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RV-8 Engine Control Cables freezing up

Have you replaced one or more of your RV8 engine control cables?

  • Yes, at under 500 hours.

    Votes: 15 38.5%
  • Yes, at under 800 hours.

    Votes: 8 20.5%
  • Yes, at under 1100 hours.

    Votes: 1 2.6%
  • I have never replaced my RV8 engine control cables

    Votes: 15 38.5%

  • Total voters
    39

edneff

Well Known Member
My mixture control has gotten to the point where I can barely get it to the ICO position without using two hands. RV-8, IO-360

There are a number of threads on this particular topic, but most of them are fairly old. I thought it was time to refresh the topic. It seems that the consensus of opinion on this is that the Vans Cables supplied with the kit are not designed for high heat environments. (best I can tell is that I Have a Vans CT Q-55 on my 850 hour airplane)

So, a poll, and two questions:

1.) has anyone found a cable that does not have the same issues as the green Vans cables? specifics and sources would be appreciated.

2.) Since I did not build this plane, do you have any tips on approaching the replacement of the cable? It looks like a lot of disassembly will be required.

Thanks
 
Only 125 hrs on mine so time will tell. I did put firesleeve and heat reflective aluminum tape around the throttle cable where it went under the engine. Nothing on the mixture cable though
 
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McFarlane

I needed slightly different length cables due to a slightly different engine and throttle body so I ordered some from McFarlane Aviation.

https://www.mcfarlaneaviation.com/section/services/custom-engine-controls/

They seem to be good quality, but since I'm not flying I can't tell you how many hours they will last.

Replacing your cables will probably not be that easy, probably a good 4-8 hours of work, plus once you get them out, you'll need to measure them carefully, order new cables, wait a week or so, then reinstall. I recommend you take care with the measurements - I didn't, and got to buy a second set.
 
Ed, Ron Schreck had the same issue on is 8 and replace a cable 3+ times due to heat. He added fire sleeve and a 3/8" cooling tube to provide some air down inside the fire sleeve. I thought it was a really clever solution. The post was a year or two ago.

I think it was a different cable but the solution would work too. On my 7 I have a 4-into-1exhaust and my throttle runs parallel to it. I added fire sleeve and measured the internal temperature, it was well below McFarlane's usage limit.

Edit: added link to Rons post - funny - it was in a 2013 thread!! Time flies in the RV world.
 
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I just replaced my mixture cable about 10 hours ago and 425 hours total. I spoke with the manufacturer of the cables Vans sells and they have improved the heat range since I purchased the original about 15 years ago.
I cut the old one up and the internal sheath seemed to have become soft and then began to roll up.
I had reflective sheathing over the portion of the cable nearest the exhaust, but no protection on thethreaded steel end. My guess is the steel end conducted heat to the intenal sheathing and caused it to bunch up
 
Thanks for all of the responses. As "rv8ch" confirms, this is a big job I am not looking forward to since I don't have the builder knowledge lots of you have.

I am going to get a quote from McFarlane. They asked me, "Will the clamp sleeves need to be threaded?" and I am not sure what they are referring to. Anybody know?

I spoke with the manufacturer of the cables Vans sells and they have improved the heat range since I purchased the original about 15 years ago.

Thanks Brad. It would seem from my survey that about half of the poll respondents had never replaced their cables... Perhaps they are using the newer more heat resistant product. Any idea when the product was improved, and what the new temp range is? Did you use the Van's cables for the replacement?
 
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Ed - just a recommendation based on my own experience - they get really bad quick - if it’s taking two hands to get it “off”, then ground the airplane now until the cable is fixed - you might only have one operation left.

Paul
 
Ed, these cables were new circa 2006. At 850 hours they are still hanging in there, right above a 4-into-1 pipe.

They're wrapped in fiberfrax, then aluminum foil tape, then the side facing the pipes got a formed aluminum tray. Double reflector over an insulator.

I seem to recall the mixture cable becoming a bit rachety very early on, then it smoothed out again.

Cable%20Heat%20Shield.jpg


Cable%20Heat%20Shield%20II.jpg
 
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Ed,
I replaced cables on previous RV8, not yours, used standard vans cables but covered them with fire sleeve and heat shield. Was surprised when I removed the cables that they would not slide by hand. I recommend you get new vans cables and follow Dans and my advice to protect them from heat.

All the installation on your aircraft is per Vans instructions so will require some getting down under to disconnect and reconnect new but it is doable.

I posted a safety issue about this years ago. All cables should be protected from heat as much as possible.

Captain Mike
Building number 5 in Alabama
 
There?s a company in California that sells better cables. I?ll have to dig to find it, but forget the van?s cables. Working great on my -8.

Ed
 
Ed - just a recommendation based on my own experience - they get really bad quick - if it?s taking two hands to get it ?off?, then ground the airplane now until the cable is fixed - you might only have one operation left.

Paul
Agree. I grounded it Sunday while I come up with a plan. Tried lubricating, no joy. Just need to decide which cable to order exactly.
Question asked by custom cable supplier:
Will the clamp sleeves need to be threaded????
 
Agree. I grounded it Sunday while I come up with a plan. Tried lubricating, no joy. Just need to decide which cable to order exactly.
Question asked by custom cable supplier:
Will the clamp sleeves need to be threaded????

Just buy the drop-in replacement from Van's. It is an $80 fix that will last years. I replaced my engine cables after about 15 years on the RV-6 and expect the current set to last that long too.
 
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Just buy the drop-in replacement from Van's. It is a $80 fix that will last years. I replaced my engine cables after about 15 years on the RV-6 and expect the current set to last that long too.

That?s what I did on the -8, and after adding heat protection, the cables have gone 1500 hours....

I used different cables on the -3, but modifying the -8 would have been painful after its was finished and flying.
 
If you want to know if the heat is affecting them go fly the plane. I think that's what's happening to my throttle cable. On the ground it's stiff, but moves. Once I'm flying it moves super freely so I'm thinking the heat is softening whatever inside is binding the cable.
 
If you want to know if the heat is affecting them go fly the plane. I think that's what's happening to my throttle cable. On the ground it's stiff, but moves. Once I'm flying it moves super freely so I'm thinking the heat is softening whatever inside is binding the cable.

Careful - when it happened to me, heat made it worse, and while it operated on teh ground, it froze up on me in flight, and we couldn?t do an idle/cutoff shutdown at the end of the flight.
 
Careful -... heat made it worse, and while it operated on the ground, it froze up on me in flight, and we couldn?t do an idle/cutoff shutdown at the end of the flight.

My main symptom was the binding of the mixture cable when trying to pull it to idle cutoff. Had to use two hands to get it shut down.

Today I removed both the throttle and mixture cables... PIA! The prop cable is still working like a champ. The governor's on the back, so it's not close to the exhaust. I disconnected the throttle cable and worked it by hand and it was binding significantly, although less than the mixture. So it will be replaced as well.

I measured them and am ordering new Van's cables.
 
I had to replace my original green Van's cables at about 500 hours. I installed heat shields and fire sleeve on my throttle and mixture cables. At 1000 hours they became stiff again and I replaced them with custom McFarlane cables. They are still going strong at 1600 hours. They are three time the price of the Van's cables, but if they last me twice as long I'll be happy since replacing cables is such a pain.
 
another version

Here's the drawing for the custom throttle cable McFarlane made for me. I've been using it for quite a while now, no issues. The quadrant end length was a little different than the original Cablecraft/Vans cable, I had to find a shorter clevis fork to work in my installation, otherwise very happy with it.
 
Here's the drawing for the custom throttle cable McFarlane made for me. I've been using it for quite a while now, no issues. The quadrant end length was a little different than the original Cablecraft/Vans cable, I had to find a shorter clevis fork to work in my installation, otherwise very happy with it.

Greg,
thanks for posting the order form for McFarlane. I am getting ready to order both a mixture cable and a throttle cable. Can you confirm the equivalent length of the standard Van's cable that this replaces? Is it a QT-60? I'm guessing because the sum of all the individual lengths is 60". I can't recall if the Van's cable lengths are listed as full overall length? Could you have specified different lengths so that the standard quadrant clevis fork would work? Did the threaded sleeve ends come with the same thread diameter as a standard Van's cable?

I put firesleeve on my original cables. The throttle cable failed after about 450 hrs. I installed a new Van's cable and did firesleeve + aluminum tape wrap + an additional heat shield. Now the mixture cable is failing at about 600 hrs.

Kyle, with an RV-6 or -7, the replacement procedure is easy enough that it makes sense to just keep buying the $80 Van's cables. On the RV-8, the replacement procedure is so difficult that I only want to do it once more. I am willing to spend the $300 or so for a McFarlane cable that will for sure last the life of the airplane instead of having to do a painful replacement every 500 hrs or so.
 
Greg,
thanks for posting the order form for McFarlane. I am getting ready to order both a mixture cable and a throttle cable. Can you confirm the equivalent length of the standard Van's cable that this replaces? Is it a QT-60? I'm guessing because the sum of all the individual lengths is 60". I can't recall if the Van's cable lengths are listed as full overall length? Could you have specified different lengths so that the standard quadrant clevis fork would work? Did the threaded sleeve ends come with the same thread diameter as a standard Van's cable?

Steve- It's been a few years. What I recall is that the threaded quadrant end was different than the standard Van's cable which required me to find a different fork as the standard aviation clevis fork was too long with the new cable. I think the one I installed is this one: https://midwestcontrol.com/shop/BTC-187S (Or, perhaps, a slightly different version from that same vendor).

I think the overall cable length was correct, just the length/size issue at the quadrant threaded end. There might have been easier solutions or a slightly different design to solve that.

Next time I have a chance I'll take some pictures for you. The new throttle cable has worked great for around 3 years and ~350 now. My original Van's mixture and prop cables have held up OK (750 hours total).

-Greg
 
Can anyone tell me when Van's cables were improved? Mine were supplied in the kit I received in late 2017. I wish I had known of these issues before installing mine. It will be a pain to firesleeve them now; might use the fiberfrax/aluminum tape solution suggested above.
 
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