Mecanum in Skyrise

Hey, my team loves a Mecanum drive style, and we’re wondering what advantages and disadvantages people see to Mecanum in Skyrise.
Feel free to give your insight.

I was personally thinking mecanums or holonomic would be almost required with all the objects on the field this year. There is not a ton of open space on the field when the game starts but as blocks begin to move around, it could get even more cramped. You would want a robot that can manuever through that so I think moving sideways would be a lucrative ability.

I also think moving sideways would help with building the tower. If you miss the tower and you just have standard drive, there is going to be a lot of repositioning in your future. I found I was doing a lot of little starts and stop this year to get perfectly lined up with the tube and that wasn’t even hard

Overall, I’m predicting speed, mobility, and maneuverability will be very important for Skyrise and sideways motion could be a useful tool.

After fully reading the game rules, we realized that building skyrise is the key and this requires a lot precision.
Therefore, i think an omni directional base is highly recommanded this year. I thought of a six motor x drive, six motor h drive and six motor mecanum drive.
I personally favor a six motor mecanum drive for this year’s competition, but i have not seen people using six motors on mecanum drive before. If we put one motor on the front wheel and two on the back, my prediction is the front motor will react to pressure more obviously than back two motors with higher overall torque. So when doing left-right movements, the base may move slightly diagonally due to the speed reduction of the front motors.
The reason i have been brainstorming with six motors is considering about the overall weight of a robot that reaches 60 inches and higher, a more reliable base is required.

Yes, drive likes that would require precision as well as speed. Side strafing going to be common, as there is no real need to move all over the field, unless your in a situation were you need more points. But with goals that are higher that this year’s high hanging bar, I can’t think of any design that won’t easily tip at those heights. With our personal experience with mecaums, they don’t necessarily offer speed, but great point-movement. I think this is a game that will utilize their capabilities wonderfully.

8059A to D teams used 6-motor based mecanum drive during Worlds for Sack Attack season.

2616C plans on using a mecanum drive, deciding between 4 or 6 motor. Speed isn’t a huge factor in this game so we could probably get away with a 4 motor drive geared 1:1.

I was thinking 8 motor high speed mecanum drive, 2 motor intake, 1 pneumatic outtake with a passive lift.

My current design involves a 6 motor drive, 2 motor lift, 2 motor cube intake, 2 piston Skyrise section manipulator, although I may dedicate 2 of those drive motor to the Skyrise section manipulator. Not sure yet.

Techna PWN used a 6 motor mecanum wheel drive this year for toss up.

I used mecanums this year and got pushed around a lot if you do make sure your heavy. x drive and a scissor lift for me.

I started this year with mecannums, but did not have good luck with them. I think that there is an advantage in being able to strafe, but mechanums did not work for me. I think that they are to sensitive to slight weight imbalances that make the robot strafe in an arc instead of in a straight line. I’m not saying they are bad, but that they are more dificult to get to work well than some people believe.

I agree they are difficult, but we put 2 motors per wheel on the back where most of the weight was and 1 motor per wheel on the front. With programming we were able strafe successfully both in driving and programming. I am not sure what the team plans for this year. We also did not have problems with being push around.

Thank you very much for this information. We are just planning to use six motor mecanum drive with 160 rpm. We are very curious about how you used programming to slove the power unbalance issue: did you slow down the back motors? Could you please share more about mecanum wheel drive?

so my biggest issue with mecanums is their size and speed. I have tried using them twice each time hoping for a different result with the configurations. Im thinking i might go with with a classic 5 wheel omni setup. i can increase the speed of the main drive wheels but still have the ability to shift side ways. Now this is only an early concept but i feel it would be highly efficient.

We really didn’t try yo solve the problem of uneven strafing with motor control, we would correct the small difference after the strafe with the gyro sensor. It worked pretty good as our match autonomous routines were very consistent. I do agree the biggest problem is their width.

Me team has found the main problem with mecanums is that the are so wide, so leave very little space for intake mechanisms at the front. This will be a bigger problem for skyrise since the objects are so, big. For skyrise it looks like maneuverability is going to be extremely important, especially since the auto loader and skyrise base are so close together, so mecanums, x-drive or a strafing wheel are going to be an advantage.

A lot of people are posting about the problems with mecanums being so big, heavy, etc. and I was going to say, I believe a holonomic drive does much of the same things without the weight and bulk. Holonomic can strafe and have many of the benefits of mecanums. It is a little inconvenient having the wheels turned in at times but it could be a good solution to the weight issue I believe. It’s also nice if you want to strafe but can’t afford mecanums.

I could be completely wrong on this stuff but from my experience, I believe they do the same thing. If I were to play next year, I would make a holonomic drive train.

Well, actually I think mecanum wheels are big indeed, but comparing to angled omni wheels they are okay. It is a decision for teams to make on either using mecanum wheels or x drive.

to make a good X-drive that does not fail, the wheels have to be very stable, and at exactly 45 degree angels from the front side and back side, this precision when building means that the base has to be solidly built in order to function well, and in toss up I found that there is a definite size cost to that sturdiness. So it’s your choice, last year we like macanums more than the X-drive, and this year I think we might stick with our old design, but the X-drive in my opinion is over all more bulky than the mecanum drive.

https://vexforum.com/gallery/files/3/9/5/9/0/8/alfe_drive.jpg

For all the complaints of mecanum wheels being bulky, unless you are going with an H or O drive, an X-drive mounted at 45 degrees will take up a triangle of 3 inches by 3 inches by four inches at best, not including metal structure, wider than a mecaum wheel including structure. (I think.)

  1. Mecanum wheels allow for holonomic movement. Therefore, a mecanum drive is also a type of holonomic drive. By holonomic, I assume you mean an X or H drive. This part of this post was quite confusing.

  2. I might be wrong, but for a typical X or H drive, it requires more metal structure to maintain structual stability compared to a mecanum drive arranged in a ‘tank’ format. The extra metal adds up; an X or H drive will probably weigh the same as a mecanum drive.

Of course, getting a mecanum drive to strafe in a straight line is hard (struggled with them on 4 robots over 2 years. We only got one of them to work.)

As for getting 6 motors on a mecanum drive, a possible design could be to power the mecanums with 4 motors, and have 2 other motors power omnis inbetween the mecanums in a wheel arangement commonly seen on chassis. Of course, this results in using 4 motors to strafe rather than all 6, but it also makes it much easier to strafe in a straight line because of the omni side rollers. Of course, this is a configuration if you just want the ability to strafe; probably not the best in tems of relying on strafing.