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RV-8 Throttle Cable question

A6PILOT

Active Member
I bought a neat RV8 and I love it. The throttle cable is stiff and I know it's heat related. I want to order the correct cable so when I take that bad boy out I have one to put in. I'm having trouble measuring the cable in the plane. Anybody know the correct length for RV8 with IO360 A1B6 with Precision Air FI ? Should I use a string or coat hangar wire to measure it?
 
Steve,

Not sure if there is a "one size fits all" solution. I have seen different builders use different cable lengths and routing techniques for the RV-8 throttle cable. Some have been purchased through Vans, others have not. You could order the cable that comes with the finishing kit for your engine only to find out that it's the wrong length.

It would probably be best to remove the cable first inspect, measure and order. This would add a few days of down time, but you would be guaranteed a perfect fit.
 
Hi Steve...

Your best bet would be to find the builder's orders list and see what he bought... or even try Barb at Vans.

Find whatever heat shield / reflective material / sleeve you can for the new one.

Andy
 
RV8 cables

There have been quite a few reports of RV8 cables getting stiff. I'm at that point in my build and I currently have the cables includes with the FWF kit and would like to replace them with better cables - mainly because the cables I have are not really round, but round with a strange cable wrapped around the sheath. Apparently this is the "old style" cable, and it's hard to seal it with the stainless steel eyeball firewall penetrations.

My plan is to measure the length with the cables shipped, and probably replace them with "better" cables. Not yet sure what I will use, but I would like to avoid replacing them every few years if possible.
 
There have been quite a few reports of RV8 cables getting stiff. I'm at that point in my build and I currently have the cables includes with the FWF kit and would like to replace them with better cables - mainly because the cables I have are not really round, but round with a strange cable wrapped around the sheath. Apparently this is the "old style" cable, and it's hard to seal it with the stainless steel eyeball firewall penetrations.

My plan is to measure the length with the cables shipped, and probably replace them with "better" cables. Not yet sure what I will use, but I would like to avoid replacing them every few years if possible.

I have had the stiff cable problem on the Val, but it has been some time now (like 800 hours on this set, which is finally starting to get stiff). I suspect that somehow the cables were improved, since I really didn't change the routing after my first ones went bad. But in the search for something different, I am going with the Aircraft Spruce 920 cables on the -3 project. They are simpler and lighter, and would take a lot less room in the -8 gear tower. they don't have threading and nuts on the ends for mounting, and adapting the Van's brackets takes a little thinking - but I have heard good things about them from the Rocket troops.
 
I ordered mine straight off VANs web store (CT Q-60) for $70. I wrapped the last 12" in firesleeve and clamped in place for some heat protection - who knows if this helps as I only have about 100 or so hours on the plane.
 
Try to lubricate your cable before you throw it away.

I bought a neat RV8 and I love it. The throttle cable is stiff and I know it's heat related. I want to order the correct cable so when I take that bad boy out I have one to put in. I'm having trouble measuring the cable in the plane. Anybody know the correct length for RV8 with IO360 A1B6 with Precision Air FI ? Should I use a string or coat hangar wire to measure it?

Before you replace that cable, try to lubricate it using a motorcycle cable oiler tool. You clamp the tool over the end of the outer sheeth of the cable. Insert the red plastic tube from a can of aerosol oil like WD40 and spray till it comes out the other end of the cable. Then install a heat shield on the cable anywhere near where there is a heat source [exhaust system] See

http://www.jpcycles.com/product/9100065

Charlie Kuss
 
Another possibility.

Just poking around on the Aircraft Spruce site, and discovered the A-1550 series cable, which according to ACS "has same design as A-920 control but with 7/16-20 threaded bulkhead fittings added at each end.". This would seem to allow their use with the stock Van's mounting configuration. The only cable stocked is a 96" for $49, but custom lengths are available, at a premium of course. I think this just moved to the top of my most-likely-cable-to-use list.
 
William... Yes - the end fittings are correct, but the distances are not i.e. the distance between lever and the cable mount, and at the other end the mount and the actuating arm, are different (and also check the "throw" is sufficient).

On a new build, maybe not too much hassle, but as a retrofit, a pain. See Paul Dye's RV-3 post on making new control brackets which you may need to do ;)

As an aside, at 410hrs we have replaced throttle and mixture once each, and I feel throttle coming on again :( Our engine / induction / exhaust config is more vulnerable than most I think, hence the problem. The 1st throttle cable when it came off did have molten (green) plastic. Interestingly even Van's said in an eMail:
We have replaced our cable a few times on our RV-8A. The inner plastic liner in the cable will not stand up to the heat. We look at this as maybe a 200 hour item.

Andy
 
Thank you all for your responses and offers of help. I have a 60 inch cable and a 70.5. I had them both overnighted from Van's. I did lubricate the heat damaged cable but I suspect it's only a temporary fix. I will ground the airplane and remove/replace the offending cable soon. Thanks again to those who answered. Steve
 
The throttle cable is stiff and I know it's heat related.

Steve, I've experimented a bit, and the most effective heat shield is a reflector backed with an insulator. Almost as good is a reflector alone, while an insulator alone is a distant third. Fabricate what you need to keep that cable cool.

Here's a pair of standard Vans cables running just above a 4-into-1. The shield is formed aluminum. The insulator is fiberfrax wrapped around the cables and covered with metal duct tape, which is also a reflector. About 90 hours now, no issues. Time will tell.

245lm46.jpg


You can also fabricate conventional reflector shields for pipe sections. This one reduces radiant heating to the throttle body and divider line.

2r5zzmx.jpg



Have fun with your new -8.
 
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