Smiths Sectric Delhi, not working

[owenyzone]

Hello all. This is my first post to this forum so please bear with me if I'm short on information or etiquette.

I have just bought a Smiths electric clock, says Sectric on the front and there's a Delhi sticker on the clock motor casing. Brit Pat.No.744204. Self Starting movement.

The problem is, it's not starting. Inside the casing there is a square clockwork box about 50mm square with the coil/motor above. In between there is a thin flywheel which oscillates back and forth when the power is switched on. It should actually be spinning I would guess, but it is just twitching back and forth as I say. I'm hoping someone will already have guessed what the problem is, if it's something common. I'm quite good mechanically but have never toyed with a clock before.

There was no cable on the clock and I have placed the live wire nearest the top ( the coil end ) with the neutral beneath.

I could take pictures and post them if that would help. If anyone has any suggestions I would be very pleased to hear them. I think the clock has possibly been on a wall in a damp place for a long time, as there is a patina of rust on the face - which is very beautiful.

[Nickthedentist]

Hello and welcome.

Does it work if you spin the rotor by hand using something insulated, e.g. a matchstick?

Do bear in mind that these clocks aren't renowned for their insulation, so assume the movement could potentially be live. Feeding it via an RCD is a very good idea.

BTW, it makes no difference which way round L & N are.

Could you post a picture so we can identify which movement is fitted. I suspect it's the Bijou, which looks a bit like this: http://www.linesi.co.uk/Resources/bijourotorrear.jpeg

N.

[owenyzone]

Hi Nick, thanks for the quick reply. I have revolved the rotor with a ruler and it might spin once but starts to twitch again. I have taken a poor quality picture with my phone but it will let you see that it's not the bijou model you have attached the link to.

Regards

[Mike Phelan]

A clean and lubricate required, methinks.

[owenyzone]

Would it need to be stripped down for this, and what type of cleaner and lubricant would you recommend?
Also do you mean just the clockwork part and not the motor? Any idea what this movement is called?

Thanks, Owen.

[Mike Phelan]

Owen,

Yes, a complete strip down but I'd be inclined to leave the motor as is for now as it seems to run.

To clean, petrol, white spirit or IPA then dry thoroughly.

Lubricant, clock oil (it doesn't creep or flow away from where you want it).

[paulsherwin]

It does depend how seriously you want to take this and what your level of expertise is. If you just want to get it working and aren't confident about fully dismantling, you can apply a tiny drop of sewing machine oil or even 3-in-one to each of the wheel shaft bearings, and clean off any obvious crud on the wheels with a soft oily rag. Wipe away any surplus oil.

This is much less satisfactory than the full clean and relube recommended by Mike but it won't actually do any permanent harm and is better than ending up with a table top covered with bits of clock and no idea how to put them back together.

[owenyzone]

I've cleaned the gears with lighter fuel and removed anything I could see and lo and behold, it lives! There is a slight mechanical noise when the clock is upright at the 12 o'clock position which goes away if you revolve the clock slightly, to the 1 o'clock upward position for example. I'm hoping this will go away after a while. I still have to get some lubricant for the shafts so maybe that will help. I baulked at the idea of removing the upper surface of the movement casing, as it looked like a mess of gears and shafts would be the result. Do any of you know if they tend to remain reasonably in position so that the upper surface can be replaced after cleaning ops?

Anyway, things are looking good so many thanks for your help.

Owen.

[Hampus]

Hi Owen.

As Paul says, you can oil it with the movement still together, this is not ideal but will probably work quite well. Most clocks of these kind ran well for decades without any maintenance at all.

If you want to try to do it the "proper" way I recommend you to take many photos, I always do that when dismantling such mechanics, it have saved me several times!

If you have not dismantled a clock before I understand that it feels a bit intimidating, but you seem to enough have mechanical skills to do it if you give it a try Do not hope for the wheels to stay in place, in fact you should remove them all to clean the ends of the shafts and the insides of the bearings.

If you do fail to get it together I have a movement of the exact same kind that I can look at to help you.

[Nickthedentist]

I think this may be the movement with lots of plastic bits which become brittle with age, so treat it gently.

http://www.electric-clocks.co.uk/SMI...ck%20guide.htm

[Hampus]

Nick, the plates are made of something like paxolin with brass bushes and the wheels are metal but I read somewhere that the next generation of movement has plastic parts.

Hampus

[owenyzone]

From the pictures, the movement is the QEMG from 1957. I dont see any plastic in the movement at all.
The clock is running and keeping good time, but the noise comes and goes. Could this be because it needs lubrication? Sometimes quite loud, other times silent.

There is a part of the mechanism which comprises a spiral screw with a cog meshing with this, like an archimedes screw driving a cog. Sorry I dont know what this type of gear is actually called. Anyway the metal surfaces are sliding over each other to an extent. I read on the forum that the cogs dont need lubrication because they dont move over each other, but in this case I think they do. Would this part then require lubrication?

Thanks again all.

[julie_m]

That sounds like a worm drive; which is, effectively, a gear wheel with only one tooth (since the gear wheel meshing with it advances only one tooth for each turn of the worm gear) and thus good for achieving large reduction ratios. Due to the large contact area, efficiency is poor; but clock hands don't require much effort to move them anyway, so it is not a problem in practice, even considering the low stall torque of the synchronous motor.

A plastic worm gear (usually nylon or acetal) has inherently low friction and should not require any lubrication (in any case, oil would react with the plastic and degrade it over time); but a metal one may benefit from a very, very tiny amount of grease. You must not use too much, or else dust will stick to it and eventually jam it up altogether