24-01-2007 17:49

Rafi Ahmed

Re: pic: Invisible Electronics!

I never thought of mounting the mecanums that way. Aren't they some of the wheels mounted the wrong way though?

24-01-2007 17:57

sanddrag

Re: pic: Invisible Electronics!

Why not take that whole chassis and flip it over for lower ground CG?

24-01-2007 18:06

Lil' Lavery

Re: pic: Invisible Electronics!

You'd get more efficiency if you flipped your front two wheels so that the rollers were pointed the other way (the rollers should form an "X").

24-01-2007 22:08

Dan Petrovic

Re: pic: Invisible Electronics!

Hmm... they look fine to me.

It's hard to tell, though.

24-01-2007 22:17

artdutra04

Re: pic: Invisible Electronics!

With a mecanum drive robot, you will need some sort of a suspension system to make sure every mecanum wheel is in contact with the floor at all times. Mecanum is far less forgiving to uneven carpeted fields that other types of robot drivetrains, and unless your robot has a suspension system it will fly off at weird and "unpredictable" angles on uneven floors, which are quite common at competition venues.

There are several ways to accomplish this. The first is that you can have each mecanum wheel pivot on one end, with the other end supported by some sort of rubber piece. (See this picture from Team 488. Team 40 also used pieces of rubber hose, although I can't quite find a picture of their mecanum module at the moment.) Your other option is to split the frame in half, a la Team 190 in 2005, and have the two halves of the frame pivot in the middle. (See below picture)


CAD drawing of Team 190's 2005 lower chassis.

25-01-2007 10:19

65_Xero_Huskie

Re: pic: Invisible Electronics!

Hmm...is that a 4-bar linkage?
Looks familiar....

25-01-2007 17:38

dtengineering

Re: pic: Invisible Electronics!

Obviously mecanums will behave weirdly when one of the wheels comes off the ground, however "Suspension" can also be accomodated through a flexible frame, especially when dealing with reasonably flat surfaces covered with foam-backed carpet. I would suggest completing your frame and giving it a test run as early on in the build as you can. (Note that at least one CD poster has reported mecanums work more smoothly when loaded... so if you are having difficultly with an incomplete frame, bring it up to playing weight for your tests.) We're experimenting with mecanum, too, and based on our previous experience with the kitbot frame we believe it has enough "give" to keep "four on the floor" for most of the competition. And if we're wrong... hey... what's one more problem to solve?

We won't, however, be planning on doing any off-roading with this robot.

Good luck, and post to let us know how it goes.

Jason