Mecanum on kop chassis
 

Was wondering if anyone has ever done a mecanum drive on the andymark kop chassis?

Seems like this year is a mecanum year, and I'm sure there are a bunch of teams that didn't opt out of the chassis this year, but would want to use mecanums.

Re: Mecanum on kop chassis
 

http://www.andymark.com/product-p/am-14u-mk.htm

Appears to be out of stock though :(

Re: Mecanum on kop chassis
 

The side plates have the required holes to have the 4 gearboxes required for mecanum.

AndyMark made this upgrade package last year. I doubt it's going back into stock again, but I'd expect a similar package to be available soon.

Re: Mecanum on kop chassis
 

I believe everything from last year is compatible again this year, the hole pattern on the chassis is the same.

Re: Mecanum on kop chassis
 

The easiest way I can think to adding mecanum to the AM14U2 is to mount cimple boxes(am-0734) to the top of the inside rails and running either chain or belts to the wheels.

Re: Mecanum on kop chassis
 

Have you checked VEXpro, they might be plastic but they are cheaper and in stock.

I'll likely buy them because I feel that they'll suit our needs.

Re: Mecanum on kop chassis
 

Last year's AM14U mecanum upgrade kit will not work on this year's AM14U2 without modification to the inner plate. You would have to drill your own mounting holes for the Toughbox Nano gearboxes and cut away part of the flanges to make clearance for the gearboxes and wheels. On the Andy Mark You Tube channel Andy says that both 4" and 6" upgrade kits will be available soon, couple days for the 4" and maybe next week for the 6".
https://www.youtube.com/watch?v=7Bum0ImD46k

I like to hear what teams that used the upgrade kit on last year's chassis thought about its performance.

Re: Mecanum on kop chassis
 

Has anyone adapted an mecanum upgrade from last year to the new KOP Chassis? I assume many teams, like us, tried to be proactive on getting parts this year and purchased the mecanum upgrade only to find that it doesn't fit this years frame.

Just wondering before we start making cuts in a frame that could cost a significant amount of money to replace.

Chris.

Re: Mecanum on kop chassis
 

We thought it was fantastic! Super easy to set up, we had it driving and correctly running a gyro within a couple of days. We had multiple weeks with which to practice with it as mechanisms were being built. We would definitely buy it again.

Re: Mecanum on kop chassis
 

I could not find any info on the AM site about which configurations of the AM14U2 will support mecanum wheels; long, wide, square? Does anyone have info on this?

Also, what size are people considering? 4 inch or 6 inch wheels?

Re: Mecanum on kop chassis
 

This is what my team is planning on doing. We are looking into a better way of supporting the motor.

Re: Mecanum on kop chassis
 

That CAD model is of last year's KOP chassis, the AM14U. This year's AM14U2's inner plate has flanges that will prevent you from mounting your wheel like that. If this is what you had intended, that is fine. If not, you will need to consider removing parts of the flanges.

Re: Mecanum on kop chassis
 

We have toughbox nanos coming in the mail, and we'll be drilling some new holes in the chassis to mount them. They're great little gearboxes, it's too bad there isn't a bolt pattern on the KOP chassis to line up with them like there was last year.

The new chassis isn't as tall as the old one, so it looks like we'll probably need some additional holes in both the chassis and gearbox to mount them securely. Measure twice (or three or four times...) and drill once.

Re: Mecanum on kop chassis
 

You're also going to have to cut away part of the top and bottom flanges on the inner plate to get the toughbox nanos to fit in this year's chassis. If you place the nano output shaft through the big hole above 3/8" bolt holes you're also lowering the frame by almost 1/2" which may affect your ability to drive over the scoring platform.

Re: Mecanum on kop chassis
 

You might not have included it in the model but you need to make sure you brace those gearboxes in another spot. One way would be two pieces of churro spanning from one gearbox to the other like it shows for the standard kit chassis.

We mounted mecanum wheels on our bot with 4 nanos and with heavy modification.

Re: Mecanum on kop chassis
 

This is the plan for our robot, mounting the TB Nano's on the AM14U2 with a modified width and length to make sure the mecanum wheels are located in the required square pattern, 90 degrees from each other. Using the closest holes in the chassis is giving us a pretty small drive base, but with some counter weights, should be okay.

This will be our first endeavor with mecanum wheels, so we're hoping this works out for us.

Re: Mecanum on kop chassis
 

Why do you say square is required?

Re: Mecanum on kop chassis
 

If not square what code adjustments would need to be made?

Re: Mecanum on kop chassis
 

It depends on your driver interface.

If you are giving the driver control of Y,X,and rotate, then no code adjustments would be necessary.

If you have pre-programmed routines in the driver interface (or in autonomous) which depend on commanding specific rotation rates relative to translation commands, then you should scale the rotate command (in radians per second) by a factor K=(wheelbase+trackwidth)/2 as shown on page7 of this document or page19 of this one.

Can you use a toughbox mini's to use mecanum wheels on the KOP chassis?

Re: Mecanum on kop chassis
 

Yes, my team is able to do direct drive to the mecanum wheels. But, it involves using a second chassis ontop of the first one. Or, mounting braces that extend from the top of the base.

Re: Mecanum on kop chassis
 

We've not yet tried a "mecanum" drive, but I have read that the wheels should be mounted such that the rollers form an "X" when viewed from the top or bottom. Am I misinterpreting this CAD drawing?

Re: Mecanum on kop chassis
 

Maybe it's a bottom view?

Re: Mecanum on kop chassis
 

I believe that even looking up at that, it's not going to make an "X".

Re: Mecanum on kop chassis
 

If it makes an "O" when viewed from the bottom, it will make an "X" when viewed from the top.

http://www.chiefdelphi.com/forums/sh...3&postcount=28

Re: Mecanum on kop chassis
 

LOL. Now, I'm embarrassed. Of course, Ether, you are correct. Never having handled one of these mecanum wheels, I had to perform a more detailed mental exercise to visualize the roller angles properly. Note to self: The roller angle forms an "X", only when viewed from the top. Thanks!

Re: Mecanum on kop chassis
 

OK, I admitted to not knowing my "X"s and "O"s. :) But, going back to the original CAD rendering, that does appear to be a 2015 KOP drive base looking down from the top.

Nope

Re: Mecanum on kop chassis
 

Andy Mark just released this 6" Mecanum upgrade kit for the AM14U2. IMHO, the 6.7:1 gearbox ratio is too low for this years game.

http://www.andymark.com/product-p/am-14u2-Mk6.htm

Re: Mecanum on kop chassis
 

One of our mentors calculated the speed of the 6.7:1 gearbox to be around 19 ft/s. Seems really fast. I wonder why AndyMark went with this setup.

Re: Mecanum on kop chassis
 

For anyone planning on using this upgrade kit (as we are) and find that it is already out of stock, I just heard back from AM that it was listed as Out of Stock when it was first posted by mistake on 1/13. It will be listed as In Stock when the 6" HD Mecanum wheels come in, expected on 1/16. The other parts are in stock and can be ordered now and separately as listed.

Re: Mecanum on kop chassis
 

I'd like to see that calculation. Could you ask him(her) to post it please?

Re: Mecanum on kop chassis
 

I get roughly the same:

(5300 rot. motor / 1 minute) x (12 rot. idle shaft / 28 rot. motor) x (14 rot. wheel / 40 rot. idle shaft) x (6*pi inches / rot. wheel) x (1 ft / 12 inches) x (1 minute / 60 sec) = 20.8 ft/sec

That's under the assumption that you're moving straight forward/backward and the mecanum rollers aren't contributing to sideways motion. Also ignoring frictional losses in the transmission. In reality I'd expect it to go a bit slower than that, but it still seems to be off by about a factor of 2 for this years game.

Re: Mecanum on kop chassis
 

I get 20.749 fps vehicle speed at 5310 rpm CIM speed for 6.7:1 gearbox with 6" dia wheels.

What I was asking about is the 19 fps.

Re: Mecanum on kop chassis
 

Does anyone really expect to get 5300 RPM from CIMs on a loaded robot? I would expect (from the current limits) that 3000 is pretty close to the upper limit.

None the less, I concur with s_forbes that it's still way fast for this years tasks where precise positioning will be a boon.

Re: Mecanum on kop chassis
 

I would think 80-90% of the CIM freespeed rpm to be a reasonable expectation for an FRC drivetrain. Regardless of that, this transmission looks like it's geared way too high. We'll likely be taking our chances with the toughbox nanos instead, though we'll have to add a bunch of ugly holes to the chassis.

Re: Mecanum on kop chassis
 

The max speed is the speed when the cims are at 5300rpm in an ideal world. In reality, some speed is lost to external influences (generally, I use 80% ideal for my calcs, but it varies). The mentor who calculated 19fps may have used a smaller loss constant.
3000rpm seems pretty low even for a relatively low-tolerance robot, but I could be wrong.

Re: Mecanum on kop chassis
 

This is wrong. Why wouldn't you be able to? Special mounting will be required though.