the size of the sprockets on your new wheels so that you are in this speed range. The traction and holding torque you gain on the bridge will be well worth giving up some speed on the field.

[jon-s]

Originally Posted by jon-s

The wheels are directly driven by the cims, with no chains connecting them - the wheels turn independently.

Oops, my bad... the driving cims are in toughbox nanos. There are 4 cims in the drive train. We drive so that the robot's longer sides are the front and back. In case it makes much difference, our robot is pretty low (about 32 in high). Right now, we only have single speed, but are considering altering the software to have at least one slower one (right now the robot goes full blast).

[jimwick]

we used a "wide" chassis configuration. at first we used 4 KOP high grip wheels, all driven. we COULD NOT turn on carpet with this set-up, even with the wide configuration.

we ended up using slippery white wheels in front, not driven, and two high grip wheels in back. we were able to maneuver very easily and pick up balls really quickly. since we could shoot reliably we scored a lot of points.

we were able to go up the bridge, but if we tipped to the other side we were not able to back up. we were able to balance, but had to be very gentle.

so overall the low traction setup worked well for us, but not so well on the bridge.

[MrRiedemanJACC]

Jim Wick,

Interesting, thanks for the information. We currently have 4 - 6" traction wheels, a Cimple box with two cims with tank drive. The front and rear are chained together. But we have too much traction also and can't turn very easily. We are considering changing our front wheels to something else. Everything is on the table as long as they are 6" due to the powertrain. We are a wide body with no intent of going over the hump. The bridge works fine for traversing from what we have seen. Good to know from you that the white wheels are borderline. We are considering going with dual omni wheels on the front. Any suggestions? Plus our next competition is week 3 so we need to act fast....

[45Auto]

Right now, we only have single speed, but are considering altering the software to have at least one slower one (right now the robot goes full blast).

You really need to contact one of the experienced local teams if it's true that the only speed you have is "full blast". There are several VERY experienced teams in the Houston area that would be glad to show you how to do proportional control to your motors so you have an infinite range of speeds between stopped and full blast.

[Cal578]

@MrRiedemanJACC:
If you put omnis (dual omnis are a little better) on the front, you will turn very easily, and have fairly good traction on the bridge. Traversing the bridge should be easy, and going up for balancing should be easy. If the bridge tips the other way while you are trying to balance, you may have some of the same trouble that Jimwick mentioned, but maybe not quite so bad since you'll have some drive on all four wheels.

If you can implement the variable speed as mentioned by 45Auto, it sounds like a very good plan for your team. Good luck!

[Garrett.d.w]

Originally Posted by MrRiedemanJACC

Jim Wick,

Interesting, thanks for the information. We currently have 4 - 6" traction wheels, a Cimple box with two cims with tank drive. The front and rear are chained together. But we have too much traction also and can't turn very easily. We are considering changing our front wheels to something else. Everything is on the table as long as they are 6" due to the powertrain. We are a wide body with no intent of going over the hump. The bridge works fine for traversing from what we have seen. Good to know from you that the white wheels are borderline. We are considering going with dual omni wheels on the front. Any suggestions? Plus our next competition is week 3 so we need to act fast....

If you are using only one CIM motor per side, then you won't have enough torque to turn. If you can spare two more CIM's for youre drive train, then do it. This will fix your problem. If you don't have the motor allowance for two CIM motors (IE, they are being used in your shooting mechanisim), then switch them out with RS775s in CIMulator gearboxes, and use the CIMs for your drivetrain.

Good luck at competition guys.

The school browser is being wierd, so I can't subscribe. If this post needs any clarification, just PM me and I'll be glad to help you.