How can I stabilize concentric tubes with an irregular cross section?

In summary, the person is having trouble finding a material to fit into the gap between three tubes and wants to know how to solve the problem.
  • #1
charanth182
8
0
Hi everyone,

I'm new to this site, so if I'm breaking any rules let me know. In particular because this is for my job. The forum rules seem very clear on the guidelines for homework for school and one can assume that personal hobbyist type questions aren't an issue but i don't see anything when it comes to work related queries.

I've run into a problem in which i have a few (3) concentric tubes with an irregular cross section (though the same as each other). Due to machining tolerances we're stuck with a small gap, mechanically it doesn't matter but perspective isn't so good as someone can easily shake the central tube making it look unstable.

I've tried finding a material to fit into the gap (Teflon, cork, PTFE, various tapes, cabinet bumpers etc.) but every item I've tried either creates too much friction or will not endure the movement of the tubes (often the adhesion gives).

I feel that i must not be alone in this problem as there is so many items out there with concentric tubing. How do they solve the problem?
 
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  • #2
From your wording, I assume that this is a telescoping device. O-rings would work if the tubes were cylindrical, so I'm wondering if you could machine grooves into the inner surfaces of the tubes and lay in beads of silicone or or similar caulking material. You mentioned that your adhesives failed, so maybe having the material physically restrained would help.
Just a basic thought.
 
  • #3
If this is a telescoping type arrangement, and if the intent is for stability--not just to fill the gap for aesthetics or a seal of some sort--you might consider a method similar to most telescoping antennas like on a basic shortwave radio or such. In between sections there is a ring fastened to end of each inside section, and from this ring radiate 3 or 4 flat pieces of flexible spring steel or phospher-bronze. These slightly curved pieces of metal wedge in the narrow gap between the walls of each section and the next outermost section, and although they slide easily the tension of these slightly curved 'springs' hold everything in alignment. I'm sure I'm not explaining it well, but if you take apart any old telescoping antenna such as TV 'rabbit ears' you will quickly see what I'm referring to. Just a thought...
 

1. What is concentric tube movement?

Concentric tube movement refers to the motion of one tube sliding within another tube, while maintaining a constant center axis. This type of movement is commonly used in mechanical systems, such as in hydraulic pumps or robotic arms.

2. How does concentric tube movement work?

Concentric tube movement works by having one tube fit inside another tube with a small amount of clearance. The inner tube is connected to a fixed point, while the outer tube is free to move. As the inner tube moves, it causes the outer tube to also move, creating a concentric motion.

3. What are the benefits of using concentric tube movement?

Concentric tube movement allows for precise and controlled motion, making it useful in applications where accuracy is important. It also allows for a compact design and can handle heavy loads, making it suitable for industrial use.

4. What are some common applications of concentric tube movement?

Concentric tube movement is commonly used in hydraulic and pneumatic systems, such as in pumps and valves. It is also used in robotics, medical devices, and precision instruments.

5. Are there any limitations to concentric tube movement?

One limitation of concentric tube movement is that it is limited to linear motion and cannot rotate. It also requires precise manufacturing and assembly to ensure smooth and accurate movement. Additionally, it may experience wear and tear over time, requiring maintenance and replacement.

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