My team is trying to decide whether or not to use a mecanum wheel drive or a holonomic. We briefly tested mecanum wheels this year but i just feel like there was some friction using them that might not be there using holonomics. Is this just me being stupid or can anyone shed some light on this?
First of all, just a little comment on the terminology. Mecanum wheels are holonomic drive wheels. Holonomic drive is a drive that allows you to move in any direction without turning. I believe you’re referring to omni wheels. I have never noticed any more friction in the mecanum wheels than in the omni wheels.
My guess is that rather than friction, it’s the extreme bulk of the mecanum wheels that is making the difference you’re seeing. Because it’s about twice the mass that your motors need to rotate compared to the omni wheels. That’s my thought anyway.
but i just feel like there was some friction using them that might not be there using holonomics.
Is this friction that you mention going forward (traction) or when strafing?
An x-drive would probably be your best beet… mecanum wheels are slower strafing and and break motors if the robot is mistreated by other robots(aka. pushing when the robot is tiring to go forward).
and we broke countless motor using the mecanum but only 1 in the x-drive…
just my input…
It was when we strafed. The deffenaetly are bigger than omniwheels so I think we’re going to use an x drive next year.
I was thinking of using an X-drive, but I heard that it was not good for programming skills. Is this true?
also consider that an x-base can be quite hard to fit a good intake mechanism amongst, most teams like mecanum drives because they can use a semi-conventional chassis and still strafe. look into fold out X-drives as a space saver if you are having problems.
One thing to keep in mind is that mecanum wheels eat sacks like there is no tomorrow. We tested this ~10 minutes after getting our objects at worlds and decided then that we more than likely would not be using mecanum wheels this season.
VERY not true at least in my opinion.
You guys are all bagging on mecanum.
My team never broke motors using them the difference is
holonomic are slow in every direction but it is the same speed in every direction
mecanum is full speed for tank drive and half speed for straifing
its about trade offs if you want to push people you mecanum but guard them well
if you want to be fast and straif most of the match but not push go holonomic
Well we all know that depends on gear ratio, and x versus H drive types. At the end of the day you still have the same drive power available if you have the same number of drive motors, and although some types of holonomic drive may have more friction than others, this won’t be a major difference between them.
This simply isn’t true. An H-drive is fastest going diagonally. An X-drive is fastest going directly forwards, backwards, left or right.
Again, sorry, but not true. Neglecting friction, mecanum drive goes the same speed directly forwards or directly sideways. This is because the rollers are at a 45 degree angle. Sin(45 degrees) = Cos(45 degrees). Of course, friction slows you down a little going sideways, but if it is half your speed, you’re definitely doing something wrong.
Very true, thanks for bringing this up. According to MIT, “Holonomic drive, in the realm of robotics, refers to the ability to move in all direction and rotate independently”. X-drive, H-drive, “Kiwi” drive, mecanum drive, and even swerve drive all do this. So it really does pay to be specific about what one is talking about.
Might you explain what this “Kiwi drive” is? I feel I have heard it mentioned, but I don’t think I ever saw it…
Kiwi drive is like X-drive but with only 3 wheels.
See an example here
Define eating sacks. Do they damage them?
Maybe this will help
My team has to turn in a sketch to our mentor before we actually start “building” so we had some time to test out a few things here they are
- You can put all of the objects in one trough
- The mecanum wheels have great traction and we built a big pile of sacks (about 25) and the mecanums drove over with no problem
And 3. There was one problem that we saw with the mecanums, you need to have a lot of space in-between each wheel on the side otherwise the robot will intake the sack into the drive train
Hope it helps
This is what Matthew was talking about when he mentioned eating sacks.
Of course there will be ways of designing around this, but the sacks do tend to get caught on the rollers because they stick out somewhat.
Hmm… I wonder if Mecanum wheels could be used as intake rollers?
I suggested this for Gateway, but I don’t think anyone actually built one. I’d like to see how it handles the sacks].
The mecanum wheels actually have more traction with the ground than any other wheel. In the traction test they beat the crap out of omni-wheels, traction wheels, and friction wheels.