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Revisiting an old hobby


AndyHull

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1 hour ago, AndyHull said:

Metamec becomes radio active.

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The electric mechanism on the second Metamec has a blown coil, so while I figure out if I am willing to try stripping the motor down and repairing the coil (unlikely, but I may give it a bash), I thought I'd see if I had any quartz mechanism in case I need a plan B.

After much rummaging through spares and a quick trawl through the junk in the attic I found what I was looking for. An "Atomic" (Radio controlled) quartz module with the correct reach to fit in place of the old workings.

I fitted the radio quartz module to a piece of clear plastic sheet, cut to match the outline of the original module which allows me to re-use the original brass screws to centre it and avoid drilling any more holes in the woodwork.

Naturally the original hands don't fit, and since they are what gives the thing the majority of its character I'm going to see if my 3d printer can produce something sufficiently similar to the originals to make it look the way the designer intended. 

If that fails I guess I could attempt to etch some from brass sheet paint them the correct shade of off white.

Until I get some traction with either the coil rewind or replacement hands, I've put replacing the missing piece of woodwork on hold.

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So now I have an even less complete Metamec that is accurate to the second (but not the hour or minute). Nobody is perfect I guess but I'm willing to chalk that down as progress... of sorts.

What does the coil look like Andy? I bought a job lot of new old stock synchronous clock spares, mainly for the five Smiths Bijou coils (sadly two of which were open circuit), but there were other coils in the lot that I haven't identified (that are all OK)....

I did use one of the Smiths coils to get this working.....

Smiths Sectric Art Deco clock 1.jpg

Smiths Sectric spares.jpg

Edited by JohnD
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18 hours ago, JohnD said:

What does the coil look like Andy?

A good question. It looks like trouble. ?

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I pulled the coil out and unpeeled the top layer to see whether I could simply resolder the feed wires to the coil, but as you can see, despite my best efforts this was not successful. Initially I was hopeful, as the original feed wire had broken from the tab due to corrosion caused by the ancient rubber insulation decomposing and absorbing moisture. The problem is though, that this corrosion may also have affected the inaccessible inner feed wire.  It appears therefore that the break lies either on the bottom attachment (which would necessitate unwinding the entire coil) or it lies somewhere in the middle.

I've attached some pictures of the mechanism and my failed attempts to fix the coil. The dimensions of the coil are in the sketch in the last picture. You can see from these images that the dimensions of the coil are fairly precise as it just manages to squeeze in to the space. Since I don't have any idea what the original resistance was, I'm a little reluctant to attempt to wind the coil with fresh wire (which I could probably do using the seweing machine), since getting this wrong runs the risk of winding a coil that runs hot which might be a little exciting,  or one that has insufficient oomph to turn the motor.

I guess I could un-spool a meter of the wire and measure its gauge and resistance, then simply count the number of turns on the coil, but frankly that does sound like a lot of work. By the same token I'd rather get it working with the original mechanism than take the easy route and fit a quartz mech.

I've put the mechanism back together for the time being, to ensure that I don't loose anything,  while I ponder what I'm going to do next.

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Wrapping the enamel wire on to the new feed wire. The core copper wire is approximately 0.04 mm in diameter, or roughly half the thickness of an average human hair. 46 awg wire for comparison is 0.039mm in diameter, so I think it would be safe to conclude this is 46 awg. However your guess is as good as mine regarding the number of turns on that coil.

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Soldering the enamelled wire on to a replacement feed wire. 

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The rear of the front plate showing some of the gears.

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The failed repair re-fitted to show the clearances.

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Those two pins at the bottom are where the feed wires would attach with tabs and the mains cable would attach from the outside.

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The "bearing". I'm not sure what exactly this is made of, but it may be graphite. It is not an electrical contact and brush, as you might think. The only electrical part of the clock is the coil.  The motor needs to be spun in the correct direction following loss of power by a mechanical contrivance operated from the back of the case.

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The spring and bushing refitted. There is a similar bushing on the other end of the motor shaft which can be accessed using the wide brass grubscrew like widget on the rear of the case with the screw slot in it.

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That strange window lets you see if the motor is turning. Presumably this was used in the factory when testing.

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The "control panel". On the left the "kick start", followed by the adjuster for the hands and the "tick/silent" control.
The bushing on this side is behind that wide brass screw. It looks exactly like the other one.

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The mains wires were originally fed in to the lower left and right holes and clamped in place by grub screws accessed from the top two holes. There was no earth. That middle hole in the bottom was for a cable clamp screw. The top two holes are therefore where you poke your screwdriver into the live terminals when the power is connected if you want to entertain your audience by connecting yourself accidentally to 240 V AC and blowing yourself across the room, with much foul language. Elf and Safety 1950s style.

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The dimensions of the coil including the sizes of the hole for the iron core.


There is a corner missing from the plastic former. This may have broken off, or may perhaps have been  removed in the manufacturing process to ensure the coil is orientated correctly while assembling.

However since the motor is not self starting, and needs to be spun in the correct direction by that knob on the back every time the power is lost, I suspect the direction of the field is not important, so fitting the coil back to front probably wouldn't make any difference.

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Edited by AndyHull
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1 hour ago, AndyHull said:

A good question. It looks like trouble. ?

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I pulled the coil out and unpeeled the top layer to see whether I could simply resolder the feed wires to the coil, but as you can see, despite my best efforts this was not successful. Initially I was hopeful, as the original feed wire had broken from the tab due to corrosion caused by the ancient rubber insulation decomposing and absorbing moisture. The problem is though, that this corrosion may also have affected the inaccessible inner feed wire.  It appears therefore that the break lies either on the bottom attachment (which would necessitate unwinding the entire coil) or it lies somewhere in the middle.

I've attached some pictures of the mechanism and my failed attempts to fix the coil. The dimensions of the coil are in the sketch in the last picture. You can see from these images that the dimensions of the coil are fairly precise as it just manages to squeeze in to the space. Since I don't have any idea what the original resistance was, I'm a little reluctant to attempt to wind the coil with fresh wire (which I could probably do using the seweing machine), since getting this wrong runs the risk of winding a coil that runs hot which might be a little exciting,  or one that has insufficient oomph to turn the motor.

I guess I could un-spool a meter of the wire and measure its gauge and resistance, then simply count the number of turns on the coil, but frankly that does sound like a lot of work. By the same token I'd rather get it working with the original mechanism than take the easy route and fit a quartz mech.

I've put the mechanism back together for the time being, to ensure that I don't loose anything,  while I ponder what I'm going to do next.

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Wrapping the enamel wire on to the new feed wire

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Soldering the enamelled wire on to a replacement feed wire. 

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The rear of the front plate showing some of the gears.

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The failed repair re-fitted to show the clearances.

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Those two pins at the bottom are where the feed wires would attach with tabs and the mains cable would attach from the outside.

RIMG0292.thumb.JPG.901299aff5f93e8b73bb0910dbae0957.JPG

The "bearing". I'm not sure what exactly this is made of, but it may be graphite. It is not an electrical contact and brush, as you might think. The only electrical part of the clock is the coil.  The motor needs to be spun in the correct direction following loss of power by a mechanical contrivance operated from the back of the case.

RIMG0293.thumb.JPG.4d17ed00d0cbdda8ebd06dd3f02587fa.JPG

The spring and bushing refitted. There is a similar bushing on the other end of the motor shaft which can be accessed using the wide brass grubscrew like widget on the rear of the case with the screw slot in it.

RIMG0294.thumb.JPG.97c13c4b2a29f957e400e2b8f0c1e9a8.JPG

That strange window lets you see if the motor is turning. Presumably this was used in the factory when testing.

RIMG0295.thumb.JPG.0c4ddda9c4ab1355693844320aaf3112.JPG

The "control panel". On the left the "kick start", followed by the adjuster for the hands and the "tick/silent" control.
The bushing on this side is behind that wide brass screw. It looks exactly like the other one.

RIMG0296.thumb.JPG.2820eb5a6b6b846ce7f5f8d29063c970.JPG

The mains wires were originally fed in to the lower left and right holes and clamped in place by grub screws accessed from the top two holes. There was no earth. That middle hole in the bottom was for a cable clamp screw. The top two holes are therefore where you poke your screwdriver into the live terminals when the power is connected if you want to entertain your audience by connecting yourself accidentally to 240 V AC and blowing yourself across the room, with much foul language. Elf and Safety 1950s style.

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The dimensions of the coil including the sizes of the hole for the iron core.


There is a corner missing from the plastic former. This may have broken off, or may perhaps have been  removed in the manufacturing process to ensure the coil is orientated correctly while assembling.

However since the motor is not self starting, and needs to be spun in the correct direction by that knob on the back every time the power is lost, I suspect the direction of the field is not important, so fitting the coil back to front probably wouldn't make any difference.

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For a second or two I thought that you were going to be in luck Andy, as that looked identical to two of my unidentified coils, but on measuring one of them I find that it was just under a couple of millimetres bigger all round...?. If it is any use though, I measured the DC resistance of the coil and it was 6.1K ohms....

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56 minutes ago, JohnD said:

For a second or two I thought that you were going to be in luck Andy, as that looked identical to two of my unidentified coils, but on measuring one of them I find that it was just under a couple of millimetres bigger all round...?. If it is any use though, I measured the DC resistance of the coil and it was 6.1K ohms....

What are the dimensions of the ones you have?

If the iron core would fit through the hole, and the coil would squeeze between the ends of the plate, it might just work.


6.1K sounds about right, I was going to guess about 10K Ohms as coils on similar items (washing machine solenoid valves for example) draw about 24ma consuming about 5W roughly, which means the coil DC resistance is probably of the order of 10K.

 

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I might explore using one of these, if I have a scrap one lying about, either as is, or winding its turns on to the metamec former.

Edited by AndyHull
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2 hours ago, AndyHull said:

What are the dimensions of the ones you have?

If the iron core would fit through the hole, and the coil would squeeze between the ends of the plate, it might just work.


6.1K sounds about right, I was going to guess about 10K Ohms as coils on similar items (washing machine solenoid valves for example) draw about 24ma consuming about 5W roughly, which means the coil DC resistance is probably of the order of 10K.

 

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I might explore using one of these, if I have a scrap one lying about, either as is, or winding its turns on to the metamec former.

Hi Andy, overall length of the plastic former is 29.89mm, width 18mm x 19.6mm, with 17.5mm x 20mm over the thickest part of the coil windings. The rectangular slot through the former is nominally 8mm x 6.5mm

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3 minutes ago, JohnD said:

Hi Andy, overall length of the plastic former is 29.89mm, width 18mm x 19.6mm, with 17.5mm x 20mm over the thickest part of the coil windings. The rectangular slot through the former is nominally 8mm x 6.5mm

Let me check if that might just squeeze in to the space.

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1 hour ago, JohnD said:

Hi Andy, overall length of the plastic former is 29.89mm, width 18mm x 19.6mm, with 17.5mm x 20mm over the thickest part of the coil windings. The rectangular slot through the former is nominally 8mm x 6.5mm

Nope. Just too tight. The maximum that you could squeeze in is 28.34mm without filing the plates Close, but no cigar. ?


The other dimensions would not be a problem, but unless I could loose 1.5mm over the length, then it wouldn't work.

Here are a couple of additional pictures, showing the rest of the mech. and the coil gap.

 

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Edited by AndyHull
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1 minute ago, AndyHull said:
 

Nope. Just too tight. The maximum that you could squeeze in is 28.34mm without filing the plates Close, but no cigar. ?
The other dimensions would not be a problem, but unless I could loose 1.5mm over the length, then it wouldn't work.

 

Here are a couple of additional pictures, showing the rest of the mech. and the coil gap.

I'd be tempted to file the two sides of the top plate Andy........

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4 minutes ago, JohnD said:

I'd be tempted to file the two sides of the top plate Andy........

I'm tempted too, since I've nothing to loose. Let me sleep on it, I still haven't entirely given up on the idea of unwinding and re-winding the existing coil. I suspect that wont work, but I'll look at it tomorrow.

Would there be any possibility of filing some notches in the coil you have, or is there not enough "spare" plastic?

Edited by AndyHull
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The coil from @JohnD arrived in the post and set about modifying the metalwork to allow it to squeeze in place of the original. An hour or so of careful filing and Dremel work and it now fits like a glove.

I also took care to ensure that the new wiring is double insulated with a few patches of Kapton tape, a nylon bushing to replace one of the original brass nuts and some heat shrink sleeving ensuring that there is little chance of this ancient synchronous motor giving anyone a shock, even if the thing is dropped or the wires are pulled. I can't remember where I got the strange dayglo green cable ties from, but since nobody will see them, who cares about the colour.

It got a good clean while it was apart as unsurprisingly it was filthy. The worm gears both had a thick pasty gunge on them that probably started life as either grease or oil. All of the bras surfaces were sticky and nasty.  

Surprisingly it worked first time. After gingerly flicking the brass starter on the rear I let it run for about 10 minutes to see if it would overheat, but it was fine. No shocks, no smoke, no nasty electrical skid marks, no scary surprises.

I then stripped it all down again and gave everything one more clean to ensure that I had removed all of the dust and filings from the modification and rebuilt it again gave it a proper oiling. This time though when I flicked it into life, it started to click ominously.

My initial fear that the insulation might be breaking down and the coil arcing were unfunded, I has simply misaligned one of the gears and it was jumping.

With that remedied I buttoned it all back up again and it is now sitting in my explosion containment test stand (the fire hearth) and whirring away with a low but pleasing hum.

The patented tick also works. If you look carefully in the pictures of the mechanism you can see that it consists of a small steel blade that rides over some serrations on a brass wheel. Each time it falls off a tooth on the wheel, it clicks.

The teeth are arranged to it ticks about twice per second. I've switched this off for the time being so I can listen out for any other strange noises it might produce.

If testing goes well, then I'll case it back up and let it run, so I can see if it keeps good time.

After that comes the tricky bit. Making a replacement for that wooden decorative trim.

Here are some pictures of my test fitting of the coil, showing the modified brass top plate, the plastic spacer and some close up shots of the gearing.

 

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Edited by AndyHull
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watchweasol if you are into Light houses like me. One of my grandfathers ended up as a principal lighthouse keeper employed by trinity house, I have his record of the Lighthouses he was stationed at, he started in 1898. Look up Peter Helil on YouTube he has some wonderful videos on them plus a few travel videos about South America with his daughter. 

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If you are really in to light houses, you also have the option of staying at one (once the covid restrictions are lifted of course).


"Rua Reidh Lighthouse, near Gairloch in Wester Ross, stands at the entrance to Loch Ewe, at one of the most dramatic and remote locations on the north-west coast of Scotland, with breath-taking views across the Minch to the Isle of Skye, the Shiant Isles and the Outer Hebrides"

.. or of course there is the Scottish Museum of Lighthouses.

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I little bit  head scratching and a lot of whittling and fettling today, followed by a lot of sanding and no doubt a lot more head scratching when I try to match the colour and the look of the grain.

I was initially going to attack a piece of wood with a router bit, but the shape is a lot more organic than I could muster with any of the bits I had, so I decided to drill a hole and chip the rest away with a mitre saw and a fret saw.

I've wisely decided to perform this operation in the log shed, as it is producing a lot of sawdust. Some from the block but probably just as much from the head scratching. ?

 

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Edited by AndyHull
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Hi  Not a bad match Andy, once stained and polished who would know.

 

Hi Old Hippy  Lighthouses are very clever things especially the mechanism which drove the prismatic system. the old ones were weight driven like a clock with a Governer  to control the speed. Apparently each light house had a different flash pattern de noting where they were sited so Mariners could check their position.

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Yes I know quite a lot about them. The weight for the clock would be housed in a tube which would be top to bottom in the center of the Lighthouse, most needed winding every 30 hours or once a day. The speed of the light because each one was different would be known to the captain. My grandfather was principal keeper on the well known Eddistone Lighthouse from 1901 to 1907. 

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4 hours ago, oldhippy said:

Yes I know quite a lot about them. The weight for the clock would be housed in a tube which would be top to bottom in the center of the Lighthouse, most needed winding every 30 hours or once a day. The speed of the light because each one was different would be known to the captain. My grandfather was principal keeper on the well known Eddistone Lighthouse from 1901 to 1907. 

It could be quite a hazardous occupation, not just because of the remoteness and the weather, but in the case of a lot of early light houses, mercury was present in relatively large quantities. The huge glass lenses were floated on circular trough of mercury to allow it to rotate on a frictionless mercury bearing. Bear in mind that the lens might weigh something of the order of a couple of tons. One of the lighthouse keepers tasks was to ensure that the mercury was free from contaminants, so periodically some of the mercury would be decanted off and strained through a cloth filter to remove the accumulated detritus. I'm pretty sure the 'elf 'n safety gnomes would have something to say about that these days. 

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I'm indulging in something a lot less hazardous, namely trying to colour match the original stain with a wash of various acrylics.

Once I'm happy with the result, I'll apply a couple of coats of agate shellac button polish and try to make it apprear as close to the original as I can.

Edited by AndyHull
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With just one coat of shellac, its still looking a little patchy and a shade or two too light, but the general colour isn't bad.

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I'll let this finish set up, and apply a few more coats tomorrow and see if it blends down to something close enough to the original for me to call it finished.

If not, then I'll sand it down some and push the base colour a little darker.

The good thing about the colour is its pretty dark, so it should be relatively easy to match. Pushing things a little darker is always a lot easier than trying to go the other way.

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Edited by AndyHull
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If any body is interested in monitoring the grid frequency to get an idea of how accurate (over the long term) these synchronous clocks are, you can watch the deviation in real time and view graphs of long term accuracy here.

https://gridwatch.co.uk/frequency?old=

image.png.d5839063347388e76488816d0b1adb73.png

Currently (pun intended) we are looking at an average of around ten parts per million, which compares pretty favourably with a typical watch quartz crystal figure of around six parts per million.

Not bad for a piece of mass produced 1950s technology, although you have to bear in mind that in the 1950s the grid frequency wasn't nearly as well regulated, but none the less these clocks were, and still are pretty good time keepers. 

Edited by AndyHull
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19 minutes ago, AndyHull said:

If any body is interested in monitoring the grid frequency to get an idea of how accurate (over the long term) these synchronous clocks are, you can watch the deviation in real time and view graphs of long term accuracy here.

https://gridwatch.co.uk/frequency?old=

image.png.d5839063347388e76488816d0b1adb73.png

Currently (pun intended) we are looking at an average of around ten parts per million, which compares pretty favourably with a typical watch quartz crystal figure of around six parts per million.

Not bad for a piece of mass produced 1950s technology, although you have to bear in mind that in the 1950s the grid frequency wasn't nearly as well regulated, but none the less these clocks were, and still are pretty good time keepers. 

Don't know about '1950's technology' Andy. I have five that were made before 1935, so really from an age when Mallard was setting the world speed record for a steam train and Frank Whittle was still in the theory stage of Jet engine development...?

 A bit more 1935 technology HERE.........

Edited by JohnD
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6 minutes ago, JohnD said:

Don't know about '1950's technology' Andy. I have five that were made before 1935, so really from an age when Mallard was setting the world speed record for a steam train and Frank Whittle was still in the theory stage of Jet engine development...?

The earliest mine could be is around 1947, since that was when Metamec was founded, but it is more likely that it is from the early 1950s.

I'd love to see a few pictures of the 1930s models. Who made them and do they work?

Electric clocks have been around a lot longer even than the 1930s, but the first synchronous mains clocks date from around then.

https://en.wikipedia.org/wiki/Electric_clock

Many years ago (back in the early eighties) an Engineering firm customer of ours in Glasgow was closing down, and moving out of an old Victorian building. Bolted to the wall in their hallway was a rather ancient but quite attractive electro-mechanical long case clock. It was way too big for me to carry, and I had no way of removing it from the wall. Nobody else seemed interested in it.

I often wondered what became of it. It didn't work, and given that the building was scheduled to be demolished, I have a horrible feeling it ended up in a skip.

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