Plastic housing for fishing line? 3

[jbendercp]

Working on a low-cost prosthetic hand design, and looking for a lightweight yet rigid material to use as a housing for the heavy fishing line that actuates fingers. Catch is that I live in rural SE Asia and need to find parts that are already used in other commonly found items (or are common building materials. etc).

Found the plastic ink tubes (the inner ink tube not the pen cylinder) to ballpoint pens to be perfect diameter and rigidity, but length, and having to unload/clean ink to be less than ideal. Any other places I might find a similar rigid plastic tubing material of similar diameter (~1mm ID), but in longer sections?

Any help would be great!

 

[EdStainless]

the cable housings on my bicycle have a fairly rigid plastic liner tube in them.
The are (from the out side) plastic jacket, wound metal reinforcement, removable liner, then the cable.
I will hunt online and see if I can find a source for just the liner material.

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P.E. Metallurgy, Plymouth Tube

 

[MikeHalloran]

I think the traditional material for pen ink tubes is polypropylene, or maybe polyethylene.
Neither bonds very well with adhesives.


Mike Halloran
Pembroke Pines, FL, USA

 

[robyengIT]

what about Rilsan PA11 - PHL as per attached brochure ?

 

[ColinPearson]

google got me here pretty fast

http://www.freelin-wade.com/extruded-tubing.html

 

[Nescius]

Regarding bicycle cable housings, the norm is a heavier wound steel reinforcement for brake cables. Shifter cable housing, however, uses longitudinal straight wires as reinforcement.

Brake cable housing is much stronger in compression, which is mandatory for braking, but can also change effective length as it is manipulated, by turning a handlebar, for instance. This change in effective length is unacceptable in a shifting system. Also, a very stiff housing (in compression) is needed for modern shifting systems...lots of indexed gears, a very repeatable mechanical relationship between the controls and the derailleurs is needed.

Shifter cable housing will burst under the load applied by a brake lever.

I *think* brake cables and shifter cables are different diameter, too.

 

[EdStainless]

Yes, bike cables are different diameters, but for this application I was just thinking of using the liner, not the steel reinforced outer sheath. There are many different reinforcing systems used, and they all work. I don't care about shift cable housing length control, I don't use indexed shifters.

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P.E. Metallurgy, Plymouth Tube

 

[kingnero]

Welding liners for a mig gun?
Those for aluminium, not the regular steel liners

 

[jbendercp]

Sorry for the delay in response, was waiting for an e-mail notification that never came.

Regarding bicycle break cables: Indeed my first iteration was with brake cables I got at the local store, but this solution (the entire cable) was much too heavy. I didn't even think about removing the inner liner. Just went back and checked though--turns out the liner is not so rigid/robust in the local cables. Will do more shopping around to see if I can find a different type.

PE/PP tubing. Had not thought about the adhesive-ness property, that may be an issue. I'll do a small test with the ballpoint pen tubes I have and see how that goes. Tubes ideally will rest in a notch, adhered with glue, and wrapped in electrical tape, so we'll see if it remains strong enough for the function.

Alternative is to make a larger finger section and bore holes instead of using a separate housing. However, don't have a good manufacturing process for this at the moment, but may have to move this direction if I can't find a suitable replacement.

 

[gbangs]

Model airplane industry uses "control rods"

Might find something that would suffice...

gbangs
TC 8.3.3
NX 8.5.3.3 MP11

 

[EdStainless]

Good call GBANGS, I had forgotten about those.

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P.E. Metallurgy, Plymouth Tube

 

[Tmoose]

" ... turns out the liner is not so rigid/robust in the local cables. "
I think those control cables rely on being constrained at the ends and even guided every now and then if long. The inner cable tension pulls the sheath into the restraints.

It sounds like you need the guide to do all the work.
Kind of like this -

http://www.mytenspeeds.com/My_TenSp...ionall_60/Ral_Int_60_Clean/Ral_Int_C_BB_1.jpg

Or this -

http://www.jensonusa.com/Campagnolo-Anti-Friction-BB-Cable-Guide

Or even a grroovy wheel -

https://cdn.shopify.com/s/files/1/0893/5272/products/46c7_1_1024x1024.jpeg?v=1456798748

 

[1gibson]

Coffee straws wrapped in whatever kind of tape gets you the properties you want.

 

[jbendercp]

Cable will be running along the gripping surface of the hand. Worried coffee stirs won't a) hold up over large cycles and b) may compress when gripping something tightly, thus choking off the control line.

Airplane control cable looks like it comes in something like $.20/ft or less, not bad! Wish though it were a more local solution. Parents coming for a visit in June, may have them bring a few feet of the stuff to try out.

Thanks for the help, keep the suggestions coming!

 

[chicopee]

All the above ideas are good but may be too expensive. I would preferably have contact with a leading ball point ink pen manufacturer such as Bic and find out who makes these inner ink tubes which the OP seems to like. Since the OP lives in rural SE Asia, such pen manufacturer may be humanitarian enough to send you free of charge spools of such tubing.

 

[dhengr]

Jbendercp:
In an application like your’s, I would be concerned that the fishing line would have a sawing action on the plastic guide tube. It would wear a groove in the plastic and ultimately wear through the plastic tube. I would look for a fairly hard, wear resistant, outer guide/locating tube and then a fairly hard, but flexible inner tube which is fixed to and moves with the fishing line at the wear points, so that the relative movement is a sliding wear (maybe lubricated) interaction, not a sawing action.

 

[kingnero]

Have you considered my above proposition? It's lightweight, flexible, and very wear-resistant.
Comes in several diameters, in the range you need. Almost everywhere available in short lengths, maybe a bit harder to find on reels.