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8 hours ago, Pacific231G said:

This is something I've been interested in for some time and I'd be fascinated, as I'm sure would others, to know more about your home made block instruments.

 

It always seemed to me extraordinary that, among the rocket launchers, giraffe cars, and exploding boxcars, Tri-ang would, in the same era,  have come up with something so geared to prototypical operation. The set cost about as much as a locomotive so they didn't sell very many and they were only in the catalogue  from 1964-1967.  I've no idea how reliable they were but I did hear about someone using a refurbished set. 

I thought Peter Denny's system of substituting lights for the needles was an excellent idea as it's very simple as I'm sure Tony (t-b-g) can confirm.

 

There are also drawings for a block insturment based on point motor solenoids in Cyril Freezer's book Model Railway Signalling but they'd have to be run at a lower voltage or in a suitable circuit as the relevant coils for train on line and line clear would have to be energised for some time. Another option would be to use cheap centre zero analogue volt meters or ammeters.  Centre zero metres seem slightly unusual these days- they used to indicate battery charging and discharging in cars and still in light aircraft for that purpose-  but I've seen them for £8-£9 each. They wouldn't be quite as sturdy as a solenoid  and you'd need to be able to get into them to substitute the block indications for the normal scale.

The other possibility would be to use servos and there's information about those used by Barry Luck for his excellent Plumpton Green layout (two position Tyer instruments)  here

http://www.lbscrmodels.co.uk/instruments1.html

 

Since model instruments aren't safety critical in the way that real ones are there are some obvious simplifications such as not including the needle that simply repeats the local switch setting (as Tri-ang did) . 

I think that one problem in offering this as a product is that anyone so dedicated to prototype operation would likely want to used miniature versions of the appropriate block instruments for "their" railway rather than a generic design.

Would you accept this BR Standard (Domino) Block Instrument.

Block_Instruments-9.JPG.5a8e64d6eacdb6b9783b2504c9c07235.JPG

(CC by 3.0. Sir Ross BA)

If you were modelling the Midland Railway

365721336_MidlandRailwayBlock_instrument.jpg.3f3bf13dcd59bacfce9d0d62f373d1bf.jpg

(CC BY-SA 2.0) David Inghams' photo of a MR instrument in Castleton East Jct. box

 

 

A miniature staff or token instrument would be a challenge (and how would the token be carried on the train?) but a tokenless block system would be a possibility. I've just been looking at a page about the BR(W) tokenless block here http://www.trainweb.org/railwest/gen/signal/tkblock.html

As I model French railways I found it particularly interesting as it seems in principle quite similar to SNCFs BMVU (single line manual block) system but simpler to build if one ignores the actual track circuits, treadles and signal lock used by the BR(W) system.

 

BTW I saw Plumpton Green in operation a couple of years ago and I'm pretty sure that the only bells were in the main "signal box", those in the fiddle yards were replaced by lights so there was no cacaphony to annoy adjoining exhibitors. I seem to also remember, on the several occasions that I've enjoyed seeing it,  Peter Denny's Leighton Buzzard  layout as exhibited by Tony  as being quite restrained in its bell sounds. 

 

 

 

 

Very informative post and thanks for the kind comment about the bells on Leighton Buzzard. We do try to be considerate of others at shows.

 

I had considered using servos for a needle type instrument and reading up on Barry Luck's design has given me some ideas, so thanks for the link.

 

A scaled down replica of a GCR pattern instrument would need the 3 positions so a sprung centre position and two servos, one to push the needle each way, could well do the trick.

 

I do like the appearance of Barry's instruments. All that lovely timber and proper brass knobs look very railwaylike.

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A scaled down replica of a GCR pattern instrument would need the 3 positions so a sprung centre position and two servos, one to push the needle each way, could well do the trick.

You only need one servo, the servo can give 3 positions.

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Posted (edited)

I remember a couple of years back being suddenly aware of the sound of Clecklewyke’s block instruments when I was at the other end of the scaleforum hall. So like others here I’ve put bog paper In to quieten the bells. But since then the layout has been only operated at home, on a fairly regular basis, and the bells really are essential to make it feel realistic.

 

In the early 90s I wrote an article in S4 News  on my block instruments. It might still be useful but it did depend on the availability of bits of electromechanical telephone exchange. These days I would use  centre off meters or servos. I would also make them smaller: mine were nearly full size. They look good but are difficult to fit on the railway without dominating it.

 

BTW I also made a computer program for my ZX spectrum running a digital version of automatic Crispin . I called it digital Crispin and somewhere in the 1990s MRJs you will find an article about it. Sadly my 10-year-old son took my spectrum apart with wire clippers to “find out how it worked”. What is more, he did the same to its replacement… But I still love him.

 

But, as Tony has pointed out, what I really want is a ready made block instrument. My eyesight is so poor now that I have had to go to RTR on 00 rather than P4 so I want one ready made. I’m sure there must be a market for them.

 

 

Edited by clecklewyke
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It might only be a niche market but, like others have said, I am sure that there is a market for someone to produce a model block instrument. I would love to incorporate one into my west highland line layouts operations even if I could not realistically issue individual tokens.

 

 

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9 hours ago, Pacific231G said:

A miniature staff or token instrument would be a challenge (and how would the token be carried on the train?)

 

No problem if you have a large walkaround layout - stick it in a hoop the size of a key ring and hand it to the driver, who will be following his train around the layout.

 

Cheers Nicholas

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45 minutes ago, Grovenor said:

You only need one servo, the servo can give 3 positions.

 

I am not a whizz on electronics but if there is an easy way to make two servos (one in each block instrument) work together to give 3 positions, using simple switches, I would love a description or brief details. I could see how a rotary switch that gives different voltages rather than an on/off could work but how to do that is beyond my knowledge.

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1 hour ago, clecklewyke said:

MIddlesbrough, yes. i was there with our mutual friend Steve “Griff” Griffiths. I don’t remember a Hymek incident. If the culprit was ignorant enough to steal a locomotive I hope he had an unpleasant shock when he tried to figure out why it kept derailing on his Peco track.

Ian

 

 P.S.  ”crescent”? My computer can’t spell Clifton. No not Clacton Clacton. I give up! These days, because of my eyesight problems, I usually dictate emails with sometimes hilarious results.

No the Hymek wasn't stolen but whoever was driving wasn't used to the ZTC 511control.

He thought he had finished driving the Hymek, opened the throttle for the next train but forgot to select his next engine. Result the Hymek and freight train left the storage yard at high speed.

Gordon A

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Posted (edited)
21 hours ago, Gordon A said:

No the Hymek wasn't stolen but whoever was driving wasn't used to the ZTC 511control.

He thought he had finished driving the Hymek, opened the throttle for the next train but forgot to select his next engine. Result the Hymek and freight train left the storage yard at high speed.

Gordon A

How embarrassing. Driving an unseen engine on the other side of the room is a common feature of DCC I find. Sound helps to identify the miscreant loco but it all adds up to Jolly Good Fun. You might remember that JGF was the Festiniog Deviationists’ mantra.

 

Back l on topic, I think that a pair of block instruments at about the price of a loco would be good value, adding far more the enjoyment of model railway operation than yet another loco.

 

To clarify, I am really thinking more about operating at home than at an exhibition. Sounds at exhibitions are another issueo. On the whole I approve as long as it’s done with discretion. One of the best layouts I’ve seen recently was Bridgewater, a 7mm layoutI which not only had train sounds and block instruments but also the sound of levers  being pushed back into position in the signal box. I thought it was fab.

Edited by clecklewyke
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Posted (edited)

 A simple question about servos and a proposal for a kit to make up a pair of block instruments-

 

(Please forgive me if this question has already been asked)

 

I use servos to drive points and signals on Bradford North Western. These all have just two positions, responding to simple on/off switches via a servo controller. To work a normal three position block instrument needle a servo would need to respond to three separate electrical inputs from a three position commutator. Are there servo controllers which can do this? I don’t think that for instance Megapoints controllers can.

 

If a servo can be made to have three positions, I.e. line closed, line clear and train on line then it would be a simple matter to manufacture an easy to assemble kit. This would comprise the following components, sufficient for a pair of instruments:

 

- servos (or could be sourced separately)

-  etched brass needles

- laser cut wooden casesincorporating servo mountings

- microswitches or push buttons

- electric bells

- printed card (or labels downloadable tile) to describe needle positions (nine closed, line clear, train on line)

- three - position commutator

- plug and play cables

They could have two needles as in the prototype (separate needles for yo and down lines) but I would accept a single needle, with the status of the opposite line indicated solely by the commutator, as in the Triang model.

 

This is the sort of project that Dave Fenton of Megapoints could do in his sleep...

 

Ian (who wou like to thank all the thread contributors, but especlajjy Richard Hodgson of our local S4Soc CRAG area group, for helping to develop  these ideas)

 

Edited by clecklewyke
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On 24/03/2020 at 22:05, t-b-g said:

 

I am not a whizz on electronics but if there is an easy way to make two servos (one in each block instrument) work together to give 3 positions, using simple switches, I would love a description or brief details. I could see how a rotary switch that gives different voltages rather than an on/off could work but how to do that is beyond my knowledge.

Simpler and easier to use analog amp or volt meters, as your block instrument indicator. 

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21 minutes ago, nswgr1855 said:

Simpler and easier to use analog amp or volt meters, as your block instrument indicator. 

 

You may well be correct but there is no doubt that a servo doesn't have to be just two positions and if there is an easy way to set one up to work three positions, as suggested above, I would be interested in hearing what it is.

 

I have seen devices where a servo mirrors the movement of a pot directly. Something like that would give you 3 possible positions very easily but only if you have somebody that knows how to do it involved. That ain't me!

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Would using sound recordings rather than physical bells be acceptable?

 

The advantages would be the instruments could be made smaller, less mechanically complicated and resourcing acceptable sounding bells might be problematic. The disadvantage being more electronics and loss of user serviceable mechanics - an electromagnet operating a striker on a physical bell I can understand, the alternative, well, I'm with Tony (t-b-g)....

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1 hour ago, t-b-g said:

 

You may well be correct but there is no doubt that a servo doesn't have to be just two positions and if there is an easy way to set one up to work three positions, as suggested above, I would be interested in hearing what it is.

 

I have seen devices where a servo mirrors the movement of a pot directly. Something like that would give you 3 possible positions very easily but only if you have somebody that knows how to do it involved. That ain't me!

 

The Block instruments on my Cadhay Sidings layout work with one servo to 3 positions of the needle.  I started with a MERG pocket money Servo kit which uses a pot to infinitely vary the position of the servo.  Working out the 3 resistances that gave the three positions was simply about turning the pot until the needle was in the right place, disconnecting the pot and measuring it's resistance.  That gave me the resistance values so 3 routes to the servo via 3 (different) resisters controlled by 2 relays gives the answer you are looking for.  I then run 2 wires from one instrument to the other in each direction (actually via CBus these days but originally it was a wire!) and these take the 2 relays to ground via a rotary switch in the right order to vary the resistance to the servo accordingly.

 

Here's a pic of the signal box with 2 instruments (one of which does not yet have it's brass "needles" attached to the servo horns).  Also bottom right you can see the block token instrument that issues token and energises the track power.

 

291018-1.JPG.7ac539424864e98310130460ab21264b.JPGd

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1 hour ago, CDGfife said:

 

The Block instruments on my Cadhay Sidings layout work with one servo to 3 positions of the needle.  I started with a MERG pocket money Servo kit which uses a pot to infinitely vary the position of the servo.  Working out the 3 resistances that gave the three positions was simply about turning the pot until the needle was in the right place, disconnecting the pot and measuring it's resistance.  That gave me the resistance values so 3 routes to the servo via 3 (different) resisters controlled by 2 relays gives the answer you are looking for.  I then run 2 wires from one instrument to the other in each direction (actually via CBus these days but originally it was a wire!) and these take the 2 relays to ground via a rotary switch in the right order to vary the resistance to the servo accordingly.

 

Here's a pic of the signal box with 2 instruments (one of which does not yet have it's brass "needles" attached to the servo horns).  Also bottom right you can see the block token instrument that issues token and energises the track power.

 

291018-1.JPG.7ac539424864e98310130460ab21264b.JPGd

 

Exactly the sort of set up I had in mind. Set resistances for the three positions. Thanks for proving to me that I wasn't  going into realms of fantasy!

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You don’t need much gubbins to make the indicators, just two electromagnets. These could be got from peco point motors. Wire them so that one attracts and one repels and shove a soft iron nail up each one to be a pole piece. The needle sits in a tube through the face, with a pointer on side and the other a bit of tin that sits between the coils. No voltage, needle hangs at line blocked, volts + the needle gets pulled one way, volts - needle goes the other way. Simples!


But don’t forget that the real Railway used lamps instead of needles for blocks as well.

 

Andy g

 

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4 minutes ago, uax6 said:

You don’t need much gubbins to make the indicators, just two electromagnets. These could be got from peco point motors. Wire them so that one attracts and one repels and shove a soft iron nail up each one to be a pole piece. The needle sits in a tube through the face, with a pointer on side and the other a bit of tin that sits between the coils. No voltage, needle hangs at line blocked, volts + the needle gets pulled one way, volts - needle goes the other way. Simples!


But don’t forget that the real Railway used lamps instead of needles for blocks as well.

 

Andy g

 

I knew someone  who did that but found that leaving power on the coils for any length of time caused overheating. No doubt getting the right coils and power supply would solve that but his H&M ones worked on 12volts DC cooked themselves!

 

Buckingham has lights and they really are simple construction. A rotary switch working two bulbs in series, one at each end. I didn't  know the real railway used lights too. That is worth remembering! 

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CDGFife,

 

This was what I saw as a possibility, but because MERG have shut down their Kitlocker, I couldn't even see what was available, but found an alternative source. I now recall seeing your postings on the Scalefour forum (actually following it all with interest).

 

What do the relays do? Did you manage to use a single MERG board to drive both the primary and mirrored servo?

 

thanks,

Richard

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2 hours ago, Winander said:

CDGFife,

 

This was what I saw as a possibility, but because MERG have shut down their Kitlocker, I couldn't even see what was available, but found an alternative source. I now recall seeing your postings on the Scalefour forum (actually following it all with interest).

 

What do the relays do? Did you manage to use a single MERG board to drive both the primary and mirrored servo?

 

thanks,

Richard

Richard

 

I use the 2 relays to switch between the three different resistance routes to define the servo position.  The NC (normally closed) output of relay 1 is connected to the input of relay 2.  NO (normally open) output from relay 2 goes to the "Train on Line" position resistance (and back to the PMP board & on to the servo).  NC output from Relay 2 goes to the "Line Blocked" position resistance and the NO output from Relay 1 goes to the "Line Clear" resistance.  I use cheap off the shelf relay modules set to a low trigger, so if neither relay trigger lines are held to ground then the servo reads "Line Blocked".  Relay 1 is taken to ground by moving the rotary switch in one direction and relay 2 is taken to ground by moving the rotary switch the other way, each switching the resistance route as above and hence giving its respective servo position.  Of course the rotary switch is on the other Block Instrument so the two ground trigger wires have to run between the instruments!

 

Just one Pocket Money servo driver (PMP3) with a slight adaption to give three resistor routes (via the 2 relays as described above) instead of the single loop to the pot as designed powers one servo to 3 positions.  I use the relay modules as they appear elsewhere on Cadhay - they are all 12v and interchangeable so I only need to carry a small spares quantity, but the 2 relays could just as easily be incorporated onto a (slightly larger ) stripboard with the PMP3 kit, I just prefer the plug and play exchange in the event of a failure.

 

One of my initial reasons for going down this road was low current draw compared to any electromagnetic solution.

 

I'll try and get a pic of the gubbins behind the instrument at some point but Cadhay is currently packed away so it might take a day or two

 

Hope that helps

 

Chris

 

Edit to answer the actual question - I have 2 PMP3s in each instrument with the local triggered from the local rotary switch and the remote from the other instrument, hence the connection between them is 4 wires - 2 triggers in each direction.

Edited by CDGfife
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Clutton, being a single line, used electric key token working (EKT). This method is used on the Severn Valley, West Somerset, Talyllyn (there must be others). Seen here is the frame and two instruments. The bells are on top, no tappers, the key tappers are in the red instruments. You can make out the tappers. Plus there is a three position switch. Key in, down key out, up key out. Trains are offered in the usual way, and when accepted, the instrument is turned to the appropriate direction. At the same time, in the staging roads, the corresponding instrument is turned, and if both are in synchronisation,  a needle points to the appropriate direction - this acts as a virtual key token. Foolproof (to a degree). A telephone is also provided for communication between the staging roads (where the driver sat) and the signal box.

 

York - 2006 (5).jpg

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From the position of the frame and instruments, a down train has arrived (you can see the end of it). The down home has been put back, but the Pensford instrument has not yet been corrected. The down instrument is also over for the down token, but the down starter has not been pulled, probably an inexperienced signalman as the route and signals should be all be pulled in this situation.

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2 hours ago, CDGfife said:

Richard

 

I use the 2 relays to switch between the three different resistance routes to define the servo position.  The NC (normally closed) output of relay 1 is connected to the input of relay 2.  NO (normally open) output from relay 2 goes to the "Train on Line" position resistance (and back to the PMP board & on to the servo).  NC output from Relay 2 goes to the "Line Blocked" position resistance and the NO output from Relay 1 goes to the "Line Clear" resistance.  I use cheap off the shelf relay modules set to a low trigger, so if neither relay trigger lines are held to ground then the servo reads "Line Blocked".  Relay 1 is taken to ground by moving the rotary switch in one direction and relay 2 is taken to ground by moving the rotary switch the other way, each switching the resistance route as above and hence giving its respective servo position.  Of course the rotary switch is on the other Block Instrument so the two ground trigger wires have to run between the instruments!

 

Just one Pocket Money servo driver (PMP3) with a slight adaption to give three resistor routes (via the 2 relays as described above) instead of the single loop to the pot as designed powers one servo to 3 positions.  I use the relay modules as they appear elsewhere on Cadhay - they are all 12v and interchangeable so I only need to carry a small spares quantity, but the 2 relays could just as easily be incorporated onto a (slightly larger ) stripboard with the PMP3 kit, I just prefer the plug and play exchange in the event of a failure.

 

One of my initial reasons for going down this road was low current draw compared to any electromagnetic solution.

 

I'll try and get a pic of the gubbins behind the instrument at some point but Cadhay is currently packed away so it might take a day or two

 

Hope that helps

 

Chris

 

Edit to answer the actual question - I have 2 PMP3s in each instrument with the local triggered from the local rotary switch and the remote from the other instrument, hence the connection between them is 4 wires - 2 triggers in each direction.

 

Many thanks for that. I actually understand what you have done and could probably make some like that from your description. 

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7 hours ago, t-b-g said:

I knew someone  who did that but found that leaving power on the coils for any length of time caused overheating. No doubt getting the right coils and power supply would solve that but his H&M ones worked on 12volts DC cooked themselves!

 

Buckingham has lights and they really are simple construction. A rotary switch working two bulbs in series, one at each end. I didn't  know the real railway used lights too. That is worth remembering! 

 

If you put a slugged relay (ie a slow to operate relay) in circuit with the coils, you can switch in a resistor in series with the coils. This will then reduce the operating hold voltage and the needles will stay put. You might be able to get the coild sto work with a resistor anyway. I'd want something like 2000 ohms min on the coils, 3-4K ohms coil resistance would be better. Never metered a peco coil, but guessing much less than that.

 

Andy g

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