Omni wheels on AndyMark dropcenter KOP tank drive

Good morning everyone,
I am grateful for all the useful and helpful comments to my last post about “swerve drive…”. I have another one question about the standard issue AndyMark KOP tank drive. I see that the AM14U5 8 in. Pneumatic wheel Toughbox Mini Bundle is not a drop center like the standard issue higrip wheels. Assembling this kit does not look significantly different from the issued KOP drive, can we swap out the pneumatic wheels and put in 6 inch traction wheels…exactly 4 traction wheels (center and back) and 2 omni wheels in the front. The rationale is that the team is still working with a Kit they are familiar with, traction wheels for frictional contact and defensive play and the omni wheels for easy turns.

If we go with the standard issued KOP with the drop-center, can we still have performance efficiency with the omni in the front and traction wheels in center and back?

Or do we go with the swap out the pneumatic wheels with traction wheels and have true 6 wheel drive with all wheels on the track using tank drive? I do take all responses very serious and thank you for the support…pardon if any of my questions seems uninformed, just trying to do my homework so that I can help my kids.

I’m not sure where you see that this kit is not drop center- it’s just an Am14u5 kit with pneumatic tires instead of HiGrip wheels, with the same frame rails. Swapping the tires with traction wheels would give you a normal kit frame.

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From the layout diagram linked on that page:

So, knowing that it is, in fact, drop center, that comes with some caveats many teams learned about back in Stronghold.

  • Pneumatic wheels typically need more drop center than normal traction wheels, which you don’t get with this kit
  • You can use the tire inflation to add or subtract drop by inflating the center wheel differently than the outside wheels
  • Pneumatic wheels are typically wider than normal traction wheels, which will impact your rail spacing.

There’s nothing wrong with having omni wheels along with pneumatic wheels if you find it necessary. But keep in mind the purpose of what you’re building. For example, pneumatic wheels would make for a great out doors demo bot, as it could drive on pretty much any terrain. But omni wheels will likely break if driven off-road for extended periods! Photo below is after an 8 hour, off-road demo at a local fair…

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Thank you for the pictures. Omni use is intended for carpeted/indoor hard flooring and not outdoor. Using in the school gym during pep fest and activities/events.

As for the top diagram…correct me if my eye is deceiving me, all three axles are on the same level? That is why I assumed in my initial post that it does not have a drop center. Great point about the amount of air inflation differential on the center and back and front wheels.

I do understand the rail spacing is impacted with pneumatic wheels because they are wider, is there a drawback from using that because of the rail spacing? not trying to be stupid or anything, just trying to be informed.

They are not, that’s what I drew the red line for :slight_smile: The line goes from the center of the middle wheel straight over - you can see it’s on the bottom part of the outer wheel. The drop isn’t very significant, but it’s the same drop as when assembled normally.

No drawback, just something to keep in mind when thinking about designing your robot!

Got it :smile: . I see it now. appreciate the feedbacks.

You may want to consider using 2 traction wheels for those in the center and omni’s for all 4 outer wheels for even better manoeuvrability. It will make a difference if the center of gravity is near the center or if it is offset towards the front or back of the chassis. Think about how the chassis will turn when using 2 or 4 traction wheels and the CG is offset.