Mecanum Newbie

Technical Technical Discussion
1

Questions:

  1. Is it easier to create a mecanum shaft or chain driven system?

  2. Would shaft driven system with the CIMple boxes be any good?

  3. How would I mount the mecanum wheels onto the shaft of a cimple box?

2

Are you talking about all mecanums or mecanums in front/back and rubbers on the others?

3

Our robot last year was a chain-driven mecanum system, so I’m not sure what you’re asking…

In terms of robustness, I would always advocate chain over direct-drive. Axles are easier to replace than gear boxes!

4

Does the KOP come with the needed spacers/ parts to run a chain driven system? Could I do this with 4 CIMple boxes?

5

I believe you’re thinking of omnis, not mecanums.

To answer your questions:

  1. There was a thread on this a while back, I’ll edit this post with a link once I dig it up.
    http://www.chiefdelphi.com/forums/showthread.php?t=85947&highlight=mecanum+direct+drive+chain
  2. We used direct-driven mecanums last year with no problems. YMMV.
  3. Put a spacer on the shaft. Put a key into the keyway on the shaft. Slide mecanum(with hub) onto shaft. Insert a bolt with washers into the threaded hole on the end of the shaft to secure(I believe it’s threaded for a 1/4"-20 bolt, but I could be wrong.)
6

The corollary being that axles are much harder to break than chains. West Coast drivetrains are pretty successful as long as you protect the shaft and wheel from direct impacts with other robots. So if you can get a gear ratio you like for direct drive, I’d honestly go with that so you don’t have to worry about chains.

7
  1. (information taken from the AndyMark.com site)
    “Drive with Axle and Hub
    If you wish to drive this wheel with an Axle and Hub, you can pick your hub by fitting any of the AndyMark hubs(except the Small DD Globe Hub) to this wheel. Hubs are NOT included in the price of the wheel. If this is your choice, then no bearing is needed. To install a hub onto a 6” Mecanum Wheel, useHardware Kit 8."
8

I too have a question about of Mechanum wheels. What is the best gear ratio (GR) to use to prevent your motor controllers from getting too hot? The CIMple Box has a GR of only ~4.8:1. Last year we used the tough box and chains and had a GR of ~13:1. At that GR we had absolutely no problems, but we really think that speed is going to be more important than it was last year. However, we still want the maneuverability of the Mechanums. Any suggestions on a safe GR that will be considerably faster than what we had last year?:confused:

9

We are thinking about doing a mecanum drive this year as well, and we have no experience with them in the past. I would say to use the standard toughbox that you guys were using, and see how the speed of your robot looks when built. If you would like even more speed AndyMark has several gearing options for the toughbox that would be just a simple gear change (but you need to design your bot to have easy access to the transmissions).

Hope this helps.

10

Well, that’s the advantage of chain – it’s a relatively simple operation to change gear ratios by using different sprockets, and sprockets are reasonably cheap and easy to get.

11

I understand that point. The question I have is what kind of GR we can get away with without burning up our Jaguars? We will definitely use chains and sprockets if we can’t get the proper GR we need. We just are not sure how to figure out what the GR needed is to be safe and still fast. By the way, we have 8" Mechanums.

12

if you can contact 2594 i bet we can find out together we are going to try the same thing.::rtm::

13

My team as well wants to implement Mecanum drive this year. I am a complete newb when it comes to programming it… Could anyone provide any insight to it at all? A labview vi with an example would be the holy grail for me right now. We were thinking of making it similar to this drive system: http://www.team1540.org/mecanum

14

I can’t find your website to share contact info through. Contact me through our website: www.intechmegabots.org

15

So would I be able to use CIMple boxes for a good mecanum direct drive? Or would toughboxes be overall better?

16

On 810, we direct drive our mecanum wheels off of BaneBots P80 planetary gearboxes driven by a single CIM motor.

17

Last year we direct-drove 8" mecanums off of toughbox nanos with their standard gearing.

18

My team wants to go with mecanum/omni this year also. no one can really tell you what gearbox is better. it comes down to your robot and what you want to do with it. i would have to double check but i think the cimple gearbox and the tough box both use the same gear ratios. so mechanically it wouldnt make a difference. my team is personally going to use the GEM 2 stage (maybe 3 stage?) gear box if we decide to go with mecanum/omni.

19

No toughboxes are 15:1 i believe, whereas cimples are something like 4.8:1

20

Last year Team 967 used 8" mecanums directly driven with regular 12.75:1 toughboxes. We’re going to do something similar again (we see no reason not to use Nanos this year), because it was nice to save some weight (no chains) and some time (no chains). It was a pretty fast drive. At its full competition weight, it needed a bit of a running start to get up the 45 degree ramps last year, so we would have geared it down a little bit for last year’s game if we had it to do over again. But this year has a flat field, so we are going with the same thing.

You would not want to directly drive 8" mecanums with 4.67:1 Cimple boxes. It would be interesting to see how much you can push the speed beyond the standard 12.75 ratio, though.