27-01-2011 08:50

ajlapp

Re: pic: 816 as of 1/25/11

That's a clean looking bot.

What does the underside look like? How do you put the wheels in?

Also, I don't see any chain tensioning features....care to expand.

27-01-2011 09:00

thefro526

Re: pic: 816 as of 1/25/11

Thanks Anthony!

The underside of the tubes looks like the top, except the slots are two inches longer (6.5" long) to allow the wheels to be put in. The extra two inches of slot on the outer wheels is biased towards the center to maintain enough material at either end of the tube to keep some structure.

Right now there aren't any tensioners in place, the axles were placed apart so that we'd use a whole number of chain links (no half-links) so the chains are pretty tight. There are holes to allow delrin idlers to be bolted into the tubes to help tension the chain a bit, but we won't know if we need them until the chain stretches.

27-01-2011 09:12

dodar

Re: pic: 816 as of 1/25/11

Probably a question with an obvious answer, but is the tower side the front or back?

27-01-2011 09:14

thefro526

Re: pic: 816 as of 1/25/11

Not all that obvious of an answer, but the tower is in the rear of the robot.

27-01-2011 09:16

dodar

Re: pic: 816 as of 1/25/11

So to me that would mean that you guys are going to have a double-jointed arm? So that you can pick up from the front, unless you are gonna scoop from the back and score from both sides.

27-01-2011 09:18

ajlapp

Re: pic: 816 as of 1/25/11

We use a cam bolt for tensioning in our boxed frame system.....works pretty good. It is especially well suited for these applications because you have axle support on both sides.



A fixed center distance will do the trick too.

27-01-2011 09:35

thefro526

Re: pic: 816 as of 1/25/11

We're planning on using a 4-Bar arm with a wrist. I guess that's technically 2-joints, but the wrist will only pivot between 0* and 90* with the floor- which is to allow for tube pickup.

Anthony, I referenced your cam bolts during the design phase for this drive, but I didn't think they'd be necessary if we could hold a respectable center to center tolerance. If we find that tensioning the chains becomes and issue down the road, it's not hard to implement your tensioner on our drive.

27-01-2011 10:19

sdcantrell56

Re: pic: 816 as of 1/25/11

Wow Dustin! I am loving the direction you guys are taking this year. This robot looks so clean and robust. What are you planning for the gripper? Pincher or roller?

27-01-2011 10:22

thefro526

Re: pic: 816 as of 1/25/11

Thanks Sean, we're trying to make up for that thing we put on the field last year...

I'm currently working on finishing up the CAD of our Claw. It's pretty much a standard Polycord Roller Claw, nothing ground breaking, but it should serve our purposes well. If all goes well, it should be done Monday or Tuesday of next week, but with all this snow that may slip a bit.

27-01-2011 10:43

rcmolloy

Re: pic: 816 as of 1/25/11

Saw this on facebook a few days ago and gotta say that this is gonna look real nice at NJ and Philly. Hopefully over the next two weeks, I'll be over to see it in action man.

By the way Dustin, that "thing" got you to the Finals in NJ last year. Just an fyi haha.

27-01-2011 10:50

ajlapp

Re: pic: 816 as of 1/25/11

Cool.

Our sponsored team, FRC3098 The Kettering Captains, will be using our setup this season....so I'm really looking forward to see how the cam bolts hold up during competition.

Agreed that you could always go to a tensioned system if you start to see excessive sprocket wear.

27-01-2011 11:00

thefro526

Re: pic: 816 as of 1/25/11

Thanks bro. By the way, even if your team doesn't come to our field, you're more than welcome to stop by to chat robots and stuff.

I'm curious as to how well they'll hold up to. By the way, where did you get your 3x4 Tubing? I've found that it's not a common size at any of our local suppliers.

28-01-2011 13:50

J.Warsoff

Re: pic: 816 as of 1/25/11

Looks very good guys! Just wondering, are you guys using a minibot? If you are, how will you deploy it?

28-01-2011 13:54

thefro526

Re: pic: 816 as of 1/25/11

Our mini-bot is currently in development, so we're not entirely sure of a deployment system yet. Odds are that it'll either sit in between the uprights and be deployed from there, either using a piston or some linear slide, or be deployed from one of the sides.

28-01-2011 15:56

waialua359

Re: pic: 816 as of 1/25/11

We have a similar drive and have never had to tighten our chain, ever from the time we put the robot together until the end of the season. We do 4-5 events per season as of late, plus demos.

28-01-2011 23:52

delsaner

Re: pic: 816 as of 1/25/11

Looks great Dustin. I am liking the tower and the robust chassis. I also like how you and your team evenly distributed your weight to compensate for your arm base (putting the compressor and the battery on one side, with your arm in the back). Looking forward to seeing the final robot at NJ.

Curiosity, are all 6 of your wheels in contact with the floor, or is it a rocker?

02-02-2011 08:53

thefro526

Re: pic: 816 as of 1/25/11

Thanks Eric. The weight distribution might still need a little work, but it's not all that bad. With more of the Pneumatic system in place and the pound and a half of Brass fittings we had to add onto the compressor and tanks the weight has shifted a bit farther forward than expected. Once the claw, arms, arm motors, and Mini-Bot system are in place it should come in somewhere around 50/50, though I'm hoping for a split closer to 45/55 or even more rear biased if possible.

Technically, the drive is a rocker, though the rock isn't much. The Center wheel is offset approximately 1/8" lower than the outer two wheels, so it has a little bit of rock but it's barely noticeable on carpet. I'm really not a fan of some of the higher offset rockers we've used in the past, they almost seemed to rock too much, but I think we've nailed this one.

Nick and I had a chance to beat on the chassis last Saturday and were thoroughly impressed with it's speed, agility and stability. Hopefully some time this week he and I will have a chance to put it through some quantitative testing to get a real feel for how it'll hold up in competition.