I have been told not do mecanum wheels by some more experienced teams and I was wondering why. The I think of it is that x drive only had two motors on in the best case scenario and mecanum could have 6 and might be slightly less powerful when strafing so I am confused
You would have to position your center of balance accurately ignorer for it to work.
Hello, I’m someone who used to religiously use Mecanum wheels but I have recently stopped using them. This was due to a variety of reasons. One of the biggest reasons is just the size of Mecanum wheels, making drive channels really thick and usually making robots wider. Another reason is inconsistent strafing, where unless your drivetrain has a perfectly centered center of gravity, it will drift while strafing making coding strafes incredibly difficult. Another reason is that mecanums don’t have great traction, this is due to their shape which is made so only a small portion of the wheel actually touches the ground, meaning they have less traction and worse power. Finally, it is pretty difficult to make a 6 motor drive using mecanums, and since 6 motor drives are the standard for competitive vex teams it means most people stray away from them. TLDR; Mecanums aren’t great due to size, bad traction, unreliable strafing, and difficulty in implementing a 6 motor drive. I would not recommend using them this season, hopefully I was able to help. Good luck in High Stakes!
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I’m pretty sure your perception of how x drives pushing power is is slightly skewed…
But why to not do mecanum wheels is
- Motors. In mecanum drives, just like x drives, the best way to get a 6 motor drive is to have 1.5 motors (an 11w and a 5.5w motor), which is inconvenient
- Lowered torque. The angled rollers on the mecanum wheels lower the torque the wheels get on the ground, almost as little as an x drive would get.
- Bad wheel sizes. Last I checked on the vex official Website, VEX has discontinued the 4 in mecanum wheels, meaning that the only legal mecanum wheels (unless you already have the 4 in wheels) is the 2 in, which are incredibly inconvenient for gear ratios
- Not truly omnidirectional. X drives have their full pushing power forwards and sideways, but can also drive at reduced pushing power/speed at any diagonal angle, while mecanum drives only have their full force forward, and while they can go perfectly sideways and diagonal, they do so at reduced speed and can’t drive in any directions in between.
I hope this was helpful.
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Mecanum is usually considered bad because it has less traction compared to other types of wheels and it requires that you have a good center of mass in the center of your robot because otherwise you will not be able to strafe well. This is especially appearent this season with home much a full mobile goal will impact the center of mass of the robot.
it just depends on your robot if your robot is going to be running into other robots, your going to be shoved around because you have those wheels, but they help you turn better so if your just doing skills challenges mecanum wheels are better.
From what I have heard, using the mecanum wheels may cause jerking and slipping which is not good if you are trying to be as accurate as possible. They are also a little slow. This is just something to let you know, and if you still have questions, feel free to ask.
I don’t think that you could do six for a mecanum drive, though I suppose technically it may be possible. I was planning on doing a mecanum drive this year, but only because I have already made code for doing so. The main issues are these: You are limited to direct drive and coding. It took me a while to figure it all out, but on the coding, you basically need your robot to be doing trig and vector ratios on the fly. The brain must calculate where you want to go (input from the joystick) and then decide how much it has to turn each wheel to get to the desired point.
This is described in further detail here on Github: How a Mecanum Drive Works | Seamonsters-2605.github.io
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I actually think that mecanum wheels are good but sometimes they are worth the effort but in last years game they were OP for us we were using 4 wheel drive 1:1
ratio and we were able to push 4 motor drives and stand our ground for 6 the strafing was useful because we were a blocker bot so if they decided to shoot we could be in front of but if they switched to bowling we could simply strafe over to the other side it was also useful for lining up our elevation but I would not recommend them for this year because they are wider then the standard wheel so less room for mechanisms but I loved them last year
here is some resources for making them
make sure they are in a x pattern otherwise they wont work or it will rotate as it strafes
here is what it looks like in a x pattern
now here is the wrong way btw they should be in a X looking from the top
wrong way below
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I’m going to add my 2 cents here,
A, because the rollers are free rolling but can roll in the direction the wheel drives trying to brake or stop without adding the omnis is, well not fun.
B, they are MASSIVE, you can get so much smaller wheels out of omni and traction
C, sizes, rn there is not a great gear ratio for either size.
D, weight, last time I checked they weight a healthy amount more.
E, there a some small inconsistencies in the drive
Overall it’s just better to run tank for size, x for maneuverability, or h for in-between.
This being said it can be ran it’s just harder and typically provides little benefit.
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I know this wouldnt solve the other problems with mecanum but could you have 2 mecanums and one omni on each side
Is H drive a good idea for high stakes because then you can strafe to place the rings more easily
I think it might be a good option