252 Cowl Flap Cable

[Ragsf15e]

Today I taxied over to do an oil change with my mechanic.  It was cold, so I put the cowl flaps halfway up to let the oil warm up while I taxied.  Well, that didn't work.  They wouldn't go up.  But they would go all the way down... anyway, long story short, when we got the cowl off, the "Bowden" cable was bent all up.  Cowl flaps actually worked fine, but the cable is connected to the indicator.  Apparently they don't slide very well in the sheath after ~40 years.  We disconnected it and were able to get kroil in there at both ends and it seems to go back and forth ok.  Straightened the end where it was bent, and actually got it to work again, but I think the cable is not long for this world.  I need to find a new one.  So IPC says it's part 650246-003/005 "wire" and "housing".  Not on Lasar's website.  If it's really a "Bowden" Cable, I think I could measure it and buy it through Spruce by the foot, however, the end by the cowl flap has the cable wrapped in a "pigtail" where it connects.  I can't see one like that on Spruce.  My mechanic said "rolling our own" pigtail is problematic, even if we try to heat the wire.  We'll either break it if it's cold or ruin the heat treatment on the part that needs to be stiff, so I should find one that's already pig tailed.  Great.

Has anyone else had experience with replacing the "piano wire" type of cables?  Did you get parts from Lasar?  Did you ever see a coiled "pigtail" connection?  How did you find the specific cable sizes you should use?

Thanks,

Drew

[EricJ]

One things that's not obvious on bowden cables is that you can lubricate it along it's length if you can flex it.   When you flex it the outside circumference opens up a bit and will admit some lubricant if sufficiently flexed.   Sometimes it's tough to do this while installed, but also sometimes there's a bend in the middle that's enough that it'll let a little oil in.   It makes it a lot more effective to lube than just trying from each end, especially if it's a long cable.

 

[N201MKTurbo]

I’ve found you don’t have to bend it. If you oil the outside, it gets in.

As far as the pig tail is concerned, I’ve heated music wire till it is red and you can bend it into any shape you need. Just be quick about it. It is usually the wire that goes bad, usually by rusting through. The wire is easy to replace, just measure the diameter and order some from McMaster or McFarlane. Just cut off any kinks on one end and pull it out the other end. If you need to form one end, do that before pushing it through.  Coat the wire with Aeroshell 6 before pushing it through.

[N201MKTurbo]

To bend a pigtail:

if you need a 1/4 inch pigtail, chuck a 1/4 inch drill bit in your vice with the but end sticking up. Set your propane torch next to the vice. Grab the long end with your left hand and the short end of the wire with a pair of pliers. Heat the wire about 4 inches from the end with the pliers. When it gets bright red, quickly move the wire to the drill bit and wrap it around the number of turns you need using the pliers. When it cools, tap the drill through the pig tail and cut the excess wire off with some dikes. If it looks like crap, cut it off and try again. You will be an expert after a few try's.

[Ragsf15e]

3 hours ago, EricJ said:

One things that's not obvious on bowden cables is that you can lubricate it along it's length if you can flex it.   When you flex it the outside circumference opens up a bit and will admit some lubricant if sufficiently flexed.   Sometimes it's tough to do this while installed, but also sometimes there's a bend in the middle that's enough that it'll let a little oil in.   It makes it a lot more effective to lube than just trying from each end, especially if it's a long cable.

 

 

1 hour ago, N201MKTurbo said:

To bend a pigtail:

if you need a 1/4 inch pigtail, chuck a 1/4 inch drill bit in your vice with the but end sticking up. Set your propane torch next to the vice. Grab the long end with your left hand and the short end of the wire with a pair of pliers. Heat the wire about 4 inches from the end with the pliers. When it gets bright red, quickly move the wire to the drill bit and wrap it around the number of turns you need using the pliers. When it cools, tap the drill through the pig tail and cut the excess wire off with some dikes. If it looks like crap, cut it off and try again. You will be an expert after a few try's.

You guys are awesome, thank you!  My mechanic did put liberal mouse milk along the cable so that might wick in as you said.  I’m on the hunt for proper size wire so I’m ready when it fails again.

[Bartman]

When I rebuilt my roof vent cable I found the piano wire at McMaster Carr. If it’s a push-pull cable, will likely find the wire you need there. 
I didn’t heat the wire to make the pigtail, but I did use a drill bit a couple sizes smaller than the pin and wrapped it around tightly about 3-4 turns.  By “unwinding” it slightly the pin slid in and when released it held in place with lots of grip. After nearly 10 years it still works perfectly. 

[Ragsf15e]

13 hours ago, Bartman said:

When I rebuilt my roof vent cable I found the piano wire at McMaster Carr. If it’s a push-pull cable, will likely find the wire you need there. 
I didn’t heat the wire to make the pigtail, but I did use a drill bit a couple sizes smaller than the pin and wrapped it around tightly about 3-4 turns.  By “unwinding” it slightly the pin slid in and when released it held in place with lots of grip. After nearly 10 years it still works perfectly. 

 

16 hours ago, N201MKTurbo said:

To bend a pigtail:

if you need a 1/4 inch pigtail, chuck a 1/4 inch drill bit in your vice with the but end sticking up. Set your propane torch next to the vice. Grab the long end with your left hand and the short end of the wire with a pair of pliers. Heat the wire about 4 inches from the end with the pliers. When it gets bright red, quickly move the wire to the drill bit and wrap it around the number of turns you need using the pliers. When it cools, tap the drill through the pig tail and cut the excess wire off with some dikes. If it looks like crap, cut it off and try again. You will be an expert after a few try's.

To find the proper thickness, do I measure it with a micrometer or do I need to completely take it off?  I’d like to order some and play with it (and improve my pigtails) before getting my mechanic to help R&R the whole thing?

[N201MKTurbo]

5 minutes ago, Ragsf15e said:

 

To find the proper thickness, do I measure it with a micrometer or do I need to completely take it off?  I’d like to order some and play with it (and improve my pigtails) before getting my mechanic to help R&R the whole thing?

Use a micrometer or caliper to measure the wire size.

[47U]

21 hours ago, Ragsf15e said:

Has anyone else had experience with replacing the "piano wire" type of cables? 

I replaced the fresh air vent door cable with the excess left over from the McFarlane PMA mixture cable I had replaced, which is cut to length in the field.  This cable has a teflon insert and the wire slides smooth as butter.  If you replace just the wire, the sheath is still 40 years old and perhaps unlikely to get all the dirt and corrosion cleaned out with lubrication.  I soaked my carb heat cable in a pan of mineral spirits for several days and running the wire through it still came out cruddy.  

Maybe order a length of cable from McFarlane and then do the swap as an OPP when you have some down time.