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UNIVERSAL SOLID WIRE VERNIER MIXTURE CONTROL CABLE

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05 Apr 2024 21:16 #1 by Brooks McNew
Replied by Brooks McNew on topic UNIVERSAL SOLID WIRE VERNIER MIXTURE CONTROL CABLE
My 415C has an ALCOR vernier mixture control which was installed before I owned it. It was installed along with the C85 Stroker STC which involved swapping out the original Stromberg carb for a Marvel Schebler MS3PA.

I don't know about the original installation, but I recently had everything disconnected to trade in the carburetor for an overhauled unit. Upon reconnecting, the mixture cable was a bit challenging for one specific reason: The mixture cable turns more than 90 degrees in its sweep, and the control wire is quite stiff. You need to stack up washers and shims on the cable to get a good grip on it, but also let it swivel a little bit so that the movement of the lever isn't bending the wire - another way to say that is that the stiffness of the wire will make it hard to push and pull the mixture lever all the way to the stops. As I found it, the lever could NOT be pulled all the way to lean cutoff.

After playing around for a while, my A&P and I settled upon a three-part solution.

1. I cut back another inch of cable sheath so there was more bare wire exposed. That added a little more flexibility but it's still rigid enough that it won't bend when pushed or pulled to the stops.

2. I got a bunch of skinny AN shim washers and stacked them three above and three below the wire, lightly greased between each shim washer. Now, even when tightened down enough to hold the wire they still have some swivel action remaining.

3. After playing with the tension on the castellated nut, I found the spot where it held the wire tight but still allowed the washers to swivel a bit. You'll know it when you see and feel it. I did find that yanking VERY hard on the red knob can cause the wire to pull through and that worried me because if that happened, I wouldn't be able to push back to full rich. So I took the dang thing apart again and added wire stops on both sides of the bolt/washer stack.

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03 Apr 2024 20:08 #2 by Keith Whitcomb
I’m about to take my aircraft out of service for a panel upgrade.  I’m looking at the possibility of replacing the original 1965 mixture cable with a vernier cable for finer control.  I’m installing an EI engine monitor.  

I see universal mixture controls on Aircraft Spruce.   Has anyone done this?  Is there anything I need to know? 

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