233 telescoping arms how do they work?

[craigboez]

Originally Posted by Triple B

I can only speak for the 233 arm on this topic. First off, a gearbox is attatched to the outside of the largest box (4d0 x 4d0 x d125 al box) at the bottom of the tower. It has a shaft that transfers power to a sprocket on the inside of the box. At the top of the box is an idler sprocket which is also the tensioner for this chain. We will call this chain 1. Chain 1 is attatched to the outside of the next box (2d5 x 2d5 x d125 al box) thru what I call the "chain anchor". The motor/gearbox drives this stage in and out directly.
The gearbox has a 10 turn pot attatched which controls the limits and also the PID control for ramping up and down the power as the tower nears its limits at each end of its travel. Now here is where it gets a little tricky, the opposite side if the 2d5 box has a shaft in the bottom with a sporcket on the inside and the outside, this is what drives the final stage of the tower. It also has an idler at the top which also acts as the tensioner for these 2 chains.
The chains both have a "chain anchor". The chain on the inside of 2d5 box is attached to the bottom of the final stage (1d0 x 1d0 x d125 al box). The chain on the outside of the box is attatched to the inside of the 4do box. The key is that the anchors are on opposite sides of the chain, this allows the second stage to use the anchor to drive the chain which extends the final stage at the same time. This is a very lengthy post and I may not of explained the subject completely but it has started an open line of communication. Ask any questions you may have and i can explain why Charlie did not like the delrin bearing blocks from 2k10.

Mike D "233 for life"

After some analysis, this is my understanding of what Mike describes.

EDIT: would someone familiar with the 254 system we willing to describe or diagram that system? From looking at all the pictures, I believe they use a different concept.

[roystur44]

Originally Posted by smart1

i have seen pictures but i still can't figure how they work. I want to know how to make one this summer. any pics or cad would be great.

Take a look at how 1986 did their arm. They used heavy duty drawer slides and a cascaded cable and pulley system. It was simple, elegant, easy to manufacture and did the job.

[smart1]

we have done many lift's with bosch 20 series with custom sliders and cable but that has it's limitations, mainly strength and weight.

[craigboez]

Originally Posted by Triple B

In our application we use the constant force springs to assist the extend function only.

Mike D "233 for life"

Would you mind elaborating on which constant force springs you use?

EDIT: I ask because I'm only familiar with the coil style constant force springs and if you used those I'm curious how they were implemented.

[Chinmay]

Try looking up negator spring or constant force spring motor. It's a really nicely packed solution to the counterbalance problem. Ill update this when I'm at a computer with some links Ect.

[R1ffSurf3r]

Originally Posted by craigboez

Would you mind elaborating on which constant force springs you use?

EDIT: I ask because I'm only familiar with the coil style constant force springs and if you used those I'm curious how they were implemented.

look at post 18, and the second picture

[smart1]

Thanks for all of the helpful insight.

[craigboez]

After looking through the pictures referenced earlier in the thread, I was able to better understand the 254 telescopic arm. It is conceptually very different from the 233 arm.

• 254 used a single piece of belt routed continuously through the assembly and then pinned to the final stage at each end of the belt. See attached for a diagram.
• 233 used two loops of chain, one to drive the first stage and then in a cascading fashion used the first stage to drive the second stage. See my previous post 39 for a diagram.

Both elegant solutions to a similar problem, and as you can see from the pics, the hardest part of building one of these is in the packaging.

We attempted to build a nylon strap driven arm, similar in concept to the 254 design, and found it very difficult to get all the rollers, idler pulleys, and pieces of slippery UHMW from colliding with each other. In the end we ran out of time, kept the first stage, and just implemented a first level hanger.

The devil is definitely in the details with these mechanisms.

[Travis Covington]

Originally Posted by craigboez

After looking through the pictures referenced earlier in the thread, I was able to better understand the 254 telescopic arm. It is conceptually very different from the 233 arm.

• 254 used a single piece of belt routed continuously through the assembly and then pinned to the final stage at each end of the belt. See attached for a diagram.
• 233 used two loops of chain, one to drive the first stage and then in a cascading fashion used the first stage to drive the second stage. See my previous post 39 for a diagram.

The devil is definitely in the details with these mechanisms.

This is correct. Thanks for illustrating this for others.

[smart1]

Originally Posted by craigboez

After looking through the pictures referenced earlier in the thread, I was able to better understand the 254 telescopic arm. It is conceptually very different from the 233 arm.

• 254 used a single piece of belt routed continuously through the assembly and then pinned to the final stage at each end of the belt. See attached for a diagram.
• 233 used two loops of chain, one to drive the first stage and then in a cascading fashion used the first stage to drive the second stage. See my previous post 39 for a diagram.

Both elegant solutions to a similar problem, and as you can see from the pics, the hardest part of building one of these is in the packaging.

We attempted to build a nylon strap driven arm, similar in concept to the 254 design, and found it very difficult to get all the rollers, idler pulleys, and pieces of slippery UHMW from colliding with each other. In the end we ran out of time, kept the first stage, and just implemented a first level hanger.

The devil is definitely in the details with these mechanisms.

Thanks again.

[fr05ty27355]

What did 254 and 233 do to pin the chain/belt to a stage? I'm wondering if they put bolts through the chain/belt, pinched the chain/belt against a toothed surface, or did something else. I'm guessing they might have had different methods since 254 used a belt and 233 used chain.

[George C]

Originally Posted by fr05ty27355

What did 254 and 233 do to pin the chain/belt to a stage? I'm wondering if they put bolts through the chain/belt, pinched the chain/belt against a toothed surface, or did something else. I'm guessing they might have had different methods since 254 used a belt and 233 used chain.

We did something similar for a two-stage cascading mechanism driven by a Gates belt. We were able to saw and file a piece of aluminum to match the Gates tooth profile. The block covered about 6 teeth and we avoided putting holes through the belt. Worked perfectly on the second try.

[Nuttyman54]

Originally Posted by George C

We did something similar for a two-stage cascading mechanism driven by a Gates belt. We were able to saw and file a piece of aluminum to match the Gates tooth profile. The block covered about 6 teeth and we avoided putting holes through the belt. Worked perfectly on the second try.

971 did a similar attachment method with a machined block to match the belt tooth profile for their elevator in 2011.

For #25 chain, you can fit #4 screws through the gaps between the rollers to fix it to something, although I don't know if this is how 233 does it or not. Another method is to drill a hole in the fixed structure that one end of a masterlink fits through.

[thefro526]

Originally Posted by Nuttyman54

For #25 chain, you can fit #4 screws through the gaps between the rollers to fix it to something, although I don't know if this is how 233 does it or not. Another method is to drill a hole in the fixed structure that one end of a masterlink fits through.

I've also used #4 Screws to fix #25 chain before, it works just fine when done right but can be a bit tricky considering the size of both the chain and the screws.

233, in 2011 at least, machines a part that appears to 'look' like a #25 chain link at either end and uses that to fix the chain to the stages. Here's a few pictures on their flickr.

http://www.flickr.com/photos/thepinkteam/5787028180/

http://www.flickr.com/photos/thepinkteam/5787033770/

http://www.flickr.com/photos/thepink...n/photostream/

[BurkeHalderman]

Has anyone tried using these to attach chain? Specifically the K-1 style connector.

http://www.mcmaster.com/#roller-chai...hments/=p1acmb

Seems like an easier option than machining an attachment for the chain.