Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

How many parts did you need per wheel?


We only needed 30 parts per wheel total. 8 rollers, 8 shafts, 8 screws, hub, Lexan piece, 4 bushings in two sizes. This does not include the sprocket or its attachments.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

I'm not an engineer, I'm a student. Thanks for the compliment.:D

Making the wheel we had at nationals (for display only) took about 2 years from initial concept through prototyping to the wheel. The first year: After seeing the ones used to remove containers from airplanes, my dad decided to try to make some. By the end of the summer, we had a set for the Robovation kit. We also had the programming to operate it. The second year: two experimental wheels were made, similar in design to the current ones. When we decided to try them this year and keep six wheels as a reserve, we had a set made. However, when we tested that set, we found that it did not have enough traction, and we could not get another set of rollers designed and built in time to test them before ship, so we went with six wheel drive. We had the textured rollers made before ship day, but have not tested to find out which roller tread is best. More testing to come at a later date.

One set of wheels can be made in about 3 days, from part production to assembly to mounting on a robot.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

i'd like to see a picture of what you've done. Have you driven with it or anything yet? no bearings? how are you're rollers attached to the hub? is that even more parts? did you mold any parts inside the rollers? are these mecanum wheels or omni/grenade wheels?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

When I first saw 357 strafe, I was driving in a match in Philly, and I don't know if they were on our alliance or the other, but I was amazed. Especially since how it worked wasn't immediately visible. I had a look later, and loved what I saw. Very nice job guys.

As for control's why not go for a keyboard and a joystick? make the keyboard be WASD, for strafing and forwards/backwards, and joystick for turning. A mouse would be even cooler, but a bit harder to implement. Would be neat to see...
I mean it works for First person shooter's, why not a robot ;)

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

A keyboard limits you a lot - allowing you to only move in 4 directions rather than an infinite amount that the joystick allows you. A mouse doesn't really give you anything that a joystick doesn't, and you have to worry about running out of room on the mousing surface. We (190) use a joystick for the direction vector (relative to the driver) and a 2nd joystick for rotating counter clockwise or clockwise. We're probably going to set it up with a single 3 axis joystick to make it more intuitive, however. The second joystick also has the issue with more experienced drivers, when they start driving it tank-drive style.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

The three axis joystick is definately what we have been looking at, but there's one problem with it - it's designed to be used from vehicle persepctive. Even in talking with Airtrax, they use the joystick for their drivers, and they said that doing it without having that first-person perspective would be difficult. so if we do, indeed give it a try, i suspect we'll be training with the joystick for a few months.
as for our current controls, we only use a single joystick.
normal: front, back and spin
trigger: direct motion in the direction the joystick is pointing
-it's actually a lot easier than dealing with two joysticks

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

We use 2 joysticks on 1083 with our omni wheeld holonomic bot. Its really easy to drive, much like what 190 does.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

double DITTO!

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Controlling an omni wheel is much different than controlling a mecanum wheel. Since the rollers are perpendicular on omni-wheels, the direction produced has almost no similarities with controlling mecanum wheel motion, which depends on the rotation and speed of each individual wheel.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Omni wheels all 45 degrees apart from each other produce exactly the same effect the mecanum wheels do, and you can control the robot exactly the same way. This is how we prototyped the code for our field relative drive and found that we needed to have the split in the chassis to have equal wheel pressure.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

the control system that i came up with for mechanums was to have 2 joysticks pitched on 45's with open loop programing. you could have a noormal tank drive hangling with the abilty still to go left and right. however your driver would have to be realy $@#$@#$@#$@# good. Of course i came up with this because im complletely useless with programing things of any nature except in legos.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

As BrianBSL said, its exactly the same. Mechanum wheels have rollers at 45 degree angles, for the omni holonomic drove you put the entire wheel at 45 degrees. There are slight differences but its still the same.

We shimed our wheels so that all the wheels are touchign at the same time. Also we have encoders on everywheel to track how fast each wheel goes. We had a suspension of sorts on our mini bot we prototyped on last year and found it wasnt super important since the field is relatively flat.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

You're completely right... I thought he was referring to omni wheels set in the same frame as our mecanum wheels. In fact, we were encouraged early on to try using the 45 degree omni-wheel set-up because of the complexities of the mecanum drive system. However, there is a disadvantage in the 45 degree omni-wheel drive train when it comes to driving over obstacles. Correct me if I'm wrong, but I think the set-up also has a harder time adapting to different surfaces.

Sorry for the lack of posts lately. I'll be answering questions more quickly more often.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

it looks like the wheels are set up so they are just easier to turn, ie less resistance for more maneuvarbility

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Sorry I took so long to respond, but here are the answers.

Have you driven with it? I only drove the EDUbot prototype. Others have driven the real thing.

No bearings? Two bushings pressed together (one was smaller than the other) formed the bearing on each side of the wheel. Nylon is slippery enough that the rollers didn't need bearings.

How are your rollers attached to the hub? The hub looks something like two thin Skyways with a connecting bar between the hubs. The rims have holes in them to hold steel axles, which are kept from falling out by a piece of lexan screwed to the outside.

Is that even more parts? No. The roller axles were labeled as shafts in the parts list.

Did you mold any parts inside the rollers? Nothing in the wheel was molded. It was all formed using SLS (a laser drawing patterns in powder). There are no parts inside the rollers.

Are these mecanum wheels or omni/grenade wheels? Mecanum, something like what some airlines use to unload containers from airplanes.

The only picture I have is of the side of the hub, nothing else was attached.