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Old 26th Feb 2020, 9:41 pm   #1
Robsradio
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Default Sangamo Rate Changer... finally!

Evening
You may or may not recall I have been after one of the for some time, but they seem as rare as hen’s teeth these days.
Well, what a lucky opportunity this was, we went to visit my step daughter and husband at the weekend, they have been having some electrical work done and what did I spy thrown on the path next to the front door as I got out of the car, a wet through inside and out Sangamo rate changer from 1972.
A bit of luck that it hadn’t found its way to the tip as it had been there for weeks apparently.
I couldn’t wait to get the lid off to see if it was salvageable inside, it was full of water in the base but the movement sits slightly raised and seemed good apart from some superficial corrosion and a little rust here and there.
I have spent a bit of time cleaning the base and it looks like new again, I just have the movement to clean and service at the weekend, but even when fully dried out and wound it works perfectly both on mains and on spring reserve (mains off).
It really is a great piece of electro-mechanical design, it runs as a normal synchronous clock when mains is on, this also keeps the spring reserve fully wound. When the mains fails a small solenoid releases the balance wheel and it runs on spring power, think it can run for around 50 hours without power.
To ensure the spring reserve part is always ready to go it gets ‘exercised’ for around 30 minutes every day by a cam and latch arrangement, but timekeeping is maintained by mains frequency in this instance.
Hope it makes sense, and thought I would share.
Rob
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Old 28th Feb 2020, 6:46 pm   #2
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Default Re: Sangamo Rate Changer... finally!

That's very nice Rob. A lucky find.

I have a few of the normal round pattern spring reserve time switches, but the rate changer seems a good deal more complex. I'm sure you know that with the round pattern switch the clockwork mechanism runs continuously, it's speed regulated by the synchronous motor. The motor gently moves the hairspring of the balance wheel to maintain mains-accurate timekeeping. I have one in here complete with solar dial ticking away in the corner. It makes the ordinary switches look small by comparison, a miracle of electo-mechanical engeneering. Some photos of the internals of yours would be nice.

Mark.
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Old 28th Feb 2020, 9:43 pm   #3
Robsradio
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Default Re: Sangamo Rate Changer... finally!

Hi Mark
I had hoped someone here may share my interest in these horological delights.
I was very lucky to get it as they rarely come up for sale, I was also lucky that any rust or corrosion was superficial. I have spent a few hours today stripping it, removing any corrosion, cleaning and oiling.
The balance amplitude was barely 180 degrees before the service, it is now around 250 degrees, spring reserve is 50 hours.
Like you I run a couple of round pattern spring reserve timeswitches too, again, another marvel of design and the method of balance synchronisation to the mains frequency is so simple but totally effective.
I have attached a few pics I took before I stripped it, just to help when reassembling.
Cheers
Rob
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Old 2nd Mar 2020, 7:09 pm   #4
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Default Re: Sangamo Rate Changer... finally!

Hi Rob,

It seems there's only two of us on this forum with an interest in time switches. I can't say I'm suprised, they are a bit of a niche area. I only developed a keen interest three or four years ago. I'm trying to stick to Sangamo products only, I've enough stuff around here. Thanks for your other pics, a most interesting device. It's nice to know I am not alone!

Attached are a few entirely un-necessary pictures of a spring reserve round-pattern switch with solar dial (with correct lattitude for my area), with a modern non-solar unit for size comparison.

As an aside, I assume that the solar dials need correcting for leap years. Is this correct?

Mark.
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Old 2nd Mar 2020, 7:24 pm   #5
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Default Re: Sangamo Rate Changer... finally!

Make that 'at least 3 interested'. I've not got any photos to hand (I may take some sometime...) but I've collected a few time switches over the years and find them interesting.

I have a couple of units with solar dials (no spring reserve though), I think made by Venner.

A normal-dial unit with spring reserve (I forget who made that),

A Horstman one (normal dial, no spring reserve but with a facility to not operate the switch on certain days of the week).

A Japanese (National) one with a Warren type motor (rotor and gear train in a sealed oil bath with the stator around it)

A very small one with a bayonet plug on one end and a bayonet socket on the other designed to go between a lampholder and a bulb.
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Old 2nd Mar 2020, 10:44 pm   #6
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Default Re: Sangamo Rate Changer... finally!

The numbers are growing!
The reason I started the interest was as a kid in the 70s our house meter board had an ‘off peak’ time switch that ticked constantly but never needed adjusting, it never meant much to me at the time, but it was a clock of sorts so was of interest to me even at that early age.
As an adult I realised that any purely mechanically rewound time switch would over a period gain or lose time and need adjusting, so I then did some digging around for answers, and discovered the Sangamo spring reserve switch with a balance wheel vibration synchronised to the mains frequency and hence no need for time corrections.
The interest went on from there and other brands and models were discovered and a small collection gained.
Mark... Thanks for posting photos of your round pattern time switch, good to see another, and a solar of even more interest. As for leap years, I guess they need correcting as they probably cater for a 28 day Feb.
Tony... It sounds as though you have a nice collection too, if you get a chance for pics that would be nice.
(My new acquisition failed yesterday, motor winding went open circuit, the moisture must have caused more damage internally, luckily I had a scrapper round pattern I could rob the motor from, up and running again now)
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Old 3rd Mar 2020, 12:02 am   #7
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Default Re: Sangamo Rate Changer... finally!

I have got a bright yellow solar one without a spring.
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