jgrizou

Hello all,

I am trying to make my own "brake cables", but really struggle to find a long roll of inner wire, say 10m, 25m or 50m in length. This is for a DIY project I have in mind involving cable-driven structures.

I could find outer cables in 25m, 30m, etc, but no inner wire. And I am not sure if buying any stainless steal wire would do as they might not be stiff enough.

Would you have any advice on where to find a kit to make cables of any length? Ideally, I am looking for compatible outer and inner cables + a way to attach/squeeze end-stops at both ends.

Thank you for your help,
Jonathan

aggiegrads

The end stops on bike cables are not crimped, they are welded, and I assume that it requires specialized equipment.

I don't know what your use case is, but every bend is going to add friction to the system. You may be able to figure out how to braze on ends to aircraft cable, but friction will increase if you are going to use really long cable runs.

mack_turtle

it's possible that you can use bolt-on cable ends added to some longer wire that was not designed with bicycles in mind. here are a few examples:
https://www.empirebmx.com/odyssey-knarps
https://www.bikeparts.com/BPC405690/...72-cable-clamp
https://www.danscomp.com/kink-desist...90blk/p1074064

there are also many such items designed for motors. I don't know the details, but they are not hard to find in an auto parts shop.

Trevtassie

Aggie has hit the spot. What you are looking for is aircraft style control wire and the associated fittings. Like bicycle cable it's laid (twisted together) so it doesn't spin when under load. Something like this https://www.amazon.com/Stainless-Ste.../dp/B00TYSAVBW do the job? tricky bit might be the diameter, seems to go 1/32 0.8mm to 1/16 1.5mm. Not going to be any good for a pushing type situation, you'll need some kind of spring return.
Proper aircraft wire is more expensive as it's certified.

tyrion

Standard brake cables are 1.6mm diameter (or 3/32"). There are lots of sources for that that aren't specifically for bicycle brakes (fishing tackle, etc). I think you'll have to experiment to see if it works well in a housing.

I'm assuming this is for non-critical purpose (or not as critical as brakes) - I wouldn't trust a DIY cable assembly for actual brakes.

dsbrantjr

50 meters of Bowden cable (which is what bike cables are: https://en.wikipedia.org/wiki/Bowden_cable) will have a lot of friction; because of this you are also going to have difficulty threading such a cable into its housing. If you can eliminate most of the bends you can just use plain cables with pulleys to make the turns; the only friction is that of the pulleys which is low. Amish farms where electricity is not used have used these techniques for decades or more to run water pumps remote from the windmill which drives them. See towards the bottom of this page: https://www.ironmanwindmill.com/pump...-windmills.htm I have seen pump systems like these where the cable(s) are supported in mid-span with a loop of rope which just moves to and fro with the cable, and also single-cable setups with a counterweight at each end to keep the cable taut. I have seen installations where the cable was 50 meters or more long.

Bill Kapaun

Closer to 1/16". Both round off to .0623". Likely they converted 1/16" cable to mm....
Totally agree about non critical use.

Maybe if the OP stated their exact intent, it might make sense. Like "why would SS not be stiff enough"? Why is stiffness "needed"?
Swaging on ones own end pieces requires equipment far beyond the "homeowner use" level. For brakes, all I can say is you better squeeze that lever as hard as possible BEFORE you think about using it.

Andrew R Stewart 

It's my understanding that most (all?) bike inner cables have the wire "balled up" within the cast on end. I've head of home soldered attempts not holding (with the resulting issues Bill mentions). The BMX/Freestyle world has a cable ends (called Knarps) that secure onto the inner cable with a tiny set screw. Andy

jgrizou

Wow thanks all for all the pointers!

I am trying to build an "art structure", where some mechanical structure open and close from a distance but it all has to be quite small and I cannot put servomotor directly at the end. Hence my question on DIY brake cable / Bowden cable. Sorry I should have explained more.

No life is at threat here indeed, and the force intended for opening/closing the structure is small.

I keep your points in mind about friction and wether stiffness/pushing if required here. I can always use a spring mechanism indeed for return. But friction is a harder one to overcome, I will have to test but I like the straight line + pulley idea.

Thanks!

WizardOfBoz

If you can use a limited number pulleys instead of a guide sheath, you might be able to get the friction down to a manageable level. But 10 meters of cable in a sheath will be troublesome.

You'd need a pretty strong actuator to "pull", and a pretty strong spring to pull on the other end (to retract).

aggiegrads

If you do make a prototype and test (kudos!), don’t forget that the apparatus will never work better than it does on the first day. Especially if installed outside, water, dust, and corrosion will make the device much more difficult to engage over time.

JohnDThompson 

Actually, they're cast, not welded. The end of the cable is spread into a "bloom," placed in a mold, and molten metal poured over the bloom. Motorcycle shops used to have equipment for this to make throttle cables and such.

Yes, aircraft control cables would probably work. Perhaps the Experimental Aircraft Association might be able to point you in the right direction?

conspiratemus1

If life safety is not an issue, the most straightforward way to make cable ends (heads, really) is with home-made Knarp-like doo-dads. Make them from short lengths of aluminum rod cut from an old pannier rack. These of course won’t fit into a bicycle brake lever but if you could design your actuator around the doo-dad you should be good to go.

The photo shows my home-made one being used to splice a too-short derailer cable onto a longer length piece that was salvaged from an Ergo shifter when the cable just behind the head started to break and fray. Because I don’t have bottoming taps, I drilled and tapped the holes for the set screws all the way through and used a set screw on each side, one to plug and one to pinch. Make sure both are right, though.

tyrion

A hydraulic system would avoid the drag of long cable in housing. Straight line pulley would be simpler.

Bill Kapaun

For long, straight runs, just use bare wire like many bikes do on top & down tubes.