Straightening straight rubber cords

[sjt1803]

My question is about straight rubber cords. The phone I just got is a D1 (202) with rubber cords. Both cords are not straight, they have developed a memory of 5 or 6 loops.
Is there a method that works to straighten these cords out?

[HarrySmith]

I have straightened Line cords by hanging them with some weight on the end. As long as they are still supple that method works great. If they are stiff, that is a different story but brings up another good question. Has anyone found a method to soften those stiff cords to make them pliable again? I have tried a couple of things to no avail.

[LarryInMichigan]

Heat can be used to straighten (or curl) rubber and vinyl cords.

Larry

[Phonesrfun]

It probably depends a lot on the condition of the rubber.  Many neoprene rubber cords I have seen have inner wires with very brittle insulation to the point where the exposed rubber from the individual wires is crumbling into dust.

The outer jackets seem to fare somewhat better, but they seem to go brittle too.

When the cords are that far gone, trying to straighten them seems to make things worse, for me any way.

[DavePEI]

It must depend on the individual cord itself. I have a beautiful NOS rubber receiver cord on one of my 1317s which I have been trying to straighten now for 3 years. It came coiled up in a package and has retained that coil. When I installed it on the phone, I thought the coil would relax with weight on it, so hung one of my wife's beanbag weights over it, which, yes straightens out the cord - until you remove the weight. Zing! The shape of the cord in the bag returns. This cord has now had the weight on it for 3 years, yet still the same! It was in the bag for 30 or 40 years - wonder if it will take that long to straighten!

Dave

[sjt1803]

Wow, after Dave's experience I better make sure I take my vitamins and get plenty of sleep if I have to wait 30 years for the fix on this!

[DavePEI]

Wow, after Dave's experience I better make sure I take my vitamins and get plenty of sleep if I have to wait 30 years for the fix on this!

Don't mean to discourage you. I just hope that someone has the cure for the problem. I could see it if the rubber had gone hard, but it hasn't on this one. It just likes to stay coiled!

I may give up and get a cloth cord for it, but it was one of the 1315/1317 MD2127 handset conversions (Transmitter hole cover plate, handset, cord, replacement hook) and they used the rubber cord along with the NE supplied conversion kit....

Photo below with the cord stretched out using the beanbag over the bottom loop of the cord!

Dave

[tallguy58]

I just tried to straighten a rubber handset cord from 1953. Hooked a paint can to the end of it and noticed that the cord in one section was stretchy, like a rubber band being pulled along its length. Left it for a couple of days and it wasn't bad. Still had that spot of stretchiness, though. Tried a second time and the next day the paint can was on the floor and the cord was snapped. Inspection revealed that the wires were broken and the inside insulation was a flaky mess. The conductors were already snapped, hence the initial stretchiness. Solid wires shouldn't be stretchy. Rubber seems to be worse that vinyl. I did successfully straighten a vinyl one which is being used daily on my 302. Put it into a "delicates" bag and threw it in the dryer on medium heat. Once pretty warm to the touch, hung a paint can on it and left it for a couple of days.

[HarrySmith]

I think a paint can is way too heavy. I usually use a handset or just a couple of pounds. Heat definetly helps. I like the tumble dryer idea, I may have to try that!

[sjt1803]

Someone suggested placing the cord in a warm/hot solution of ammonia, 2 parts water to 1 part ammonia for around an hour until the ammonia evaporates to soften the rubber.
If someone tries this I would keep the ends of the cable out of the solution.

[Bill]

In the antique radio community, restorers encounter lots of rubber buttons, bumpers, grommets, sleeves, pads, vibration isolators, etc. If they have gotten brittle, an often-mentioned solution is to wipe (or soak) them in brake fluid. Never tried it, but ...

Bill

[HarrySmith]

I know brake fluid causes rubber to soften AND swell. This was an old mechanics trick for a slipping automatic transmission. Put 1/2 bottle of brake fluid in and voila!  No more slipping. For now. It would swell the seals and gaskets so the internal pressure would increase. I don't think we want cords to swell but it may only be a small amount. I might try it on a junk cord.