Pneumatics or Mecanum

[chaparoel]

What you think is better:
Pneumatics wheels or the Mecanum wheels ?
Why?

[Canon reeves]

It depends on your strategy, but:

Pneumatics:
- High traction

- Can act as shocks for the robot when crossing defenses

-Doesn't allow you to be pushed in a direction perpendicular to your wheels

-Allows for simpler drivetrain

-You only have to power two sides of your drivetrain, so better motor
allocation with 3 motor gear boxes

-Can climb over obstacles (depending on drivetrain)

-Defending your tower is always an option if something fails

Mecanum:
-Can strafe

-Can be pushed in any direction

-Likely not enough traction to go up the ramps, and definitely not over the defenses like the moat and bumpy road.

- Less dependable, more to go wrong

-If you use 4 wheels, the most power you can give to each wheel would likely be a CIM and miniCIM, so not as fast as a robot that uses 6 CIM motors in its drivetrain

-Little to no use on defense, most robots can push you around

Your team can choose which ever it thinks is best for your strategy, but I highly recommend not using mecanum wheels. If you think its worth it, just compare it to other drive trains using a decision matrix with objectives such as durability, multi-functionality, ease of build, and complexity.

[Dumper FTW 435]

I don't know why you're limiting to those two options. I think treads are worth considering if you haven't already.

In terms of those two, I would definitely say pneumatics for the same reasons Canon Reeves posted. Most of the advantages you get from mecanums are not going to help you very much this year, and this years fields really highlight the disadvantages of mecanums.

[Demonic_]

Originally Posted by chaparoel

What you think is better:
Pneumatics wheels or the Mecanum wheels ?
Why?

Pneumatics pros:[list]
Shock absorbers
Better traction
Pneumatics cons:

• Leaking is a constant threat

Also, you should consider using tank drive. It prevents the wheels from getting tangled too much, and can provide better traction.

[Team34Guy]

Pneumatics seem to be an obvious answer so far. The tread option is gaining traction(pun intended), but we've had limited experience with them in recent years. I love the maneuverability of the Mecanum, but, as other posters have already mentioned, they will have problems getting over obstacles. Off topic....
but I'm loving Stronghold so far. Our entire team is engaged in this endeavor right now...strategy, scoring, drive selection, etc. WTG First on Stronghold

[Kevin Thorp]

Umm... great discussion, but I think this technical category is intended for fluid power pneumatics: compressors, cylinders, valves, etc.

[Kevin Leonard]

For this game? I have no idea why you would even consider mecanum wheels unless the only defense you intend to be able to cross is the low bar.

Mecanum wheels are generally poor for traversing field obstacles, and the ability to strafe doesn't help you whatsoever in this game.

Pneumatic wheels are a great choice, but not the only choice for this game. Think about your team's priorities when making this decision.

[CalTran]

Originally Posted by Kevin Leonard

Mecanum wheels are generally poor for traversing field obstacles, and the ability to strafe doesn't help you whatsoever in this game.

For sake of discussion, an argument could be made that they help line up with taking shots on the goals and maneuvering around a possible defender in the courtyard.

[tStano]

Originally Posted by Kevin Leonard

For this game?
Mecanum wheels are generally poor for traversing field obstacles, and the ability to strafe doesn't help you whatsoever in this game.

This is a very cramped field, and the goal is pretty small. It would be useful for lining up because theres not too much room y turns and whatnot to get your non-holonomic robot 'a few inches over but in the same orientation'. It would be bad for traversing obstacles, but the team could have a mechanism for opening sally port/drawbridge or be short. Playing defense with mecanum is possible. You can still hit an opponent while shooting, you can still get in people's ways; you won't win pushing matches, but everything else you can be fine at.

[IndySam]

Mecanum:
-Can strafe yes

-Can be pushed in any direction Absolutely not true

-Likely not enough traction to go up the ramps, and definitely not over the defenses like the moat and bumpy road. "Definitely" Have you tested them?

- Less dependable, more to go wrong Absolutely false.

-If you use 4 wheels, the most power you can give to each wheel would likely be a CIM and miniCIM, so not as fast as a robot that uses 6 CIM motors in its drivetrain Maybe

[cadandcookies]

To bite at the OP's original question, it depends 100% on your strategy. Neither is inherently better than the other.

I would recommend that you take a hard look at your strategy for this season, and ask yourself which wheel's characteristics fit your strategy the best. I would argue that for this game, pneumatic wheels (specifically AndyMark's 8" offering) are a far more flexible option, but I can see a couple of niche strategies where mecanum can be a valid option, and I also haven't seen any actual testing of mecanum wheels over the obstacles, so while there is a great deal of speculation that they will perform poorly, it is possible that there may not be as many issues as one might first assume.

[evanperryg]

I'll restate what I've said in many threads like this. I don't care how your robot moves, as long as it gets the job done well. The drivetrain is one aspect of the whole that cannot be isolated as the only factor of success. Is the drivetrain important? Yes, extremely. Is it the only important thing? No. Good mechanisms make a good robot, and the base is not the only mechanism.
Personally, I don't like mecanum because I feel it's too easy to bully mecanum robots, especially in a game where alignment is key. However, my team has been in a situation where, as the 8th seed alliance captain, the 2 best remaining robots were both mecanum. (this was 2014, by the way) Did we care? No. We picked them because they were the best, and they fit our strategic goals. What matters is that you're completing tasks consistently and quickly, regardless of what kinds of wheels help you do that.

Tl;dr: I don't care if you use hot dogs for wheels. If you're scoring points, and you fit the strategy, it's fine.

[CalTran]

Originally Posted by evanperryg

Tl;dr: I don't care if you use hot dogs for wheels. If you're scoring points, and you fit the strategy, it's fine.

10:50PM, 1/14/16: I predict that hot dog wheels will grace Einstein before Mecanum wheels will. You heard it here first.

[Kevin Leonard]

Everyone here is posting this wishy-washy stuff about how it depends on your strategy and that mecanums could have uses, but the OP asked "which do you think is better", and whenever asked that question in a game with defense, I'm going to respond with traction wheels.

Sure, you can absolutely build an extremely competitive robot that does every task in the game with mecanums. It is possible. But if you don't have experience with mecanum (and even if you do), traction is going to be simpler, better at pushing, and is easier to make traverse obstacles(8" pneumatic wheels will get over obstacles easier than 8" mecanum wheels when controlling for other variables).

Both have advantages, but unless there's some really specific use case where mecanum is the overpowering option (like it may have been in 2015), or you have tremendous experience and driver practice using mecanum, go with traction wheels.

[cpapplefamily]

I'm a new mentor this year. The team always wanted mecanum and this past preseason I helped them successfully get them working with 8" wheels. We are designing for mecanum with an option to abort to 6" drop center 6 wheel drive. We are hoping for lowbar, agility shooting, helping open doors, defence. The traction up the ramps worries me.