We received multiple requests for more information during and after the Central Illinois Regional.
So here’s a link to our CAD file for anyone who is interested.
CAD FILES
http://www.pwnagerobotics.com/index.php/doc-list/public/23-swerve-drive
This looks really nice! I remember when I first saw the CIM in wheel idea… took away the clunky look that I always found swerve modules to have.
Importing the STEP file into SW right now to take a better look. How did it hold up/perform through competitions so far? Do you have any video/more pictures?
work of art:D
We didn’t have a single issue with it at the Central Illinois Regional.
http://www.thebluealliance.com/match/2014ilil_qf4m1
Check out the impact we deflected with 58 seconds left.
I just uploaded a technical paper one of our students, John Duffy, wrote about Team 2451 Pwnage 2014 swerve drive. There are many additional pictures that John created, exploded views, section views, etc. There is also additional specifications and descriptions for your viewing pleasure.
So proud to be an alum and now mentor of this team, and all of the great work the students have put into this years robot. We knew it was going to be tough to execute the swerve drive this year with it being our first competition swerve but they did a fantastic job. If you can, I suggest taking some time to take a look up close at the Midwest Regional this weekend, or hopefully St. Louis in a couple weeks.
-Nick
Awesome module, I’m amazed that you’ve somehow managed to pack everything into an even smaller space than the Nutrino’s design from 2012!
The gear teeth look pretty clean cut in this image, how did you guys manufacture the gear for rotating the module and the ring gear reduction for the wheel? Also, will this be in St. Louis this year?
Awesome module, I’m amazed that you’ve somehow managed to pack everything into an even smaller space than the Nutrino’s design from 2012!
The gear teeth look pretty clean cut in this image, how did you guys manufacture the gear for rotating the module and the ring gear reduction for the wheel? Also, will this be in St. Louis this year?
I’ll let Kevin or a student answer your question about the gears, but I can tell you that the team is not currently qualified for STL. The team were quarter-finalists at Central Illinois, and will be competing this weekend at Midwest (so fingers crossed).
-Nick
Wow…I love it
I was a bit skeptical of the delrin rollers as bearings when I first saw it but now that I’ve read your reasoning I love them.
This makes me wish 192 had started swerve earlier…
Do you have any close-up videos of it in action? Or a picture of it from the top? I know you provided the CAD file, but (to me) it’s not quite as awe-inspiring as the photograph 
It’s actually a bit bigger diameter than the Neutrino one
But the slight size increase was for features that are definitely worth it from a reliability/quality standpoint.
I’m very happy they chose to make it as it is a very cool example of what can be done.
Good luck at Midwest to 2451.
-Aren
You’re required to qualify so that I can get a look at them in real life
As a kid who grew up using 71’s crab drive, and seeing how big and clunky our drive was this module is amazing I wish I would of went to Midwest this year just so I can see this thing in person.
I love the low look of these swerves, I curious if you have trouble with tangling your wires. Does your software know when to unwind the swerves? How long does that take?
Our team did a non coaxial crab drive a few years back, and we didn’t enjoy it very much. This year we did our first independent coaxial setup.
I love the low look of these swerves, I curious if you have trouble with tangling your wires. Does your software know when to unwind the swerves? How long does that take?
Our team did a non coaxial crab drive a few years back, and we didn’t enjoy it very much. This year we did our first independent coaxial setup.
I’ll answer this, as most of the team will be busy for the next few days and may not have time to answer. The modules have somewhere around 350 degrees of freedom on their rotation. There are hard stops to ensure that the module does not rotate past those 350 degrees in either direction so that the wires do not become tangled. However it is included in the code and the modules will automatically rotate the opposite direction 180 so occasionally it has a slight delay but due to the gearing on the banebot that rotates the module, it does this very quickly and doesn’t effect driving too much. This is also a reason the drivers have been given so much practice time.
If slip rings were installed on each of the modules, then coaxial performance would be possible, such as the ones Bomb Squad uses this year. Up until they posted the info about theirs, we had trouble trying to find a slip ring module available on the market that was rated for the right specs and was not giant or extremely heavy.
We actually manufactured our own slip ring last year and while Al from 111 and Head Inspector said it would perform fine and he would pass it, there are no custom electrical systems allowed on an FRC bot, and it even uses custom slip rings as an example. Maybe one day they will revise that rule. Probably not though.
-Nick
Thanks for the quick response. I like your simple code solution, and it looks to not make a large difference in your driving performance. Do you use drive encoders? Sense your already raping wires anyway, it seems like it might be worth it for you guys.
I’m also curious if you give me an estimate amount of time spent on machining and assembling all those custom parts. we spent quite a bit of time on ours, and they only require five parts to be cut on the CNC mill.
To answer your encoder question:
So magnetic tooth counters were mounted to measure the speed of the wheels. There is an encoder mounted above the wheel mounted to the banebot motor assembly (which you can see in the CAD image) which measures the rotation of the modules.
As far as an estimate of hoe much time was spent on machining, I can tell it was a lot. I cannot give a good estimate hour wise, so I’ll leave that for Kevin or a student, but we work at a company called Genesis Automation who we would not survive without and have access to CNCs, quite a few mills, lathe, bandsaw, etc.
-Nick
Wow, this is really something guys. Great work!
Any chance we could get a few more of those sweet, sweet, hi-res photos? The CAD really isn’t doing the rest of it justice.
Do those holes in the hubs create any sort of airflow to the CIM (sort of like a fan?)?
Not to derail too much, but can you talk a bit about your frame? Am I correct in thinking that it’s basically VexPro Versaframe, but with the world’s mos insane bellypan?
I can speak about the frame. The team basically designed the bottom level first out of the 1x1 VersaChassis tubing to easily mount the modules to the frame. By making the 3x3 looking grid type pattern, this made the tubing surround the large gear for pivoting which we like to protect it, and it still allowed for plenty of ground clearance, not that much was needed for this year.
I wouldn’t say the bellypan is that crazy, it basically just covers the bottom of all the tubing to anchor it together. Then a second layer of the same tubing layout was put above the first, with vertical pieces connecting them around the perimeter of the frame. The middle two rails on the upper level were upgraded to 1x2 VersaChassis tubing because they had a lot mounted to it and the team felt it best for that area to be stronger.
Other then that the frame is just some sheet metal brackets to tie the whole thing together with rivets.
Let me know if you have more questions.
-Nick
This is for sure the coolest part I’ve seen all year, and is quite possibly my favorite robot mechanism ever. This makes swerve’s weight and space more reasonable. I spent the last 30 minutes going through the CAD drawing.
A few questions-
How did you guys make the gears? Was it wire edm/waterjet, or did you guys make them on a mill w/ an involute cutter?
There was a prototype of this module in from of 2451’s pit last year, and I was impressed then. Seeing how it performs in competition is absolutely amazing!
