Metamec Electric Clock Repair

[Mike Phelan]

... or a stiff nailbrush. FWIW there shouldn't be any sort of lubricant on the wheel teeth, but anything's possible!

[paulsherwin]

If untouched since manufacture the wheels should be dry, but these clocks are over 50 years old and there's every chance it has been got at at some stage. Modern mineral oil lubricants are usually pretty harmless in these mechanisms even if applied incorrectly, but years ago people would try to lubricate clocks with castor oil based household oil or even cooking oil like olive oil.

WD40 will cause these symptoms if somebody sprays it everywhere and doesn't clean it off. WD40 will remove crud effectively but will dry to a viscous oil deposit which will eventually form a gungey mess. If you use WD40, always remove it afterwards with a rag, and relubricate contaminated surfaces with clock oil, machine oil or sewing machine oil.

[Jimboger]

Hi all,

I have now taken the clock apart and I am cleaning the parts prior to reassembly and oiling.

I am just wondering how to go about cleaning the metal parts of the clock that remain attached to the main body (apologies if I am using incorrect terminology). As you can see from the pictures, they are quite dirty. Can I just attack with a cotton bud and isopropyl making sure not to leave any threads in the mechanism? Could I feasibly dip the back plate (the smaller one with just one piece of mechanism attached)?

Many thanks again, Jim

[Mike Phelan]

Hi Jim,

Give it all (except the coil) a scrub with a stiff brush. IPA is fine.
The plate with the worm on it is better if the arbor with the worm can be removed but if that's difficult, leave it on and just oil its pivots.

Pivot holes in the plates: after cleaning the plates, something like a cocktail stick can be used to clean the holes.

[Jimboger]

Good news gentlemen...mostly at least.

I have dismantled, thoroughly cleaned (wheels), reassembled and oiled (pivots) the clock and it is working again. Thanks to all on here for helping me to get this far.

Unfortunately, there is a problem.

I have run the clock for about 6 hours now and it is running slow (about 3 mins per hour on average).

The problem would seem to be related to a visible issue with the second hand. Though it normally moves smoothly, during one in every two revolutions (minutes), the second hand jumps over a second, continues for two seconds and then halts for four seconds before continuing on its merry way.

Here is a video of the problem: https://vimeo.com/164611520

Any suggestions? I hope this is not fatal for the old clock - we have come a long way!

Jim

[mark_in_manc]

I guess it might make sense to run it with the back off, and see if you can see what gear is jumping out, and back in, to mesh. Since the problem is apparent at the 'high speed' (seconds) end of the clock, I'd check the mesh of the worm wheel and the pinion on which it acts; there have been a few of these on here (mine included) where this has been problematic.

[TonyDuell]

Another guess :

Is this a self-starting movement (the motor runs when you plug it in, rather than you having to flip a starting lever)?. If so, is something gummed up there with old grease? It is possible it is engaging when it shouldn't, stopping the motor and giving it a kick.

[Mike Phelan]

To prove whether it's Mark or Tony's suggestions, see if the rotor is stopping or not.
It is a self starter.

The arbor with the worm on it often has eccentric bushes and if not adjusted correctly can make it come out of mesh (#26) or make it too tight and stop the rotor (#27).

[Jimboger]

Thanks both,

Tony - the movement is self starting but I have just cleaned all of the components so I don't think they can be gummed up?

Mark - do you mean that one of the gears (most likely worm wheel) is probably broken/defective? I guess that if this is the problem, repair is not possible?

[Jimboger]

Originally Posted by Mike Phelan

To prove whether it's Mark or Tony's suggestions, see if the rotor is stopping or not.
It is a self starter.

The arbor with the worm on it often has eccentric bushes and if not adjusted correctly can make it come out of mesh (#26) or make it too tight and stop the rotor (#27).

Mike - thanks very much. Apologies for posing some very basic questions but I am getting a bit lost in terminology.

What is "the rotor"? How will I recognise it visually?

As regards the "arbor" and the "eccentric bushes", do you mean that I need to adjust the brackets that hold the worm onto the clock plate?

See #23 for an image of the worm wheel.

[Mike Phelan]

Jim,

The rotor is the part that goes between the two parts of the coil in your first pic. It's not shown in your pic so presumably you had removed it.

Yes, the brackets.

If any wheels are actually broken they can be replaced but we'll cross that one if / when we come to it.

[Jimboger]

Great - thanks Mike - I will open it up again and report back later.

[mark_in_manc]

Originally Posted by Jimboger

Mark - do you mean that one of the gears (most likely worm wheel) is probably broken/defective? I guess that if this is the problem, repair is not possible?

Not quite - if the worm wheel comes intermittently out of mesh with the pinions (small gear wheels) with which it engages (driven by one at one end, driving a larger one by the worm scroll) then it would do the kind of thing you describe. Others have thought the wheels / worm were worn out at this point, but it is possible that the holes in those brass tabs which take the pins which hold the worm in place - shown in your pic - have gone oval and allowed everything to move around a bit.

I put some pics in this thread when I fixed mine, which show what I mean.

https://www.vintage-radio.net/forum/...d.php?p=721068

Not to steer you the wrong way - there's always a tendency to deomonstrate one's own (actually rather bodgy) fix to a problem which the next guy doesn't have!

That clip on the worm-wheel is the thing which automatically stops the clock if it starts off going backwards when power is frist applied (a 50% probability) and gives it another chance to start the right way. It seems odd that this would happen regularly when the clock is in motion, but it would make the hands pause a short while.

[Jimboger]

So...I have reopened the clock, attempted to adjust the brackets holding the worm in place, taken apart and cleaned the potentially offending parts and re-oiled after reassembly. Unfortunately, the problem persists.

Here is a video illustrating the stall from inside the clock: https://vimeo.com/164695593

Perhaps it is wear to the wheel that meshes onto the worm that is causing the problem - I don't think I recognised how worn it was when I originally took the clock apart. As it happens, it is the same worn wheel shown here in post #1 https://www.vintage-radio.net/forum/...d.php?t=111353

Reading further through that discussion, I note that there's a fair bit of play in the holes (which are oval rather than round) for the pinion for my clock's worm. Perhaps that is causing the misalignment? Starting to think that this fix may be out of my league.

Any advice gratefully received as ever.

Jim

[Jimboger]

Sorry Mark - just missed your post but I think you may have identified my problem. Is the fix that you did something that a novice could attempt? Do you need angle grinders/welders or such? Jim

[mark_in_manc]

Wow, if you can use an angle grinder and welder to fabricate parts as small as these, my hat's off to you

If those holes in the tabs holding the worm are oval, then one might imagine that the worn side would be that _away_ from the gear you are trying to mesh with. The forces created by the meshing gears push the worm away, and its (quite fast, for a clock) rotation wears away at what we might call the _back_ of that hole, or to be more fancy, bearing.

That means the 'front' of that hole closest to the gear we are trying to engage with should be unworn - that is, still in the right place. So to find out if the wear in the clock wheels (which can be seen in your last video - they look a bit chewy!) can be lived with, you can try and run it whilst pushing the worm bearings to the front of their bearings - the unworn location. Try this with the end of a small screwdriver and see if it works.

If it does, you just need something to replace the screwdriver, since your fingers will start to ache after a few hours. Mike (who knows about clocks, unlike me) would probably suggest enlarging the hole and making a new bearing insert to take up the space between shaft and hole. A small lathe would be useful here, though (Mike?) these things might be available to buy with an ID (inner diameter - hole!) to suit your worm shaft, and an OD (outer diameter) to suit the newly enlarged hole in your bent plate.

For me, I screwed a small piece of brass onto each bent bracket (I did both ends), to force the worm shaft to the correct (frontal) location in its bearing. That's what my pictures are about in the thread I linked to. The clock has run fine 24/7 since that thread, whenever it was. If you were very careful indeed, even superglue might work to hold this bodge on, though I tapped for a very small bolt. Mike will probably protest that you (and I, for that matter) stand a good chance of emptying the tube of superglue into the clockwork, and that such an approach courts total disaster. Since the pins pull out of the end of the worm, one might even take the worm out and solder small plates on to ensure its correct location on re-assembly.

Any use?

[andrewn]

My clock is still running well more than a year since repairing it. I definitely encourage you to try and repair it. I managed to improve the chewed gears by carefully scraping with a scalpel blade to sharpen the edges.
Andrew.

[emeritus]

This is interesting. When I was a student, I had an old Metamec alarm clock that exhibited the same symptoms, the second hand periodically going into reverse briefly. I found it would run OK on its back, but it would then move about because it then rested on the hour setting knob, which rotated when the clock was running. I solved this by making a shallow frame from cardboard and sticking it on the back of the clock to keep the knob out of contact with the table. It ran perfectly then, possibly due to gravity moving the gears into positions where their unworn portions meshed. Being operated on its back was no problem to me then because I only needed it to get me up in the morning: unlike my clockwork alarm clock, it would buzz for over an hour if you did not turn it off. Possibly another project for the "round tuit" pile, as it is still in the loft somewhere.

[AC/HL]

More of a "down from it" then!

[Mike Phelan]

Originally Posted by mark_in_manc

Wow, if you can use an angle grinder and welder to fabricate parts as small as these, my hat's off to you

At least you didn't use a sledge hammer, Jim!

A small lathe would be useful here, though (Mike?) these things might be available to buy with an ID (inner diameter - hole!) to suit your worm shaft, and an OD (outer diameter) to suit the newly enlarged hole in your bent plate.

It might be worth getting a bush and a broach for the job, but otherwise Mark's solution above is fine.
I did a clock repair in Germany for a friend and found a local clock repair shop helpful and could get me the necessary parts easily (that was in Wangen).