118 Crab Module Conference Presentation
 

Are you curious about crab drives?
Looking to expand your knowledge on swerve drive trains?
Want a chance to discuss the details of making a successful wheel box?

As a late addition to the 2009 FIRST Robotics Conference, The Robonauts will be presenting a session on the evolution of our crab drive wheel box. The official schedule has yet to be updated, but we will be presenting at 8AM Thursday Morning.

Lucien and I will be covering an in depth and technical view of our wheelbox along with justification for many of our teams design decisions. We will share insight from six years of using this crab module and why we've settled on the point we are at.

This presentation will be beneficial to any students or mentors who are thinking about building a crab drive. Building a crab drive can be a nightmare to undertake and we want to use this opportunity to help anyone by sharing everything we have learned. We will have wheel modules from our last 5 robots, a slew of spare pieces, and Pro/E models from 6 years of robots for all to play with.

I want to highly encourage team members to attend the Robotics conference, be it our session or any others. This is an excellent opportunity to learn from some of the top mentors and teams in the country. You can never learn too much!

Re: 118 Crab Module Conference Presentation
 

Room #?

Re: 118 Crab Module Conference Presentation
 

· Added – Robonauts Crab Drive Wheel Box (Thursday at 8AM in C203)

re: Colleen Shaver
FIRST Robotics Conference Coordinator

Re: 118 Crab Module Conference Presentation
 

I wish I could make it, but I won't be at Championship this year. Can you guys post the presentation somewhere or make it a CD whitepaper after Championship?

Out of curiosity, how much time does it take for you to assemble one whole module? Our team designed a 3-wheel independently steered crab drive system for the first time this year, which worked surprisingly well for our first attempt. One of the disadvantages was that it was not very easy to maintain. If one part failed, the entire module had to be disassembled, part replaced, and reassembled. In our second to last qualification match the drive motor on our rear module (an RS-545) burned up. As soon as the match ended, our whole team worked as fast as possible to get it replaced. We had about an hour and 10 minutes between matches, and by the time we got the last nut tightened down, our last match had just started and we missed it. If we decide to do crab drive again next year, one of our goals will be to increase serviceability.

Re: 118 Crab Module Conference Presentation
 

Midwest 2007, almost this exact situation happened to us, except ours was a couple loose screws. We had the time and would've finished but they decided to run our next match 15min ahead of schedule and as a result we missed our first ever qualification match.

The next swerve only broke once, and took 5 minutes tops to fix that one thing.

Re: 118 Crab Module Conference Presentation
 

how long is the presentation?

its too bad i won't be arriving until thursday night, i would love to listen to this.

Re: 118 Crab Module Conference Presentation
 

Man, I want to go to this. How long will it be, because as the driver/second in command of mechanical department (take that Ryan), I will need to be with the robot most of the time.

Re: 118 Crab Module Conference Presentation
 

I'm going to see if I can get some people not working in the pits on our robot to this. I have no idea if any of our teammates will be "free", but I think it would be cool if some of our pit recon guys stopped in for a minute.

Re: 118 Crab Module Conference Presentation
 

I really wish I could be there. Instead I'll be taking a Statics midterm at UT. I'll be up there friday. Maybe I can swing by your pits and get an impromtu presentation?

Re: 118 Crab Module Conference Presentation
 

Could this presentation be posted online? Maybe after the actual presentation for those who could not go to Atlanta this year?

Re: 118 Crab Module Conference Presentation
 

The presentation is scheduled to last 45 minutes.

You can come by and avoid the large fiasco of 350 teams trying to enter the pits all at once. 8 AM is early enough that you can't miss practice matches or robot building action.

The 2008 presentation videos and powerpoints are stored on FIRSTs website, so perhaps this year's presentations will be also.

Re: 118 Crab Module Conference Presentation
 

I am going to try to go

and as far as recording goes i can bring my equipment to capture it to my computer I just don't know how it would work because I would need a video feed that I could tap into. If someone who has been to the conferences before could tell me more about how its setup as far as recording goes I would be very grateful

Re: 118 Crab Module Conference Presentation
 

I'll be there. We have some great ideas to try to revolutionize what FRC drive trains are seen on the field, and a couple of them require crab modules. I'm finalizing some research, etc, and have some (hopefully) pretty specific questions that will either be very easy or hard to answer. I also like how the focus of this conference is on the 'why' of the decisions rather than the specifics of 'what' for each decision.

Re: 118 Crab Module Conference Presentation
 

Isn't there another conference at that time?

Re: 118 Crab Module Conference Presentation
 

i agree with others that you should post a video of the presentation or a white paper.

If I didnt have physics lab thursday night at FSU i would totally be there.

Re: 118 Crab Module Conference Presentation
 

Thanks to all that attended. Lucien and I were absolutely stoked that so many showed up. We really hope that we were able to answer some of your questions. Our only regret is that we weren't able to manage our time very well. It would have been great to keep chatting before Andy Baker kicked us off the stage for his presentation. =)

One follow up question that I was asked a number of times over the weekend (by whom I don't remember) was what we used for our bevel gears. They are 15 tooth, 12 pitch miter gears from McMaster. The part number is 6843K13. Sorry I couldn't answer you on the spot, but I hope this information finds those inquiring minds.

Re: 118 Crab Module Conference Presentation
 

Any chance that you could post the presentation for those that misssed it?

Didn't know you went to UT too.

Re: 118 Crab Module Conference Presentation
 

darn! i can't believe i missed an opprotunity like this!
does anybody know of any other sourse of information i can find about swerve drives?

Re: 118 Crab Module Conference Presentation
 

This thread might be usefull to look through

http://www.chiefdelphi.com/forums/sh...ad.php?t=77050

Here are some pictures

http://www.chiefdelphi.com/media/photos/31077

http://www.chiefdelphi.com/media/photos/33335

http://www.chiefdelphi.com/media/photos/31312

http://www.chiefdelphi.com/media/photos/31078

http://www.chiefdelphi.com/media/photos/28444

http://www.chiefdelphi.com/media/photos/14556

If you look around CD there are plenty more places that you can find swerve/crab info.

Re: 118 Crab Module Conference Presentation
 

I'm sneaking the module plate that was handed out into our next batch of powdercoating. Maybe that will convince the next batch of mentors to do crab, and to do the right way :cool:

Re: 118 Crab Module Conference Presentation
 

Hello, I attended this conference last year and thought it was great!

I have to admit this year, when I saw the game, one of my first thoughts was: "I can't wait to see 118's crab this year!" I was at first disappointed when I heard you guys had built a 6-wheel-drive; however, I was not let down in the least when I saw your mid-build video! ;)

Our team designed and built a crab drive last year; however, didn't implement it on our robot. This year, I'm looking to make a new and improved one for the off-season. I was pleased with the result with the exception of the bearing to mount the pod and the encoder mount for the steering motor. In your talk you mentioned using a pair of radial/thrust bearings. I can't remember which two suppliers you recommended for these... I think it was Silverthin and one other. What was the other? Do you have specific part #'s for these bearings?

Thanks for you time and expertise!

Re: 118 Crab Module Conference Presentation
 

i love your crab drive guys, great designs

Re: 118 Crab Module Conference Presentation
 

The silverthin bearings are the less expensive versions of Kaydon bearings.

www.silverthin.com, I believe SA or SAA works. In my crab module research, I've found it really depends on the diameter of the vertical shaft and diameter of your intended vertical housing that will determine the inner and outer diameters.

All in all, if 1885 has the funds to do a prototype crab this offseason we will use this* for the thrust bearing and cut pieces of this** (with grooves in the inner housing for lithium grease) in order to cut down on the costs. Even though the bearings are slightly heavier, they're much less expensive. Combined with some other tweaks to the overall setup of the drive train, the preliminary CAD shows it will be 32lbs or less with every nut, bolt, and chain link.

Hope this helps.

*p/n 5909K43
** p/n 6391K27