AndyMark Parts Feedback 2015

[JesseK]

Now that champs has completed, what were the strengths and areas of improvement for the AndyMark line of COTS products? What new products would teams like to see that are in the same core vein as the current AndyMark or their other suppliers (such as 221LLC)? In what useful or unique ways did you use these products that you wish to share? What nuances or undocumented features did you find with them?

• I'd like a way to purchase the Churros in bulk. They are the #1 used COTS part on our robot this year, as funny as that sounds.
• Our DART actuator didn't get onto the final bot, but it was great for prototyping. It doesn't seem to like axial loads, but that can be dealt with via proper design. It would be nice to swap out different motors for it, however.
• I know that 3373 used the Swerve & Steer module, and the only problem they had was zeroing the absolute encoder. The worked through that, but otherwise had no mechanical problems in their swerve this year.
• We also have really liked specific gearboxes for their toughness over the years. I'd like to see either mount holes or a kit made available to use a pneumatic cylinder and a locking pin directly into the initial stage's steel gear for some of them. Holding a game piece steady at a specific height seemed to be a barrier for some teams this season since they didn't realize they needed it until after then entire subsystem was assembled.

[marshall]

900 ran into a lot of issues with the GEM gearboxes this year. Granted, we were doing derpy stuff with them so derpy issues were bound to spring up. We shocked the AM crew in St Louis with the multitude of failure modes that we found for the GEMs. We are going to try and write a paper about them once we get some time.

To be clear, 900 <3's AndyMark. They are easily one of the best suppliers out there and amazing to work with. We do derpy things to their gearboxes because we can, not because we are looking to blame them for making bad gearboxes. Seriously AM folks, you rock!

[wilsonmw04]

We used two new AM parts this year.

1. 4" mech wheels: We found them to be robust and very smooth. We only had one roller failure. It was on the practice robot. We wore out one of the brass rollers/rivets. It was easily repaired with a bolt. Not really complaining about the failure because that robot was driven very hard by my drivers. We actually caught air going over the scoring platform in an attempt to tip the robot over. We will use these wheels again.

2. Raw Box: This was used to power our two cim elevator. The worm screw was ALMOST un-backdriveable (is that a word?). With a little programming it easily kept a 6 tote stack at the proper elevation. No failures and would use again.

[marshall]

Originally Posted by wilsonmw04

2. Raw Box: This was used to power our two cim elevator. The worm screw was ALMOST un-backdriveable (is that a word?). With a little programming it easily kept a 6 tote stack at the proper elevation. No failures and would use again.

We broke two of those as well. They are good gearboxes provided you capture the output shaft solidly. Overhung loads on those gearboxes cause problems though.

[IKE]

As an LRI, I came across several teams that were getting hot motors and/or voltage drop outs. A common issue I saw was:
Kit bot modified to 6" wheels with no other mods. The effective free speed for this arrangement is quite high (something on the order of 20 FPS). This lead to a lot of hot motors.
I also helped a few teams that had placed a gear backwards in the gearboxes. There is a small offset that helps keep the gears from dragging on the housing. this drag resulted in hot motors as well. It might be good to add a current check on blocks for a chassis to see if you have un-necessary drag. this can be done with the PDP board and your laptop. Might be good to add a diagnostic tool.

[wilsonmw04]

Originally Posted by marshall

We broke two of those as well. They are good gearboxes provided you capture the output shaft solidly. Overhung loads on those gearboxes cause problems though.

We didn't support our shaft this year. It was running two different chain loads. I will keep that in mind for next year.

[marshall]

Originally Posted by wilsonmw04

We didn't support our shaft this year. It was running two different chain loads. I will keep that in mind for next year.

Well, we were trying to drive a 7 foot arm with 20 pounds of dynamic load on the end of it... so, yeah... YMMV.

[mrnoble]

We tried both the AM mecanum wheels and the Vex models. We used the 6" standard AM's on a demo bot without incident for 40+ hours before breaking a roller axle. We decided to go with the AM HD wheels for our comp bot and were very happy. Smooth and very strong and durable. We are planning to make hubcaps for them for Cow Town; they look like they deserve something pretty.

[Pratik Kunapuli]

341 used originally used the Banebots 220 series gearbox and they seemed very good to get an initial idea of reductions, especially with the add on 4:1 reduction. Since then, we changed to a SuperShifter for our elevator and have had no complaints since. We locked it into high gear, but the shifting was smooth when we were playing with it. The best part of the SuperShifter was the ability to set it and forget it. We never had to open it up to service it, and once the encoder was set it worked for the rest of the season.

[Munchskull]

We used the gears form the kit of parts drive train, my only comment would be, can they please be made of aluminum next year?

[Oblarg]

The worm in the WormBox consists of a plastic worm on a metal bushing. The connection between these two is not as strong as it should be (it appears to be a rather weak interference fit), and so under load the plastic can slide on the bushing and get pushed into the CIM mounting hole, causing lots of friction and eventual failure.

We discovered this before it became unmanageable and, with the help of the NASA machine shop, were able to push the bushings back into place and secure them there with pins. Such pins should be standard to prevent this from happening in the first place. Other than that, they were surprisingly durable for plastic gearboxes and the encoder mounts were very handy. Would purchase again, provided this problem is fixed.

We also received a hex hub that wasn't bored anywhere close to straight, and was unusable. We seem to encounter little QC problems like this every year, and while they're not crippling they are a constant annoyance.

[Michael Hill]

We ran into a couple of issues with AM parts this year. First off was shearing off the output shaft of the PG-188 when back driving it. That was not expected at all. We ended up taking off the PG-188 in the end anyway. Second was having an issue with the AM Planetary gearbox. The shaft was undersized by a few thousands (we mic'd it out). It looks as if it was made to 5/16 rather than 8mm, so the press fit gear we were using was slipping on the shaft. We tried knurling the shaft, and that seemed to work, but we eventually replaced it with a MiniCIM after finding some weight because we were unsure about how long the knurl would last.

The tough boxes worked great. We CNCed a new face plate out of .050 2024-T3 to lighten them up a bit and that worked a treat. We also used a couple of 32dp gears from AndyMark, and we didn't have any issues with them, so that's a plus.

[Oblarg]

Originally Posted by Michael Hill

We ran into a couple of issues with AM parts this year. First off was shearing off the output shaft of the PG-188 when back driving it. That was not expected at all.

Had this problem last year when we used two of them, direct-driven, to actuate our roller arm (after both failed as described, we switched to pneumatics). If you look at the spec sheet, it actually does specify that this is the standard failure mode if you exceed the maximum rated torque - I was surprised, too, until I looked it up.

[Michael Hill]

Originally Posted by Oblarg

Had this problem last year when we used two of them, direct-driven, to actuate our roller arm (after both failed as described, we switched to pneumatics). If you look at the spec sheet, it actually does specify that this is the standard failure mode if you exceed the maximum rated torque - I was surprised, too, until I looked it up.

If you open up the PG-188 gearbox, the shaft has a couple of triangular notches in them. That's where ours broke. I'm not sure if they're put there to create a known failure mode or not. If so, I'm guessing the thinking is that it's relatively simple and cheap to replace the shaft rather than the gear assembly.

[MrForbes]

Originally Posted by IKE

As an LRI, I came across several teams that were getting hot motors and/or voltage drop outs. A common issue I saw was:
Kit bot modified to 6" wheels with no other mods. The effective free speed for this arrangement is quite high (something on the order of 20 FPS). This lead to a lot of hot motors.

We did the 6" wheel mod to our kit chassis, and we also changed the gears (we used some gears from older AM transmissions). It worked great! we had some 6" white wheels left over from something else, and we notched the ends of the chassis so they'd fit.

I also helped a few teams that had placed a gear backwards in the gearboxes. There is a small offset that helps keep the gears from dragging on the housing. this drag resulted in hot motors as well. It might be good to add a current check on blocks for a chassis to see if you have un-necessary drag. this can be done with the PDP board and your laptop. Might be good to add a diagnostic tool.

The instructions sort of show the offset on the gears, but don't explain it nearly well enough for most students to notice.