pic: Jester Drive:Mecanum Wheel Drive Train

team 211 has a very similar drive aswell

Do you guys know how much actual Pushing power you have? I know with Mecanum wheels you need alot of traction or else you wont get very far in a pushing match…
And do you know your speed with them?
I’m guessing with 4 wheel CIM Motor drive your getting about 6-8 Fps or am I wrong?

Just to clear a few things up…
This is a mecanum wheel hybrid completely manufactured by our team. The rollers are configured on 45 degree angles on our custom hubs. In order for the wheels to achieve their designed motion, each roller’s bearings are actually molded into their urethane rubber material. The angles make an “X” pattern.

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Forward motion is achieved by driving all four wheels forward, the same concept applies for backward. Though there is a specific way to do it with these wheels, spinning can also be done in the traditional tank steering manner.

The translational movements are achieved on a screw principle. Diagonal wheels move in the same direction while the other diagonals move in the opposite. For example, the front right and back left move forward, while the others move backward. The roller configuration causes the robot to “slide” left and right.

These wheels can also achieve omni-directional movement: for example, spinning about its own axis while driving in an arc.

The mecanum wheel’s rollers prevent the robot from being pushed freely like traditional onmi-wheels.

No one get at Pitt was able to push on you for an extended period of time anyway. You just strafed and sidestepped them.

How is the 3 degrees of freedom (spinning while translating) development coming? I would love to see that at Philly.

Hey, I see it now!
Great job, this is an idea I would never have thought of. I like this design a lot. In this game, maneuverability is important and you should definitely have that under control. What is it like to drive? I have never driven an omni directional robot and I am curious. It looks excellent :cool:
Good Luck!

We have an early code for the three degrees of motion. However, being able to use it is a completely different question. It’s not so much a code issue as it is a driver issue. We would have to use a “flight stick” and training a driver to control a truly omni-directional robot would take time. We are definately planning on doing demos with it, but i’m pretty sure it won’t show up in *this year’s * competition. Maybe you’ll see it at a post-season event. :wink:

Way to go guys - That’s an awesome setup… We’ve done most of every drive system so far and this maybe one we’ll try next just because it’s so cool.

Ellery

The method I have thought about using is having on regular 2 axis joystick for controlling the translation (robot moves in direction of joystick and at a speed relative to the magnitude of the distance from the stick from its “home position”). Then, you can the x axis on another joystick to control turning. So now you are able to control the robot in 3 ways. You can use the one stick to translate and then turn, you can drive in a “wheel and throttle” method, using the Y axis on the translate stick to control speed and the turn stick to control turns, like normal tank drive.

Or…

You can incorporate a gyro into your control algorithm, and keep the translate stick absolute to the field. This means if you push the stick forward you will move away from your drivers station at 0 degrees, no matter which way the robot is facing. This could help in controlling the “3rd dimension of motion”

Wow… I need to play around with one of these drive bases. :stuck_out_tongue:

hello guys i was wondering were you guys got those wheels because next year if i can get my team to go along with it i would like to try something similiar ty :smiley:

BEFORE you commit to doing the mechanum drive, be sure you know what will happen and have a backup plan. We almost did it, but we decided that our design, which is closer to 190’s than 357’s, did not meet our requirements, so we are currently getting ready (very slowly) to try the next stage of design. The problems observed both on ours and 357’s: a) lack of pushing power, and b) slow sideways motion. Both problems may be fixed in later editions and/or by other teams. So, test now, and if you decide to do it, good luck!

Same thing. I know some teams are able to make these molds themselves because they have the resources available, but for smaller teams with less resources, where would you go to buy such wheels, and about what is the price? Our team hasn’t decided on a drive system for next year yet, but I would really like to propose this system and these wheels as a possibility for the team, thanks.

I don’t know if mechanum wheels are sold at the size a FIRST team would want. There are commercial models–used to unload those baggage containers from airplanes and very large.

A few questions for 190 and 357 what Material were the rollers made out of and what material is around them. Also what are the diameters of your wheels. Finally, how did you attach the hub of the wheel to the shaft.

After reading the problems with these wheels I think they are a great
concept however if people would take a closer look at the commercial ones. They have less rollers then the ones I have seen produced and they seem to by at slightly less then a 45 this i think would help going sideways. Just a thought. :slight_smile: To 190 and others who have tried this thank you. Thank you for giving them a chance and seeing them in action really helped. OH almost forgot u might want to lose traction actually off the rollers to help sideways movement.

Drew Disbury The Tech Tigers
team #1251

I talked to 357 and they said they made theirs out of the same stuff skateboard wheels are made from. I think 190 used rubber but am not sure. 330 used nylon on their wheel set. Yes, nylon.

190’s wheels were cast from urethane. 60A durometer Urethane, if I remember correctly.

We didn’t have a huge issue with lack of pushing power, although we rarely got into pushing matches because of the maneuverability it gives you (unless they have you pinned up against something you can almost always get out by going sideways. As far as sideways speed, because our drive was field oriented (pushing the joystick moved the robot in the direction you pushed the joystick, not in the direction relative to the front of the robot), we actually limited our forward speed to equal the speed we could move sideways. That way going full speed, you can move along a vector while spinning without it looking like you changed speed at all. I suppose that we could have added a “turbo” button to allow you to go full speed when you were moving forwards, but we never really had an issue with speed. In fact, we actually decided that we needed to gear it down a bit for our demo season as it is too fast for the average elementary/middle schooler who drives it during one of our demos.

As far as making them, it was quite a task to take on. We didn’t know that there would be 4 identical motors in the kit this year (a requirement for this type of drive), so we had no plans on how to do it until after our 1 week of planning. We spent nearly 4 weeks actually manufacturing the wheels including making the molds and casting the molds (casting them was quite the learning experience). There is no affordable source to buy them that we found - in fact it would probably be cheaper to draw up prints and have a machine shop make the parts. The couple places we found that sell them are all custom runs in the thousands of dollar range for a set (which would blow you way out of budget as far as the $3500 limit). The most expensive part is the labor - especially in machining a hub like 357’s uses.

im glad that fixed the whole pushing issue…for us, we are a strong robot we can put forward reverse VERY well, but ppl notice our omni wheels, and just push us on our side… on that corner and we get pushed around really easy…(the omni wheels just roll). those are awsome.and a great fix to that problem… once i get home i will post a picture of those wheels in real life. (from 357). i took a picture with my camera :D.

me along with a few others on our team are thinking on an alternative to those wheels… as they dont translate so fast etc…but normal omni wheels caused us problems with defence… if we find a better solutn i will post it …

also… would you guys (357) be willing to make a few sets of those wheels and sell them?

Hey all.

Just wanted to clarify a few things. Our rollers were cast from urethane rubber, at a derometer of 80. We had to play around with the derometer a bit until we settled on this one, it gives a good balance between pushing and release of friction.

Also, the type of mecanum wheel we decided on came after looking at all of the different designs, including those used by 190. Here are the reasons we chose the type we did:
-Our wheels require a significantly less amount of parts
-The orientation of 190’s rollers have them being held externally on either end. This gives significantly less ground clearence and also more exposed materials. The fact that our rollers are held on the inside give us much more clearence and keeps parts unexposed.
-The design we chose has two separate rollers at one position, while the other designs call for a single large roller. This large roller prevents friction from being released as steadily, and therefore draws more power without delivering more pushing power.

Keep the questions rolling…

Thats awesome… i was truley scared when i saw that video :stuck_out_tongue:

so to slide right you put the front 2 wheels going back and the front 2 going foward?
Am impressed
Well done :stuck_out_tongue:

Keep the questions rolling…

lol as per request. I got another one in looking at your rollers 357 has two separate rollers, where as 190’s are one whole roller. Would this make a significant difference?

Thanks again,Drew

Team 1251 The Tech tigers

2004- rookie all star award winners UCF regional
2005-finalist at UCF with 845 and 1270
2005-Palmetto Finalist with 25 and 301
2005-Palmetto Xerox creativity award.