When rebuilding a Ham-M style rotor, studs can be used in place
of the 1/4-20 bolts from the factory. There is room to increase the size
to 5/16-18, and to use a better grade material at the same time.
Grainger sells a bag of 10 pieces of 5/16-18 type 316SS studs at a
reasonable price. Grainger part number 21 YN26. Drill the (4) bolt
holes to 1/4 inch, to the bottom of the hole. Tap the re-drilled holes
to 5/16-18 thread. Use a suitable lube when drilling and tapping.
Kerosene is usually the choice of us older machinists.
Clean the gorp out of the threaded holes. Install the studs to
the bottom of the tapped hole. Two 5/16 nuts jammed together will allow
the stud to be bottomed out in the threads. Use Loctite on the stud end
in the rotor housing only, nowhere else. Un-jam the two nuts used to
install the stud, and tighten the bottom nut against the case for a jam nut.
Repeat the above for three other studs. Be careful where the
Loctite is used!.
With the case turned to it's upright , normal position, use a
combination of nuts and flat washers to mount the rotor to the tower
plate. By using the full four inch length of the studs, the bottom
surface of the case will be about 2-1/2 inches above the rotor plate.
From the top down, the sequence is : (1) nut (2) nut (3) flat
washer (4)rotor plate (5) flat washer (6) nut (7) nut. If regular low
carbon nuts are used, they won't gall on the stud. With the rotor
elevated, the cable is easily routed, the rotor can be lowered for
clearance to slip it out of the mast, all sorts of good things. Jam
nuts keep everything where it belongs. This is a quick and dirty how-to,
but it works. I have installed studs in a rotor mounted in a TX455
standing upright.
Mike W5CHR
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