pic: Recycle Rush Re-design

[KohKohPuffs]

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

[GeeTwo]

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.

[Chris is me]

Originally Posted by GeeTwo

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.

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.

[JohnSchneider]

Originally Posted by Chris is me

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.

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

[KohKohPuffs]

Originally Posted by JohnSchneider

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

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?

[Max Boord]

Originally Posted by KohKohPuffs

Would the solution here be to use like 1x1 box tubing with the appropriate angle brackets? Or is there some better solution?

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.

[KohKohPuffs]

Originally Posted by Max Boord

PVC pipe or aluminum tube with carbon fiber rods. Bent sheet metal would probably work although ive never made them myself.

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

[asid61]

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.

[DaveL]

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

[KohKohPuffs]

Originally Posted by DaveL

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

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.

[DaveL]

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

Dave

[EmileH]

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

[nuclearnerd]

Originally Posted by KohKohPuffs

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.

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

[GeeTwo]

Originally Posted by nuclearnerd

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

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:

Originally Posted by EmileH

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

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.

[AdamHeard]

Originally Posted by JohnSchneider

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

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.