We’ve kept it quiet all season, but here it finally is.
Here are all the technical specs;
-Wide 6 wheel with center wheel closer to back of robot.
-Traditional West Coast Drive with all hex axles
-Single CIM per side, ~ 14 fps
-25.75" wide opening for ball intake.
-Intake is is “slant” of the “7” shape, and is powered by dual CIMs.
-Exhaust is the short (~1’) run pointed slightly downwards, and is powered by 2 Fisher Prices and 2 545s.
-Exhaust can recieve balls from intake, or from hopper. Intake can load balls into hopper as well.
-The Pulleys are 2" OD Black ABS with a 1" CenterBore (bored to 1.125" on end for bearrings/hubs).
-All 10 pulleys on the robot are the same part, but are assembled with different bearrings or hubs (Well same hub, different part bolted to it) to make 3 unique pulley types.
At Champs we’ll be having a contest to guess how many inches of round belt we are using (totally stolen from 1501 and their rivits). It wasn’t intentional, but I’m fairly certain we’ve used more than any other robot, ever.
All but one gear is an AM product, which saved a great deal of machining time for us. In total we use 10 plate sprockets, 10 of the 22T 7075 sprockets, 4 of the AM planetary pinions, 4 Aluminum gears, and various other AM gears.
Overall, I’d like to think it’s very simple, and we’re real happy with it so far. And yes, it’s too orange.
The holes are something I invented a while back to [strike]irritate the kids[/strike] use as a standard mount. It’s a #7 (.201) Hole on a 1/2" hole pattern. It actually hasn’t been used much so far, as we got close on weight we started welding things on (and haven’t had many last minute additions) along with the fact that because the kids were whining, we didn’t do every face, so we mounted to some faces lacking holes. #7’s are great as they are a #10 bolt clearance, tap size for a 1/4-20 and work fine with normal 3/16" rivits.
Some were done on a drill press with a jig, some were done on a manual mill.
If it were done for weight, it wouldn’t be worth it, as each .201 diameter by 1/16" long disk removed must be extremely light. .0002 pounds actually.
As for the RC car tires, we use 28 on the intake, 14 per pulley, and an additional 14 on the exhaust pulley that touches the hopper. With the 6 in drive, that’s 48 “wheels”.
We never actually bought precision shaft, just ended up using rod and polishing it.
We haven’t noticed any ABS fatigue, and the intake pulley doesn’t bend at all in that picture, probably an artifact of the cropping in photoshop. There is a 1" OD, 1/8" wall 6061 tube running down the center of him that does a pretty good job of keeping him straight. However, any pulleys without such a sleeve put under high tension do bend, so most pulleys on the competition robot have at least a 1/32" wall thick sleeve.
One of my favorite robots this year, if only because it rivals Team 100 in orange-ness
I have couple basic questions about fabrication, it seems like you did some of the same things we did, but much better. How did you join your urethane belting together? Where did you purchase the ABS tubing, and why go with ABS instead of PVC? Judging off of McMaster’s prices PVC seems like a much much cheaper material choice. And last question, how deep are the grooves in your ABS, and have you had any problems with belts skipping off?
I love the design, any tips you can offer would be appreciated, our only belt system doesn’t look remotely as good as the 5 you guys have on this bot. Excellent job 973!
After looking at all the material properties, we chose (guesstimated) that ABS was the best material to go with.
We actually bought 2.5" OD ABS and had it turned to 2" OD. A local machine shop specializes in tubing and it was no problem at all for them. They were turned to 2" OD, cut to length (they held 29.5 to 3 thou!), gundrilled at 1" thru, and finally bored to 1.125" for 1/2" on each end. After all that, a 1/4" round grooving tool was used to groove 3/16" deep. In hindsight 1/4" would be better, as we’ve had some small issues with belts jumping, but most jumping issues were solved when we used properly tensioned belts; I think I only saw 2-3 belts jump at LA.
In terms of price, it’s not cheap stuff exactly, but we always do our homework and shop around. We think if you’re buying massive amounts of material from mcmaster, you’re doing something wrong. I think we ended up going with Interstate Plastics, who had it for somewhere around $16-19 a foot after haggling.
We weld our belts with a soldering gun with a spade tip and a jig we bought on ebay for specifically welding round belt. Works great. In terms of strength, there is no difference between that and a Jig would made that was basically two plates with matching slots, but it’s certainly easier to use. We initially trimmed them with dykes that were custom ground to have no back angle, but while being lazy I found that a table belt sander works great (not sure if fine grit is required, it’s what we used and it worked great for us).
Wow, thanks for the detailed response! Seems like you were fortunate to have that machine shop with tubing capabilities, probably not something a lot of teams could pull of with a basic lathe. In any case, thanks a lot for the insight! Good luck at Las Vegas and Champs!
We’re using our pneumatic tube cutters for our new belting when it comes in. The cutters work wonders in stopping pneumatic leaks, so we’re hoping to get a clean cut on the Rounthane every time. We’re using the tiny gator connectors for everything though, because we couldn’t get welding to work during the build season :o .
Making the grooves wasn’t too hard for us, I was referring more to putting a 1" ID through the entire 26" tube, is there a way to do that too? I’m not a very skilled machinist at all, I just know enough to get by. Does 254 drill out the middle of their rollers?