Rempe self-winding - questions on electrics

Discussion in 'Electric Horology' started by flynnr2, Aug 12, 2018.

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  1. flynnr2

    flynnr2 New Member

    Sep 10, 2016
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    All,

    I have a Rempe self-winding clock, the mechanism itself is running fine but have a few of questions on the electrics.

    1) Arcing over the years appears to have burned a hole in one of the contacts which completes the circuit to tension the spring (see attached photo) - any recommendations on how to best remediate that?
    IMG_0089.JPG

    2) The electrics in the Rempe does not have a resistor to cope with flyback current and arcing (hence the problem above presumably). It seems sensible to add one as it can be done in a transparent and easily reversible way. I've read the various threads on resistors, diodes, & varistors but have a few additional questions:

    a) The electrics engage every 6 - 7 minutes, so that is approximately 81,000 times per year. Is that a concern for varistors (there were some allusions to their performance degrading over many cycles)?

    b) I am not sure how to appropriately size either a diode or a varistor and would appreciate any and all help. The relevant inputs I believe are
    - 0.6 ohm resistance across the coil
    - 3.3 volt battery supply
    Which gives 5.5 amps & 18.15 watts to contend with.

    Cheers in advance,

    Rick
     
  2. etmb61

    etmb61 Registered User
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    I'm not familiar with your clock, but typically there is a contact button of some sort riveted in the end if the leaf spring for the actual circuit. That looks like too perfect a hole for arcing.

    300px-Mechanical_relay.jpg

    Just saying.

    Eric
     
  3. sophiebear0_0

    sophiebear0_0 Registered User

    Nov 5, 2012
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    Rick

    I'm not familiar with the Rempe. Does it work on a similar principle to the Barr/Poole clock ? These clocks use a Hipp Toggle to energise an electromagnet to lift a weight. These typically "wind" after 30-40 seconds. These use silver buttons to act as electrical contacts.

    I am not sure there is a true consensus on the best method for arc suppression on electromagnetic clocks. You often see diodes fitted in Eureka clock - though these are obviously not part of the original design.

    ATO clcoks (the model without self-wiping contacts) actually used a resistor as part of the original design. The shunt resistor was typically 5000 ohm with a coil resistance of 1200 ohms.

    There is an interesting article by Rob Elliot which discusses the pro's and cons of various repression methods. He recommends a resistor in the order of 10X the coild resistance (Spark Quench)

    I would be interested in seeing some more details/photos of the Rempe clock once you get it sorted.

    Best regards,

    Peter
     
  4. flynnr2

    flynnr2 New Member

    Sep 10, 2016
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    I have never seen one of these movement, nor is there evidence of a rivet which has fallen out rattling around in the case, so open to suggestions - certainly the perfect circle could have held some sort of riveted contact at some point.

    A more detailed picture of the contacts
    - the tensioned spring causes the plate on top of the coils to pivot up
    - which ultimately releases the spring steel(?) on the left
    - to connect with the brass rod on the right
    completing the circuit

    IMG_0085.JPG
     
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  5. sophiebear0_0

    sophiebear0_0 Registered User

    Nov 5, 2012
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    Rick

    There is a brief description and a few photos of the Rempe on the ClockDoc website (Album: Rempe Manufacturing Company)

    I've also attached a photo from the web which shows a close-up of the solenoid. Sadly not great quality.

    Regards,

    Peter

    Rempe.jpg
     
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  6. flynnr2

    flynnr2 New Member

    Sep 10, 2016
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    Another photo found online (auction site) - difficult to tell precisely, but does look like a brass contact rivet in the contact on the coil side.
    17666_D.jpg
     
  7. Berry Greene

    Berry Greene Registered User

    Oct 2, 2017
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    What a coincidence! Yesterday I bought an electrified wind to a balance regulated clock in a charity shop. It was filthy inside & out. I have given t a good clean and the movement is working when the spring is powered.

    I don't want to teach my grandmother how to suck eggs here but I will just say there is a miniature electric motor attached to the Swiss 7 jewelled mechanical movement that is called each hour to re-wind the remontoire (is it?) that powers the clockwork. There is no sign of any spark suppression.

    This is a DC circuit until the switch opens or closes. The motor is inductive and therefore we have high inrush currents and BEMF to contend with. This causes higher voltages and instant currents that can go way beyond the quiescent running condition. AC components both remove & deposit material from the contacts but the DC is all one way which gradually erodes the contact points - just like an old fashioned car with coil & points. A capacitor fitted across the contacts at least provides an ac by-pass path.

    A diode can also be used as a "catcher" to restrict the extent of the voltage peaks. It might need to be a Zener diode or better still a form of Varistor. I don't know of any in the low voltage range. Anybody? I do know they aren't particularly reliable but then again they are usually operating with much higher voltages (in my experience).

    This is an issue which I had not considered until I came to this thread of the Forum. I was just interested to see if anyone else had posted anything on this kind of electrification. I also wondered what sort of date you might put on a clock like this? The case is made from heavy gauge real brass IMHO. It had been lacquered although I had to remove it to stand any chance of cleaning it up. I will probably wax it rather than re-varnish it.

    I have taken a few pictures. I'll post them when they have been downsized to a suitable size for transmission.

    Best regards, BerryG
     
  8. Berry Greene

    Berry Greene Registered User

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    Fr mvmnt Rear motor Reg adj Motor o/p drive
    Electric mantle clock - (7).jpg Electric mantle clock motor-2.jpg

    Cam switch LH - Mainspring wind gear Motor at rear mvmnt front
    Electric mantle clock mvmnt-3.jpg Electric mantle clock mvmnt-4.jpg

    Assembled & cleaned Rear with PP3 battery
    Electric mantle clock - (11).jpg Electric mantle clock - (10).jpg

    Dial cleaned up
    Electric mantle clock dial-1.jpg

    I have one concerning question:- When battery is tired the motor stalls with lowered current running until battery finally discharges. This means heating of motor coils. I wonder - is this injurious? Would a re-chargeable be better choice where the voltage drops off a cliff? Just a thought. Anybody know what was recommended here?
    Rgds, BerryG
     
  9. sophiebear0_0

    sophiebear0_0 Registered User

    Nov 5, 2012
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    Berry

    Thanks for posting the photographs.

    Looks to be an interesting clock - and a good spot on your behalf.

    The issue of shorting the coil on a low battery is interesting. I don't know the answer. I do however own a number of battery driven remontoire clocks (Reform-type) that potentially suffer from the same potential issue. Low battery power can be insufficient to operate the kick wind and it ends up with current passing through the solenoid, potentially causing local heating as the battery drains. In practice I have not suffered any incidents, and my main line of defence is to change the batteries on a regular interval.

    I am not convinced that using a rechargeable battery would make a great deal of difference in practice. Although as you say, the coil would experience less sustained heat as the power dissipates more rapidly.

    My guess on age of your clock would be 1970-1980. There is an very good article by David Read (AHS 2011) entitled "The Electric Remontore". He mentions that the electric rewind was usurped by direct balance impulse / quartz around 70 years after the first introduction of the remontoire movement. The early ones were introduced around the beginning of the 20th century.

    Sorry I can't shed any light on your clock. I look forward to hearing from others who may have something more detailed to offer.

    Regards,

    Peter
     
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  10. Berry Greene

    Berry Greene Registered User

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    Wow Peter!
    Thanks for that response - very uplifting.
    And the article you quoted is really a treasure to supplement the clock.

    It's going well BTW - some slight regulation to the rate needed perhaps. Gains marginally.
    When I have a better idea of what to expect by way of battery life I will post again to complete the picture. My Ni-Me-Hy PP3 has a 200mAh capacity. It doesn't sound very much does it? I can tell you that the motor takes 35mA (peak) and lets say it runs for 2 secs every hour (or 48 seconds a day). That's somewhat less than 6 hours of winding. The intermittent use plays to our advantage here giving the battery recovery time.
    From that I get an expectation of 428 days. {Subject to verification and actual experience}.
    I did read a "400 day" description of a similar clock. Seeing the 1970 time-frame for the production it seems likely it would seek to compete with the torsion "anniversary" variety I suppose.
    Hey! How about a solar panel to boost the battery? Perpetual motion doth approach us!
    Thanks again for your interest.
    Best regards, BerryG
     
  11. sophiebear0_0

    sophiebear0_0 Registered User

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    #11 sophiebear0_0, Aug 24, 2018
    Last edited: Aug 24, 2018
    Berry

    By way of comparison, I have just checked the resistance of the solenoid on the Reform. I get a value of around 10 Ohms, although I'm not very confident on my meter at such low resistances. The clock uses a 4.5 volt supply, so at 10 ohms would be drawing around 500 mA. So the power would be around 2 watts, compared with around 0.3-0.4 watts for your clock. The Reform contacts trigger about every 7 minutes, but the power-on time is obviously very low.

    You can buy high capacity pp3 batteries which are around 800 mAh.That said, its probably better and cheaper to stick with the conventional power battery and change it more frequently.

    Regards,

    Peter
     
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  12. Berry Greene

    Berry Greene Registered User

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    Peter that doesn't sound right to me. Even a short blip of such current from a PP3 - nope unlikely. A rechargeable will do it mind but it sounds wrong.
    There's one thing to remember here. The DC resistance is not the same as the ac ohms (more properly called Z for impedance). Coils revolving in magnets produce a large BEMF (back voltage) because such a motor is in fact also a dynamo. So the inrush current might be very high but it is opposed as soon as the motion starts and falls back very quickly. Strange as I suppose that sounds!
    Another allied issue. If you were measuring the ac current into the motor (some meters will do but...…. See below) it would rise with the load. The more work you ask of it the higher the current (Watts) will be.

    NOTE: The meter measures the current by actually measuring the voltage drop across a shunt resistor. This is in series with the supply and will reduce the applied voltage. By how much depends on the shunt value and the actual current. I hope that is making sense. The problem is that the full voltage of the battery won't be applied. Yes you can get a very good idea - so longs as the motor still runs BUT it will have an error. The best multi-meters have very low resistance shunts for this reason.

    Regards
    BerryG
     
  13. sophiebear0_0

    sophiebear0_0 Registered User

    Nov 5, 2012
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    Berry

    You may well be right. As I say, I do have doubts about my cheap multimeter ! I have only tried measuring the resistance of the coil, rather than actually the current through the circuit when powered.

    The Reform clock just operates a solenoid which kick winds a small mainspring. You can definitely see sparking as the spring winds down and the contacts approach closure. If the contact gap setting is not correct, it is possible to get sustained sparking. The clock then sounds like a buzzer.

    Unfortunately I am not aware of any detailed technical specifications for the Reform type movements. Great if anyone else can chip in with some details. My experience is that the Reform movements are not very forgiving when the battery voltage falls below the design voltage of 4.5 volts.

    It will be interesting to hear if anyone else on The Forum has come across your clock. I've done a quick internet search - but can't find anything.

    Thanks again for sharing the info. Very interesting.

    Best regards,

    Peter
     
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  14. Berry Greene

    Berry Greene Registered User

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    #14 Berry Greene, Aug 25, 2018
    Last edited: Aug 25, 2018
    Erratum. Slight error in my last post which I am now unable to edit. In the paragraph beginning "Another allied issue" I have written "ac" when of course I really mean "DC" - even though it may not be steady current starting with a "spurt" or inrush current to get the motor started. In this respect BTW a "motor" includes a solenoid. In fact sometimes certain types of solenoid are actually called a "linear motor."
    Another useful feature some multi-meters have is a "MAX" or peak lock. This freezes the maximum reading seen since you press the button. I have used it with great success when measuring the starting current of my car battery. For that though you need a clamp type device which is hooked around the battery cable. It converts huge amps to mV and you use the multi-meter to read its output.
    Hey I am way off topic. I think a fine is in order! Sorry about that. Yes of course I will pay up. :<))
    Regards, BerryG
    P.S. I am loving that link you posted on electric remontoire clocks. Great stuff.
     
  15. Berry Greene

    Berry Greene Registered User

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    Peter. I don't like to hear of the sparking (arcing). As posted previously it will erode the material at the points. I think I would try the effect first of fitting a capacitor across those points to subdue it. I can't think it would alter the action but you never can tell! Start with a 0.1uF or perhaps a 0.25uF. It needs to have an appropriate working voltage rating but I doubt any would be too low. Here's the real deal but a bit expensive:
    https://uk.farnell.com/cde-mallory/254m06qd150/arc-suppression-snubber-network/dp/2409734
    Here is the data sheet for it:-
    www.farnell.com/datasheets/1725110.pdf?_ga=2.228044125.1300235979.1535183583-2036890564.1535183583
    Or on Amazon:- https://www.amazon.co.uk/Bosch-Suppression-Capacitor-0-25uf/dp/B005LMB074/ref=sr_1_1?ie=UTF8&qid=1535183888&sr=8-1&keywords=0.25uf+capacitor

    Gosh these do seem expensive! Am I really that old - that far adrift? These used to cost pennies!
    Here you are this is a better price. Just as good It's just an ordinary run of the mill capacitor:-
    0.22uf capacitor | eBay (0.22uF is a newer "preferred" value)
    Regards, BerryG.
     
  16. sophiebear0_0

    sophiebear0_0 Registered User

    Nov 5, 2012
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    Thanks Berry

    So that has brought us back nicely to the original topic of spark suppression. Thanks for taking the time to pot the links.

    The article I cited in my earlier post by Rod Elliot seems to suggest that a resistor is a preferred option. Certainly that was the approach used by ATO. Interestingly I do own a Japy electrique clock which has a very similar movement to the Reform (albeit a little more bulky). This does have a parallel resistor as part of the original design. I also seem to recollect that the Kienzle 606 has a resistor as part of the base design (though I may be wrong !!). Both these movements work of 1.5 volts.

    One thing I have found with the Reform movement is that the knurled nut used for setting the contacts gap is prone to moving with time. Perhaps this is not too surprising because the kick wind action is quite vigorous as the contacts close. I have found that a dab of locktite works well to prevent the nut moving.

    My experience is that the Reform-type movements, once set up, do work pretty well and don't require much ongoing attention. They are however pretty noisy as the solenoid activates every 7-8 minutes.

    Thanks again for sharing your knowledge.

    Best regards,

    Peter
     
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  17. Berry Greene

    Berry Greene Registered User

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    Oh it's a pleasure to exchange Peter.

    I'm a hobbyist clock collector. I've had a largely unfulfilled interest since my childhood. I did electronics for a living and I am supposed to know about it! The use of a resistor to quench the spark is odd as no matter how you connect it, and how small its value, it represents wasted power. A battery system working on 1.5 precious volts, can't afford to waste anything. IMO of course!

    The frequency of the remontoire re-charge seems to vary wildly. You mention 7-8 minutes, and John Harrison's was every 30secs. The one I have here "whirrs" every …..? ….? Well I am still trying to assess that. It's not altogether consistent, varying between 45 & 80 mins in the table I have so far assembled.

    I love this unexpected variation. It's so nice to have the electric connection accepted by horology. There is understandable resentment towards the quartz because it has buried much of what was once a proud & clever industry.

    Nevertheless, I particularly appreciate the step in accuracy afforded to the mechanical escapements of yesteryear (pendulum & balance wheel) by electrification. The even impulse a remontoire gives - the consistency of a magnetic impulse to a pendulum or balance lets me see them as they could be. Fine measurers of passing time.

    My motorised remontoire isn't loud but it catches you unaware. A bit like a bee or wasp it startles rather than frightens. The burst is surely no longer than 1.5 secs??

    I will be looking into other electrified clocks now. Thanks so much for the encouragement.
    Regards, BerryG
     
  18. Berry Greene

    Berry Greene Registered User

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    I have been reading through the various links and previous posts on the electric remontoire and general "electrification" rather than electronic devices. That is something I should have done before jumping in here with my ideas of spark suppression. However, these were not wrong - merely incomplete.

    This link Spark Quench in particular, pretty nearly covers it all. I have no issues with a word of what is said except the drawings (reproduced below). The capacitor solution is, for my money, shown incorrectly. It probably crept in from when modifying the same drawing because this chap obviously knows what he is talking about.

    spark-f5.gif

    I would want the capacitor (0.1 - 0.25uF) to be placed across the switch contacts. This provides an ac by-pass {LLH dwng}. I like the Zener diode solution too - it is even better, - but again I'd put them across the contacts. to limit excesses. Surely it is the energy that appears there that we need to snub out and not that within the solenoid.

    A capacitor across the solenoid will just lower the natural resonance frequency. It might affect the ability of the energy to jump the switch gap but I doubt it. It might also reduce the energy available to do the "work". Anything across the coil will absorb its energy and its ability to do its job.

    Here is purpose made device:- 1N6276 datasheet & applicatoin notes - Datasheet Archive It is rated at 16V. That would subdue the arc.
    1N6276 Datasheet PDF - Datasheet4U.com

    This brings us to the best electronic solution which is a transistor switch. Once under consideration it is but a short step to the complete replacement of the contacts with a magnet and Hall effect transistor. However I completely understand those who would say they need to keep more of the originality. You just want to extend the life of those contacts!

    The ideal transistor switch would have NO physical contacts. A magnetic operation would obviate that. However there will be those who might wish to retain the original switch contacts and just take advantage of the much lower current a transistor needs to pass through the contacts thus to extend their life. Unfortunately, even this is not necessarily so straightforward! Some materials such as gold don’t tarnish and will work well with low currents. Other materials however, DO tarnish and rely on a small arc to clean or “Whet” them. Those with a mechanical "wipe" action are better in this respect but inevitably, they will in time wear away. It seems to me that all the clock circuits make a high demand on the switches. My own remontoire (which brought me here) is now determined to operate every 40 mins. It might occasionally skip a wind and go to 80 mins but never longer. Working on the former means the switch operates over 13000 times per year. That sounds more than enough and yet it pales into insignificance with some electric clock demands, does it not? More information please.

    I'm here to learn & to discuss.

    I cannot now leave this subject without a rather incomplete mention of the switch contact materials. What various metals do under arcing and wear & tear is somewhat interesting. It would be even more so if this writer had more knowledge than he currently does of the various metals used. I recall from my electronic relay days that there were different contact metals for differing applications. Alas not what they were! Iridium ? Gold? Platignum ? Those sorts of metals I think

    Let us just consider what we would like:- Highly conductive, hard wearing, non tarnishing, arc resistant, non-oxidising, good dielectric strength. Did I not say affordable? :<))

    There are "schemes" to help with some of these problems. Physical self wiping, snap hysteresis action, specially developed alloys.

    Best regards, BerryG
     
  19. flynwill

    flynwill Registered User
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    That is indeed a well-written article, and I agree that the back-to-back zeners is a good approach, I like the fact that it is a polarity in-sensitive, meaning that someone with less electrical knowledge is less likely to get wrong. One option the poster doesn't explore is a diode plus a resistor in series, which I think would work well also, but does require that the resistor be chosen to be about 5-10x the coil voltage. This works the same as the resistor alone but eliminates the power loss to the resistor while the coil is activated.
     
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