Otter switch - how did we get here ?

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Otter switch - how did we get here ?

Post by drcdb15 » Thu Feb 01, 2018 11:36 am

Right, Otter switches. Now I know an otter switch is a thermal cut-out device, but seeing several references* to them recently made me wonder about them... what exactly *is* an otter switch? Why an 'otter'? (cue joke: stops things getting any 'otter, boom boom), and so on. [please don't tell me this really *is* the origin of the name!]

So, naturally I turn to Mr Google, then Mr Wikipedia... but - nothing! Otter Controls make them, of course, and they were the de facto thermal cut-out of the 60s and later, but even the Otter web site gives no historical detail. But bi-metallic thermal switching technology goes back far farther than the past 60 years, and most of today's 'otter' switches are solid state (thermistors I imagine) devices, yet I cannot find anything which describes the history and development of these devices, which seems very odd given their ubiquitous and very important role in the modern world.

Can anyone out there throw any light on this for me? Why did they suddenly become used in the 60s? What was used prior to that, or did earlier vehicles not have water cooling ? (!), why Otter Controls, did they not have any competitors? And with today's solid state switches, presumably from a host of different suppliers, why are we still talking about 'otters' ?

* specifically, poring over the GTE wiring diagram Fig 4 in Section T of the manual, which is awash with them... well, I've found 4 so far...


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Otter switch - how did we get here ?

Post by philhoward » Thu Feb 01, 2018 11:44 am

The original was made by Otter Controls, as you've found. Not sure if they still are but there was a bit of folklore relating to the fact they live in water?

I think they were amongst the first to make thermostatic fan switches widespread, certainly within British cars (even used in the E-type Jag) and certainly came to the fore when BL started fitting engines in sideways and moved the radiator to the front where it worked better. Obviously most vehicle electric manufacturers also made their own (Bosch, Marelli etc) but I guess it's like Vacuum cleaners are generically referred to as "Hoovers" - it's the name most associated with the device.

Saying that, whereas the Otter switches were generally held in with a seal and a clip - usually - (hence could be mounted in a normal hole), others went with a conventional threaded fitment which would then mean something a bit chunkier to take that thread.


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Otter switch - how did we get here ?

Post by drcdb15 » Thu Feb 01, 2018 12:05 pm

philhoward wrote:
Thu Feb 01, 2018 11:44 am
Obviously most vehicle electric manufacturers also made their own (Bosch, Marelli etc)
So did neither Lucas nor Smiths make them? They were surely the primary UK automotive electrickery suppliers of the day, so how did Otter get in on the act ? Otter seems just to have sprung up from nowhere and suddenly out of nothing is a major supplier to an entire industry... and yet there is no recorded history?! Seems most odd... did Otter have something patented that established its position? If "the Otter switch" was so seminal, why is there no history of it anywhere?


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Otter switch - how did we get here ?

Post by philhoward » Thu Feb 01, 2018 12:09 pm

Either Lucas or Smiths made a version as well (as they would!) - I've no idea why Otter continued the same as they did on the sidelines but they didn't make them just for cars. Used their "technology" in boilers and water heaters IIRC.


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Otter switch - how did we get here ?

Post by Roger Pennington » Thu Feb 01, 2018 3:42 pm

drcdb15 wrote:
Thu Feb 01, 2018 11:36 am
Why did they suddenly become used in the 60s? What was used prior to that, or did earlier vehicles not have water cooling ? (!
I think the solution to that is simple - earlier vehicles did often have water cooling, but systems were much simpler. Where fan assistance to that cooling was required, they normally had a straightforward mechanical fan operated off the crank nose (or alternatively the "fan belt"). It was only later, as electric widgets became more widespread, that people realised that mechanical fans were A. inefficient, as they ran all the time and soaked-up power, and B. noisy. So electric, thermostatically-controlled ones took over and the otter switch made it's appearance! :D


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Otter switch - how did we get here ?

Post by gordini5 » Thu Feb 01, 2018 3:58 pm

Was working on my Kenlowe engine pre - heater unit at the weekend. Noticed the 3kw heating element made by Otter too, either that or it's the built in thermostat.



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Otter switch - how did we get here ?

Post by Elizabeth's dad » Thu Feb 01, 2018 4:44 pm

Roger Pennington wrote:
Thu Feb 01, 2018 3:42 pm
I think the solution to that is simple - earlier vehicles did often have water cooling, but systems were much simpler. Where fan assistance to that cooling was required, they normally had a straightforward mechanical fan operated off the crank nose (or alternatively the "fan belt"). It was only later, as electric widgets became more widespread, that people realised thy at mechanical fans were A. inefficient, as they ran all the time and soaked-up power, and B. noisy. So electric, thermostatically-controlled ones took over and the otter switch made it's appearance! :D
Indeed, the GTE of course originally came with an engine driven fan, although soon replaced by electric with otter switch. The mechanical fan became listed for towing in addition to the electric jobbie. Does everyone refer to an 'otter switch' or is it only people whose cars are fitted with a genuine otter product?


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Otter switch - how did we get here ?

Post by drcdb15 » Thu Feb 01, 2018 5:15 pm

Elizabeth's dad wrote:
Thu Feb 01, 2018 4:44 pm
Indeed, the GTE of course originally came with an engine driven fan, although soon replaced by electric with otter switch. The mechanical fan became listed for towing in addition to the electric jobbie. Does everyone refer to an 'otter switch' or is it only people whose cars are fitted with a genuine otter product?
My old Kitten was also an 'always on' fan, belt driven, and that was 1978 - mind you, the engine design *was* 1932 :shock:

But as regards colloquial use of "otter", what triggered this was my finding these switches labelled explicitly as "OTTER SWITCH" in the circuit diagrams of the GTE manual, which is for the SE5. It just gives me the impression that this switch *must* be an Otter switch - it doesn't mark the light switches as LUCAS or the heater blowers as SMITHS. So why call these Otter switches rather than just 'cut-out' or 'overheat' etc?

It seems most odd to me that here we have an apparently completely ubiquitous term for a widely used item, and no-one seems to have any idea how it came to be. In other cases, like Omnibus (and then bus), and Hoover and more recently Google, the origins of all of these were trademarks and/or company names, and the origins and slippage into common use are well documented. It puzzles me too that in an industry already at the time dominated by Smiths and Lucas, how did Otter suddenly jump in and get this niche all to itself? It's not as if they were aleady huge in some other market sector (or were they?) and they could easily move into an automotive application in high volume before Lucas/Smith got themselves sorted out.


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Otter switch - how did we get here ?

Post by scimjim » Thu Feb 01, 2018 5:24 pm

drcdb15 wrote:
Thu Feb 01, 2018 5:15 pm
It puzzles me too that in an industry already at the time dominated by Smiths and Lucas, how did Otter suddenly jump in and get this niche all to itself? It's not as if they were aleady huge in some other market sector (or were they?) and they could easily move into an automotive application in high volume before Lucas/Smith got themselves sorted out.
I think they were making industrial bi-metallic switches in the 40s, so were the industry leaders when automotive applications came on stream.


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Otter switch - how did we get here ?

Post by 747PETE » Thu Feb 01, 2018 5:59 pm

This reminds me of a few years ago when I asked in a nuts and bolts shop for some P.K.screws...they were at a loss.What I wanted were self tappers,it’s just that as a young lad😀 we called them P.Ks after “Parker Kaylon” The 1940s manufacturer! Then there was Halfords last year,they thought “Jenolite” was a new sort of........headlight bulb🙄🙄🙄🙄



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Otter switch - how did we get here ?

Post by drcdb15 » Thu Feb 01, 2018 6:35 pm

Well, I think I may have the answer: As Jim says, bi-metallic switches were well known in the 1940s, but "our story begins" with Eric Taylor, in Buxton, Derbyshire, in 1948. Eric was obviously working on the design of bi-metallic strips, typically E-shaped, and looking for ways to mass-produce them. I don't know, but I would guess this arose out of war work research. Anyway, Eric filed a patent application around 1948 (GB no 600,055) which I haven't looked at, and he then filed a further one (GBPA 657,434) in February 1949 where he claims the method of deliberately crimping the shape to deform it, so as to make it snap between two otherwise stable positions.

According to the original documents, at this time Tayor is working on his own. However, by 1961 Taylor is with (or set up?) Otter Controls Limited, based at Otters 'Ole, Market Street in Buxton, and by this time they are employing one Ronald George Waring. He is the sole inventor on GB patent 954,233 which claims the bimetallic snap switch components originally developed by Taylor set in a watertight casing which is inserted into a fluid flow of changing temperature... well, I don't need to spell this out.

The key point is, that 1961 patent had extraordinarily broad scope - it covered the very concept of a bi-metallic strip-based snap switch being encased in its own electrically and thermally conductive housing and inserted into a fluid flow to use the temperature of that fluid to control 'other devices' - such as a cooling fan. The patent is most elegant, and has essentially only a single claim (there are about half a dozen dependents but that's trivial). The point is - and this is only my own interpretation - that single patent pretty much must have tied up the entire UK market on this type of switch. Which explains why there was no practical alternative, and hence why they came to be known colloquially as Otter switches. Nothing to do with the joke I mentioned, or anyone's name, but an archaic street name in Buxton. Dave Mac would be proud !!

Otter was ovbiously then (as it still is) quite savvy when it came to patents, as two others were filed around the same time, and today they have around 800 filings. There was obviously competing development going on in the US at the same time, and doubtless around Europe too, so I wouldn't be surprised (though I don't know and haven't researched it) if these switches are known by some other local name outside the UK.

As I say, this is all my speculation, but it would explain why the name became syonymous with thermal cut-outs, and why the established auto electrics firms didn't get to play.

High Peaks Noggin, I hope you will add this information to your local annals :lol:
espacenetDocument.pdf
(24.56 KiB) Downloaded 66 times
espacenetDocument(1).pdf
(18 KiB) Downloaded 55 times


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Otter switch - how did we get here ?

Post by drcdb15 » Thu Feb 01, 2018 7:21 pm

Been doing a bit of digging into Otters 'Ole - I can't find it on Google maps, but a recent planning application http://planning.highpeak.gov.uk/portal/ ... KID=213948 shows it's still there, along with Otter Court. From the site plan it looks as if the original Otters 'Ole has long been submerged by more modern buildings, and this application is to turn the original offices into townhouses (sounds like TwoGates history repeating itself!).

A search for Otters Ole on Google Images was more revealing - I found a number of magazine adverts, showing their new wonder switch - and it is exactly like the patent drawings, which makes me more sure that Otter owes its market position to its 1961 patent and the earlier ones covering the bi-metallic strips production process.

It's interesting to see in one of the adverts of the time (1961) Otter takes a swipe at Lucas, saying Lucas parts can (should?!) be properly controlled using Otter switches :lol:
Im1962AE03-Otter.jpg
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Im1962AE07-OtterConts.jpg
Im1962AE07-OtterConts.jpg (115.64 KiB) Viewed 5187 times
AE196210-OtterCon.jpg
AE196210-OtterCon.jpg (101.61 KiB) Viewed 5187 times


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Otter switch - how did we get here ?

Post by scimjim » Thu Feb 01, 2018 9:18 pm

Worthy of a sticky I reckon :D


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Post by cannonball » Thu Feb 01, 2018 9:48 pm

Just like a miniature kettle thermostat, ones similar to these
https://www.todocoleccion.net/repuestos ... ~x69512229
were used in the heater speed control of the Rover sd1.



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Post by scimjim » Thu Feb 01, 2018 9:52 pm

SE5a electric windows also use otter switches as thermal overload cutouts.


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