Team 95 Hard At Work - 2015

[JamesCH95]

Some more parts from the Prototrak. We neglected to take many pictures this weekend.. I promise more soon!

[who716]

Originally Posted by JamesCH95

Thanks! We are as well.

Bring your cards and pegs, we'll play cribbage on the robot while we wait for eliminations matches! I swear we'll be on the same alliance one of these years... I still regret not picking you guys in 2012 when we had the chance.

The hole patterns are for the chassis style we've adopted - plates and standoffs, like last year's robot. It plays well to our strengths, i.e. plasma cutter and Prototrak and has proved to be elegant and robust.

lol

[JamesCH95]

The main arm is ostensibly together and operating.











It runs really smoothly and quietly. The air cylinders do a great job counter-balancing the arm. It needs no motor input to hold position without an RC, with the RC it needs a slight input to hold position, but nothing that two CIMs aren't up to the task of doing. So far it seems that the base is quite stable with the arm moving, like math said it would be. Tonight we'll be driving around with the arm out, that should be interesting. Hopefully some video will get uploaded soon!

[s_forbes]

Cool stuff! Some questions:

• Looks like pneumatic cylinders are being used to offset the weight of the arm, and you switch them from push to pull depending on what side of the robot the arm is on? Clever. (Edit: doh, nevermind, I see you already described it, and should always pull the same way)
• Are those black brackets you use to connect the chain and cable ends off the shelf parts or fabbed?
• What's the mystery material you have lining the edge of your gripper, and how well does it grip? We're still in the hunt for a good material.
• What's with that big metal truncated icosahedron in the background?

Thanks for posting your build, it's fun to follow.

[JamesCH95]

Originally Posted by s_forbes

Cool stuff! Some questions:

• Looks like pneumatic cylinders are being used to offset the weight of the arm, and you switch them from push to pull depending on what side of the robot the arm is on? Clever. (Edit: doh, nevermind, I see you already described it, and should always pull the same way)
• Are those black brackets you use to connect the chain and cable ends off the shelf parts or fabbed?
• What's the mystery material you have lining the edge of your gripper, and how well does it grip? We're still in the hunt for a good material.
• What's with that big metal truncated icosahedron in the background?

Thanks for posting your build, it's fun to follow.

Correct, the cylinders always 'pull' and thus need no controls. They also provide some nice damping in the arm system and act as the hard-stops.

The chain tensioners are OTS from Team 221: http://www.team221.com/ Nice product, nice interaction with their salespeople too.

The mystery material is from McMaster, it's a rubber edging material: http://www.mcmaster.com/#8507k72/=vv663c It has been working "okay" but not spectacularly. We have another style from McMaster to try that has foam gasket on it and some 3M grip tape, similar to what's in the KOP, that 1519 recommended to us that we're going to test.

The aluminum soccer ball, bolted into the mouth of a 3ft tall steel velociraptor, were two plasma-cutting and welding projects for the class we share the shop space with: Industrial Mechanics and Welding.

Glad you like the thread!

[dradel]

How long is the arm from center of pivot (looks like it pivots over top of chassis) to end of grabber?

[JamesCH95]

Originally Posted by dradel

How long is the arm from center of pivot (looks like it pivots over top of chassis) to end of grabber?

On the order of 70in when it is horizontal. It can reach past the center-line of the RCs on the step without disturbing any totes in the landfill.

[dradel]

So you guys must be right at the limit on the 78" height restriction then.

Very cool concept!! Can't wait to see some video of it operating !

[JamesCH95]

Originally Posted by dradel

So you guys must be right at the limit on the 78" height restriction then.

Very cool concept!! Can't wait to see some video of it operating !

Indeed! We are at about 77in at the moment, dictated by pneumatic tubing. About 76in for the tallest bit of metal.

Here is a video from a few days ago of the initial completed arm testing.

https://www.youtube.com/watch?v=vSCOoGvhOaY

The grippers did not actuate because the 12v/24v jumper was not set properly on the PCM.

[dradel]

I hate when the jumper is in the wrong position !!! Makes it harder to blame on Programing lol

[Bryce Paputa]

Is that #25 or #35 chain on the arm? Very similar concept to part of our robot. What's your thoughts about container tug of wars?

[JamesCH95]

Originally Posted by Bryce Paputa

Is that #25 or #35 chain on the arm? Very similar concept to part of our robot. What's your thoughts about container tug of wars?

#25

I think that container tug-of-wars will only occur at very high-level of play and may result in one, or both, of the robots suffering damage, and will likely result in more than one up-turned RC.

[JamesCH95]

We changed out our 6in wheels for 4in wheels. We decided that the improvement in fine control and current consumption was worth not being able to drive over the bump. Our geared free speed dropped from the 14-15ft/s range to the ~10ft/s range. Control is improved and we got a little more clearance on the 78in height restriction.

[Nathan Streeter]

Originally Posted by JamesCH95

We changed out our 6in wheels for 4in wheels. We decided that the improvement in fine control and current consumption was worth not being able to drive over the bump. Our geared free speed dropped from the 14-15ft/s range to the ~10ft/s range. Control is improved and we got a little more clearance on the 78in height restriction.

Sounds good! IMO, pretty much anything over 10fps is overkill this year. Will you still be able to drive over the scoring platform if needed?

I think we have an adjusted speed of something like 7fps on our 6" mecanums... I don't think we've actually measured it yet, but it seems about perfect for our strategy (so far!).

[JamesCH95]

Originally Posted by Nathan Streeter

Sounds good! IMO, pretty much anything over 10fps is overkill this year. Will you still be able to drive over the scoring platform if needed?

I think we have an adjusted speed of something like 7fps on our 6" mecanums... I don't think we've actually measured it yet, but it seems about perfect for our strategy (so far!).

Crossing might be iffy at best. We're planning on staying 'far field' for the whole match, i.e. never coming to the human player station side of things. The possible exception being immediately after auto, where we may want to grab cans/totes in auto. In that case we'll just drive around them.