Smiths thermometer

[Clamity]

I came by this today. It's a Smiths branded mechanical thermometer, made in England.

As well as moving left to right, the bar changes colour depending on the temperature.

I had though it would look good in my camper van as it mounts vertically or horizontally, but it turns out the bimetallic strip mechanism is totally undamped so it's only good for static installation.

The bezel is not in great condition either. The printed scale is pretty faded, but worse it looks like it has been prized off in the past and re-glued on, leaving marks all over it where the metal has stretched.


I think it looks pretty good and it's satisfyingly heavy so would like to keep it and put it right, but how to go about it? Is it even possible to flatten the bezel out without wrecking the printing? Otherwise, how could I go about making a new scale? It's got a sort of satin finish to it, like anodized aluminium (which is probably what it actually is).

[Clamity]

Here's what it looks like inside...


The drum has a simple bimetallic clock spring at the left hand end. Unfortunately there's no damping of any kind. I don't think a felt damper would work as there would be too much stiction. Maybe there'll be a way to graft on the magnetic arrangement out of a car speedo.

I figured the scale is probably past saving so I bit the bullet and took it off by soaking in IPA and going at the rubber glue that was under there with a long bristle brush. The metal is very thin and it made quite a mess of it.



Just made a start at a new one by scanning the old one and tracing round it in Inkscape. An hour later faffing with fonts and curves, I have this...


...which on paper looks like this (not decided on a colour yet):


The Internet didn't turn up a match for the typeset of the SMITHS logo, so I just traced that, imperfections and all. (The 'S's don't match at all.) Funnily enough the best matches I could find for the rest of the text was plain old Arial and Impact for the digits. I think only the 5's and the 0's are noticeably a bit off.

Now I just need to work out how to print in block colour onto ally, or some other shiny substrate. The original was actually the grey background silk screened onto aluminium foil, so the lettering is the metal surface. It had probably just oxidised a bit in places.

[jonw]

Brilliant!!!

I have a Smiths bakelight mantle clock from the 50's. Shows what was made back then.

[Clamity]

Cheers jonw. I think Smiths goes back a long way and they did a lot of stuff besides car gauges over the years. This one was new to me though and I just like the shape of it.

I worked out a really simple way to slug any vibrations. Salvage one incredibly powerful magnet from a dead computer hard disk...


(These tend to be found glued onto a thick piece of soft iron which I just grip in the vice and bend a bit with pliers enough to get a screwdriver in to prize the magnet off. I've not broken one yet, but these magnets are brittle apparently.)

...Then stick to the thermometers steel base plate and slide into place directly under the drum with a plastic tool.


Now the rotation is very heavily damped due to induced eddy currents in the drum over the magnet. The magnet is stuck very firmly to the steel base and there is about a 1 mm gap between it and the drum above.

This wouldn't have worked if the drum was made of anything magnetic or was non-conductive. Luckily it is drawn from a sheet of aluminium, so ideal for this.

[chairchild]

clever git lol

Love the retro Smiths stuff!

[robinmasters]

Couldn't you acid etch the scale on, then paint in the holes?