We were so hopeful, six 8-inch pneumatic wheels from Andy Mark configured in a drop center, about 1/8" being directly driven by a CIMPle Box with 2 cims on each side, front and rear tires chained up. Our hopes were dashed when it pulled the batteries way down and refused to do much moving. We loosened chains, thinking maybe there was some binding, but not much better results. We are troubleshooting this, and the most likely remedies we’ve come up with are to lower the center wheel some more or switch to omnis on the corners. I read somewhere that direct driving any wheel from a CIMPle Box is a bad idea because you lack torque. I’m wondering if the gering may be our primary problem that we could correct by not direct driving and using a smaller give on the CIMPle Box. We currently have 26 tooth gears on each of the wheels. Thanks in advance for your insight. Hope all of your builds are going well.
I misunderstood your original post when you said “Our hopes were dashed when it pulled the batteries way down and refused to do much moving.” I read that to mean the robot wouldn’t go forward.
If the primary problem is turning, then your problem is most likely a combination of (a) need more gear reduction (as others have posted) and (b) 1/8" drop is not sufficient for pneumatic tires
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I just re-read the above. Are you saying that the center wheels are direct-driven and the front&back wheels have a gear reduction?? If so, that’s not a good idea.
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I’d go with removing some traction at one end of the robot, too–I’ve seen one of the Toughbox’s closer relatives, the 2006 KOP gearbox, have trouble turning a 6WD drop-center when all 6 wheels (6", in that case) were pneumatic. Replacing one end with lower-traction kit wheels worked in that case.
Can’t remember–I want to say it was in the 1/8 range, but it’s been 6 years. Might have been more. It turned with the 6 pneumatics… but it bounced all over the place when it did.
Yes, that’s the fastest and simplest way to get close to the right ballpark. It’ll still be a pretty fast drive with pretty high power demands, but it’ll move.
You can purchase a modification for the Toughbox to bring the ratio down to ~15:1. AndyMark currently lists it as out of stock, so your best bet would be to install stock Toughboxes and plan for this mod to get better performance. If you or any teams nearby could machine the part from AM’s drawings, that’d work too.
I’ll let a real engineer explain the math behind drive gearing - but it’s a valuable lesson to learn.
If you could modify one of the worm gear boxes from andymark to use two cims it would put you near the perfect ratio, It may also be similar in the required mounting method to your current gearboxes.
