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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I'm a sucker for old electronics so when I saw this relay a few years ago at an antique mall for ten bucks I had to buy it. I'm still looking for an original AVOmeter.
It's a relay made by Weston Electric company in 1917. It has a 24V coil with a SPDT 24VDC contact. So why even bother? Only thing I can think of is an isolation relay. It has a giant magnet of unknown composition, maybe AlNiCo.
The relay works OK, and AFAIK it's the last one of it's kind remaining (SPDT). Some guy on the internet has some other models, but they are SPST. I'd like to put it to good use, but what should I make it do? It's not like it's going to burn out any time soon.
Edit: Oops, I forgot pics of the bottom. I removed the sheet metal cover so you can see things, and I also removed the cardboard spring cover too.
There are some inductors there, one bigger than the other. No clue what they do.
All the springs are adjustable, so I can change the tension of the "swingy part". This means I can make the coil run on any voltage I want (no more than 32V though).
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
It's not an isolation relay, it's a measurement and control relay. Look at the min and max operate voltages on your 5th picture.
Use a variable power supply and a DMM to see if it's in spec. I suspect you can adjust the voltage it switches at by altering the tension of the "swingy part".
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Thank you for showing us your lovely and enviable treasure. You could use it to start a generator when your battery bank voltage runs low.
Similar "wrought" magnets are also found in old telephone magnetos and meters like this one:
I wish I knew what the magnets are made of -- presumably some kind of steel. They predate Alnico, which AFAIK is always a cast alloy that is notably brittle and coarsely grained. (By the way, beware of references which fail to mention that the principal component of Alnico is iron.)
The quest to improve magnetic softness (for transformers & motors) and magnetic hardness (for permanent magnets) must be an interesting story. If you'll pardon a quote from the W reference: "The development of alnico began in 1931, when T. Mishima in Japan discovered that an alloy of iron, nickel, and aluminum had a coercivity of 400 oersted (Oe), double that of the best magnet steels of the time."
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Well it's definately out of spec because I was playing with the spring to see how low a voltage it could operate on. 1.7 volts seems to be the minum.
I also cleaned up the magnet before I took these pictures. It was patch-ily yellowed in some places so I cleaned off the patina with a paintbrush dipped in HCl. It bubbled for about half a second and a rotton egg odor appeared, probably hydrogen sulfide. The acid didn't affect the magnet itself.
So what forms a sulfur patina and doesn't react with HCl? It wasn't AlNiCo or the acid would've attatcked the magnet.
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A relay from tesla's time.
