pic: Jester Drive:Mecanum Wheel Drive Train
 

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

whoa... those are hot wheels. Do you have any real life pictures of them? I'd love to see.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Ditto!

Dave

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

That whole system looks very heavy... Is it?

Where do get wheels like that?

Awesome Job... Very impressive

-Ryan

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Ok i'm sure i'm not the only one who has little idea of what i am looking at. Are those wheels supposed to give better traction? Or are they a form of multidirectional wheels?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

I'd guess they're a variation of omni-directional drive, providing more traction in a forward direction. Look's really cool - but a bit complex!

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

The robot when completed, with arm, without any lexan protection was around 86 lbs. The wheels, wheel molds, were created by team members under the assistance of mentor Mr. Crane (aka mold master). They are omni directional, www.airtrax.com has a great video of the wheels in use. Mr. Crane talked to the people in airtrax to get what was needed for the molds. Our first molds were made of a nice blue clay, that wasn't very symetric, we then moved to a silicon mold. We will have a display in the pits if you see us in drexel or nationals. If your in pittsburgh now, you should stop by.

[edit] To see the airtrax video: click on the link provided, click on the picture labeled sidewinder, then click on video

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

The wheels will allow us to drive omni-directionally. Right now we drive forward/ reverse and sideways. Here is video of us driving sideways. http://www.first.udsd.k12.pa.us/AIA2005/video.html We can also spin inside our own footprint. The design makes us very agile. With more programming time and a custom circuit we hope to drive omin-directionally with accuracy. Our initial controls had too much drift in it.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

WOW, looks awesome.

This is something new to me, kodos to your team on buildign such an innovative and manuverable robot.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

I think WPI had wheels similar to these on their robot this year. I'll try and find a good picture of them.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

These wheels are similar but very different to the "grenade" wheels. These wheels are specifically designed for the purpose of allowing slip so the the robot can move laterally left and right as well as provide decent traction for forward and backward movement. However i do not believe, from what i have read on the"grenade" wheels, that they allow for this type of movement. To the best of my knowledge the grenade wheel is just another way to create an omni-wheel, but please correct me if i am wrong. The total weight of the entire robot is 105 lbs. In fact that is with no "speed" holes at all.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

I'm glad we weren't the only ones crazy enough to try something like this. Out of curiosity, how do you guys control the robot?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

I stand corrected. Yes we do control the robot.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Oops, major typo there. I meant "how do you control the robot", but I left a word out. Are you using one joystick for translation and another for rotation, modified tank steering, or another method?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

i'm assuming team 190 has pretty much the same wheels, and when i saw them at BAe, my jaw hit the floor...they are AWESOME. My only question is, do htey make it easier to push around? also, i noticed team 190 had some trouble controlling it early on...how exactly DO you control it??

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Because of the orientation of the rollers, a mecanum wheelbase is never in a position where it can be pushed without skidding. In the worst case scenerio, where the robot is pushed on a diagonal, there are still two wheels with rollers whose axes are aligned parallel to the pushing force. I can't speak for the Jesters, but if their rollers are anything like ours, they have pretty good traction and pushing resistance.

On 190, we have our controls set up with a one stick to translate the robot and a second stick to control rotation. I know that they were having trouble getting everything working at BAE, but the system worked pretty well in the shop.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

We use one controller. If I remember correctly, mind you i'm not on the drive team and have not driven the robot, i believe we use the trigger + direction for translational drive, and the button to spin. As stated above, We are not easily pushed because of the orientation of the wheels. they form to make a shape such as:

\ /
/ \

It is noticable on the drawing above. The wheels allow for slip so we can be pushed with enough force and so that it does not damage parts for the drive train (easily, all things break).

I hope this answers your question.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

those wheels look so awesome
all they all custom made by your team

has anyone been able to find a place to buy them
i know that my team wanted to use them what was unable to find them for purchase

and without a decent shop we have almost no choice but to not use them

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

As stated previously, yes they were all created by the team. Hand mixed, and hand poured. That includes the molds we have used to pour them into.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

My team and I have had a design using these wheels for the past two years now but have not found a way to produce them. It is great to see that a couple teams have done it successfully. Good Luck at your regionals. I will be sure to stop by your pit at championship.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

team 211 has a very similar drive aswell

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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.

\\\ ///

/// \\\

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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!

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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. ;)

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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. :p

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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 :D

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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!

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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. :) 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

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

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...

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Thats awesome... i was truley scared when i saw that video :p

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

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Keep the questions rolling...[/quote]

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

did making those wheels take up a lot of your build season time?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

The one roller vs. two roller difference is indeed significant. Two rollers allow for more controlled motion because of better release of friction. One roller wheels have a 50% higher coefficient of friction causing for more draw and no extra pushing power for the cost.

To answer another question, building the wheels was a very long process. We prototyped throughout the summer in our SRP (Summer Robotics Project)... our team doesn't have an off-season really. Anyway, deciding to make and use these wheels during the six weeks isn't really feasible. There's a lot that goes into the process, from hubs to molding rollers. You cant go out and buy these wheels pre-made, so there's a lot of hardworking and trial-and-error stuff that goes into it. But it's a fun process, and when you finish, you feel like you've accomplished something awesome (cause you have).

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

We haven't done any tests on the two roller model, as we decided that the machining difficulty for the hub was be far too great and supporting the rollers from only the middle would be difficult. I highly doubt that it is a 50% higher coefficient of friction - the only way it would hurt you is if one roller was going to be spinning at a significantly different speeds. I'm no ME (I'm an EE), but doesn't the coefficient of friction deal with the actual force you apply to the ground, meaning you would actually have more pushing power? I agree that the two roller design is better, obviously Airtrax had a reason for using it, but I think you are blowing it out of proportion a bit. The single roller design is much easier to manufacture, although it is more parts. (The hub is simply a piece of square 3x3 aluminum stock with the corners cut off). We had absolutely no issues with pushing power.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

Thanks Alex. :) as the engineer from beach bots said think and have a back up plan before u get into doing this. Making these is extremely labor intensive and you have to make them from scratch I have seen prints for wheels like 357 and there a whole off season's worth of work as Alex stated.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

It's not coefficient of friction... sorry i hadn't had coffee yet. The 50% figure comes straight from the studies Airtrax performed. It's that the single roller model has 50% less release of friction. The two roller model has two independent rollers, meaning that either side can move either forward or backward, so one could be spinning in a different direction than the other allowing for more release of friction.
The one roller design does not limit pushing power, but it draws more juice to get the same pushing power as the two-wheeled design.

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.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

The wheels themselves dont turn in order to achieve translational movement, that is one of the major advantages. The direction of motion is determined by the speed and rotation of each individual wheel.

Mecanum Wheel CAD Drawing
 

Ken, would you mind sharing the CAD drawing of your Mecanum wheel? I need one for a project I'm working on.

Thanks, pablos.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

What is the outer diameter at the widest and thinest point or your roller? Also what kind of shaft (matierial, width, length, nut/end connector) did you use to hold it all together?

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

to anyone who is savvy with these mechanum wheels,
could you maybe put together a white paper on these?
i know it might take a while to put together, but it would sure be helpful.

Re: pic: Jester Drive:Mecanum Wheel Drive Train
 

1072 is working on one for the offseason.

Our requirements are - easy manufactureability (ie nothing more than a rotary table, manual mill and a lathe... ), high traction (via gum rubber rollers, we'll have to see about this one) and efficiency (split wheels)

We'll see how it goes, and if it goes well, we'll post the results. Next week, spring break, fun fun fun! =)