I think there are three different insulators involved here.
1) The cast aluminium housing with brown glass/ceramic ribbed insulator.
This has stamped/cast-in numbers PC82495C-220 (bottom) 222 (top)
2) The cast-iron with phenolic insulator 'sandwich' issued with the WS19.
This has "Base, Aerial Assembly" PC82495C-285 and
PC82495C-286 (for the bottom) and -282 (for the top)
3) A later high-voltage ceramic insulator with number PC82495C-295 for use with the WS52 and WS43 (Canadian). (Which I do not have.)
My suspicion is that the cast-alloy one is the original design and was found to be unsuitable as being "too fragile", "too expensive", "not repairable in the field" and/or "impossible to produce in the quantities required". It's two aluminium castings, which would have to be machined, and a glass/ceramic insulator that was cemented in place. Aluminium was required for aircraft use and difficult to machine, and production would be complicated (and slow). If the insulator broke it would be difficult to replace (drill it out?).
Item 2 is much simpler: two fairly rough (externally) steel castings and a moulded phenolic insulator held together by bolts (plus a clamp lever to get a good contact between the top casting and the mast). Simple and cheap to produce in quantity and can be repaired in the field with spare parts and a spanner. Also considerably more robust than the first type.
Item 3 was to solve the power loss problem, and may not have been produced in large quantities because there were not that many WS52s built.
Has anyone seen Item 3?
Note: I have a "Campbell" instruction manual, but the parts list has been excised from the back and a different one (matching the WS19 common one) pasted in. I need to dig that out and look at the actual text to see if it describes the insulator in detail.
I've also got various "odd" parts of the aerial kit for WS19 - the original set of wire aerials on wooden board winders, and a 5-section clip-together set for use with insulator strings (3 x glass shells on a rope with a snap-hook at each end), plus a long halyard + pulley, again with snap hooks for the mast and wire aerial. The aerial had ben transferred to an American RL-29 winder from its original (I suspect) reel. I think I have an unissued sectional aerial still on the reel, but can't find it at present.
Chris.
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