233 telescoping arms how do they work?

[ASmith1675]

Awesome stuff. Thanks for all the info about these mechanisms.

When we've built these cascaded telescoping lifts/arms in the past, we've used a winch system for the first stage. What I'm having trouble wrapping my mind around with both of 233's and 254's telescoping arms is where the extra chain/timing belt, goes when these mechanisms are extended. Or are just the cascaded sections using the timing belt/chain?

Always trying to come up with better solutions, and these are the type of mechanisms we're all striving to make (in some small way).

[Pat Fairbank]

Originally Posted by Smitty1707

What I'm having trouble wrapping my mind around with both of 233's and 254's telescoping arms is where the extra chain/timing belt, goes when these mechanisms are extended.

In this year's arms, the other end of the belt comes off the bottom pulley and then goes back up inside the bottom of 1x1 tube (the last stage), where it is clamped.

This section of belt (from the pulley to the bottom of the last stage) is what takes all the tension when the arm is being retracted. This way, the force exerted by the weight of the robot while climbing is just transmitted through the (large) bearings and shaft supporting the bottom pulley, and not on any of the tiny ones where the belt doubles back on itself.

The beauty of using a telescoping arm for hanging, in my opinion, is that there are no moments exerted on any of the stages during retraction.

[CENTURION]

If I'm reading this thread right, the arms are basically a condensed version of this right?

[Lil' Lavery]

Originally Posted by CENTURION

If I'm reading this thread right, the arms are basically a condensed version of this right?

That's similar to 254's arm, in that it is a multi-stage, continuous lift.

If I understand MikeD's post correctly, 233's multi-stage arms are essentially cascaded lifts, but the second stage does not return to the original power source (and is instead driven "passively" by a sprocket that is turned as the first stage extends).

The key difference for both arms is that all the stages are nested within each other, which presents numerous challenges and advantages.

[CENTURION]

Originally Posted by Lil' Lavery

That's similar to 254's arm, in that it is a multi-stage, continuous lift.

If I understand MikeD's post correctly, 233's multi-stage arms are essentially cascaded lifts, but the second stage does not return to the original power source (and is instead driven "passively" by a sprocket that is turned as the first stage extends).

The key difference for both arms is that all the stages are nested within each other, which presents numerous challenges and advantages.

Ah, okay, yeah we used a cascade like the 233 one you describe in 2011 to raise/lower tubes.

Yeah, the nesting sounds very hard to do. Maybe if I get bored over the summer I'll CAD up something

[Tom Line]

Originally Posted by CENTURION

Ah, okay, yeah we used a cascade like the 233 one you describe in 2011 to raise/lower tubes.

Yeah, the nesting sounds very hard to do. Maybe if I get bored over the summer I'll CAD up something

The nesting is only really difficult if you want to put it into a very small package. Pink's arm and Poof's variation show true engineering elegance in packaging, from the wide rollers to the usage of belt (low profile) to the threading of the linear springs through the system.

The question that you'll also have to answer is the orientation of the constant force springs. Do you use them to extend the arm and only pull one way with your motors? Do you use to retract the arm so they help you lift the robot, but power the arm in both directions?

It's a really awesome design that I wanted to understand to put it in our 'toolbox'.

[MichaelBick]

If somebody is still having a hard time understanding how the poof's arm works, I took many pictures which are posted here: https://drive.google.com/folderview?...&usp=sha ring

[Triple B]

In our application we use the constant force springs to assist the extend function only. It offsets the weight of the manipulator on the end of the tower/elevator. The motor/motors have plenty of power for lifting the robot and we use a locking type ratchet to hold the weight up after the buzzer but the idea of having the motor/motors stalled out to hold position while the tower is extended is not, in my opinion, a healthy one. This year we did an elevator and used constant force springs to assist the elevator in lifting our shooter deck, it weighed in at about 18lbs. I find it ironic that we did an elevator and the Poofs did telescoping towers this year

Mike D "233 for life"

[Nemo]

To the people who have posted in this thread: I just want you to know that after the school year ends, I'm going to devour the information in this thread, including both the pictures and written explanations. I am looking forward to trying to figure out the guts of one of these arms and working with some students to create a model of something we could build. Thanks very much for all of the posts.

[Steven Donow]

Originally Posted by Nemo

To the people who have posted in this thread: I just want you to know that after the school year ends, I'm going to devour the information in this thread, including both the pictures and written explanations. I am looking forward to trying to figure out the guts of one of these arms and working with some students to create a model of something we could build. Thanks very much for all of the posts.

If only it were possible for Pink or 254 to send everyone here an arm

[Lil' Lavery]

Originally Posted by DevenStonow

If only it were possible for Pink or 254 to send everyone here an arm

I think the postal service might question why disembodied limbs are being shipped around the country.

[Triple B]

good one Sean, and you are correct on your earlier post about the passive drive of the third stage on pinks tower.

[M. Mellott]

Originally Posted by Nemo

To the people who have posted in this thread: I just want you to know that after the school year ends, I'm going to devour the information in this thread, including both the pictures and written explanations. I am looking forward to trying to figure out the guts of one of these arms and working with some students to create a model of something we could build. Thanks very much for all of the posts.

Seconded. These are some great idea to digest! Many thanks as well!