Cable/winch vs. chain for telescopic arm

[VEN]

Hey guys,

In 2005 we had a telescoping arm which was extended by jackscrews. It was SLOW and loud. We do not have a lot of experience with telescopic arms. Does anyone have any experience with succesful extension of the arm? We are leaning towards the cable/winch as a more compact/lightweight solution but we would like to hear from others.

Thanks,

Vova

[dtengineering]

I think it was the Needel presentation on Manipulators and Mechanisms at this page http://www.usfirst.org/community/frc...t.aspx?id=1112 that had some good info on lifts and such.

Even if that isn't exactly what you are looking for, there is lots of great information on the FIRST curriculum pages.

Jason

[Madison]

Originally Posted by VEN

Hey guys,

In 2005 we had a telescoping arm which was extended by jackscrews. It was SLOW and loud. We do not have a lot of experience with telescopic arms. Does anyone have any experience with succesful extension of the arm? We are leaning towards the cable/winch as a more compact/lightweight solution but we would like to hear from others.

Thanks,

Vova

For simple, two segment telescoping arms, I like using roller chain.

Our 2005 robot had two such arms. You can see them here: http://www.chiefdelphi.com/media/photos/20233

The chain was a complete loop that ran up the outside of the arm and around a sprocket at the end of the first segment. It then passed inside the tubing, between the first and second segments, and was bolted through the links to the inner piece of tubing. We used delrin blocks as linear bearings to make it all slide easily and to space the inside segment from the outside segment properly.

[Tatsu]

We used a 3 track setup (so 3 tracks 3 carriages) and cable would be the only way to go in something like that.

Cable is annoying though, has a tendency to get everywhere and slice weak pulleys.

[billbo911]

Originally Posted by M. Krass

For simple, two segment telescoping arms, I like using roller chain.

Our 2005 robot had two such arms. You can see them here: http://www.chiefdelphi.com/media/photos/20233

The chain was a complete loop that ran up the outside of the arm and around a sprocket at the end of the first segment. It then passed inside the tubing, between the first and second segments, and was bolted through the links to the inner piece of tubing. We used delrin blocks as linear bearings to make it all slide easily and to space the inside segment from the outside segment properly.

This is a very simple yet elegant design. It works well and is easy to implement and build. We used a similar design in 2005 with the exception of using cable instead of chain.
To add a third (fourth, fifth,sixth....) section, run a cable/chain loop that is attached to the bottom of the added section over a pulley/sprocket on the top of the next outer intermediate section and secure it to the section next further out. A pulley/sprocket on the bottom of the intermediate section(s) is highly advisable as well.

[Robo_Cat_379]

does anyone have a picture of there telecopic arm??

[Jeremiah Johnson]

Originally Posted by Robo_Cat_379

does anyone have a picture of there telecopic arm??

Heh... good question. Wish I had a picture of 648's 2005 robot, it would be a perfect example of an easy winch mechanism used to raise and lower an arm. We're building an extention on our arm again this year. We had 3 sections.

[Robo_Cat_379]

i would love to see a picture

[DonRotolo]

Google "crank up tower" and look at the mechanisms used for antenna towers that use mautiple sections to go from 20 feet to 120. The same basic idea works for robots.

2 years ago we used a simple elevating tower, a 24" stroke 3/4" dia pneumatic piston provided the lifting force, we telescoped 1 x 2 rectangular tubing inside 1.5 x 2.5, using HDPE wafers to keep the inner tube centered.

Don

[Jeremiah Johnson]

Okay... after searching CD-Media for "648" I have found a picture of our robot. I had forgotten that I posted it. Um... you can see the nylon pulleys near the bottom. Unfortunately I don't have a closer picture.

648

Little Better Picture