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-   -   Climb Stopping Mechanism (http://www.chiefdelphi.com/forums/showthread.php?t=154311)

AdamHeard 03-02-2017 16:05

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by waialua359 (Post 1640001)
Sorry, I'm slow. I dont quite follow?

When you hit the wall on top, your motor will go to stall (unless you're current limiting) and push very hard on the top.

Now imagine everything in the system is a spring, you're going to compress/stretch parts of the robot/field and load everything up.

Now there is a ratchet on there preventing you from backdriving (and you can't go forward any more as you're already loaded pretty firm into the field).

Now that's how you lock yourself onto the field.

waialua359 03-02-2017 16:12

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by AdamHeard (Post 1640016)
When you hit the wall on top, your motor will go to stall (unless you're current limiting) and push very hard on the top.

Now imagine everything in the system is a spring, you're going to compress/stretch parts of the robot/field and load everything up.

Now there is a ratchet on there preventing you from backdriving (and you can't go forward any more as you're already loaded pretty firm into the field).

Now that's how you lock yourself onto the field.

In 2010, we created a simple ratchet pawl system that worked for our climber. It should release if we at least carry the robot, releasing weight tension.

AdamHeard 03-02-2017 16:15

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by waialua359 (Post 1640018)
In 2010, we created a simple ratchet pawl system that worked for our climber. It should release if we at least carry the robot, releasing weight tension.

You won't be able to release weight tension as you're literally clamping the field. Can't go the other way because of the ratchet as well.

s_forbes 03-02-2017 16:16

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by Daniel_LaFleur (Post 1640002)
The light does not go on until a full second after the plate is pushed.
Hope your knot holds.

I'm expecting at least one case where a robot yanks its stopper knot out of the davit this year, especially with the crazy ratios that people are putting on their climbers.

waialua359 03-02-2017 16:18

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by AdamHeard (Post 1640021)
You won't be able to release weight tension as you're literally clamping the field. Can't go the other way because of the ratchet as well.

Well, I guess we shall see.:)

llung 03-02-2017 16:19

Re: Climb Stopping Mechanism
 
The current measuring method works very well. We've used it in other instances in the past and plan on using it this year for the climber mechanism.

JesseK 03-02-2017 16:20

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by AdamHeard (Post 1640021)
You won't be able to release weight tension as you're literally clamping the field. Can't go the other way because of the ratchet as well.

Interesting point. How is 973 dealing with this?

AdamHeard 03-02-2017 16:24

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by JesseK (Post 1640025)
Interesting point. How is 973 dealing with this?

If you have a ratchet and are planning on stalling against the top for the full second, it needs to be able to disengage under load OR you need some way to remove the load.

Cory 03-02-2017 16:39

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by waialua359 (Post 1640023)
Well, I guess we shall see.:)

Prepare to be disappointed. There's nothing special about the scenario Adam has outlined. Any system with a ratchet and pawl is going to behave exactly as he's explained. We had this happen multiple times in 2010 with our kicker and our hanger. It's a HUGE PITA when it happens. We had to use a giant flat head screwdriver and apply major force to the pawl to lever it to disengage. This is assuming you have a pawl that's actually accessible. If you're using a ratcheting wrench you're totally screwed.

Imagine trying to release a ratchet strap that has been ratcheted to significant tension. If you try to pull the release with your fingers without taking up some of the load with the handle, you will never get it undone. You have to release tension off the release bar in order to move it. This is exactly what will happen in the scenario outlined above.

Poseidon5817 03-02-2017 16:43

Re: Climb Stopping Mechanism
 
It is legal to remove the rope from the field without removing the robot from the rope. So couldn't you have two team members support the robot, while another team member releases the rope from the davit?

Cory 03-02-2017 16:46

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by Poseidon5817 (Post 1640040)
It is legal to remove the rope from the field without removing the robot from the rope. So couldn't you have two team members support the robot, while another team member releases the rope from the davit?

No. Read the above. You have nowhere to support the robot to. You can't force it up because it's already pushed the touch pad to it's hard stop. The rope will be under hundreds of pounds of tension at that point. You cannot push the robot higher and therefore cannot relieve the tension.

waialua359 03-02-2017 16:49

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by Cory (Post 1640043)
No. Read the above. You have nowhere to support the robot to. You can't force it up because it's already pushed the touch pad to it's hard stop. The rope will be under hundreds of pounds of tension at that point. You cannot push the robot higher and therefore cannot relieve the tension.

This is a good point. I had assumed the same also as an alternative without carefully thinking about it.
I do recall your 2010 robot and didnt realize you had those issues also.

waialua359 03-02-2017 16:53

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by Cory (Post 1640037)
Prepare to be disappointed. There's nothing special about the scenario Adam has outlined. Any system with a ratchet and pawl is going to behave exactly as he's explained. We had this happen multiple times in 2010 with our kicker and our hanger. It's a HUGE PITA when it happens. We had to use a giant flat head screwdriver and apply major force to the pawl to lever it to disengage. This is assuming you have a pawl that's actually accessible. If you're using a ratcheting wrench you're totally screwed.

Imagine trying to release a ratchet strap that has been ratcheted to significant tension. If you try to pull the release with your fingers without taking up some of the load with the handle, you will never get it undone. You have to release tension off the release bar in order to move it. This is exactly what will happen in the scenario outlined above.

Ours is accessible so looks like we will have to bring that large flat screwdriver head.:p
Or we can also do the other suggestion earlier with the current draw. Lots of time left to figure this out since our climber already made and it works.

AdamHeard 03-02-2017 16:56

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by Poseidon5817 (Post 1640040)
It is legal to remove the rope from the field without removing the robot from the rope. So couldn't you have two team members support the robot, while another team member releases the rope from the davit?

Read what I posted again, you're literally champing the field and that rope will be under significant tension. Good luck.

Ken Streeter 03-02-2017 17:36

Re: Climb Stopping Mechanism
 
Quote:

Originally Posted by Daniel_LaFleur (Post 1640008)
Yes, but if you wait to stop your winch until AFTER the light comes on you will be putting the full power of your winch + the weight of your robot pulling on the rope for that second.

That's probably a decent amount of force (at least 300 lbs)

Just FYI, I agree with your point that teams need to have a solution to the problem.

However, in this circumstance, the force applied on the rope after hitting the stop at the top isn't "the full power of the winch + the weight of the robot pulling on the rope..."

Rather, it's the maximum of the two. (Which is likely to be the "at stall" torque from the winch.)


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