22-12-2015 19:02

asid61

Re: pic: Recycle Rush Re-design

What power is in the elevator? In the drivetrain?
Why BAGs for the grabbers over 775s or something similar?
What size wheels are those? Can it go over the step?
You look like you're going over the height limit in the picture due to the can stabilizer elevator, not sure if I'm just seeing that wrong.
The only thing I would add to this would be some way to stabilize the stack as you move, as right now it looks like it could topple fairly easily with a quick turn.

22-12-2015 19:11

KohKohPuffs

Re: pic: Recycle Rush Re-design

-4 CIMs are going to drive, and 2 RS-775s are going to the elevator at 1:10 reduction
-Wheels are 6in diameter, but I haven't tested with the scoring platform. I could probably add an idler wheel in the middle or something like that
-One of my friends on the team actually pointed this out that I might be going over the height limit. I measured the height to be dangerously close to 78in, but I think if I shorten the arm bars 1 or 2 inches it should be fine.
-I never thought of a stack stabilizer before... perhaps I can utilize the box tubing that the intakes are mounted on?

22-12-2015 19:17

KohKohPuffs

Re: pic: Recycle Rush Re-design

Oh right, as for BAGs vs RS-775s for the can burglars, I think it was motor stall that motivated me for BAGs over 775s, although now I'm kind of wondering why I chose BAGs in the first place

22-12-2015 20:38

GeeTwo

Re: pic: Recycle Rush Re-design

Why handle burglars? The window for lining these up is much smaller than for lid burglars. I just went to check an RC that I happen to have here at the house (yes, yes I do). The lid hole is at least five times as large as either handle, and it seems that a slight over/under reach is not nearly as likely to push the RC off the step onto the other side of the field. With "question mark" shaped arms, teams were able to reach the top holes over the landfill without violating the height restrictions.

22-12-2015 21:01

R.C.

Re: pic: Recycle Rush Re-design

You can still stall the 775pro. You just can't do it at max voltage for very long. Look at the data here: http://motors.vex.com/775pro

22-12-2015 21:38

Chris is me

Re: pic: Recycle Rush Re-design

The window to hit is smaller, but the arm can be shorter with this technique, which results in a lighter arm that can theoretically be moved faster. There is also no contest for the grabbing location if you go for the handle versus the top of the lid. It's a design tradeoff that doesn't necessarily have a right or wrong answer - very successful teams used both methods to burgle cans on Einstein.

22-12-2015 22:08

JohnSchneider

Re: pic: Recycle Rush Re-design

Actually at a certain point the weight of the arm doesn't matter at all. Or you end up snapping it by going too fast

22-12-2015 22:46

GeeTwo

Re: pic: Recycle Rush Re-design

To optimize a shorter arm, the pivot should be much higher. With the pivot near the floor as shown, the difference is minimal or negative, especially if you insist on a linear arm for the grabber.

While there may be no contest for engagement with the RC, there is still certainly a contest for control of the RC if it has been grabbed by an opponent either above or aside before you pull it off the step.

22-12-2015 22:49

KohKohPuffs

Re: pic: Recycle Rush Re-design

971's offseason robot had can grabbers made of carbon fiber, and they go decently fast. It's kinda similar to my can grabbers, so I wouldn't worry as much about snapping.

If I wanted to aim for the opening in the lid, how would one physically make that sort of geometry? It's not like one can bend carbon fiber to meet its needs (or can you?). Would the solution here be to use like 1x1 box tubing with the appropriate angle brackets? Or is there some better solution?

22-12-2015 23:27

Max Boord

Re: pic: Recycle Rush Re-design

PVC pipe or aluminum tube with carbon fiber rods. Bent sheet metal would probably work although I never made bin grabbers out of it myself.

22-12-2015 23:56

KohKohPuffs

Re: pic: Recycle Rush Re-design

I believe that 649 doesn't have access to sheet metal resources. As for PVC, I'm a bit concerned. Two weeks ago, I made swords out of that material for a Hamlet skit, and one person dropped it, and it broke into three pieces. It could've been the fact that it had holes cut in them, but I would feel safer using something more reliable

23-12-2015 00:30

asid61

Re: pic: Recycle Rush Re-design

I have seen videos of 971 doing their own carbon fiber layup. It seems tedious, so you could just use 3d printed or custom made endcaps for regular CF tubes and just stick the hook on the end like that.

23-12-2015 02:13

DaveL

Re: pic: Recycle Rush Re-design

Nice job!

About picking up the can.
- Is there a 2nd elevator section hiding behind the stack?

- How does the robot grab the bottom of the can?
(elevator pivot or another mechanism)

Dave

23-12-2015 02:48

KohKohPuffs

Re: pic: Recycle Rush Re-design

Nope, there's only one elevator, and that's exclusive to stacking. Also, the elevator is really short: it can lift up to the second tote level; after all, stacking really only occurs at that level.

To answer the second question, the robot has a four-bar linkage arm powered by 2 BAG motors (okay is there like a thread about BAGs vs. 775s somewhere?). That lowers down and actuates a pneumatic claw to grab the bin. I do not need a pivot for the claw, because the geometry of the four-bar automatically controls the angle of the claw to be horizontal with the ground.

23-12-2015 02:49

AdamHeard

Re: pic: Recycle Rush Re-design

The weight doesn't directly matter, but the inertia of it certainly does for acceleration.

a 6' arm versus a 5' arm w/ all other variables held constant will have substantially less inertia, which allows higher accelerations for same power.

23-12-2015 07:53

DaveL

Re: pic: Recycle Rush Re-design

Interesting.
Check out team 4488. They have an amazing robot!
https://www.youtube.com/watch?v=VpZazV3wP1s

Dave

23-12-2015 09:04

EmileH

Re: pic: Recycle Rush Re-design

What is the gear reduction for the versaplanetary on the BAGs driving the can grabbers?

23-12-2015 09:33

nuclearnerd

Re: pic: Recycle Rush Re-design

You might consider lifting a little higher so you can do co-op.

23-12-2015 10:11

GeeTwo

Re: pic: Recycle Rush Re-design

I haven't looked at the CAD, but from the render, it appears you need more than just lifting higher to score co-op. The elevator bracket appears to be fixed on the horizontal axis, and the way it supports a tote means that it cannot be extended outside of the robot frame. This could probably be enabled without additional actuators but would certainly require greater complexity to push the totes out while being supported by the elevator.
The intake rollers also appear to be at a constant altitude and possibly location, interfering with the coop score. The rollers would need to move out of the way (or better, up so that they push the totes out).

Edits:
Oh, I see that now. That does mean that (as currently mounted) they would not be useful to help place the elevated stack on the step; another mechanism would be required.

Also, I was curious about the RC lift - do I understand correctly that it would be a two-step process to cap a stack of fewer than six totes? That is, you'd have to score the short stack, then back up a bit to score the RC atop it. Not a showstopper, but an interesting trade-off.

23-12-2015 10:54

EmileH

Re: pic: Recycle Rush Re-design

The intake rollers do actuate out - it's hard to see from the render but there is a pneumatic piston there.

23-12-2015 22:02

KohKohPuffs

Re: pic: Recycle Rush Re-design

Yes, there are pistons that actuate the intakes in and out. As for the bot's ability to do coopertition, I never intended this to have that function. Maybe the intakes are high enough to do it, and if it does, then I can use the intakes to roll the yellow totes out. However, for this bot it's all about the stacking. If this were in a competition, I would love the 40 points from the yellow totes, but making consistent stacks looks better for scouting. That was my logic for that.

As for dropping a stack less than 6 totes, yes the bot does have to back up a little because of the bin grabber arm. It's a disadvantage, but I kind of also wanted to do such a mechanism because I never made such things in CAD before, and I wanted to try it out.

23-12-2015 22:29

GeeTwo

Re: pic: Recycle Rush Re-design

Noted, and respected. Just trying to clarify the decisions that led to this design.

Again, noted and respected; just clarifying.