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a substitute for Ebonite (for Marconi PS213A) ?

Jun 29th 2016, 02:44

WB5AGF

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I've given myself a task .... that being to make a copy of the
Marconi PS213A Morse Key.

I'm aware that GØNVT makes a key based on the PS213A
(but there are differences) and G3YUH had made copies in
the past (but he isn't making them anymore). My intent is to
try-and-make as near an identical a key as I can.

(My 'yardstick-of-success' would be that you could site down
at a real PS213A or my key and not detect any difference
in the way the two keys feel in use.)

One of the problem I'm facing is that the original Marconi key
used 'Ebonite' (vulcanized rubber) for the base - finding a
source is proving daunting. I've even downloaded Charles Goodyear's 1844 Patent but when I read it I lose-heart ....

At one time bowling balls were made of what was called
Ebonite but it isn't clear to me if it is really the same thing
or if a 'trade name' was being used for something different
than Goodyear's 19th century creation.

Thoughts ? Suggestions ? (I'd really rather not try and saw
a bowling ball in half.)

- Paul, WB5AGF
Jun 29th 2016, 14:06

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
https://en.wikipedia.org/wiki/Ebonite
Ebonite is also known generically as hard rubber. It has a temporary sulfur odor when rubbed.

https://www.amazon.com/s/?ie=UTF8&keywords=hard+rubber+block
You can buy a hard rubber block on Amazon

Zack Lau W1VT
ARRL Senior Lab Engineer
Jul 1st 2016, 19:13

WB5AGF

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Hi Zach;

I've got an inquiry off to one of the sellers on Amazon, asking if they know the hardness of the rubber blocks they are selling.

In a prior discussion (with a very decent fellow in the customer support group of a rubber company in Minnesota) it was brought to my attention that products make of rubber (including modified rubbers like Ebonite) have their physical characteristics described (one of the tests) by their resiliency to being deformed when a predetermined force is applied over a small surface area (it's called the ' Shore Durometer ' test). My research indicates that Ebonite would feel, if we were to have a piece to press on, quite hard (about like a hard plastic).

In this ' quest ' of mine (imagine me as a knight on a might steed ..... OK maybe you don't want to imagine that ...) to build a ' proper ' PS213A I've been very aware that a significant goal is that the key will 'feel' to the user just like a real PS213A and since I don't have one as a sample I have to hope that by staying with the right materials, and the same dimensions, that whatever I build will closely match the performance of the real thing.

- Paul, WB5AGF

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