Jump to content
Moose

National Electric Watch Cleaner - refurbing

Recommended Posts

Hi all.

I have got a National Electric Watch Cleaner and as expected the heating element is bug***d (sorry, not working). Everything else is OK and the motor and bearings are nice smooth with good control from the speed dial. With a bit of TLC (and rattle-can black) it will provide me with good service.

Does anyone know if the heating element from the Elma RM80 (90) is a good match for this machine? It basically just needs to operate at mains voltage and fit into the space where the old element used to fit. I could use it without the heater and just bodge something with an old hairdryer to provide a warm airflow, but I am hoping that the Elma element could be used. Has anyone ever tried this?

I am going to re-wire it and makes sure it is up to current safety standards, as it still has its original (seriously old now) wiring scheme. New Jar seals will be needed but I have some aviation fuel/chemical grade 3mm rubber gasket material I can hand cut to suit, so that will be OK. The jars and lids are sound and just need cleaning (and the seals). And it has a complete set of baskets, which is a plus.

I have included a photo of the old heating element for a size reference. Unfortunately for me, Elma do not state size of their replacement element.

 

 

IMG_1539.jpg

Share this post


Link to post
Share on other sites
17 hours ago, yankeedog said:

are the heating coils removable?

I would say not. The entire assembly is and I was hoping to wire in the Elma Heater. Working on the assumption that you turn it on, it gets hot enough, you use it, then you turn it off again. I think the Elma element must be self regulating, or designed to operate at a certain temperature. Looking at the Elma spare part in the catalogue, there is a simple two-wire connection, same as this one.

 

IMG_1538.jpg

10.jpg

Edited by Moose
Added Elma Element image.

Share this post


Link to post
Share on other sites

It looks like an old fashioned stove element to me, or possibly a very old kettle element. What are the dimensions of the space it needs to fit in?

Is the thing on the metal disk a thermal fuse, or a thermostat?

If it is a stove element, then you might be able to adapt a modern one to fit.

https://www.ebay.co.uk/sch/i.html?_odkw=6%40+stove+element&_sop=15&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=6"++cooker+element&_sacat=0

 

https://www.ebay.co.uk/itm/futura-kettle-element/192929243765?hash=item2ceb7aa275:g:9oIAAOSwH5xc6nm3

https://www.ebay.co.uk/sch/i.html?_odkw=5"++cooker+element&_sop=15&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=kettle+element&_sacat=0

You may need to add in your own thermostat to get these to cut out at a reasonable temperature, I'm pretty sure you don't need to boil a Rolex to get it clean.

https://www.ebay.co.uk/itm/5PCS-KSD301-Temperature-Switch-Thermostat-50-C-150-C-Degrees-Celsius-NO-NC/272790891850?hash=item3f839aad4a:m:mqXL_j-yLhgkW5JDPzzM-ug

Edited by AndyHull

Share this post


Link to post
Share on other sites

Don't forget to ensure the thing is correctly earthed and that you are on an RCD protected circuit if you are testing any modifications, we don't want any hair raising incidents. Bangs and electric arc flashes may make good youtube content, but only if you are not part of the fireworks.

Share this post


Link to post
Share on other sites

BTW you can also buy kiln elements, in various power ratings, which might do the trick. Do you know what the original power rating of the element was?

Example -> https://www.ebay.co.uk/itm/AC-220V-2500W-Heating-Element-Coil-Pottery-Kiln-Furnace-Resistance-Restring-Wire/202496373526?epid=25030666425&hash=item2f25b97316:g:LW4AAOSwyiFb5PWO

 

 

Share this post


Link to post
Share on other sites

One further thought, if you are feeling particularly brave, you could purchase the nichrome wire and re-make the element, however you would need to know the specification of the original coil, its total hot resistance,  the gauge of the wire, its total length and the resistance per foot/meter of your chosen wire, so you could make something to match.

https://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=nichrome+wire&_sop=15

.. but a suitable kettle element (or perhaps two in series) and a suitable thermostat sounds like a much simpler substitution.

Edited by AndyHull

Share this post


Link to post
Share on other sites

The basic dimension is shown in the photo, 75mm diameter. The other “thing on a metal disk” is the replacement heating element for the Elma RM80/90.

What would be useful to know (but not information I can find online), is what diameter the Elma replacement is and, if it is also a 240 volt element.

if anyone out there uses an Elma 80/90 it may be easy to see it in the bottom of the drying chamber. Or maybe a circuit diagram was supplied with the machine.

At £45 for an Elma element, I’m not sure I want to take the risk of buying one just see if it will work.

Otherwise, I will just as likely refurb it without a heater, and keep an eye open to see what might come up. I can always blow some hot air in from a hairdryer or something to get a drying effect.

Share this post


Link to post
Share on other sites

it looks like all the sections are still there . it's just a coil of nichrome wire.Form the ends so that you can hook the sections together, it will work. for how long is anybody's guess, all you need is continuity.

Edited by yankeedog
content

Share this post


Link to post
Share on other sites

I dont know about the ID of the coils but you could also cut sections , of oh say 12 AWG solid conductor wire and insert them inside the coils connecting the sections together.just so it's inserted for a few turns on each side. it will get hot.

Share this post


Link to post
Share on other sites

I'm certainly going to explore some of the options mentioned here, thanks. From what I have found out, is that the heating output is around 200 watts, so not too much. 

Share this post


Link to post
Share on other sites

If you decide to fix the existing heater I would tackle the problem as follows.

Count the coils.

Figure out the diameter of the coil.

The total length of wire in the existing coil is is Coil Circumference multiplied by number of coils or if you prefer...

2 * Pi * 'Diameter' * 'Number of coils' 

... since the diameter of the coil is much easier to estimate.

Nichrome wire is rated in Ohms/meter, this figure will be on the spool. The exact figure depends on the gauge of the wire,  so you should be able to work out the total resistance of a new coil.

The old coil can be cobbled together by twisting (not soldering) the coils together using bits of copper wire, per Yankeedog's suggestion.

You can then measure its approximate resistance, which should be close to what it was when new, or at least close enough for the purposes of this game.

You can probably get a rough estimate on the old coil's resistance using a micrometer to work out the wire gauge, then multiplying that by around the figure obtained from new wire of similar gauge, or even by guessing at 4 Ohms per meter.

More details here -> https://en.wikipedia.org/wiki/Nichrome

In other words, it should be possible to create your own coil, using a spool of cheap nichrome wire from ebay, a suitable round stick to form it on, and a little arithmetic. It can't be that hard, since the Victorians had this figured out long before we came on the scene. Mind you, they were still starching their hat brims with mercury, so perhaps health and safety wasn't their strong suit. 

Ohms law states that for resistive power in a DC circuit, Watts = V^2/R so you should be able to tell if you are in the right ball park with your calculations, based on that and your estimate of 200 Watts.

The fact that we are actually dealing with AC power and the fact that the resistance changes with temperature mean that this is an estimate, but probably close enough to tell if we are in gentle heating or explosive melt down territory.

I do, of course, completely absolve myself from any responsibility if your experiments set the cat's tail on fire, or result in lots of smoke and loud profanity. Also 240v AC is dangerous etc.

In summary, get the correct gauge of nichrome wire, wind the correct number of coils of the correct diameter, try it, but don't forget your safety glasses,  and work on a heatproof surface, since hot globules of exploding nichrome can be very "interesting".

Share this post


Link to post
Share on other sites

All excellent advice.

BUT...

I have decided to purchase a modern 200W PTC heating element. It looks much like the one used by Elma in their new machines. It's about 75mm by 35mm rectangle shaped and can be mounted on the existing heatproof plate without issue. As standard is gives me 200W heat output at 220/240 volts and is self regulating - all I need to do is turn it on and off. 

To be honest, I did consider re-constructing the original, but then if more modern (and safer) technology is available, I may as well use it. I suspect it is a better solution that trying to hand produce a new element for a 50's or 60's heating element, as interesting as that might have been to actually try. Bottom line is that what I need is about 200 watts of safe, controllable heating. A PTC heater is the safest option for me.

Mind you, if anyone out there wants my old element to try to repair it, they are welcome to it for the postage cost from me to you.

If anyone is interested, the cost of the element is only £25 from Farnell, vs £45 to get the official Elma element from HS Walsh. For my money, it's exactly the same thing, only the Elma version is mounted on a steel plate. If you take a look at my earlier photo, you can see the PTC heater mounted on the circular plate.

200w 220/240v PTC Heater

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing

    No registered users viewing this page.

  • Topics

  • Posts

    • I certainly did not want to replace the motor, as this is so very visible, all attempts at maintaining the illusion of originality would fail. A solution to the problem could only be achieved with a safer, replacement speed control, which could work with the original mains voltage motor. Fortunately, these are readily available in the form of a Pulse Width Modulated (PWM), motor speed controller circuit. These will take in the 220V incoming mains supply and provide a variable output of between 50V and the incoming supply voltage. These are well known devices and proven to work with even simple (old) motors. So, a PWM circuit was obtained (at incredibly reasonable cost), and measured up. In an attempt to at least have the "illusion" of originality, I was determined to use the original hole for the rotary speed control, as well as the original Bakelite control knob. With the shaft on the rotary potentiometer too short for this, I had to do some more metal bashing. As can be seen below, I used the old rheostat as a donor, for a short length of it's shaft, which I would mate to the new potentiometer, allowing the Bakelite knob to operate. This was cut to shape and filed to mate with the new potentiometer shaft. This was then soldered together and thus ready for installation. You can see in the photo, the size and technical comparison between the old rheostat and the new PWM controller circuit.  
    • Next up is the motor speed control. I did think long and hard about my original aim of maintaining as much originality as possible. And, there is no doubt that the original speed control rheostat was a) original and b) functional. But - as I was an electronics technician in an earlier life, and also health and safety professional in a more recent life, the safety aspects weighed heavily upon my concience. Logic played it's part as well - with the original rheostat put back into service, albeit with some hand-made guarding to keep out the fingers of the unwary, it would be safe-ish, for me to use, as long as I kept my wits about me. BUT NOT SAFE FOR ANYONE ELSE unaware of what was underneath. Only the knowledge of what lurked underneath would be keeping me safe, but anyone else might not have a second chance. As can be seen from the photo below, all of the wire on the resistors is not only unguarded, but within millimetres of the level of the base. Also, the incoming mains terminals to the rheostat are also dangerously unguarded. With today's knowledge, it is difficult to fathom how this ever could have been considered safe to use.
    • Back to the job in hand. I managed to find the cork I thought I may have had, lurking in a box under the stairs. It was the most part of an A4 sized sheet, so more than enough for my purposes - to sit the jars on whilst they are in the machine. Looking at the metal bases, I really can't be convinced if there ever was any cork or any other material for that matter there. But for me anyway, the idea of the glass jars sitting directly on the metal base just seems wrong and I would prefer some cork there as a cushion. It's about as tidy as it needs to be, given the shape of the metal webbing. I suppose I could have cut-out squares of cork, but then it would leave potential weak, unsupported areas of cork, which would likely need some form of strengthening. Anyway - this application suits me and helps the jars sit a bit more stable in their locations. Whilst I am in the vicinity, so to speak, I have also added an earth lead which will bond the chassis to the incoming mains lead, once fitted. This is visible in these photos.  
    • A little further research and then on with the show... A quick browse through patent databases, shows that one Saul Lanzetter applied for and was awarded a patent for this design of watch cleaning machine in October 1937. A brief narrative is reproduced here: Interestingly, the patent application is entitled "Improvements in apparatus for cleaning watch parts and other small parts of machinery." It may be reading too much onto this title to assume that there may have been a previous patent, pre-dating this one, as this one refers to "improvements". Also of interest, there were 2 patent applications from US companies in 1944 and 1945 which cite the Lanzetter patent, and three from Germany in 1956, 1960 and 1961 (only one of which was actually published), which also cite the Lanzetter patent as a reference. Incidentally - the two US patents refer to machines which look strikingly similar to the National Model VI-C above, and the National No 4. machine in the earlier advert, showing the four jars side by side ( this seems to be referred to as a lab machine, rather than a repair shop machine). Naturally, all patents or applications referred to above are now expired. For me anyway, I think this may clear up which watch cleaning machine may have come first (at least in this machine format anyway): The S. Lanzetter National Electric Watch Cleaning Machine, circa 1937.  
    • Impressive work. The barrel and mainspring look almost new, and the remaining pitting is no worse than some lesser movements left the factory with. I'm looking forward to the next installment.
×
×
  • Create New...