Sticky control cables

[BMW_X6M]

I just removed and sent my cables to McFarlane for measurement and ordered replacement cables. I am getting the Vernier Assist on the throttle cable, and a normal Mixture cable. This is for a RV-9A with O-320 and CARB with standard Van's routing and bracket. My throttle cable tension was starting to wear in the aluminum thread area. Both old cables had rubber boots on the engine side that were cracked.

I was very impressed with the quality of the cables I saw at OSH last year. But these are more expensive cables. The throttle cable is $310 and the mixture cable is $250. I have included a link to the custom order forms.

http://1drv.ms/1Oej71W

[RV8Squaz]

I just threw away my second set of Vans cables and will not go back. I have 1100 hours on my IO-360 RV-8 in 9 years. I had all kinds of heat deflectors and fire sleeve. I don't know what else I could have done to protect them.

I decided to do as BMW X6M above did. I spoke with Tim Paine at McFarlane and sent him my Vans cable and some measurements for overall length. Hopefully, I'll never have to replace these cables again. They are expensive (about 4 times the cost of the Vans cables), but I feel it will be worth it if I don't have to suffer through stiff cables for 2000 hours. We'll see how it goes.

Jerry Esquenazi
RV-8 N84JE

[Chkaharyer99]

I removed the throttle cable on my RV-8 today. It's equipped with Titan IO-360, Bendix FI and Vetterman exhaust. Almost 700 hours TT.

The throttle quadrant was getting difficult to manipulate/actuate while the engine was cold. Once hot, not so much.

The cable crossed over two exhaust pipes on its way to the firewall. Both exhaust pipes have heat shields clamped to the pipe to shield the throttle cable from radiant heat. The throttle cable also had about 5 inches of fire sleeve over the cable in the area where it crossed the two exhaust pipes.

After removing the cable I discovered the outside green sheathing that covers the throttle cable was melted to the inside of the fire sleeve. It actually took quite a bit of force to remove the fire sleeve from the cable. I had to cut the fire sleeve length wise to get a look. The spot where it melted was directly over the area where one of the exhaust pipes crossed. The melted portion was about 2 - 1/2 inches long. The pipe closest to the FI servo was was where the melting occurred. The area where the second pipe crossed the path of the throttle cable did not exhibit any signs of melting despite the two pipes having almost identical heat shields.

I'm considering wrapping the exhaust only in the areas of where these two pipes intersect the throttle cable.

Also, if I could create a small air gap between the heat shield and the fire sleeve surrounding the throttle cable, I think that might help.

Heat rises. What if the cable was routed underneath the exhaust pipes instead of over the top? Any one ever try this?

I really like the idea of using the McFarland Aviation product.

Any one using these care to comment? Any advise/comments are appreciated.

Any

[longline]

might be converting control runs to use stainless steel Bowden cables. No liners to melt/jam. Bug nuts on engine end. Cable clamps on the quadrant end.

I have no idea how much more force would be required to move the controls, maybe a bit more. A somewhat more complicated build, however.

[RV8Squaz]

Originally Posted by Chkaharyer99

I removed the throttle cable on my RV-8 today. It's equipped with Titan IO-360, Bendix FI and Vetterman exhaust. Almost 700 hours TT.

The throttle quadrant was getting difficult to manipulate/actuate while the engine was cold. Once hot, not so much.

The cable crossed over two exhaust pipes on its way to the firewall. Both exhaust pipes have heat shields clamped to the pipe to shield the throttle cable from radiant heat. The throttle cable also had about 5 inches of fire sleeve over the cable in the area where it crossed the two exhaust pipes.

After removing the cable I discovered the outside green sheathing that covers the throttle cable was melted to the inside of the fire sleeve. It actually took quite a bit of force to remove the fire sleeve from the cable. I had to cut the fire sleeve length wise to get a look. The spot where it melted was directly over the area where one of the exhaust pipes crossed. The melted portion was about 2 - 1/2 inches long. The pipe closest to the FI servo was was where the melting occurred. The area where the second pipe crossed the path of the throttle cable did not exhibit any signs of melting despite the two pipes having almost identical heat shields.

I'm considering wrapping the exhaust only in the areas of where these two pipes intersect the throttle cable.

Also, if I could create a small air gap between the heat shield and the fire sleeve surrounding the throttle cable, I think that might help.

Heat rises. What if the cable was routed underneath the exhaust pipes instead of over the top? Any one ever try this?

I really like the idea of using the McFarland Aviation product.

Any one using these care to comment? Any advise/comments are appreciated.

Any

Hello Charlie,
I only have about 250 hours on the McFarlane cables since I replaced the last Vans set. The Vans lasted about 500 hours each time. I now have 1350 hours on my plane. The McFarlane cables appear to be a high quality product. However, they are 3-4 times the cost of the Vans. Even if I only got 1000 hours out of the McFarlane cables, I would still be happy since they are such a pain to replace. Good luck!

[Chkaharyer99]

Originally Posted by RV8Squaz

Hello Charlie,
I only have about 250 hours on the McFarlane cables since I replaced the last Vans set. The Vans lasted about 500 hours each time. I now have 1350 hours on my plane. The McFarlane cables appear to be a high quality product. However, they are 3-4 times the cost of the Vans. Even if I only got 1000 hours out of the McFarlane cables, I would still be happy since they are such a pain to replace. Good luck!

Thanks Jerry. I will give McFarlane a call next week. Did you go with a 60 inch cable? I there any chance they have your specs on file?

Thanks again!

[Chkaharyer99]

Originally Posted by longline

might be converting control runs to use stainless steel Bowden cables. No liners to melt/jam. Bug nuts on engine end. Cable clamps on the quadrant end.

I have no idea how much more force would be required to move the controls, maybe a bit more. A somewhat more complicated build, however.

Thanks for the suggestion Scott. I'll check them out. Are you using Bowden cables?

Thanks,

[petercavallo]

Hi,
Regarding the Cables available from Vans, we found it seems they get hard to move over time (harder and harder) seems that when we cut them open the outside Teflon liner starts to fray and jams up the cable (slowly it seems so it provides lots of warning)
Best we can tell the problem is caused/exacerbated by the cable restrained too tightly the contact point of the restraint is where the cables Teflon liner seems to fray. (let us know if you found the same)

The fix (it seems for this particular problem) is to not have the cable restrained too tightly keeping the cable free to move a little

Regarding heat and other issues ......other solutions I guess



Peter
RV 6.2