One is being drilled and one is waiting to be drilled.
Started March 3, 2007
The Throttle, Mixture, Carburetor heat (and Prop if you have a constant speed prop)) control cables must be run from the instrument panel to the engine. These control cables have an outer casing of spun wire to protect the cable wire, which runs runs inside. To work properly, the cable casing must be immobilized no more than 3" from the throttle or mixture control arm. The casing is held ridged and the cable (wire) inside the control cable moves back and forth moving the throttle or mixture arm.
You can buy cable retaining clamps, however in the spirit of saving some money and learning something new, my friend Mickey Whittenburg showed me how he makes control cable clamps. These are easy to make and are extremely effective.
First cut a couple of pieces of 1/4" aluminum bar or plate stock to 7/8" wide x 1 1/2" long. Drill and bolt the two pieces together with 3/16" bolts, spacing the bolts about 7/8" apart. Now file and smooth the combined (bolted together) pieces until they match on all sides.
Next, drill a hole that is about .015" to .020" smaller than your control
cable casing, through the middle of (between) the combined pieces as shown
here:
One is being drilled and one is waiting to be drilled.
Here is the finished product after drilling:
Since the hole is slightly under-size, when you tighten the bolts down,
the ribs on the cable casing dig into the softer aluminum creating a very
stable hold-down for the cable.
Before splitting the two halves apart again, use your file to make a small notch on one end of the both pieces so you will know how they go back together.
The cable gets encapsulated between the two halves and bolted to a solid standoff near the carburetor. It is important that the standoff be solid and be bolted to the carburetor or engine itself so that it can move with engine and be part of it.
I have decided to use a piece of .060 steel plate (4130N) to make my control cable mounting bracket. It will bolt on between the carburetor and intake manifold.
First I bent a 2" wide flange along one side of the plate. Then the
carburetor was placed on the plate to determine where the throttle cable
will align with the 2" flange. Using the carburetor gasket as a guide,
the bolt hole pattern and main carburetor throat holes were laid out on the
plate. The large center hole was cut with a hole saw:
Next the mounting bolt holes were drilled. Now we could slip some bolts
in, mount the carburetor to the plate and starting getting all of the cable
attachments lined up. Here is the plate ready to receive the
carburetor:
Note that part of the 2" flange had to be cut away to clear the throttle
arm of the carburetor.
Now the carburetor was placed on the bolts so we could figure out exactly
where the cable hold-down clamps need to be installed:
The carburetor and bracket are actually upside-down in the picture. When
mounted on the engine, they will be the other way around.
Moving the throttle and mixture controls through their full range, you will notice that they move in a semi-circular fashion, not just straight (linear). Therefore, the cable must bend side-to-side some to follow the movement of the control arm. The idea is to have the cable perfectly aligned with the control arm when the control arm is closest to the cable hold-down clamp. Any bending of the cable should occur when the control arm is furthest away from the hold-down clamp. This is because the cable is more free to move side-to-side when its extended and not so free to move near the hold-down clamp.
The throttle cable perfectly aligned with the 2" flange because when we located the carburetor mounting holes, we measured it that way.
The mixture control arm is a different story. It does not align with the
flange, but is about 1" over from the flange. My options were to either
put in some sort of 1" spacer for the cable hold-down clamp, or to move the
flange over 1". I opted to move the flange.
A new piece of 4130 was cut 2" wide and about 6" long. It was bent
to about 45 degrees and then tack welded in place as shown
below:
As you can see, the hold-down clamp is now aligned with the mixture control
arm.
Here is the mounting bracket at this point:
Next, to save some weight, I will cut away everything that is not needed to make this bracket functional.