cable housing ??????????????????

[HeartCoppi]

Why is cable housing so reinforced???

How badly/poorly do you ride that cable housing needs to be reinforced?

I found a teflon liner available from a high tech welding shop.

Its used for the welding wire to travel through the hose to the torch. The wire is usually 1mm or 1,2mm. The teflon reduces the friction on the wire,a and the liner is a small tube which is quite difficult to compress.

Interesting is that it is less than a third the weight of conventional cables.

Frankly I dont bump into anything with my bike that damages the cable housing, cos I love my bikes.

So I am trialling this alternative for on bike durability. 

[straatvark]

Reinforcement is not to protect the cable. Think about the exposed sections of cable on MTB etc.

[deanbean]

hi tarboy reinforcing is to stiffen the housing for accurate shifting.Tell me more about the housing. It may be what i need for a project of mine. Would it be abrasion resistant. Name shop etc. Cheers, DS

[Ox_Wagon]

The steel in the housing is there to stop the housing from compressing. 

 

From Sheldown brown's website:

http://www.sheldonbrown.com/gloss_ca-g.html#cable

 

Housing

The outer sleeve through which a brake or gear cable is pulled. The housing transmits an equal push to counter the pull on the inner cable. Traditional housing consists of a tight spiral of steel wire, usually coated with plastic. Newer versions have synthetic liners to reduce friction. This type of housing is still used for brake cables. See also Bowden cable.

With the advent of index shifting, greater precision was required, particularly for handlebar-mounted shift controls. For this application, "compressionless" housing is now used. This differs from traditional housing in that the wire part consists of a bundle of parallel wires, running more-or-less parallel to the cable. This reduces the tendency of the housing to change effective length when it flexes as the handlebars turn. This type of housing should not be used for brake cables, as it is likely to rupture under the higher loads involved in braking.

Some more info: http://www.sheldonbrown.com/cables.html

 

 

 

 

Ox_Wagon2009-06-23 10:15:30

[Tieffels]

So you imply, by mentioning bumps and the act of squeezing the tube between your fingers, that the reinforcing is required to protect the cable from collapse? That is not the actual case. The casing/liner/housing has to oppose the tension in the cable itself. Think about pulling your brakes: Newtons 1/2/3 law states that every force has equal and opposite force. The tension or force in the wire is opposed by the housing, That is why the more bulkier brake housings are called linear compression housings. Your plan could work for lengths of cable between mounts on the frame, i.e where the cable is not bounded on one side by either the shifter or derailleur.<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Hope that makes sense.

 

[Johan Bornman]

Think twice before calling (ex) Sheldon Brown in question.

 

That aside, there are two tapes of cable housing.

 

1) Brake cable housing. This is made up of a Teflon liner on the inside, a tight coil of flat steel ribbon around that and a plastic/vinyl casing around that. The liner reduces friction, the coil resists compression and the outer protects against it scratching your bike, rust, etc etc.

Brake cable inner is 1.5mm thick and made from seven (IIRC) steel wire strands wound in a relaxed helix around each other in opposing directions.

 

2) Gear Cable Housing. This is made up of a Teflon inner liner, a loosely wound HELIX of steel wires (Note the difference from brake cable) and a vinyl outer. The inner of a gear cable is 1.2mm thick and made of about 5 steel wires wound in the same way as a brake cable.

 

Brake cables undergo huge compressive forces and the tight coil prevents the inner from bursting through the outer cable under tension. Should you use a gear cable housing on a brake, the cable easily bursts through the loose helix of a gear cable outer.

 

The gear cable outer is designed to provide less friction than a brake cable outer, as required by index shifting and weakish derailer springs.

 

Both these cables are designed so that one strand does not become relatively longer than the rest in the bunch, when they go around a bend. If you don't understand that concept, take a handful of thin plastic rods (as thick as spaghetti, but I can't think of a suitable example right now) and bend the bunch. You'll notice that those on the inside of the bend now protrude from the rest. By winding them in a helix, this doesn't happen 'cause they all bend equally much in the type of corners cables take on bicycles.

 

Back to plain Teflon liner in place of proper cable outer. On a brake cable application the liner will simply burst or compress into a long sausage concertina. It cannot take compression.

 

On a gear cable application it may work, depending on the outer's ability to go around bends without kinking, it's very tight fit to the inner cable (a slight tolerance will cause problems) and its durability. It will most likely fail on the latter point. I'm sure it has been tried.

 

Finally, it is not reinforcing in there. Reinforcing suggests some sort of strength additive. This is an anti-compressive and anti-kink component inside the cable. Semantics I suppose.

 

Johan Bornman2009-06-24 00:39:20