[Collins] wanted 75s-3b parts

[Dr. Gerald N. Johnson]

Good point, I forgot that detail. A metal shaft probably will make the 
RF stage oscilllate from the stray coupling between the shielded 
enclosures. Look at the home store or garden store for fiberglass rods 
used for tomato takes, electric fence posts, and supports for flags on 
bicycles and ATV. Some are quarter inch diameter, then could be sanded 
to have the flats. The flats need to be fairly straight so all the 
switch wafer contacts are centered. They would be most precise if made 
with a milling machine compared to a drum sander.

73, Jerry, K0CQ Technical Adviser to the Collins Radio Association.

On 8/6/2011 1:04 PM, Glen Zook wrote:
> The original band switch shafts were NOT metal!  They were made from phenolic and from fiberglass.  I don't know what effect using metal would have.  Maybe some, maybe none at all.
>
> A replacement shaft can be fairly easily be made using a 1/4th inch diameter wood dowel.  It does take some "elbow grease" and a piece of sandpaper on a flat surface.  Just make sure and keep the sides that you are reducing parallel to each other.  The rounded end can be made by forming the sandpaper in a cylinder and rotating the rod.
>
> It is a bit of a "pain in the posterior" to make a new shaft.  Not hard, just time consuming.  There is not much stress on the shaft except for the rounded end and the set screw.  That is why it needs to be hardened in some way.
>
> When the rod is finished, I would coat the rounded end with epoxy to get a more durable surface to which the set screw attaches.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Sat, 8/6/11, Dr. Gerald N. Johnson<geraldj at weather.net>  wrote:
>
> The band switch shaft seems to be a problem. Used to be we could buy switch index assemblies with long shafts, at least surplus. Its basically a double flatted quarter inch diameter shaft. I measure the flats as being 3/16" inch apart to the nearest .001" on a switch in my switch box. Most everybody used the same shaft dimensions. But the usual sources I checked today don't admit ever hearing of such an item or their computer search engines are faulty. It would not be a difficult machining task with a vertical or horizontal milling machine and a piece of 1/4" aluminum or steel rod. Aluminum would machine easier and not rust, though I think the original was steel and plated after machining. I can't tell from my manuals whether it was made or purchased. It could have been supplied either way and probably over the production life of the S-line (also used in the 32S) it was both made at Collins and purchased. It could also be turned in a metal lathe staring
>   out with 3/16 x 1/4" stock and turning the 1/4" dimension round. I think it would mill easier than turning that long length which will tend to bow away from the cutting tool while the entire length can be supported on the milling table.
>
> That shaft is not a tough duty job, so one might make a temporary shaft sanding, filing, carving, routing, or sawing on a hardwood dowel, though a bit of 1/4" dowel I picked up last week didn't make it home in one piece it was so poor quality.
>