Melted Control Cables

I just did a condition inspection and found that the prop control cable on my -10 had melted the outside cover (it passes along the left side of the sump and up to the govenor at the front left of the O-540.

Troy Thompson who signed off on the inspection said he thought it was from heat soak. He said during a group X-country one of the RV-8s had the throttle freeze after a refueing stop. Apparently it got so hot that the inner liner melted and froze the cable.

Mine was not that bad and it still functions normally. However, I bought HeatShield 270012 Thermaflect Sleeve 1/2" ID x 3' Heat Shield Sleeve for $16 from Amazon. It is rated for 1100 degrees F. I saw some evidence of the same with the throttle and mixture cables too.

The strange thing is that the -10 has over 360 hours and I have owned it for 18 months and over 150 hours. I check the engine very carefully at each oil change and did not see any damage at the end of October during the last oil change.

Here a a couple of pictures.



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Ground?

Is there a chance your starter current is flowing down that cable? Doesn't look like there's a real source of heat close by.
Tim

tim2542 said:

Is there a chance your starter current is flowing down that cable? Tim

Click to expand...

That would be much more likely than heat soaking...

No.

You would really know about it every start if it was.

My prop control cable is the same. Actually it is worse. It seems to only affect the outer plastic. The inside is working perfect.

Dont stress.

BTW ours has 750 hours on it and the cable was like this from somewhere sub 100 hours. I can't recall it not being that way.

This seems to be a common theme amoung RV-10s that have been flying for awhile.

Tim has a good write up on his site here.

Cablecraft has another level of sheathing (Black) that adds another 50-80 degrees of protection over the green sheath models that Vans sells.

I'm just finishing my FWF and will problem add the orange firesleeve as well for extra protection.

check to see if you have a exhaust leak

Black cables

I've replaced all of mine with the black ones mentioned above for the very same reasons.

Vic

Recently found some melted green sheathing on one of my cables....after 220 hours. Looks like radiant heating (and your pipe is about the same distance), but I have no idea why it has showed up after this much run time. Maybe a cascading failure.....first you melt a thin spot and expose some steel, which allows the darker steel to absorb more radiant heat, which raises the temperature of the remaining plastic sheath?

Anyway, it's now wrapped in fiberfrax and shiny reflective aluminum tape.

Express sleeve

Aircraft Spruce sells a product called Express Sleeve, PN 09-02060, which is a high temperature insulation with reflective mylar the uses hook and loop closure so you can put it around a cable, hose or wire without feeding it from one end. I have heard of RV-8s having melting problems on their throtle and mixture cables, so I put this product over mine where they are closest to the exhaust. Seems to work well.

brad walton said:

Aircraft Spruce sells a product called Express Sleeve, PN 09-02060, which is a high temperature insulation with reflective mylar the uses hook and loop closure so you can put it around a cable, hose or wire without feeding it from one end. I have heard of RV-8s having melting problems on their throtle and mixture cables, so I put this product over mine where they are closest to the exhaust. Seems to work well.

Click to expand...

Interesting product.

I guess I'll need to contact ACS to see what length you get for $27.95. The text states it comes in 3' and 12' lengths, but the purchase box just has a quanity of 1 by default. If that's the per foot price, it's expensive.

Showplanes do a bracket so you can route the cable over the top of the cylinders. I wonder if this would be a better solution?
As anyone used their setup?

http://www.showplanes.com/ecom-prodshow/Propeller-Governor-Control-Bracket.html

Cheers

Peter

Houston I have a problem

I?m working on an IO-360 (RV-9). I installed the exhaust pipes last week (four stright no crossover) and the pipe from the number 1 cylinder get about 1? from my throttle/mixture cables. I?m going to have to do something. How hot will the #1 exhaust pipe be when it gets back to the oil sump (maybe a 1 to 1 ?? from the cylinder)? Do I need to move the cables or do you guys think some kind of protection will do? Maybe fire sleeve and the ACS express sleeve?

It looks so nice where it is?

Thanks

Take a look at the conductor. if it is dull and more white rather then bright copper, it is likely a current issue more so then thermal soaking. if under the insulation it is bright, insulate it!

Tumper said:

....the pipe from the number 1 cylinder get about 1” from my throttle/mixture cables.

Click to expand...

Won't work without careful shielding.

This has been working about 250 hours, but I've not unwrapped it, nor have I stuck a temperature sensor in the bundle.....fiberfrax under aluminum tape, all behind an aluminum radiant shield:



The section which recently melted is here....a good distance from the pipe:

EGT's 2" down the pipe run 1400 deg... so the pipe will be cherry red. I'm think'n that's SMOKEN HOT

I have been frying throttle cables for over 1500 hours now. I'm on my third or fourth cable. (I lost count.) I have heat shields all over my exhaust pipes and have wrapped the cable with fire sleeve as well as silver reflective wrap. The problem with wrapping the cable with anything is that the cable is in a hot environment for long periods of time and regardless of what you wrap it in the cable will eventually get heat soaked. The last time I installed a new cable I enclosed it in a fire sleeve and I routed a blast tube to blow cool air into the sleeve. I have my fingers crossed and hope this one lasts.

Is there any sign og wear and tear from the tie-wrap in the melted area?(pic in first post)

If so, maybe the tie-wrap has worn down the outer part of the cable, thus making it more exposable to heat-soaking?

In such areas, I prefer to use two Adel-clamps connected together to avoid rubbing.

An alternate method is to use three tie-wraps connected together so they form an "8". That will create a little distance beetween the two parts, thus avoiding rubbing.

cables

I'm on my 3rd forward mounted governor cable. My throtle and mixture run near the exhaust below no porblem 520 hours. The Throtle and mixture are heat shielded. I did not until this last one heat shield the governor cable. The cables look great no melting but the inner plastic melts then freezes the control. Here is hopeing the new one lasts.

rleffler said:

Interesting product.

I guess I'll need to contact ACS to see what length you get for $27.95. The text states it comes in 3' and 12' lengths, but the purchase box just has a quanity of 1 by default. If that's the per foot price, it's expensive.

Click to expand...

Bob,

The $27.95 price is in line with what Amazon and various auto racing supply places charge for a 3' section, so I would assume that is what you'd get from ACS. I just ordered a 12' section of the 0.5-1.0" sleeve for my airplane ($86 from Amazon), since I currently have the exhaust off and it will be convenient to install at this stage. I figure anything I can reasonably do to help the control cables last longer will save money in the long run.

The one thing I'm worried about with this product is how the velcro is attached to the high temperature bits - glued or sewn? - and how heat-resistant the velcro itself is. I'll report back in this thread when I receive it and do a bit of testing.

mcb

Express sleeve

Hi,

Looking at this page on the Canadian ACS site seems to show that you are right - about $27 for 3 feet. (Click image to go to the site)



Seems like a really great idea - please let us know if it works.

Regards,
Mickey

This came up recently on another thread and others recommended some thermoshield that could be wrapped onto the cables without having to undo the cables. It is adhesive based, but some rtv on the ends would help as well.

http://www.aircraftspruce.com/catalog/eppages/thermoshield.php?clickkey=7518

Test results

I received my 12-foot length of Express Sleeve material from Amazon and did a bit of testing with it. Here is what you get in the package... the velcro closures are are sewn with regular thread onto what looks like E-glass tape with a shiny foil backing on one side:



What I was most interested in testing was the product's general suitability for use in the engine compartment, i.e. fire resistance. I'm less worried about heat mitigation for the control cables - which have a known and gradual failure mode when subjected to engine compartment heat - than I am in avoiding introducing an unrecognized hazard forward of the firewall.

I cut off a 1.5" length of exhaust wrap, attached it back to itself in a loop, and suspended it from a piece of piano wire over a concrete floor. I then subjected it to a one-second blast from a propane torch from a distance of six inches away. The exhaust wrap immediately ignited and proceeded to burn vigorously for about thirty seconds, until the majority of the velcro was consumed.



From observing the way the flame spread, I would not be surprised to find that a longer piece of this material, lit at one end, would continue to burn along its entire length like a candle. However in the interest of not burning my house down I did not attempt to test this hypothesis.

The velcro material, as well as the thread attaching it to the glass (??) cloth, was essentially completely burned up. The metallic coating was burned off the exterior where touched by flame, and the inside face of the exhaust wrap was blackened.



In order to make a comparison between the exhaust wrap and the aviation-grade firesleeve I already have installed over my control cables, I performed an identical test on the latter material. The exterior surface was charred but not melted, and it did not burn. The inside showed no evidence of distress.



This was certainly far from an exhaustive (or even realistic) test, and does not prove or disprove the product's ability to perform its intended function - it is, after all, billed as heat-resistant, not fire-resistant. It's probably fine for an automotive application, where you can pull over and climb out if something catches fire. However, its apparent flammability is enough for me to conclude that I don't want it installed near my airplane engine.

I still have 11.9 feet of the stuff, so if you want some for your go-kart or dune buggy you're welcome to have it, as long as you're willing to come pick it up.

mcb

Thanks for running that test and posting the results!

Dave

Simple solution

If the plastic velcro concerns you, take it off and staple the heat shield material to itself around the control cable

DanH said:

Won't work without careful shielding.

This has been working about 250 hours, but I've not unwrapped it, nor have I stuck a temperature sensor in the bundle.....fiberfrax under aluminum tape, all behind an aluminum radiant shield:

The section which recently melted is here....a good distance from the pipe:

Click to expand...

I have an RV-8 with IO-360, Bendix Fuel Injection, Vetterman crossover exhaust.

My green Vans throttle cable, which was encased in fire sleeve, had a melt down where it crosses over the top of the first exhaust pipe and is being replaced.

In order to examine the throttle cable post-mortem I had to cut the fire sleeve lengthwise to open it up because the green outer plastic on the throttle cable had permanently baked it self into the white fiber inside the fire sleeve where it crossed the first pipe.

The area where the cable crosses the two exhaust pipes is shielded with the traditional stainless steel shields mounted to the exhaust.

I've been searching threads for solutions before I proceed to reinstall my new cable and came across DanH's idea. I bought some 1/8" FiberFrax and the aluminum tape and I am considering an aluminum channel like the one depicted in Dan's design.

The design appears to have merit in that it allows for heat shedding or dissipation somewhat like a heat sink. Being open on top, it appears that it would prevent an oven like effect.


Dan (or anyone using this idea),

Is it still working? Would you do it again the same way or would you try something different?

I'm also considering a blast tube but don't want to pressurize the lower cowl and inhibit engine cooling and cowl air output flow.

Maybe I need to lose the Vetterman crossover exhaust and go with a Vetterman design that allows maximum distance away from the cables.

Replacing these cables on an RV-8 with a quadrant is not an exciting chore. Those who have done it know what I'm saying.

Thank you for sharing your ideas and experiences.

Charlie, it's still working fine at 670 hours. That said, even I am surprised.