Team 254 Presents: Dropshot Technical Binder 2016

[Greg Woelki]

Originally Posted by bigbeezy

would a waterjet be able to do 20DP gears?

Yes. We did it this year for our hood's sector gears and our waterjetting sponsor didn't have to do anything special for them. (Picture)

[Travis Covington]

Originally Posted by Dan Petrovic

Can I get some more information about the 2" OD surgical tubing that was used on the intake? After searching for 2" OD black rubber tubing on McMaster, the only result given was nitrile tubing with a 60A durometer hardness. Is this the same stuff?

Bringing the OD down to 1.5" (still black opaque) returns latex tubing with a hardness of 40A, more in-line with what Banebots uses on their wheels.

Is there another supplier where 2" latex tubing is available?

I think this is an error and we are in fact using 1.5" OD latex tubing as you are finding on McMaster.

[Cory]

Originally Posted by Michael Hill

Awesome robot as usual.

I've been curious about your turret gear. It looks similar to 1114's from 2012, but from my guesstimates, it's 20dp @ 16.1" Pitch Diameter whereas 1114 had a much larger geartooth (something like 10-12dp). One of my main concerns is actually having our waterjet sponsor cut teeth that small (I've been contemplating turrets lately). Was it relatively easy for your sponsor to do or was there anything special you had to do to the gear design to make it easier to manufacture? I'm guessing going to 0.125" aluminum made it easier, but is that enough?

Depends on the water jet nozzle diameter. Our sponsor can't do anything a .035" diameter stream can't fit into. That diameter stream will just get into the root of a 20 dp gear tooth. It would not work for our hood gears, had we attempted to water jet them.

There was really no special design consideration. This was done on a very new water jet with a tilting head to compensate for stream lag and eliminate taper, which basically cuts perfect parts.

[TheModMaster8]

Is their anyway we could get a CAD download link of the robot?

[jkelleyrtp]

How was your experience with mechanum wheels for an intake? Are you likely to use them again in the future?

[s5511]

How did you guys have 3 positions on your utility arm using pistons? During matches, it looked like there was an all the way up, slightly raised, and completely down position for the arm.
Also, are the 1.5'' bore pistons which raise the utility arm mounted directly to the arm? It doesn't look like in it your pictures, but I can't exactly tell.

Thanks!

[sanddrag]

I've only had a chance to skim it, but once again, very nice looking, and a valuable resource to other teams like ours. Thanks for releasing this.

I'm curious to know what pneumatic wheel hubs those are, or if you made them. Are there any additional photos of the wheel hubs?

Also, the PDF text looks to have exported as a raster image rather than as vector text. Not sure if you meant to do that.

[Travis Covington]

Originally Posted by sanddrag

I've only had a chance to skim it, but once again, very nice looking, and a valuable resource to other teams like ours. Thanks for releasing this.

I'm curious to know what pneumatic wheel hubs those are, or if you made them. Are there any additional photos of the wheel hubs?

Also, the PDF text looks to have exported as a raster image rather than as vector text. Not sure if you meant to do that.

Wheel hubs are custom, but very similar to the WCP ones. The obvious difference is that these are sized for the 8" pneumatic tires, and as such, have similar dimensions to the AM plastic hubs. Not a lot of weight savings though. Probably not worth the effort for most.

Our guys are updating the PDF now. Nice catch!

[Ashwin Adulla]

Originally Posted by caume

What do you use as a thrust bearing for your turret? Also, why do you only use two CIMs in your drive? You need moar pushes

We have 7 bearing assemblies along our turret gear which you can see if you look closely on page 16. Each bearing assembly consists of 3 ball bearings in the following order: a large bearing, a small bearing, and a large bearing (I do not know the exact bearing size). Each bearing is separated by a small shim and is lined up along a 10-32 screw with a locknut threaded at the bottom of the screw. The locknut is not tightened to its fullest extent in such a way that as the two large bearings sit upon the top and bottom of the plate connecting the two sides of the superstructure, they are able to slide along the plate's surface in addition to the small bearing with can rotate freely as it contacts the inner edge of the plate.

[AdamHeard]

Originally Posted by Ashwin Adulla

We have 7 bearing assemblies along our turret gear which you can see if you look closely on page 16. Each bearing assembly consists of 3 ball bearings in the following order: a large bearing, a small bearing, and a large bearing (I do not know the exact bearing size). Each bearing is separated by a small shim and is lined up along a 10-32 screw with a locknut threaded at the bottom of the screw. The locknut is not tightened to its fullest extent in such a way that as the two large bearings sit upon the top and bottom of the plate connecting the two sides of the superstructure, they are able to slide along the plate's surface in addition to the small bearing with can rotate freely as it contacts the inner edge of the plate.

1601 (large bearing) - R3 (small bearing) - 1601.

R3 handles the radial load, 1601 acts as the thrust load (but has a sliding contact on the face of the bearing ring).

[JesseK]

Thanks for posting!

[Cherry254]

Originally Posted by jkelleyrtp

How was your experience with mechanum wheels for an intake? Are you likely to use them again in the future?

We experienced some jamming and stalling issues but that was because the intake geometry was not perfect. Additionally, neither roller extended past the weldment so we were not able to pick up Boulders from the edge of the intake. The major issues with the intake were separate from the use of mecanum wheels.

[seans341]

Thanks for posting this! I noticed that turret compatibility was a significant factor in the overall design process. What did you notice about the game that made a turret so appealing?

[Cherry254]

Originally Posted by s5511

How did you guys have 3 positions on your utility arm using pistons? During matches, it looked like there was an all the way up, slightly raised, and completely down position for the arm.
Also, are the 1.5'' bore pistons which raise the utility arm mounted directly to the arm? It doesn't look like in it your pictures, but I can't exactly tell.

Thanks!

The Utility arm can go into 4 positions using deployable hardstops and kickstands. Its 4 states were drive mode, Low Bar mode, Starting configuration and hang mode. The pneumatic cylinders mounted to the plates extending down at the bottom of the arm as seen on page 21. Below see the deployable hardstops.

[Cory]

Originally Posted by seans341

Thanks for posting this! I noticed that turret compatibility was a significant factor in the overall design process. What did you notice about the game that made a turret so appealing?

Low robot with a blockable shot that had to be in one specific place on the field to make shots, or have the front of the robot normal to the goal to shoot was clearly going to be a death sentence at high levels of play.