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Old 25th Oct 2018, 11:41 pm   #1
Phil G4SPZ
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Default Ferranti Model 7 synchronous alarm clock seconds hand broken

I’m restoring this pre-war Bakelite Model 7 ‘alarm clock with floodlit dial’ which has a broken seconds hand. On removing it, the pointer quickly parted company from the centre, having been stuck there with something like Evo Stik by a previous owner...

This is a very delicate aluminium pointer. Can anyone recommend a reliable method of repair, or alternatively suggest where I could obtain a replacement?
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Old 26th Oct 2018, 8:52 am   #2
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Phil,
Have you a pic of the centre collet on the broken hand?
Is the seconds hand on top of the minute hand or next to the dial?

Maybe get a new hand from M&P or Cousins and fit the original collet.
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Old 26th Oct 2018, 4:33 pm   #3
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Hi Mike, thanks for the suggestions. Photo attached. This seconds hand fits on top of the minute hand as is driven by the centre arbor, which measures a few microns over 1.5mm in diameter, or about 0.060”.

I’ve had a look at Cousins’ seconds hands but can’t see anything like what I need. I think these Ferranti hands are prone to breaking on removal, as I’ve had a few of these clocks where it’s been missing altogether! If possible, I’d like to retain the original hand and collet as the counterweight is quite attractive.

I’m going to try thoroughly cleaning the parts, clamping them in position and using a dot of clear Devcon 2-ton epoxy. It takes hours to set but I’ve had some success using it on other delicate repairs.

Phil
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Old 26th Oct 2018, 5:30 pm   #4
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Quote:
It takes hours to set
So does Araldite Precision, all the better for a good bond, gives time for the atoms to get used to each other.
 
Old 26th Oct 2018, 7:51 pm   #5
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Hi Phil,

Ah yes - one of those. Your idea is probably best as they break with it being difficult to get the hand off in the usual way, having no flat central part.

It will keep the original hand as well.
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Old 27th Oct 2018, 9:49 am   #6
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Success!

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Old 27th Oct 2018, 12:16 pm   #7
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

That looks to be the same model of alarm clock my parents had when I was a youngster, although theirs was brown.
I don't know what happened to it, it's long since gone.

Andy
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Old 27th Oct 2018, 1:52 pm   #8
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Well, mine is in a brown Bakelite case, and I had one myself many years ago as a schoolboy. I don’t know what became of that, but nostalgia got the better of me and I started to look for another. This is it!

Depending on which catalogue entry you read, this model was introduced in 1936 or 1938. The movement is in good order and apart from a drop of light oil on the rotor bearings, a new 3.5V bulb and a good clean and polish, it hasn’t taken too much work to restore it. Once it’s reassembled and has a new flex, I’ll post a pic of the finished article.
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Old 27th Oct 2018, 8:54 pm   #9
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Photos as promised.

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Old 30th Oct 2018, 10:58 am   #10
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

How about 6 o'clock, 12 o'clock and about 2:46 or 9:16 ?
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Old 30th Oct 2018, 11:58 am   #11
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

I rather like that little clock! The dial light is a nice touch too. Might have to hunt one down myself now

Regards,
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Old 30th Oct 2018, 10:19 pm   #12
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Quote:
Originally Posted by Herald1360 View Post
How about 6 o'clock, 12 o'clock and about 2:46 or 9:16 ?
I've just worked out what you're getting at! 9.16 is correct, but shouldn't it actually be 2.43 rather than 2.46? The time shown by the hands in the first photo was the actual time at which I took the picture. The second pic was 'posed' for the camera just to show the light working.

Lloyd, you're clearly a man of good taste. Sadly, my wife doesn't share our appreciation of pre-war clock styling. After one night in the bedroom, on test, the clock has been relegated to my workshop where it is very comfortable. It sits next to a radio-controlled digital clock locked to the atomic standard, so it shows me at a glance whether the 50Hz mains frequency is ahead or behind. The synchronous clock can be several seconds ahead of or behind the atomic standard clock.
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Old 30th Oct 2018, 10:40 pm   #13
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

I think it is about 2:46- the hour hand won't have reached 3 so the minute hand needs to be just above 9 (45) for symmetry.

I've seen quite a few posed clock pictures set at about 1:51 so given your second symmetric picture I just ran with that idea.

Well spotted anyway, must be just the way an engineer's mind works- somewhere a bit off centre on the "spectrum"!

Now, what about all the times when the hands are exactly aligned with each other?

12:00..................
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Old 30th Oct 2018, 11:16 pm   #14
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Oh, sorry Chris, I got hold of the wrong end of the stick. Following on from your 6 o'clock (and 12 o'clock) ideas, I thought you were looking for positions where the hands were opposed but in-line, rather than equally spaced above or below the 9-3 horizontal line! So 9.16 is actually not symmetrical, then; it should be nearer 9.13.

Never mind. As you say, most clock pictures are posed symmetrically at roughly 9 minutes to 2 or 9 minutes past 10, at which point the hands are both approximately 54 degrees either side of the vertical.
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Old 31st Oct 2018, 5:39 am   #15
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

I believe the only time that all 3 hands align (on a centre-seconds clock) is 12:00. I think there was a proof of this in one of Martin Gardner's columns in Scientific American, but I am not going to search all his books for it now.

If you consider just the hour and minute hands, I think they align 11 times between 12:00 (included) and the next 12:00 (not included).
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Old 31st Oct 2018, 9:10 am   #16
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Someone has worked this out quite succinctly:

http://datagenetics.com/blog/november12016/index.html

It’s interesting how these threads develop! We are now actually discussing two separate phenomena, the initial one being positions of hand symmetry (5-to-1, 10-to-2 etc) and secondly hand alignment where the minute hand hides the hour hand (5-past-1, 10-past-2 etc). I suppose these are all downsides and points of ambiguity of the analogue clock display although, let’s face it, this has served us pretty well for centuries.
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Old 31st Oct 2018, 11:05 am   #17
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Time to trot out a favourite of mine.....

A quick glance at an analogue display will normally tell you approximately the right value but a quick glance at a digital display will nearly always tell you precisely the wrong value
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Old 31st Oct 2018, 11:28 am   #18
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

Absolutely true! I’ve known for years that when people look at a clock they rarely need to know the time. Usually they want to know how long they’ve got before their next appointment, how late their train or bus is, how long it is till home time, or something similar.

Analogue displays are perfect for a quick glance visual snapshot of the instantaneous value. I guess this all started with the sundial!
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Old 1st Nov 2018, 11:54 am   #19
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

How does it derive the 3.5v for the lamp?
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Old 1st Nov 2018, 12:55 pm   #20
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Default Re: Ferranti Model 7 synchronous alarm clock seconds hand broken

There’s a tapping off the coil. I think the bulb is under-run for long life, but it can be replaced easily from the rear by removing the back. A switch operated by a cam on the 24-hour alarm setting arbor turns the lamp on at around midnight and off again at around 8am. A manual switch allows the lamp to be permanently extinguished.
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