Rewinding coil for Smiths Clock. - UK Vintage Radio Repair and Restoration Discussion Forum

slderiron · 19th May 2011, 9:53 pm

Hello,

I've begun the mammoth task of unwinding and rewinding a coil for a Smiths clock. Its a clock pertaining to a Goblin Timespot. Doing this by hand so hopefully may get it done before xmas!

Whilst coming roughly halfway unwinding, I was puzzled to come across a paper wrap between the coils (pictured).

Do I need to add a bit of paper when rewinding? Whats the purpose of the paper in between the coils? I assumed this would be a simple unwind and then rewind with same type copper coil. Thanks, john.

Mike Phelan · 20th May 2011, 9:19 am

John

Are you sure it's a Smiths? Usually Goblin clocks are their own design.
I've never seen a paper on one of these (nor on any electric clock coil) so maybe it was rewound previously at some time.
I'd be inclined to ignore the paper.

You're very brave winding such fine wire by hand. When I've tried it in the past the wire breaks after 20,000 turns!

slderiron · 20th May 2011, 10:12 am

Thanks Mike,
I believe its a Smith's clock, I think I recall reading that somewhere. Its a D25 type, infact the exact type in your article on how to overhaul these clocks. I believe you may be right about the paper insert being part of an old repair, the wire directly below the paper is not as uniform as the rest of the coil. I wasn't aware you could patch repair a coil in this fashion, I thought such a repair would create more stress on the repaired part of the coil.

I've built a handmade jig that turns by hand, and I've been practicing soldering the thin coil wire to the connecting wire. I thought I'd give it a shot as it would give me immense satisfaction if I could get the clock working again. Failing that I will have to find a company/outfit that repairs these coils.
Regards, john.

SeanStevens · 20th May 2011, 11:08 am

I've had guitar pick-up coils rewound - by a Gentleman called Armstrong (son of the famous guitar maker).

He used an electric motor and a speed control (I think it was from a sewing machine or similar) to allow an even wind (controlled by hand)

SEAN

Leon Crampin · 20th May 2011, 11:33 am

I wouldn't waste time and effort rewinding clock coils to original specification.

Do the arithmetic and wind the coil for (say) 24V AC and power your clock from a wall transformer power supply - obviously without diodes.

If you're really brave, wind the coil for about 50V AC and use a series capacitor - but do your arithmetic very carefully and watch out for a series resonant condition which will generate high voltages.

Driving a clock via a transformer works every time and the repair will last - coils wound by hand with 47 SWG wire have a high probability of insulation breakdown.

Leon.

broadgage · 20th May 2011, 12:36 pm

I would agree that 24 volts AC is the way to go.
Although not true to the original, it works as well and is not an ireverseable change.
It would also allow the use of lightweight "figure of eight" flex to the clock, which is now frowned upon for mains voltage.

kalee20 · 20th May 2011, 1:13 pm

I'd persevere with the original wire and turns!

But it is important to have a uniform method of tension and a steady winding speed.

As for the paper, I would forget it. It may have been there as part of a repair (in-line joint), or it may have been there simply to reduce the chance of one of the last turns of wire slipping down and touching one of the first, and excessively stressing the enamel insulation. But usually, if there is any concern about this, there would be rather more interleaving.

Leon Crampin · 20th May 2011, 3:32 pm

But if you persevere with the suicide 47 SWG mains powered coil, you really ought to earth the metalwork as well.

Leon.

slderiron · 20th May 2011, 4:38 pm

Thanks for the advice. I don't think I could go 24v route as the clock feeds of the mains alongside a valve radio, and the radio needs 240v for the valves. Its from a 1940's era radio alarm clock. I suppose there is a way of doing it but I'd rather keep it to the original spec. I'll do the 'suicide' route.... I've made the jig to create as little stress on the wire as possible when rewinding, with even tension. Hopefully I'll get a result.

Chipmunk · 22nd May 2011, 11:05 pm

Just a little thought about the purpose of the paper. It may have as someone said, been from a previous rewind, but when done halfway through the winding, will prevent one turn (or more) from 'sinking' down through the layers to the bottom, where it would have a high potential with reference to the other wires. I've seen this done on high voltage transformers to keep the windings in circa.100 to 120v 'layers' with paper between the layers. If you do go the rewind route, it might be worth including 2 sets of paper (cigarette paper will do fine as it's thin and even has gum on it to stick it in lengths). That would keep the separate 'parts' of the winding to a maximum of 80v in reference to each other.

slderiron · 23rd May 2011, 12:14 am

Thanks. I might consider doing this. But given that I'm winding by hand I'm not sure that its likely any of the windings would sink, or I'd at least notice it. It may have been a precaution taken when wound by machine.

TheGoblin · 5th Jul 2011, 7:07 pm

The Time Spot radio/alarm was made by Goblin (BVC) Ltd who made their own clocks and used them in Teasmades as well. The coil you want will be found in any Goblin Teasmade from 1947 ~ 1974 provided it has a sweep second-hand. Easy to find on eBay and can be swapped over in minutes. Forget about rewinding.

19th May 2011, 9:53 pm	#1
slderiron Retired Dormant Member Join Date: Dec 2010 Location: Reading, Berkshire, UK. Posts: 108	Rewinding coil for Smiths Clock. Hello, I've begun the mammoth task of unwinding and rewinding a coil for a Smiths clock. Its a clock pertaining to a Goblin Timespot. Doing this by hand so hopefully may get it done before xmas! Whilst coming roughly halfway unwinding, I was puzzled to come across a paper wrap between the coils (pictured). Do I need to add a bit of paper when rewinding? Whats the purpose of the paper in between the coils? I assumed this would be a simple unwind and then rewind with same type copper coil. Thanks, john. Attached Thumbnails

20th May 2011, 9:19 am	#2
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Rewinding coil for Smiths Clock. John Are you sure it's a Smiths? Usually Goblin clocks are their own design. I've never seen a paper on one of these (nor on any electric clock coil) so maybe it was rewound previously at some time. I'd be inclined to ignore the paper. You're very brave winding such fine wire by hand. When I've tried it in the past the wire breaks after 20,000 turns! __________________ Mike.

20th May 2011, 10:12 am	#3
slderiron Retired Dormant Member Join Date: Dec 2010 Location: Reading, Berkshire, UK. Posts: 108	Re: Rewinding coil for Smiths Clock. Thanks Mike, I believe its a Smith's clock, I think I recall reading that somewhere. Its a D25 type, infact the exact type in your article on how to overhaul these clocks. I believe you may be right about the paper insert being part of an old repair, the wire directly below the paper is not as uniform as the rest of the coil. I wasn't aware you could patch repair a coil in this fashion, I thought such a repair would create more stress on the repaired part of the coil. I've built a handmade jig that turns by hand, and I've been practicing soldering the thin coil wire to the connecting wire. I thought I'd give it a shot as it would give me immense satisfaction if I could get the clock working again. Failing that I will have to find a company/outfit that repairs these coils. Regards, john.

20th May 2011, 11:08 am	#4
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: Rewinding coil for Smiths Clock. I've had guitar pick-up coils rewound - by a Gentleman called Armstrong (son of the famous guitar maker). He used an electric motor and a speed control (I think it was from a sewing machine or similar) to allow an even wind (controlled by hand) SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

20th May 2011, 11:33 am	#5
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Rewinding coil for Smiths Clock. I wouldn't waste time and effort rewinding clock coils to original specification. Do the arithmetic and wind the coil for (say) 24V AC and power your clock from a wall transformer power supply - obviously without diodes. If you're really brave, wind the coil for about 50V AC and use a series capacitor - but do your arithmetic very carefully and watch out for a series resonant condition which will generate high voltages. Driving a clock via a transformer works every time and the repair will last - coils wound by hand with 47 SWG wire have a high probability of insulation breakdown. Leon.

20th May 2011, 12:36 pm	#6
broadgage Nonode Join Date: Jan 2010 Location: North Somerset, UK. Posts: 2,130	Re: Rewinding coil for Smiths Clock. I would agree that 24 volts AC is the way to go. Although not true to the original, it works as well and is not an ireverseable change. It would also allow the use of lightweight "figure of eight" flex to the clock, which is now frowned upon for mains voltage.

20th May 2011, 1:13 pm	#7
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: Rewinding coil for Smiths Clock. I'd persevere with the original wire and turns! But it is important to have a uniform method of tension and a steady winding speed. As for the paper, I would forget it. It may have been there as part of a repair (in-line joint), or it may have been there simply to reduce the chance of one of the last turns of wire slipping down and touching one of the first, and excessively stressing the enamel insulation. But usually, if there is any concern about this, there would be rather more interleaving.

20th May 2011, 3:32 pm	#8
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Rewinding coil for Smiths Clock. But if you persevere with the suicide 47 SWG mains powered coil, you really ought to earth the metalwork as well. Leon.

20th May 2011, 4:38 pm	#9
slderiron Retired Dormant Member Join Date: Dec 2010 Location: Reading, Berkshire, UK. Posts: 108	Re: Rewinding coil for Smiths Clock. Thanks for the advice. I don't think I could go 24v route as the clock feeds of the mains alongside a valve radio, and the radio needs 240v for the valves. Its from a 1940's era radio alarm clock. I suppose there is a way of doing it but I'd rather keep it to the original spec. I'll do the 'suicide' route.... I've made the jig to create as little stress on the wire as possible when rewinding, with even tension. Hopefully I'll get a result.

22nd May 2011, 11:05 pm	#10
Chipmunk Triode Join Date: Mar 2007 Location: Southampton, Hampshire, UK. Posts: 30	Re: Rewinding coil for Smiths Clock. Just a little thought about the purpose of the paper. It may have as someone said, been from a previous rewind, but when done halfway through the winding, will prevent one turn (or more) from 'sinking' down through the layers to the bottom, where it would have a high potential with reference to the other wires. I've seen this done on high voltage transformers to keep the windings in circa.100 to 120v 'layers' with paper between the layers. If you do go the rewind route, it might be worth including 2 sets of paper (cigarette paper will do fine as it's thin and even has gum on it to stick it in lengths). That would keep the separate 'parts' of the winding to a maximum of 80v in reference to each other.

23rd May 2011, 12:14 am	#11
slderiron Retired Dormant Member Join Date: Dec 2010 Location: Reading, Berkshire, UK. Posts: 108	Re: Rewinding coil for Smiths Clock. Thanks. I might consider doing this. But given that I'm winding by hand I'm not sure that its likely any of the windings would sink, or I'd at least notice it. It may have been a precaution taken when wound by machine.

5th Jul 2011, 7:07 pm	#12
TheGoblin Retired Dormant Member Join Date: Jun 2011 Location: Coulsdon, Surrey. Posts: 5	Re: Rewinding coil for Smiths Clock. The Time Spot radio/alarm was made by Goblin (BVC) Ltd who made their own clocks and used them in Teasmades as well. The coil you want will be found in any Goblin Teasmade from 1947 ~ 1974 provided it has a sweep second-hand. Easy to find on eBay and can be swapped over in minutes. Forget about rewinding.