Mecanum vs The Barrier

[Charmander]

My team is strongly considering Mecaum this year. However, we are a little concerned about the 4 inch high steel barrier. We did some tests and our 8 inch mecanum bot can go over the barrier without too much problem. However, we are a little concerned about if the mecanum wheels will get worn out over time. The wheels are delicate and ramming into the 4inch high steel barrier can't be the best thing. We might go for 10inch heavy duty mecanum wheels but would either set of wheels get worn out considerably?

To put it delicately: Those wheels are gonna be broken in 2 by match 3.

Mecanums have no traction, and worse, are very fragile. Most teams will be going full speed to get over those ramps, and if you do that with mecanums, then they'll get broken before they become useful. Not to mention, it'll be hard to get any traction on the bridges.

If you do use mecanums, then be careful, use them the grippiest way possible, and double check your choice.

[Unglued]

Don't do that if you want the wheels to last..

The barrier can be overcome with enough momentum but your wheels and frame are taking a hit every time.

[Marc S.]

Keep in mind, the barrier has a 1/4"(1/2"round) fillet on both edges, this will reduce wear.


SuperNerd256, pneumatic wheels will go flat, and the mecanum rollers are replaceable.

[davidthefat]

Unless you put "skis" about a centimeter off the ground.

[MattC9]

We used mechs. in 2010, never again. They were destroyed because of the 2010 bumps, I can't immagine what the barrier will do to them.

[ayeckley]

Originally Posted by MattC9

We used mechs. in 2010, never again. They were destroyed because of the 2010 bumps, I can't immagine what the barrier will do to them.

Counterpoint: We used mechanums in 2010 and they were not destroyed by the bumps.

[vhcook]

Originally Posted by MattC9

We used mechs. in 2010, never again. They were destroyed because of the 2010 bumps, I can't imagine what the barrier will do to them.

Ours actually held up fairly nicely in 2010 through two regionals, and we were back and forth on the bumps a lot.

The center rail this year is a bit more severe, particularly you're trying repeated high-speed traverses. I'd definitely be concerned about bending the roller supports out of shape. Traction could also be a significant concern, particularly on the bridges when they're tipping.

[Ankit S.]

One more thing about Mechanum wheels vs. the field.

The key is not carpet, which is plastic, and will turn your Mechanum wheel robot into a "spin my noisy wheels" robot. In addition, if you do have any intention on balancing, Mechanum wheels may have a problem with that as well.

I suggest that you and your team thinks a little more about it, runs some tests (if possible) about mechanum wheels on the field, and carries spare 8 inch wheels to competition, so if your wheels break/are ineffective, you will be able to switch them out.

[Mr. Lim]

Team 1310 used 8" mecanums in 2010, and used them to go over the bump.

I won't claim that the forces are the same as going over this year's barrier but at least I can share some real experiences.

The wheels lasted through 2 regionals. We had to replace 2-3 broken rollers I believe, but broken rollers didn't cost us any matches IMO. You can lose one roller, and it doesn't impact you that much during a match. The bigger problem is that the driveshafts eventually bent a bit. They never failed completely, and in fact we never did replace them, because it was so difficult to get the wheels off the bent shafts.

We had to hit the bump pretty fast in order to carry enough momentum to get over the bump, so they took a pretty good beating.

However, 1310 employed a very very simple suspension that probably save both the wheels and driveshafts from a lot of damage. Some would argue that you should have a suspension when doing mecanum regardless, to ensure all 4 wheels are touching the ground as much as possible.

If I were to consider mecanum for this year with the intention of going over the barrier, I doubt I would do it unless I also put serious resources into a suspension system.

A few practice / build season video from 1310 in 2010:
http://www.youtube.com/watch?v=PneD_...0&feature=plcp

[ratdude747]

maybe the uber-heavy 10" steel plated mecanums... those would hold up...

http://www.andymark.com/product-p/am-0298.htm

keep in mind they are HEAVY....

[Lil' Lavery]

Originally Posted by SuperNerd256

To put it delicately: Those wheels are gonna be broken in 2 by match 3.

Do you have any concrete evidence to support that claim?

[Joe Schornak]

My team is prototyping a variation on a mecanum system that should reduce the impact on our wheels. Each mecanum wheel will be paired with a traction wheel positioned ahead of the mecanum and raised so that it doesn't contact the ground while driving normally. When the robot drives over the barrier, the traction wheel will contact the barrier first and lift the front of the robot, putting the mecanum wheels in a more advantageous position to drive over the barrier. I'll probably post a picture or a detailed drawing once our design is more finalized.

Originally Posted by SuperNerd256

To put it delicately: Those wheels are gonna be broken in 2 by match 3.

Mecanums have no traction, and worse, are very fragile. Most teams will be going full speed to get over those ramps, and if you do that with mecanums, then they'll get broken before they become useful. Not to mention, it'll be hard to get any traction on the bridges.

If you do use mecanums, then be careful, use them the grippiest way possible, and double check your choice.

We used mecanums last year and in a 2010 summer project, and have never encountered the problems usually associated with them. They have excellent traction on a variety of surfaces, and while a mecanum bot wouldn't win a pushing contest against an 8-wheel roughtop-treaded gear-shifting defensive beast, we have pushed tank drives around with no problems. Our newest set of wheels, from AndyMark's current line of mecanums, have survived use on multiple robots, and they will survive through this year's competition. As long as you design your drive system so that the barrier impact point is not at the very front of the wheel, so more of the force is directed into pushing the bot over the barrier than into deforming the wheel, you should have no problems.

[Chickenonastick]

Just imagine what the bump will look like following a regional.

[Charmander]

After reading all the posts so far, it seems that more people believe the mecanum wheels will be able to handle it. Would it be wise to put in the money (and weight) to buy the 10 inch heavy duty wheels over the 8 inch wheels?