935 as of last night [Archive]

Chuck Glick

30-11-2006, 17:07

http://img124.imageshack.us/img124/4173/proto1li9.jpg
This is RaileRobotics prototype mecanum chassis 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?

Dan Petrovic

30-11-2006, 17:17

*wipes a tear from eye*

It's beautiful...

Chuck Glick

30-11-2006, 17:20

how well does it drive?

Jonathan Norris

30-11-2006, 17:20

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.

Billfred

30-11-2006, 17:27

Beautiful.

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

Dan Petrovic

30-11-2006, 17:36

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.

Madison

30-11-2006, 17:41

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.

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.

railerobotics

30-11-2006, 17:44

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.
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.

Madison

30-11-2006, 17:47

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.

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.

Dan Petrovic

30-11-2006, 17:53

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.

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

railerobotics

30-11-2006, 17:53

how well does it drive?
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.

railerobotics

30-11-2006, 18:11

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.
http://img245.imageshack.us/img245/7/img3065bw5.jpg
Thank you very much for your input. Does this look better.

Madison

30-11-2006, 18:20

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

Yep, that'll do it.

Did you switch them just now?

railerobotics

30-11-2006, 18:23

Yep, that'll do it.

Did you switch them just now?
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.

Ben Piecuch

30-11-2006, 18:57

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

Jeremytice

30-11-2006, 19:05

Awsome awsome awsome! Great job you guys. I would also like to see some video of it in action.

Donut

30-11-2006, 19:16

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

Dan Petrovic

30-11-2006, 19:29

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

Yes, it looks much better :D

Bill_Hancoc

30-11-2006, 20:48

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)

bjimster1

30-11-2006, 22:40

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

<R15> Prior to the Kick-off: Before the formal start of the robot Build Season, teams are encouraged to think as
much as they please about their robots. They may develop prototypes, create proof-of-concept models, and
conduct design exercises. Teams may gather all the raw stock materials and COTS items they want. But
absolutely no fabrication or assembly of any elements intended for the final robot is permitted prior to the
Kick-off presentation. Any MECHANISMS assembled prior to the Kick-off presentation may be used for
prototyping or educational purposes, but MAY NOT be used on the final ROBOT.

looks nice tho

Billfred

30-11-2006, 22:44

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

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

DustinB_3

30-11-2006, 22:48

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

Lil' Lavery

30-11-2006, 23:00

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.

DustinB_3

30-11-2006, 23:07

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

David Guzman

30-11-2006, 23:43

Awsome machining.

Congrats to 935 on that robot it looks amazing.

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

MrForbes

30-11-2006, 23:55

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"

JamesBrown

01-12-2006, 01:37

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.

DustinB_3

01-12-2006, 08:27

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.

techtiger1

02-12-2006, 13:11

(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.

psyco_klown

02-12-2006, 18:03

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

GUI

02-12-2006, 23:45

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.

s_forbes

03-12-2006, 04:10

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.

You mean this one?

http://img182.imageshack.us/img182/9559/mecanumfr3.jpg

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

Gabe

03-12-2006, 04:33

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?

psyco_klown

03-12-2006, 11:56

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

GUI

03-12-2006, 12:07

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.

Madison

03-12-2006, 12:10

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

What's the intended implication here?

GUI

03-12-2006, 12:18

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.

Greg Needel

03-12-2006, 12:23

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.

Billfred

03-12-2006, 12:34

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.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.

railerobotics

06-12-2006, 14:46

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.

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.

trilogism

06-12-2006, 17:53

efoote868

06-12-2006, 18:05

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

ChuckDickerson

06-12-2006, 19:07

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.

GUI

06-12-2006, 19:22

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.

Sgraff_SRHS06

06-12-2006, 20:40

But hey!

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

Doug G

06-12-2006, 21:48

You mean this one?

http://img182.imageshack.us/img182/9559/mecanumfr3.jpg

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

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.http://www.travisusd.k12.ca.us/vanden/clubs/robotics/New%20Site/pics/DSC02034.jpg 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.

trilogism

07-12-2006, 18:02

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.

We would if we had money.

If the rules don't provide for such a system, then it just won't be used.
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.

s_forbes

07-12-2006, 18:12

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.

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!

EricH

07-12-2006, 20:07

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.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.

Doug G

07-12-2006, 23:34

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!

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.

NextPerception

03-01-2007, 14:09