I am interested in finding out the history of the RE Thompson company and also the details of the Bakelite Signal Arm repeater instruments that they made such as what types were made and the years they were made, does anyone know where I can’t find such information ?
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Signal Arm Repeater Instruments
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I don't know of any books specific to the subject but signalbox.org has some useful photos and a forum section where you could find out more. I used to have a large collection of block instruments and repeaters and I knew one collector who went to the RE Thomspson factory and either bought or was given a number of brand new repeaters still in their wrapping paper. From memory I think that SYX repeaters were interchangeable with RE Thompson repeaters so there was probably an industry standard as regards dimensions etc.
signalbox.org
Lever Frames – The Signal Box
signalbox.org
Hi Pinza-C55 thanks for the reply
For some time now I’ve be unable to access the SignalBox site I’m waiting for a reply at the moment as to why this is happening, Question where is or was the RE Thompson company located?
I believe the SYX Repeaters that were used on the SR their diameter was governed by the lever spacing any other manufacturers of a repeater type instrument would probably do the same to cover all types of Lever spacings from the smallest upwards the 6 SR/SYX repeaters that I made are approximately half size 56mm in diameter
For some time now I’ve be unable to access the SignalBox site I’m waiting for a reply at the moment as to why this is happening, Question where is or was the RE Thompson company located?
I believe the SYX Repeaters that were used on the SR their diameter was governed by the lever spacing any other manufacturers of a repeater type instrument would probably do the same to cover all types of Lever spacings from the smallest upwards the 6 SR/SYX repeaters that I made are approximately half size 56mm in diameter
After a bit of Googling I’ve found the company website (I think). They date back to 1948, however there is no mention about signalling products. https://www.rethompson.co.uk/about-us/
When I'm at St Albans South box on Wednesday I'll see if any of our repeaters were made by this company, and if so what type and date made they have on them - if they have any markings, that is!
Re the signalbox.org website, I have had a quick look through it but can see no mention of this company. (I've had no problems accessing it, by the way.)
Ashley Hill
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Thanks John
The problem not being able to access the Signalbox for the last few months was with our internet provider they altered some settings to try and speed up our service but in doing so we lost the ability to access sites (unknown to us) so they have now put us on the default setting again and all is good.
Hi Ashley thanks for the names & photo is it possible for you to take a closer photo of the makers plate my eyes aren’t good enough to see the one you have sent.
Ashley Hill
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This is about as close as I can get without it being blurred.
Thanks Ashley well done, what type of instrument is this label on?
Ashley Hill
Established Member
A 1947 pattern lamp repeater.
Regret I could not find any manufacture's markings on the repeaters I looked at this afternoon at St Albans South. The most common marking was a small paper label inside mostly JAXXXX where XXXX was a four-digit number and a BR test label, usually from the 1950s or 1960s giving details of resistance and minimum voltage for operation. Even the three on display in our museum and not fixed to anything gave no details on the back of who made them. Sorry!
Hi John
Thanks for trying do you remember what the minimum voltage and resistance was on the label? I’m curious
Yes, the majority are 250 ohms, some are 50 ohms and all work with around 0.8 to 1 volt.
Hi Ashley
You didn’t need to take another photo for me after all, my daughter is staying with us tonight and I asked her if she was able to read the first photo you sent me I was curious to see how bad my eyes were getting, she looked at the photo and touched on it and low and behold a full size photo emerged I didn’t know I could do that, Live and Learn.
Hi John
Thanks for that, at 50 ohms that would have drawn some current could there have been another coil or a resistance in series, that also makes me think is the power supply batteries or from mains supply?
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Possibly. Some signalling circuits require proving that the arm is in a certain position (I don't know the full details - my professional career had nothing to do with railways!) and therefore there could be a relay coil in series with the repeater. Most signal repeaters would have been operated from primary batteries at the signal end and the power system inside boxes was often secondary batteries kept charged from the mains where the mains was available.
In our simulator at St Albans South none of the repeaters are of course connected to signals and suitable series resistors are used to drop the voltage to the correct level for each repeater from the driver circuits operated by the computer.
Hi John
I just thought about the 50 ohms again and at only one volt using the formula E=IxR it would have been only 20 ma if my maths is correct ( correct me if I’m wrong) so that’s not too bad for a continuous operating coil I was thinking 3 volts or more, one volt or less isn’t much compared to the running of coils in other equipment, the likes of block instruments have a greater distance between them hence a higher voltage compared to the distance of a signal arm Repeater to the furthest signal from a signal box so is able to run on a lower voltage makes sense, I never knew what voltage these repeaters worked on I always thought it would have been around 3volts.
Ashley Hill
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Your maths is OK! Don't forget all these external circuits to the box went over the 'telegraph' wires alongside the track. The wires for signal repeater and other similar circuits had a typical resistance of 12 to 15ohms per mile so quite significant with a 50ohm coil at the other end! Major telephone and telegraph circuits used larger wire sizes with a resistance per mile of 4 to 6ohms/mile. (Information from "Railway Signalling and Communications" originally published by the LNER and reprinted by Peter Kay, ISBN 1 899890 24 6)
Hi John i do have all these books and I keep forgetting the mass of information they have, anyhow what I found interesting was that it stated hard drawn copper should be used around loco sheds / London area and industrial towns due to its corrosion resistance but could break easy from surface damage the repeater circuits used cadmium copper that had obviously a poor resistance to corrosion and also had the lowest breaking strain but could no doubt flex more “I suppose good for the likes of windy areas” In FIG 156 the wiring diagram of the combined Arm and light repeater shows a couple of resistance‘s in series with a repeater of 350 ohms, this circuit is running by 6 vdc / centre taped battery, so the question here is we’re there different coils ( resistance) fitted in different repeater’s for certain applications? or did they just change over the years due to manufacturing techniques or newer circuit designs requiring a repeater that operated differently from the older models. The six SR/Sykes repeater’s that I have made can only pick up at about 6 vdc but work perfectly at 8 vdc and run at about 40 ma the problem I had was that these repeater’s are half size so it was a bit of a challenge to make a working mechanism to fit, the weight of the needle hangs downwards by gravity to point to the Wrong position the mechanisms for the two Tyers and one Walters instruments that I have just made can pickup at 3 vdc but these are full size and are Perfectly balanced which makes all the difference the Walters instrument is balanced by the balance weight on the signal arm whereas the Tyres instruments have a balance weight on the main shaft behind the face plate the Wrong position of these instruments are about 45 degrees so these are balanced to this position.
The diagram shows several variations in one circuit for different circumstances. The tapped 'Vitreous Resistance' cut the current down to below the 8mA that operated the 1,000 ohm relay in the Light indicator unit, so when the Expansion Contact in the lamp became open the relay dropped out and initiated the light indicator. The 350ohm relay or resistance in series with the arm repeater depended on whether or not other electrical interlocking required to know the position of the arm. (A polar(ised) relay would only operate when the arm was in one particular position.)
The signal repeater circuit in Fig 157 shows only one cell for each position.
Don't forget the diagrams showed mainly LNER practice - other railways used similar but not necessarily identical circuits so may have well used different coils.
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