McFarlane Quadrant Control Cables

[scsmith]

I just finished replacing my throttle and mixture cables with custom McFarlane cables. These are substantially higher quality than the standard cables that Vans sells.

It is the job from he** and I hope I never have to do it again. All indications are that these cables are designed with materials that can tolerate the high temperatures experienced by the throttle and mixture cables routing near exhaust pipes despite using radiative heat shields, fire sleeve and aluminum foil wrap.
My first throttle cable lasted about 500 hrs, although it was showing signs of roughness after 400 hrs, and I let it get worse for a while. (arguably a bad idea - you could find yourself unable to move the throttle on a flight, although it seems the degradation is slow and frequent use seems to keep it movable). The replacement cable has 100 hrs on it, and was already showing some signs of roughness. The mixture cable, with 600 hrs, was starting to get pretty rough and stiff too. After removing it, I can not pull the cable by hand.

If you have a side-by-side RV, maybe the cables are easy enough to change that you are content using Vans cables and replacing them periodically, saving a pretty good chunk of money. But if you have an RV-8, it is a major pain, so do yourself a favor and get MacFarlane cables. If you are just building now, do it now. If you are replacing yours, do it once and hopefully never again.

The McFarlane custom cables are quite a bit more expensive, $350 each, but wow are they SMOOTH. Here are some tips and thoughts for ordering custom cables. Download the order form from the McFarlane website. It has provisions for "swivel type" and "standard" engine controls. You want the swivel type.

Box A and F are the fully extended length at each end. For an exact replacement of Vans cables, use 6.5" for both of these. However, I have always found that with the Delux Quadrant in the RV-8, I have a hard time adjusting the cable connection so that the levers can go full forward. So I ordered cables with 6.0" length. This allowed the levers to go full forward, and just barely enough adjustment at the engine end to make up for the lost 1/2" length by setting the outer sheath jam nuts right at the back end of the threads. One might consider ordering cables with 6.0" at one end, and 6.5" at the other end, which would solve both problems.

The throw or travel shown on Vans website is 2 1/8" so that is what I ordered, and what I got. This is measurement G.
But when I measure Vans cables, the throw is closer to 2 1/4". With the new cables, I found that 2 1/8" is just barely enough throw to get full travel on the throttle and mixture. In hind sight, I should have ordered 2 1/4" travel. I don't see any down side to having a little extra travel.

The retracted length measurement boxes B and E are greyed out, but I put numbers in there anyway. Just subtract the travel from the max length. E.g. 6.5 - 2.125 = 4.375"

The remaining box D is the length of the cable housing. If you use a 60" Vans cable, (measured as overall length) then subtract one fully extended length and one retracted length. E.g. 60 - 6.5 - 4.375 = 49.125"

Finally, note on the order form that the cable housing ends should be 7/16-20 thread, indicate that you do not want the additional firewall wear sleeve, and check the boxes for 10-32 threads at the ends.

Use one form for each cable. They take about a week once the order is confirmed.

While I'm at it, here are some tips for changing the cables. First, disconnect all cables from the engine, and remove the firewall eyeball seals, so that the cables can slide freely through the firewall. Then take the quadrant out, and pull it into the cabin a foot or two, to give yourself room to properly do all the clevis connections and cotter pins. If you have a rear throttle pushrod connecting to the quadrant, disconnect the pushrod from the rear throttle lever, and then unthread it from the clevis on the forward quadrant.
On reassembly, don't forget to put the firewall eyeball parts onto the cables before making all the engine connections.
And in honor of Vic Syracuse, DONT FORGET THE JAM NUTS ON THE CLEVIS CONNECTIONS TO THE LEVERS OR THE ROD-END CONNECTIONS TO THE ENGINE CONTROLS.

[Amazon-1]

In my RV10 i had this exact problem at about 500 hours. In my under construction RV14a (using the RV10 throttle quadrant) i will definitely follow your guidance!

Thanks

Bruce

[scrollF4]

I bought the McFarlane Vernier-assist throttle cable for my RV-7A...night and day improvement in quality, smoothness, and temperature tolerance. I particularly like it for formation flying.

Wait: Vernier-assist and formation flying? Yes. This is not a true Vernier push-button throttle. It's a normal-looking black knob throttle, but you can twist it to micromanage manifold pressure like the blue prop and red mixture knobs. But when it's time for straight-pull/push power adjustments for formation flying, it's outstanding.

The IO-360-M1B/RV-7A combination uses Van's 50.5" cable, which is a length not normally stocked at McFarlane. Thus, I had to spend about $450 for a custom cable. I ordered a new Van's cable as a reference, laid it out and took the measurements that Steve discusses above (returned the Van's cable for a refund). Don't do like others and use the stock McFarlane 60" cable and try to loop it around up under the panel to take out slack. That'll allow too much play in the cable for precise throttle control.

Bottom Line: The McFarlane Vernier-assist cables are VERY smooth, great for formation flying, and precise for MAP control.

[N941WR]

I have a center throttle quadrant in my -9 and now have almost 1000 hours on the original Van's cables with no issues.

I wonder why some have issues and others don't.

[RV8Squaz]

See this thread and my post, msg #18:

http://www.vansairforce.com/communit...d.php?t=170300

[scsmith]

Originally Posted by N941WR

I have a center throttle quadrant in my -9 and now have almost 1000 hours on the original Van's cables with no issues.

I wonder why some have issues and others don't.

I assume it has to do with proximity to exhaust pipes. Different sump and exhaust arrangements presumably allow different clearances. With the fwd induction sump and crossover pipes, the cables run pretty close to the pipes. Radiation shields and fire sleeve no doubt help some, but not enough.

[David Carter]

Originally Posted by scrollF4

I ordered a new Van's cable as a reference, laid it out and took the measurements that Steve discusses above

Sid - are you able to share those measurements? I've been thinking about making the same upgrade to my RV-7A with the Superior O-360-B1A2.

Thanks!