Lifting mechanism for hanging

[Michael Kapp]

It has been suggested that we should finish what we are working on now before attempting to design a lifting mechanism if we have time. I think that we have the overall idea of tanner's chassis solidified, and we just need to perfect it and work out the kinks, and we have the manpower and resources to go ahead and begin working on a lifter mechanism. I would really like to start working on it thursday or saturday.

[Sunny]

It has been suggested that we should finish what we are working on now before attempting to design a lifting mechanism if we have time. I think that we have the overall idea of tanner's chassis solidified, and we just need to perfect it and work out the kinks, and we have the manpower and resources to go ahead and begin working on a lifter mechanism. I would really like to start working on it thursday or saturday.

A couple of things that immediately come to mind.

1. It seems Dallas has an extremely good idea. I like it, and I think others will like it as well. A group can work with him.
2. The *primary* component of the lifting mechanism that needs work is getting the hook up. Creating a hook is not hard, and creating a winch to lift the robot is not hard either.
3. There needs to be a "group" whose main goal is this design. If we can create a group, then all might be well.
4. The talk right now is that we can use a CIM to lift the robot, but a couple of things with that.
a) If we use a CIM, we can't use one for the kicking design
b) We can possibly use a window motor. Window motors have an absurd amount of torque, and I think they might work just as well as a CIM.

I will look more into window motor RPM vs. Torque Curves and put up some basic calculations.

EDIT: I found some stuff on the motor, but I'm not sure what kind of reductions they go through when they are passed through the gearbox that's attached.

- Sunny

[Michael Kapp]

I have a great idea for a way to lift the hook.You know how 80/20 bars can interlock so that they slide against each other? well, interlock three long bars and attach pulleys at the top and bottom of each bar. place a rope from the bottom pulley of the first to the top pulley of the first to the bottom pulley of the second to the top of the second to the bottom of the third and attach it at the top of the third. attach the hook or whatever to the top of the third bar. then take a motor and attach the start of the rope to the shaft like a winch and run the motor. since the sections of rope along the length of each bar cannot change length, the sections from one bar to the next will shorten, causing the second bar to slide up the first and the third bar to slide up the second. the result is a tower slightly shorter than the combined lengths of the bars, and the hook is on top allowing the robot to grab the tower and winch itself up. Best of all, as we winch ourselves up with the separate winch mechanism, the 80/20 tower is re-collapseable by spinning the motor backwards and letting gravity do the rest. See the attached picture (made in powerpoint)!

This could work very quickly and is resource-efficient.

[Tanner]

*cough*

Patrick's idea for 2007. Same idea. I remember it working though I'm not sure how we held the 8020 together, perhaps those nice white pieces that held the 8020 together. For some reason I remember parts of it binding though. Wonder if I can find any pictures... Hmmm.. I'll look.

-Tanner

[Michael Kapp]

*cough*

Patrick's idea for 2007. Same idea. I remember it working though I'm not sure how we held the 8020 together, perhaps those nice white pieces that held the 8020 together. For some reason I remember parts of it binding though. Wonder if I can find any pictures... Hmmm.. I'll look.

-Tanner

*wonders how tanner can remember an obscure, unused idea from 4 years ago*

The 80/20 can be interlocked with itself. just slide two pieces together lengthwise and they hold on to each other. no white pieces necessary. remember in 2007 how when we initially unfolded, a small bar interlocked with the top section fell down so that it was interlocked with both sections, binding the sections together? similar method, different application here.

[Tanner]

*wonders how tanner can remember an obscure, unused idea from 4 years ago*

The 80/20 can be interlocked with itself. just slide two pieces together lengthwise and they hold on to each other. no white pieces necessary. remember in 2007 how when we initially unfolded, a small bar interlocked with the top section fell down so that it was interlocked with both sections, binding the sections together? similar method, different application here.

Well, I was working on that team. So...

That would probably work, I just can't remember how we did it back then. Whatever it was, it worked pretty well.

One thing that was kind of hard was pulling the string/rope to move it up though I don't think it would be that hard with a motor. You probably don't want to hold the motor in that position for a long time though.

-Tanner

[Sunny]

*wonders how tanner can remember an obscure, unused idea from 4 years ago*

The 80/20 can be interlocked with itself. just slide two pieces together lengthwise and they hold on to each other. no white pieces necessary. remember in 2007 how when we initially unfolded, a small bar interlocked with the top section fell down so that it was interlocked with both sections, binding the sections together? similar method, different application here.

Well, I was working on that team. So...

That would probably work, I just can't remember how we did it back then. Whatever it was, it worked pretty well.

One thing that was kind of hard was pulling the string/rope to move it up though I don't think it would be that hard with a motor. You probably don't want to hold the motor in that position for a long time though.

-Tanner

I remember that design too. Not hard to remember if you focus for a bit.

The way they did it back in '07 was that they used the 80-20 wheels that we have to create the locking parts. I believe the issue that was happening with that, is that when going 10 feet in the air, that required upwards of 4 units, and with the weight of some "manipulator" the system did tend to bind.

I don't think that's a bad idea either. The reasons I'm not sure if it'll work are
A) To have two 3 bars of that length, each bar would have to be 28" long at least
B) I'm not sure how stable this thing will be. We want to be able to grab and hang on...so I'm not sure.

I think Kapp's lifter is very easy to prototype, It's just mounting it on the robot will be the interesting part. Maybe we can have this system fold out or whatever.

And as for the thing, if we use a window motor to power the elevator type of thing, the motor should have more than enough torque to put it up there and hold.

[Tanner]

Example of what a team did to hang from the top for a attachment device.

http://www.chiefdelphi.com/forums/showt ... post917274

-Tanner

[freds]

Sunny, if we use the idea Dallas had, the springs we would use are called torsion springs. We would want to use the 180 degree springs.

Look at the specs and see if you can pick one out - torque or force. I think ones having 2" leg lengths would be best.
http://www.mcmaster.com/#torsion-springs/=5rgwm4

Assume we have two pieces of alum channel 36" and one piece say 12". We have to spring this to life plus a piece of rope, not much weight and then some hook at the top.

They do not provide the weight of the channel: http://www.mcmaster.com/#4592t31/=5rgxiw

[Sunny]

Sunny, if we use the idea Dallas had, the springs we would use are called torsion springs. We would want to use the 180 degree springs.

Look at the specs and see if you can pick one out - torque or force. I think ones having 2" leg lengths would be best.
http://www.mcmaster.com/#torsion-springs/=5rgwm4

Assume we have two pieces of alum channel 36" and one piece say 12". We have to spring this to life plus a piece of rope, not much weight and then some hook at the top.

They do not provide the weight of the channel: http://www.mcmaster.com/#4592t31/=5rgxiw

OH, These are just the parts I was looking for!!!

I saw a team using them on their kicker, but I wasn't sure exactly what they were. Apparently they mount right onto the axle they give one heck of a kick. The team got around 60 feet of x distance and at least 30 feet in the air. I'm not saying we need to do that. It just seems like something that we can test out really quickly.

Back to the original purpose of the springs, 180 degrees sounds good, but I'm wondering how well the springs *hold* at that position. We might want to get the ones that go 270 degrees just we can ensure the mechanism unfolds quickly and efficiently. Maybe we can use a similar locking mechanism back in '07 to lock them into place.

Looking at torque calculations...Um.. a 38" piece, half way is 19". It would be safe to assume that it has uniform mass across the bar, so that the mass's torque vector at that point would be 19" away. So based off that, the torque required to lift the the arms should be 19 * weight of the arms. But since there are two arms, they will unfold and that will add to the length...so...eh.

I would think that to be safe, the spring at the bottom would need to have a torque of roughly 38 in*lb...but even then, That's pushing it. We might want to go max torque on this one.

http://www.mcmaster.com/#torsion-springs/=5rhawb

The one that's one bar above doesn't have to be as much. Around 22.5 in*lb should be alright.

http://www.mcmaster.com/#torsion-springs/=5rhb4s

And then to flick out the little piece at the end, we just need something around 10 in*lb.

http://www.mcmaster.com/#torsion-springs/=5rhb4s

(I choose one with 9.5 for this one because the 7/7.5 didn't have a 180 degree angle)

I'll see if I can hunt down the team's stuff that did the spring kicker.