935 as of last night
 

This is RaileRobotics prototype mecanum chassis as of last night.

Re: 935 as of last night
 

all I can say is WOW. There seem to be many teams trying out this mecanum chassis! :D

Looks good, have any other pics, like closer up, the mecanum modules, and maybe some video?

Re: 935 as of last night
 

*wipes a tear from eye*

It's beautiful...

Re: 935 as of last night
 

how well does it drive?

Re: 935 as of last night
 

That is beautiful, I hope it runs as good as it looks. I hope we get a game this year that will better take advantage of these types of these very maneuverable drive systems.

Re: 935 as of last night
 

Beautiful.

Would you run it like that, or would there be some protective frame around it? (Or bumpers, even?)

Re: 935 as of last night
 

I'd hate to burst your bubble, but are those mecanums in the wrong position?

I think the wheels need to be switched front to back or left to right.

I may be wrong, though.

Re: 935 as of last night
 

It'll work as pictured, but I agree that the wheels are backward (or upside down) and should be rearranged.

We didn't quite understand the importance of how the wheels were arranged until we made the same mistake ourselves. It became obvious pretty quickly.

Re: 935 as of last night
 

The side the wheels are on is irrelevant as long as the angle of the rollers is different from left to right and front to back. In other words the rollers either need to point in or out but not both left or both right.

If the wheels were to be switched from the current position then it would require the oppisite input to strafe left or right.

Re: 935 as of last night
 

Actually, the position of the wheels is quite relevant to how the chassis will perform on the field.

As your wheels are arranged currently, it's possible to rotate your robot in place while under no power. During a match, a competing robot could push you at the corner, causing your robot to spin in the same manner. There's no way to apply power to oppose that motion.

Re: 935 as of last night
 

Also, it seems like it wont rotate as well when the wheels are being driven.

Re: 935 as of last night
 

It drives much as a Mecanum should, albeit it does have a tendency to drift around the floor. This is mostly due to the fact that the robot weighs less than 50 pounds and we have been driving on polished concrete.

Re: 935 as of last night
 

Thank you very much for your input. Does this look better.

Re: 935 as of last night
 

Yep, that'll do it.

Did you switch them just now?

Re: 935 as of last night
 

Yes we did change them now. It took us less than 5 minutes to change our wheels. We pull out the side bearings and the drive shafts and can switch the wheels from the bottom of the chassis.

Re: 935 as of last night
 

Coolest feature of this robot? The built-in lifting handles at the top corners of the side plates!

What are your gear reductions from the CIM to the wheel? The gear meshing with the CIM output looks huge? I'm guessing it's somewhere around an 80 tooth?

Looks very nice. As always, I'd love to see some video.

BEN

Re: 935 as of last night
 

Re: 935 as of last night
 

That. Is. Crazy. I definitely want to see how this fairs in next year's competition.

Re: 935 as of last night
 

Yes, it looks much better :D

Re: 935 as of last night
 

That is an amazing looking piece. Nice to see some quality craftsmanship. One question the front plates are attached to the side by 12 allen bolts. Are these just threaded into tapped holes on the side plates and if so how large are the holes and how solid is the frame since it is a narrow material being held by small bolts.
Did you make the wheels yourself or did you buy them?

Very nice work. i wish my team had a waterjet (if thats what you used)

Re: 935 as of last night
 

so i guess the rule regarding building the robot only during the 6 week period after kickoff was just a suggestion? interesting

looks nice tho

Re: 935 as of last night
 

The rule covers building the competition robot. This is prototyping, which can happen at any time.

Re: 935 as of last night
 

We used a CNC machine, not waterjet and we bought our wheels from andymark.

Re: 935 as of last night
 

Do you have any kind of suspension system for the modules (it doesn't look like it, but I may just be missing it). Many teams have had problems with vector-based drivetrains (such as mecanums) when one or more wheels loses contact with the ground. The typical solution is some sort of suspension. Check out what team 40 and 357 did with their bots in 2006, and what 488 is doing with their prototype for examples.

Re: 935 as of last night
 

As of right now we don't have any kind of suspension. We may play around with that idea, though.

Re: 935 as of last night
 

Awsome machining.

Congrats to 935 on that robot it looks amazing.

On the front and back plate, what thickness is it?

Re: 935 as of last night
 

just curious, since the rollers are not curved, does it vibrate a bit when driving on a smooth surface? seems the wheels would be a bit "lumpy"

Re: 935 as of last night
 

What is the traction like with the AndyMark's? From what I have heard the wheel can make alot of difference in how easy the drive is to defend against(ie push around)

Also it doesn't look like it is going to float to well and all those holes are going to be tough to water proof for the game this year.

Rally though, it looks great hopefully the game this year will be one where you can make good use of this drive system.

Re: 935 as of last night
 

The robot does vibrate quite a bit on a smooth surface and there is less vibration on carbet. As for traction we were able to push our mentor around while he was sitting a stool on polished concret.

Re: 935 as of last night
 

(smirks) Mecanum (smirks) OH well I suppose it's one of the better looking chassis with these wheels I have seen. Hopefully for you guys this years game requires mobility and doesn't have stairs :rolleyes:. The good news is you have now till ship if you do use that chassis to figure out the programming because if you want any descent driver controls and a good autonomous mode it will take till ship to get it right. Other then that I have a few questions how much does it weigh as shown, what made you want to prototype this kind of drive system and with all the machining access your team obviously has why not make your own Mecanum wheels other then for the sake of saving time because we all know you've been working on this for a while and probably had the time in the off season. I can't wait to see these systems at competition, good luck to 935.

Re: 935 as of last night
 

as a quick rule of thumb to putting the mecanums wheels on the right way is that the rollers should face towards the middle making a X

Re: 935 as of last night
 

Wow, that's beautiful. Seeing as everyone is posting pictures of their mechanum bots, I'll have to get one of our mechanum t-shirt shooter.

Re: 935 as of last night
 

You mean this one?



The frame looks a bit stiff if you ask me...

Re: 935 as of last night
 

That if one HUGE launcher!!! You are going to use up you air really fast unless you refill on board. Is it directly connected to the reserve tank or do you have a firing tank in between?

Re: 935 as of last night
 

i love that you used a vex controller on the t-shirt launcher

Re: 935 as of last night
 

We can get about six shots off on one tank of air (filled to 125 psi). I'm not sure of the specifics on the air setup, as I was not on the build team.

Re: 935 as of last night
 

What's the intended implication here?

Re: 935 as of last night
 

I think he's getting at the fact that if the frame flexes a little, it can cause the whole robot to go in a different direction than intended, and we don't have a suspension to ensure even traction for all the wheels.

Re: 935 as of last night
 

very nice, my favorite part are the handles that are built in. I wish more teams would think of lifting when they design their bots.




A general question to prototypers: Why do you pocket your plates? I understand that for competition where weight is a factor but for prototyping it seems a bit excessive.

Re: 935 as of last night
 

My theory: It lets them know if they're being too conservative with it or not. If you slam your frame into fifty cinderblocks without so much as a ding, perhaps you can afford to get a little crazier with it for the competition robot. But if your robot caves in by so much as breathing on it the wrong way, then it's time to dial it back.

Re: 935 as of last night
 

Even in prototypes weight is always an issue. How much material can we eliminate? How will the drive react to the frame? With the ablity to download autodesk files to CAM and to estimate weight with autodesk this really helps us in not always starting over completely at times.

Re: 935 as of last night
 

Can you get the same holonomic motion with the mechanums
as you can with the omniwheels?
Our programmer is more than eager to program a holonomic robot,
and we weren't sure if mechanums would give us the same ability.

Re: 935 as of last night
 

Yeah, thats why theres so much of a hype. Truely Holonomic drive, and a bit more resistance without special configurations. And they look cooler :) .

Re: 935 as of last night
 

As I drool over the beautiful chassis and envy the Mecanum maneuverability, I have to wonder how your design will change for competition if FIRST was to say throw us a curve ball and not give us 4 CIMs this year?

2004 - 2 CIMs
2005 - 4 CIMs
2006 - 2 CIMs in the kit and you were allowed to buy 2 more
2007 - ?????

I love the chassis and applaud the development as practice and learning experience for your team but I never make any assumptions about the KOP or the rules until after we inventory our kit and read the rules twice after kick off.

Re: 935 as of last night
 

I'm pretty sure most teams (i know mine is) are building mecanum robots to experiment, get used to the setup if they decide to use it, or just for fun. If the rules don't provide for such a system, then it just won't be used.

Re: 935 as of last night
 

But hey!

There may be the CIMs on steroids again (without the raising-Core Body Temperature effect of course and BALCO and Team Phonak)

Re: 935 as of last night
 

You NERDS!!! You took the Regional Award Winner from us last year at the Davis Regional; and now you're stealing our idea!!! Just Kidding!! But we are doing the exact same thing as your mecanum cannon robot. You're just a bit faster than us slow pokes. Here's our old Cannon Bot design which we are replacing the drive system with our new mecanum drive train design. We're just now CNCing the transmission plates and writing a basic code - vector only, no rotation. It'll be around X-mas by the time we're done.

Re: 935 as of last night
 

We would if we had money.

Thats what we've been trying to convince our mentors about, but they don't want to let us.

Also, if in the first week of build we all agree on a design that turns out to be the absolute worst possible design and we come in the second week and try to change it, our mentor wouldn't let us. He would only let us change it after various prototypes and showing him multiple times how inefficient it would be to utilize that design.

Re: 935 as of last night
 

Sounds like fun! Our team would do anything for a CNC milling machine (at least I would). I don't think our team has had a chance to do any serious programing to ours yet; right now it is a safety hazard and needs to be cleaned up.

Keep us posted!

Re: 935 as of last night
 

Holonomic (omni) and mecanum give the same abilities, but the mecanums are easier to put on a kitbot. Also, omni's can be really easy to push around/spin; mecanums are much harder.

Re: 935 as of last night
 

Safety Hazard - do tell!!

We've started a program that will just read in ch3 and ch4 from the vex transmitter for simple FWD/BWD/LFT/RT and those angles between, but at some point we'll work in some rotation code - which is the tough part. We've made our class an ROP class which came with some initial funding - enough for a CNC Jr., BandSaw, Sander, Cordless Drills, trailer, some metal and of course a set of Mercanums to play with. The CNC really opens up some possibilities and raises just as many issues. It's easy to get into a mindset that the CNC can make anything you want - when in reality there is still a lot of work and time that goes into making each part.

Re: 935 as of last night
 

Speaking of Canon Bots...
ours isn't mecanum though :(
just a suggestion to team 1726, once you go CO2, you never go back. You get hundreds of shots before you have to refill your tank.