New Vex Mecanum
 

Has anybody tested the new 2015 Vex six inch mecanum wheels?

How well are they doing?

Re: New Vex Mecanum
 

We are building chassis this weekend. I expect the new wheels to perform about the same as the old ones. Durability is the issue. Time will tell on that.

Re: New Vex Mecanum
 

Yes. Vex tested them:

Re: New Vex Mecanum
 

I swear Ether is one of the few people that searches posts for an answer before he posts. Thanks Ether for setting a good example!

Re: New Vex Mecanum
 

The OP might have been asking for real world testing. After the issues with VEX's last iteration, I would consider that prudent.

Re: New Vex Mecanum
 

Wouldn't real world testing be competition? So the next best thing would be the kind of testing that Aren did.

Re: New Vex Mecanum
 

Perhaps they did competition test them? I haven't seen any data on CD or the VexPro website with test data. All I know is that they were tested and that they were tested...

Unless you email VexPro, you probably won't know how the wheels were tested. For all we know they could have tested the wheels with a 50 pound robot, which is unlikely but without data we don't know.

Re: New Vex Mecanum
 

We bought a set of the new rollers and installed them on last year's machine. We've been running it around the shop as vigorously as possible for the last two days. We have experienced zero breakage and only normal signs of wear.

We have decided that Vex solved their issues from last year and we have confidence in the new design.

Re: New Vex Mecanum
 

If I remember correctly, most folks would have said the exact same thing at this point last year.. Last year's model failed after more than a few hours of usage.

Re: New Vex Mecanum
 

FYI Aren Hill IS Vex, he is one of the engineers there. I'm sure he'll provide more data on their testing if you ask.

Re: New Vex Mecanum
 

Correct. We can still tell a difference though. The signs of looseness and fatigue showed up early last year. They didn't start breaking until after extended use. We aren't seeing the looseness occur yet. I'll post an update after another week or so.

Re: New Vex Mecanum
 

We have a set as well, and will hopefully be running them Saturday. We'll post any info as we go along.

Re: New Vex Mecanum
 

Exactly the purpose of my post.

Re: New Vex Mecanum
 

So driving a robot around with mecanum wheels on FRC regulation carpet wouldn't be "real world testing"? Well, I live about 20 minutes away from IFI (where Vex HQ is) and out of the 15+ times I have been there to pick up parts, last season, only maybe two times I didn't see robots driving around doing things. I can vouch and say I know VEX test their products in a "real world" format because I have seen it and talked to VEX employee's about it.

Re: New Vex Mecanum
 

All, the testing we completed with the 6" mecanums was fairly simple, four wheels, properly oriented, test bed weighed up to 150lbs (max robot with batteries and bumpers), and then handed to a High school intern who has no regard for the safety and well being of the wheels.
He was then told "break these" and came back after several hours of driving with the rubber worn off the rollers, no broken tabs.

I later found out his testing included driving around on sidewalks and over significant bumps and door jams, in addition to running around on FRC carpet.

Note, we are also working on specific testing on the current field with additional weight for the game pieces, we expect positive results given the previous testing described above.

Hope this answers your questions,

-Aren

Re: New Vex Mecanum
 

Was the driving robot centric or field centric going down that sidewalk :D

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I apologize, I should have been more clear in my post. I was attempting to say that Aren did indeed say they were tested but did not provide the testing means.

He has now provided the details that were missing.

Re: New Vex Mecanum
 

All it took was to ask him to post more detail (as I did in an email to the address he gave).

Re: New Vex Mecanum
 

I know, I prefer public information to private. Unfortunately, many teams won't go through the process to contact a company to acquire information. Personally, I would love to see the testing processes used on all AM and VEX products on the product webpages.

AndyMark did a great job documenting their tests on their Mecanum wheels, while haven't seen any quantifiable data on the VEX wheels.

I'm curious how the VEX wheels would hold up if they were put through the same tests as the AndyMark wheels.

Re: New Vex Mecanum
 

Do you consider the AndyMark tests in the linked document to be more "real world" than the Vex tests?

I'm curious how the AndyMark wheels would hold up if they were put through the same tests as the VEX wheels. :-)

Re: New Vex Mecanum
 

Not only that but he is scary fast at it too...

Re: New Vex Mecanum
 

Thank you for the information. Can you comment on the 4" wheels and the testing they under went last year and what they are going through this year.

Re: New Vex Mecanum
 

The Drill was exactly the same, except they were mounted in a 2014 Drive In a day, rather than the test bed we'd used for the 6" wheels, which was a 2013 Drive in a day.

-Aren

Re: New Vex Mecanum
 

Nah, I'm pretty sure he just memorizes everything on the boards.

Re: New Vex Mecanum
 

Any new Vex reports after another week of trial?

Re: New Vex Mecanum
 

We have been driving for almost 2 weeks now and we have no broken rollers. We even accidentally ran into a wall at full speed. Bent frame but no broken rollers.

Re: New Vex Mecanum
 

A time-lapse video of the new 6" Mecanum Wheel Recycle Rush test is now up on the VEX YouTube page: https://www.youtube.com/watch?v=aLwbjCPZ958

Test conditions:

• Chassis: 2013 Drive in a Day with custom upper structure to hold weight
• Weight: 118 lb (barbells)
• Field: "Regulation" Recycle Rush practice field. Scoring platforms made out of plywood and covered with HDPE.
• Duration: 4+ hours (excluding battery changes, motor cooldown, etc).

We were pleased with the results. Tl;dw version: no broken rollers, just some worn rubber.

Re: New Vex Mecanum
 

[quote=Grant Cox;1437686]A time-lapse video of the new 6" Mecanum Wheel Recycle Rush test is now up on the VEX YouTube page: https://www.youtube.com/watch?v=aLwbjCPZ958
QUOTE]

How does this compare to the tests done last year? Or, did last year's wheels break under similar tests?

Re: New Vex Mecanum
 

Thanks, great video.

We went with the Vex wheels so we could get on with our build several weeks ago. At the time Andymark was out of stock. Given the response from Vex and I gambled on their wheels.

Looks like the redesign is working well! On less thing to worry about.

We are just about complete and should be able to run our bot soon.

Re: New Vex Mecanum
 

We've been doing a lot of fancy software development on our little Nanotube-based test robot while the competition robot is being built. We did have one roller break at the base where it interlocks with the hub. That was after maybe three hours drive time. We're hoping this is just an isolated case. This robot is about half the weight of an FRC robot and wasn't doing anything crazy at the time. It was no big deal to repair but we don't want to make a habit of it.

Re: New Vex Mecanum
 

For that VEXpro video, I thought that the regulation scoring platforms were 16 degrees and 2 inches high, not 4 inches?

Re: New Vex Mecanum
 

Were they the new 2015 wheels?

Re: New Vex Mecanum
 

I assume so, just received them in early January.

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Was this per chance a wheel with 2 roller packs taped to it?
If so the rollers on the wheel were the old variety, while the two packs taped to the wheel were the new variety.

-Aren

Re: New Vex Mecanum
 

Yes it was. Does that mean it's the older design? It would have been nice to include a note to that effect. We thought VexPro was just being their usually nice selves and including backups. I suspect many teams have just mounted the wheels as they came from the factory. Oh well, better to know now!

How can we tell the difference since we have several sets and some came with the upgraded wheels and some did not?

Re: New Vex Mecanum
 

Oops. Uh.... chute door?

(Thanks for pointing that out. The field was correct, the video descriptions were not.)

We haven't done any tests with pre-2015 rollers on a Recycle Rush field, but recommend making the switch if you still have any kicking around. The "break these" tests that Aren described above were for the 4" and 6" wheels with new rollers. This test was essentially a refined version of those, on a realistic field, with a camera rolling.

Re: New Vex Mecanum
 

This was the transition point from old to new, we had existing inventory of the 6" wheels with old rollers on them, and rather than open each one up and replace the rollers, we attached two replacement roller packs of the new style to the product (enough to completely update the wheel).

This just gives you some more run time overall and was more productive than us scrapping the old rollers entirely.

-Aren

Re: New Vex Mecanum
 

Seeing VEXPro say that the platform (Although accidentally) 4 inches high gave me more of a heart attack then it should have, and I'm a 2 year alum! :yikes:

Re: New Vex Mecanum
 

The new rollers are curved at the base on both sides. The old rollers were curved on one side and flat on the other.

Re: New Vex Mecanum
 

That's great and I would have done the same thing. I'll bet a lot of teams didn't know why they were getting extra rollers and put the wheels as-is on their robots. I hope they read this!

Re: New Vex Mecanum
 

Hmmm. We placed two orders and received replacement rollers with each order.
Not overly excited to read this news. If I had known we were getting the old style wheels I would have not ordered. Very unhappy that there was no note with the order indicating that we could/should change rollers out to the new style. Now with less than two weeks left, I was lucky to read this thread (others will be less fortunate). This will cost us a few hours of valuable build time by pulling off wheels on two bots and trying to figure out which wheels are the new and old style, and then replacing. Not a happy customer.

Re: New Vex Mecanum
 

Here's the picture of what VEXpro did to make their wheels stronger:

http://content.vexrobotics.com/vexpr...ed-mecanum.jpg

I think it will do just fine, but our team wants to wait one season to see how they preform, considering that we had 5 rollers fall off of one wheel during a match last year

Re: New Vex Mecanum
 

Just to add some information:

Our wheels have been doing decent until this weekend when we were running them all day. They started developing serious play. We were forced to swap them out for the new rollers. It cost us a few hours but it rolls much better now. If anyone was curious about the insides of an old roller, here you go.

Re: New Vex Mecanum
 

Just wanted to update that our first set of VEX Mecanum (6inch) wheels have lasted through build, practice and one regional. We have an extra set, just in case, but we don't think we'll have any issues.

Re: New Vex Mecanum
 

I'll add a report from our team as well. Wheels performed fine through two Regionals and tons of time on the practice fields. After grinding against a 2x4 for a couple seconds however, one of the wheels' rollers developed a troubling wobble. The robot was up on blocks and one of those blocks was wedged against a wheel. Not really a typical use case, but damage was certainly done to it. We ran it for a while but eventually swapped it with a fresh wheel. The rollers were holding together just fine, it was just as if their mounting had loosened up a bit.

Re: New Vex Mecanum
 

After extensive practice with the practice robot including running over the platforms many time at full speed, and 1 regional so far with the competition robot, we've had no issues at all with the 6" mecanums, other than 3 missing standoffs inside one wheel, but that was quickly corrected by VEXPro.

Absolutely love them.

Re: New Vex Mecanum
 

To add on a slightly different data-point:

We've been using the VEXpro 8in mecanum wheels which I believe have the same tabs as the OLD 6in and 4in.

The wheels have been holding up nicely, one set been through a regional and a few hours of practice, the other set seeing ~20 hours of usage. We're seeing wear in the roller bearing (bushing?) such that the rollers can now wiggle side-to-side. We're concerned that this may be the beginning of the failure mode that was seen on the OLD 6in and 4in wheels, can anyone who used the older wheels confirm or describe the failure?

We suspect that the wiggly bearings are allowing the rollers to rub against the tabs and lock up, but we don't have enough data/knowledge about mecanum to put any weight behind this claim.

One other thing, how do other teams fasten to these wheels? We're using #8-32 bolts into the tapped holes, but because of fear of shearing the plastic, these loosened over time and came out. We've added longer bolts, tightened them up more, and haven't seen any more of these failures yet, but we were wondering what is the recommended/common practice for attaching to these wheels. (We also saw similar failure in the bearing retention bolts, but these have just been removed).

I expect most of this post will be irrelevant once VEX have moved all of their 8in stock from last year, but more data is good right?

Re: New Vex Mecanum
 

Last year we ran 4" VEXpro mecanums and it was a rough year. We eventually gave up on mecanums mid-way through the season of 2014. VEXpro admitted the failure and eventually sent us replacement rollers for all the wheels we ordered.

This year we switched to 6" VEXpro mecanums, we have yet to have a single failure. We struggled to find weight to add our h-drive so switching to mecanum really helped progress our robot capabilities without sacrificing weight.

The new VEXpro plastic clamping bearing blocks have been giving us a couple failures in normal drivetrain usage. We are looking at swapping to aluminium bearing blocks.

Re: New Vex Mecanum
 

We had received two old wheels and two new wheels with our first order, and had unwittingly put all four on the robot without replacing the old rollers with the new ones that were included. The old rollers quickly wore out; the roller shaft was not rigidly held in place and allowed the rollers to bind up on the wheel body.

The new rollers seem to last really well. We did notice that they become a bit harder to turn by hand after a lot of use, but I'm not sure that it's enough to affect the driving. We may do an experiment at some point to see how a well worn wheel performs next to a brand new one.

A bit off topic, but can you elaborate on the failure mode? I think that we may be using more vexpro parts in the future, and I'm really digging all of the inexpensive plastic components they make.

Re: New Vex Mecanum
 

Harder to turn?? The rollers should spin freely.

Re: New Vex Mecanum
 

Yes, ideally they should spin with no resistance. New wheels have very little friction in the rollers. After lots of use they have a little bit more friction. I don't know how much more; this is a qualitative observation and I don't have any numbers. It may still be in the range of "negligible".

Re: New Vex Mecanum
 

I will just start another thread on the topic.
Plastic Clamping Blocks

Re: New Vex Mecanum
 

The 8in. have had the "reinforced" design since last year. So the ones you bought this year have the same reinforcing that the 4's and 6's have. The wiggling is the same thing that we saw and we replaced the wheel before it got any further.

Re: New Vex Mecanum
 

We have been using the 6 inch wheels this season, no issues so far through practice and TWO districts.

Shouldn't have any issues at States or worlds *knocks on wood* ::ouch::

Re: New Vex Mecanum
 

This is incorrect, the 8" wheels do not have the new revision rollers yet, this is due to transition time of inventory (8" wheels are less popular).

The 8" wheels do hold up better than the older 6" and 4" counterparts though due to significantly less deflection when rolling at each roller tab.

As always, email me with any questions,

-Aren

Re: New Vex Mecanum
 

We're using the 6" Vex Mecanums, and have been very pleased with them!

If you have the old rollers on your 6" Vex Mecanums, definitely switch to the new ones! We had received the mecanums assembled with the old rollers assembled and a pack of new ones to put on... we put the mecanums with old rollers on when we made our practice bot (we make the practice bot first), and were generally underwhelmed with how it strafed slowly, but it was our first mecanum drive. When we made the competition robot we put new rollers on so that we'd never have to make the change... we were stunned how much more smoothly it performed, particularly when strafing (when the rollers are spinning fastest)! We didn't initially realize the difference was almost entirely the old vs new rollers, but eventually realized it...

Through two events with the comp bot and many hours on the practice bot, all our 6" Vex Mecanums with new rollers are holding up very well!

Re: New Vex Mecanum
 

Thanks for letting me know. And so that you know, whichever representative I spoke to on the phone back in January assured me that the 8" wheels DO have the new revision rollers. This was months ago, so I assume the rep isn't giving that info anymore. We likely would have gone with the 6" had I known.

And it's important to mention, then, that the feedback I gave about the rollers becoming wobbly was about old version rollers, not new ones. I would edit my old post, but it has been too long.

Re: New Vex Mecanum
 

I was a little curious where you heard that, apparently I did not keep them completely up to date, apologies for that. If you have any similar questions in the future please email me.

-Aren