What you think is better:
Pneumatics wheels or the Mecanum wheels ?
Why?
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.
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.
Pneumatics pros:
Shock absorbers
Better traction
Pneumatics cons:
[LIST]
- 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.
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
Umm… great discussion, but I think this technical category is intended for fluid power pneumatics: compressors, cylinders, valves, etc.
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.
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.
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.
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*
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.
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.
10:50PM, 1/14/16: I predict that hot dog wheels will grace Einstein before Mecanum wheels will. You heard it here first.
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.
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.
Which ramps in particular? Things like the Cheval and Ramparts, the ramps that lead up to the Defenses in general, or the ramp that is the Batter (the front of the tower)? I suggest building whichever one you have fear about, “splurging” on a bit of correct material to cover them with, and get testing ASAP.
I just wanted to say that unless you’ve tested this, it’s all just hypothetical.
In 2010, my team used mecanums, and that ramp was a much greater angle than those seen on this year’s field. We did not have any issues going up and over.
Don’t entirely rely on other people’s opinions, make your own judgements based on your experience and testing!
(I will forever have a love for mecanum, but I might be biased since my coffee table is mecanum drive 
)
Partial Quote:…"(I will forever have a love for mecanum, but I might be biased since my coffee table is mecanum drive)"
Lol…Now I know exactly what “Special Personal Project” I am going to order that wonderful tank chain tread for now! I’m going to turn my living room coffee table into a Stronghold Defense crossing capable coffee table. It may be too heavy for our robot, but it surely isn’t for my future coffee table bot.
Our living room is small (the house overall is large though), and we have a matching very comfortable loveseat and large couch and a chair that are all seating position reclining, so everyone is always moving the coffee table a couple inches at a time, all about the center of the room (just a little bit, but I’m always straightening it up later-“anal type A” that I am), as feet get very close to it when reclining.
They will be able to move it about using a tethered controller and their smart devices, laptops, or ipads.
Thank’s for that idea. (I would have never thought of doing that…ever!)
Just wait until my glass & tile squares topped wooden coffee table is going over and through all the team edition of the defenses with the practice bot before season end (besides the Low Bar of course), that the students have been putting together all week. (It certainly won’t be FRC Legal, as it will certainly violate the 120" perimeter frame rule (I think I will just mount a nicely stained marching dark cherry wooden electronics shelf about a foot below the glass top), and I’m not putting the bumpers on it, or it certainly won’t fit our living room space again. (Though I admit that it would look really cool w/ legal 8" each direction reversible Blue/Red bumpers perfectly in the bumper zone on each corner & our Team 60 numbers, so maybe I will notch the wooden legs so they can be added or removed on a whim).
There were a lot of mecanum’s in Rebound Rumble and those ramps were a wicked angle, plenty of mecanum’s last year in Recycle Rush (is the angle of the ramps really any different this year?) Low Bar, Sally Port, Drawbridge, and Portcullis are all ramped but flat going through Defenses. (If one could push down & climb the Rebound Rumble ramps, one should certainly be able to push down & climb the Cheval de frieze too I’d certainly think). Moat isn’t that tough, Rock Wall ehhhhh - I don’t know about that 1, or the Ramparts without some killer type suspension added. I wouldn’t even attempt to tackle the Rough Terrain without same killer suspension added…Like Monster truck suspension added.
Put Mecanum’s in an “X” pattern to shoot though and it does not push around as easy as many think (especially if backed by rail and wall right in front of the opposition alliances RH Drivers Station.
I’m willing to bet we see at least 1 Supershooter this year that figures out how to sit in the Spybot only position and shoots into top goal only (or maybe even top & bottom), using the curveball effect, and has not much of a drivetrain at all (just enough to crawl over to and climb on the Batter to Surround & or Scale and can collect from 2 sides so robot defense against it is a bit lessened.
We will probably see at least 1 Spybot Supershooter without any drivetrain at all…But, that bot will not make it out of the qualifying matches due to not being able to surround/scale the tower…And it will skew the RP results highly at that specific event! (I certainly could be wrong about not making it out of Q matches if it finishes a low team count event top 8 and ends up an alliance captain due to shooting very well and so many others helping them w/ Defense RP’s and scoring high by making all shots high and accurate leading to high scoring auto & tele, while others fail to surround/scale against them).
Said bot will never move anywhere once placed in that Courtyard corner except during the last 30 or so seconds of a match. Count on it happening.:yikes:
** Setting that X pattern once surrounding on the batter. Certainly No Rolling Off.
I disagree highly…The ability to strafe for a fast Courtyard Supershooter being fed boulders at a fast clip by a Low Bar Specialist and a Killer fast Defenses Specialist at the same time, who can avoid a single defender pusher bot that cannot strafe, can and will work wonders in this game. I’d bet big money on it.
Give me that same fast Low Bar bot you just described as a partner please…I will open Sally Port, Drawbridge, & Portcullis for them and we will also kill them off by going bumper-to-bumper right through together w/ a boulder each on each trip and damage each Defense really fast…especially if they can strafe as it will make it easier and quicker during the “here, hold this door for me while I cross & boulder load up, then join you in a second” phase.
Personally The Heavy super low CG Chain Driven Tank Treads- 2 sprockets high out, 2 low in and a slightly dropped center low idler so it looked like a tank (Driven just like a tank also w/ 2 joysticks and shifting, boulder collector(s) rear and front as supershooter feeders/low goal delivery), are my favorite though, but my 2 favorite partners would certainly be a FAST STRAFING Mecanum Driven Courtyard Only Supershooter & a FAST STRAFING Mecanum or high grip Low Bar Specialist.
Together we’d Rule the KINGDOM (I’ll take care of all those other nasty Defenses with a smooth fast moving super tank, and I’ll open more doors for you than you can possibly imagine w/ my Killer Tank! It won’t matter what they throw in front of us, we’ll together have them all covered). You Low Bar, will strafe that Neutral Zone snatching boulders away like magic. Now just figure out how to get all that into a simple short 14" high, and at least ramp climbing (clearing), package. That is the tough part! And Supershooter plants all our ammunition high and accurate. And runs circles around that defender.
I’d go 1 step further (use your 15" and put a drop down loop on the front of Low Bar & I’ll put a drop down pin on the rear of my tank in that same space-Pin goes in the loop we are towing in low gear), and I’ll carefully & slowly pull you over whatever obstacle you wish to help Damage that they threw in front of us…But, please, please, please Low Bar Specialist Damage that Low Bar strategically, because I certainly cannot. Not that I absolutely need to either. Lol.
Why are people insisting you play this game all by yourselves…Didn’t they learn anything from 2012, 2013, 2014, & 2015? It is all those games combined! It takes TEAMWORK…Teamwork will win and Damage Defenses and Capture the Tower in STRONGHOLD. (The single boulder per robot/per carry or defend in courtyard, makes it a required teamwork strategy to win game).