2015: Mecanum or Slide?
 

For 2015, which would you choose?

Re: 2015: Mecanum or Slide?
 

swerve. agility is ever more important the more confined you are and you have that bump to deal with

Re: 2015: Mecanum or Slide?
 

i think slide because you need to be fast

Re: 2015: Mecanum or Slide?
 

Tank drive.

Re: 2015: Mecanum or Slide?
 

another option

http://www.chiefdelphi.com/forums/sh...2&postcount=12

Re: 2015: Mecanum or Slide?
 

Ether,

Are you suggesting this is a viable option for the game this year? Or just opening our eyes to other configurations that should be considered? (because you just opened mine...)

Because at first glance this looks easy to implement mechanically, not so sure if it is for programming, but you basically laid out the kinematics.

Plus there is no drivetrain arms race in the game this year, so traction and power aren't as important as it has been in the past.

Re: 2015: Mecanum or Slide?
 

No. Just tossing it out there to show that the "mecanum or slide" choice is a false dichotomy.

For more info, follow the link to Jared Russell's post.

Re: 2015: Mecanum or Slide?
 

Personally, I would prefer a slide drive. It grants the most mobility at the least amount of complexity. It can be mechanically implemented similarly to a tank drive (save for the sideways mobility wheels), which is a style of drive train that Team 20 is accustomed to. Also, it still has more traction than mechanum, which may come in handy on the slick HDPE scoring zones.

Just my 2 cents

Re: 2015: Mecanum or Slide?
 

what is "slide"? never heard of that one

Re: 2015: Mecanum or Slide?
 

Ok that makes good sense. Thanks, your opinion is highly valued and thought you might have been on to something!

Re: 2015: Mecanum or Slide?
 

Me neither but check out http://www.chiefdelphi.com/forums/sh...ad.php?t=96193

Re: 2015: Mecanum or Slide?
 

While you're waiting for an answer, try searching. It's easy.

http://bit.ly/147cKeb

Re: 2015: Mecanum or Slide?
 

VEX Teams also call them H drives.

Re: 2015: Mecanum or Slide?
 

I would go with slide because it provides maneuverability and speed but doesn't have the problems with balance that mecanum does. it would take a lot of engineering to make sure that the entire robot is balanced both with and without the totes on it.

Re: 2015: Mecanum or Slide?
 

Why would slide necessarily be faster than mecanum?


In what way is slide less complex than mecanum?

Re: 2015: Mecanum or Slide?
 

The key to a proper mecanum isn't a perfectly balanced robot, it's a suspension system. have each wheel be able to bounce up and down and you're set. Once you've finished that, programming is almost simply than skid steer code.

Re: 2015: Mecanum or Slide?
 

Slide. Since pushing power isn't very important this year slide allows teams to only use 3 motors and gain holonomic motion. It's simpler to understand and program as well, and it can be designed lighter than a mecanum drive since it only requires 3 gearboxes.

Re: 2015: Mecanum or Slide?
 

Not quite. You actually need a keyring full of keys.

http://www.chiefdelphi.com/forums/sh...3&postcount=41

Re: 2015: Mecanum or Slide?
 

Our team is doing the final design matrix to choose this tomorrow. I personally favor slide, as it has all of the advantages of mecanum with the speed of tank drive. Only problem is weight...

Re: 2015: Mecanum or Slide?
 

Do you mean weight in comparison to mecanum or in general? I'm trying to see what why a slide drive would be so heavy.

Mecanum
4 wheels
4 gearboxes

Slide
~5 wheels
~3 gearboxes

Does a wheel weigh similarly as a motor and gearbox?

Re: 2015: Mecanum or Slide?
 

Did you mean "all" literally?

Re: 2015: Mecanum or Slide?
 

Keep in mind the weight difference between a mecanum and omni wheel.

Re: 2015: Mecanum or Slide?
 

http://www.chiefdelphi.com/forums/sh...39#post1420039

Re: 2015: Mecanum or Slide?
 

amen

Re: 2015: Mecanum or Slide?
 

drop center allows for turning on the center of the robot for quick maneuverability i like that option

Re: 2015: Mecanum or Slide?
 

I second that

Re: 2015: Mecanum or Slide?
 

Who said you have to use gearboxs for mecanum or H-drive? Save your weight and use a single reduction...unless you plan on playing defense on your own alliance. There are some nice new resources from vex that will make this super easy for some teams.

Just a tid bit: If your doing H-drive or "slide"....please don't solid mount your strafe wheel and expect it not to weaken or break when you hit the bumps.
-Ronnie

Re: 2015: Mecanum or Slide?
 

How much do mecanum wheels cost and where can I get them? Are they COTS items?

Re: 2015: Mecanum or Slide?
 

AndyMark: http://www.andymark.com/Mecanum-s/53.htm
VexPro: http://www.vexrobotics.com/vexpro/mo...um-wheels.html

Both AndyMark and VexPro are VENDORS.

Re: 2015: Mecanum or Slide?
 

What are the size restrictions for the wheels? Can I put 4" wheels on my robot?

Re: 2015: Mecanum or Slide?
 

but with tall robots and heavy loads they will be very tippy

Re: 2015: Mecanum or Slide?
 

Yes you can put 4" mecanum wheels on your robot seeing how both vendors offer them.

Re: 2015: Mecanum or Slide?
 

Consider though that it might not let you go over the ramps.

Re: 2015: Mecanum or Slide?
 

I like WCD for this one, it's a lot faster than mecanum (the other option my team has the resources to use) and is maneuverable enough to do what it needs to do. Our team did really well in Stack Attack with tank drive. I don't think WCD or tank are out of the option.

Re: 2015: Mecanum or Slide?
 

Why do you say that?

Re: 2015: Mecanum or Slide?
 

because it is true. If you have the same gearboxes with the same motors, the wheels rotate at the same speed, but mecanum looses some of that due to the way the wheels are angled.

Re: 2015: Mecanum or Slide?
 

Why do you need to be fast in this game?

A better way to look at this game is analyze where your robot needs to go and what is between you and that point. How do you get from these points the fastest? Will that route change during the match? If so how do you overcome that?

Re: 2015: Mecanum or Slide?
 

Re: 2015: Mecanum or Slide?
 

Is there a rule prohibiting you from putting 4" wheels on your robot?

If you want to use 4" mecanum wheels from AndyMark, make sure to order this set of wheels and not this set, which is designed for FTC robots and is not rated for the weight of an FRC robot.

(VexPro only sells one type of 4" mecanum wheel, and it's rated for FRC robot weights.)

Re: 2015: Mecanum or Slide?
 

Just be careful on using slide if you are using 2"x1" frame because that middle wheel is likely to be damage by going over the platform

Re: 2015: Mecanum or Slide?
 

Why would you gear two different drive systems the same?

Re: 2015: Mecanum or Slide?
 

I wish that paper addressed the "top speed, and thus the 'feel' of accelerating, in the sideways direction is less than the forward and reverse direction." I still don't know if that one is true.

Re: 2015: Mecanum or Slide?
 

However if you used slide you would have to build a kind of suspension system to prevent the center wheel from being snapped off when going over the bumpity bump

Re: 2015: Mecanum or Slide?
 

Going to ahead and say without proper motor management swerve might not be optimal. The standard swerve I see takes 2 cim's per module with 3 modules. That is using 6 cims.
Now if you don't use all 6 cims you would have in theory 3 spare cims. Thats a lot of motors for super structure.

Re: 2015: Mecanum or Slide?
 

Most swerve drives I've seen have four modules with 1 CIM each, although I have seen one offseason swerve drivetrain that used 3 modules.

Re: 2015: Mecanum or Slide?
 

From what I understand, theoretically a mecanum can go sideways at the same speed that it goes forward. However, it is a lot more lossy in that direction and as a result you go slower.

Re: 2015: Mecanum or Slide?
 

It's true, and it's discussed in this paper at the bottom of page3 and top of page4.

Re: 2015: Mecanum or Slide?
 

Our team is definitely going mucanum drive this year. we thought about slide drive but thought this was a bad option as the center wheel would be the only contacting wheel when going over the scoring platform. Also we have an old mecanum robot that we were able to get driving today and found it had no problems going over the scoring platform. We even strapped 4 batteries to one end for a really bad weight distribution and did not see much change in the drive performance. We were quite surprised at this as we do not have a gyro or suspension on this old bot. We were so impressed that we are not even going to use a gyro or suspension this year for our robot.:o :o :o

Re: 2015: Mecanum or Slide?
 

I hope you're ready for the exaggerated claims that will follow in response to this statement.

Re: 2015: Mecanum or Slide?
 

Any chance you posted video of that somewhere? I'd sure bookmark it.

Re: 2015: Mecanum or Slide?
 

No we did not post any vids, But i can see if we can get vid of it on monday.

Re: 2015: Mecanum or Slide?
 

Bomb Squad has used 3 modules for years.

Re: 2015: Mecanum or Slide?
 

We have video of us using a plywood board to support totes outside the frame perimeter of a mecanum but I think it was scrapped cause at the end the driver made a mistake and caused the totes to fall on me. I'll poke around and see if I can figure out who had it and if they still do

Re: 2015: Mecanum or Slide?
 

We did the same things with the totes to. We even duck-taped the totes on to some protruding arms but they feel off the first time we hit the scoring platform at speed.

Made me wonder how stable a stack will be when it is held by the robot.:o