233 telescoping arms how do they work?

[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.