So these questions are for those who have used both the Mecanum Drive and the X - Drive.
Maneuverability - Which design easier to control when driving in a tournament? Arcade or Tank drive?
Reliability - Which design is more consistent when programming autonomous?
Prefer? Which design do you prefer and why?
I’ve built neither before, but I’d assume that if you have any holonomic drive, arcade is superior because that way you can control the speed of your strafe and you can move diagonally.
An x drive has superior maneuverability and speed, but a mecanum drive has better pushing power and holds up to defense easier. I personally prefer the x drive do to its higher maneuverability. Also a well practiced driver can use the maneuverability of the x drive around most defense. Also arcade control is better for either
X-drive is superior to mecanums in every way except it’s ability to climb. If you don’t need to climb onto anything, then go with an X-drive.
I would argue mecanums are the best for most situations, because they fit into normal drivetrains, don’t take up much space compared to an x drive, perform well in autonomous, and are good at climbing. In most other ways, I believe they are equal to an x drive. The other factor is that an x drive must be a square, and cannot be a rectangle. One of my friends teams switched from an x drive to mecanums this year, and their performance was improved greatly by having a 25 hole wide drivetrain, which mecanums allowed.
X-Drives do not have to be square. They can be rectangular, and with decent build-quality/programming their wheels can even be offset from one another.
Mecans are better because they have more pushing power. X drives are 1.41 times faster than tank (google it if you must), but they have like no force behind them. Speed and torque is a tradeoff. Mecan wheels are the superior choice if you have access to them.
The disadvantage of mecanums is that they strafe slower than X drives. The torque loss in X-drives can be accounted for by using smaller wheels. The problem with x-drives however is that they are more complicated to build, and create more opportunities for axles to be ever so slightly misaligned and cause excess friction. This can be overcome with attention to detail, but for newer teams it can be somewhat difficult. A lot of it, however, comes down to personal preference, and what the current game requires teams to accomplish.
A solution to the speed disadvantage with mecanums is simply gearing them for speed. Although this takes up some more space if you plan accordingly you can have a better balance of speed and pushing power along with the strafing abilities.
We used the Mecanum wheels with the high speed motors. They seem to work fine and motors did not overheat, but the strafing was not always accurate.
Yeah weight distribution can throw off strafing sometimes.
Portalstorm4000, the reason you would most likely want it to be square is so you would have the most building space, because the x drive already takes up a lot. Mecanums don’t have this issue, so it would always be better to put mecanums on a rectangular drive.
Mecanums fit between 7 holes at a minimum without modifying anything, but the rollers don’t stick out too far past 2 inches, so if you space it right and use low strength gears you can fit a geared mecanum drive into 7 holes on each half of the chassis as well. If you’re gearing for speed I’d recommend switching to 600RPM motors and gearing it down with a 7:3 external ratio.
This is incorrect. For an x drive and tank drive with the same wheel size and max rpm, the tank drive is 1.4 times faster. The reason x drives lack pushing power is that their wheels push against each other in the direction opposite to the movement, wasting torque that is applied in the same direction in a tank drive.
While this would seem to be the case at first glance, it is not. Here’s a good video to demonstrate:
And here’s the math behind it:
Unlike an x-drive which can turn very easily without even having to turn the omni wheel rollers, a mecanum drive has a lot of friction when turning due to the rollers dragging.
We discovered this in turning point with our 8 motor 1:1 turbo mecanum drive which would always burn out during matches from turning.
This is probably not a problem with V5 though due to the much higher torque of the motors unless you have a very heavy robot and/or a very slim chassis, although the friction might affect turning accuracy during auton.
I personally prefer mecanum drives due to them being much simpler to construct and having higher pushing power in the forwards/backwards direction.
For control, I prefer arcade with strafe on one stick and turning+forwards/backwards.
Na i’ta’int. The link in the post above mine has an article about the math behind it. X drive is faster.
This can be easily resolved by using some of the smaller Omni wheels. @Dave_Macaroni did this and had some decent success with it.
This also helps save space at the same time.
From my experience with x drives and mecanums, mecanum drivetrains have the potential to be wobbly when turning because of the rollers, and the x drive has a higher potential to burn out, even using v5. For one of the teams at my school which had an x drive, the burning out was enough of a problem at 200 rpm that they had to switch to 100 rpm cartridges to counter the issue.
Interesting… could the burning out be because of a misalign shafts? Our team had the same problem until we fixed that issue. Chassis was slightly misaligned.