Block Bells

[ikcdab]

I think rmwebbers will be interested in a pair of block Bells I have made for my friends layout. This layout is in two lofts, and so communication is required between the lofts. I originally make one set, but superseded then with these that are to a more prototypical design.

First we have the two cores for the coils:

 

These are then wound with 0.65mm copper wire. Loads of calculators online for working out the number of turns on the coils, I mostly didn't understand these and so I just went with around 750 turns on each coil which is around 33m of wire. 12v supply. That seems to give a powerful magnet. Wrapped the completed coils in insulation tape.

 

I have gone for two coils in each bell (the GWR seemed to use 4) and I wired them in parallel.

 

The original GWR bells seem to have the clapper attached to a metal flap that moves when the coils are energised. With my smaller size, I was worried about the flap not dropping back when the coil is de-energised so I opted for angle steel.

 

This L shape gives a counterbalance to allow the clapper to fall away. Also seen in this picture is the microswitch tapper.

 

Here is the completed internal works.

 

You can see that I have epoxied a steel rod as a pivot that rotates in wooden bearings. When the coil is energised, it attracts the steel angle and thus the clapper.

 

Here is the complete bell.

Built into a plywood case. The bell gong is mounted on an M4 bolt. This means that I can adjust the gong up and down to give the best note.

The bells work very well. Nice clear tone of the right volume. Just need to complete the second one now!

 

All comments welcome!

 

Ian C

 

 

 

 

 

[Michael Hodgson]

I have some very similar to this that I bought somewhere.  My cabinet making skills aren't up to your standards.

 

On the prototype the tapper is essentially a morse key.  That is, you can hear a metallic tap when you send a code.

You can't hear your own bell, the tapper operates only the one at the far end, and of course (unlike many model railways) it's too far away to hear from the sending signal box.

 

A microswitch like the one you are using may  approximate to the "feel" of the original, but it will still seem odd not to hear the code you are ringing.  If you can hear the bell ringing in the far loft, it'll be OK though.

 

The bell itself looks like a real one?  I have used models made from bells from an old-fashioned  telephone* or even a bike bell.  On prototype bells I haven't noticed a difference in tone by adjusting the height of the thing but you may be right.  What I have seen to create different tones is a lump of something solid (epoxy etc) glued to the inside, or a slot cut with a hacksaw.  Different size/shape is of course the way it was done on the prototype.

 

You probably don't want to follow prototype circuitry.  On the prototype a major cost is the lines wires and their maintenance.  Only one wire (plus earth return) is used to connect the two bells. The circuit disconnects your own bell from the line when sending before connecting the sending battery to line (break before make contacts).  On your model, you will need two line wires, one for each direction, but you might also be running them off a single power supply.  

 

I'm not familiar with GWR circuitry, but I suspect the other two coils may have been a relay circuit, ringing the bell indirectly with the local battery but operating the relay using the battery at the sending end.  One of the problems with block circuits is that a higher voltage is required if intermediate boxes can switch out of circuit and close; some sort of amplification by repeater relays may be necessary to overcome this.   

 

* advantage of telephone bell is you can rip the whole mechanism out of the phone &  modify it to single stroke.  This saves the hassle of winding your own coils and making your own hammer assembly.  But it won't look as pretty.

[RailWest]

It is certainly the case AFAIK - and from all the examples which I have seen - that GWR block bells used for block working on double-track lines did contain relays driven by the line wire circuit, which switched current to the bell coils from a local circuit. The block bells used with electric train staff or electric key token circuits had no tappers (worked by the plunger in the staff/token instruments) and no relays of their own, usually being controlled from relays in the instruments instead. AIUI the bell coils local circuit was usually about 6V.

Edited October 6, 2021 by RailWest

[5BarVT]

55 minutes ago, RailWest said:

It is certainly the case AFAIK - and from all the examples which I have seen - that GWR block bells used for block working on double-track lines did contain relays driven by the line wire circuit, which switched current to the bell coils from a local circuit. The block bells used with electric train staff or electric key token circuits had no tappers (worked by the plunger in the staff/token instruments) and no relays of their own, usually being controlled from relays in the instruments instead. AIUI the bell coils local circuit was usually about 6V.

I’m looking at a circuit now!  Bell relay connected to line which drives the bell fed at 12V through a 15ohm resistor.

Paul.

[ikcdab]

4 hours ago, Michael Hodgson said:

I have some very similar to this that I bought somewhere.  My cabinet making skills aren't up to your standards.

 

On the prototype the tapper is essentially a morse key.  That is, you can hear a metallic tap when you send a code.

You can't hear your own bell, the tapper operates only the one at the far end, and of course (unlike many model railways) it's too far away to hear from the sending signal box.

 

A microswitch like the one you are using may  approximate to the "feel" of the original, but it will still seem odd not to hear the code you are ringing.  If you can hear the bell ringing in the far loft, it'll be OK though.

 

The bell itself looks like a real one?  I have used models made from bells from an old-fashioned  telephone* or even a bike bell.  On prototype bells I haven't noticed a difference in tone by adjusting the height of the thing but you may be right.  What I have seen to create different tones is a lump of something solid (epoxy etc) glued to the inside, or a slot cut with a hacksaw.  Different size/shape is of course the way it was done on the prototype.

 

You probably don't want to follow prototype circuitry.  On the prototype a major cost is the lines wires and their maintenance.  Only one wire (plus earth return) is used to connect the two bells. The circuit disconnects your own bell from the line when sending before connecting the sending battery to line (break before make contacts).  On your model, you will need two line wires, one for each direction, but you might also be running them off a single power supply.  

 

I'm not familiar with GWR circuitry, but I suspect the other two coils may have been a relay circuit, ringing the bell indirectly with the local battery but operating the relay using the battery at the sending end.  One of the problems with block circuits is that a higher voltage is required if intermediate boxes can switch out of circuit and close; some sort of amplification by repeater relays may be necessary to overcome this.   

 

* advantage of telephone bell is you can rip the whole mechanism out of the phone &  modify it to single stroke.  This saves the hassle of winding your own coils and making your own hammer assembly.  But it won't look as pretty.

Thank you for the reply. The microswitch i used does give a certain amount of feedback: i think you can 'feel' the taps as per a prototype example. My only reservation is the longevity of the microswitch, given the very robust jabbings it might get from the signalmen. If the micros fail, then i do have a backup plan to make some much more robust ones on the morse-key principle.

 

As for bell gongs, these are all ex-doorbell and are very old! They each do have slightly different tones which is sufficient for our purposes. Loft number 1 has two signalboxes, each working to a single box in loft number 2. So its only Loft 2 that needs differing tones. I looked widely for other shapes of bell gongs, but couldn't find any at a reasonable price anywhere. I did just miss some nice ex-GPO bells on ebay, but luckily the old doorbell gongs work very well. The height of the bell has no bearing on the tone. The adjustment is to make sure that the clapper strikes the edge of the rim which i have found gives the clearest tone. These bells look quite high, but this is to ensure that there is sufficient "throw" on the clapper arm to ring the bell properly. 

Meanwhile, my new coil of wire has just arrived so tomorrow i am winding the next two coils!

Ian C

[Claire RJ]

Seing that Ian has posted concerning the block bells which he has made for my loft layout, you will probably appreciate that it was only once we had both lofts available and joined together as one integrated railway that block bells became very desirable. The whole layout is quite a complex system featuring a total of five stations, four junctions and a motive power depot, all based on actual places in the West Country. It was necessary for me to run two 12 core cables  through the cavity wall from the original loft into the extension loft, of which 4 wires of the 12 on each side of the lofts are for the block bells. Many years ago my two sons and I had dabbled in a crude form of bell system in just one big loft, which was something which had appealed to me as it would add an extra layer of reality to running a layout based on real places. I had acquired some bells with this sort of installation in mind and these are now in use in Ian's units. The other wires are for section isolation and for the colour light signals which control and give permission for trains to run from one loft into the other. When I first installed these bells with no one in the other loft to hear them I was not sure that they were working because I could not hear the one ringing from one loft to the other, so I said to Ian  that I did not think they were working. So when I discovered that they were, it was a most rewarding thing, because it would be unrealistic to be able to hear them ring from one loft to the other, and is the reason why there is no point in us putting bells in between all the other stations,

[Michael Hodgson]

6 hours ago, ikcdab said:

Thank you for the reply. The microswitch i used does give a certain amount of feedback: i think you can 'feel' the taps as per a prototype example. My only reservation is the longevity of the microswitch, given the very robust jabbings it might get from the signalmen. If the micros fail, then i do have a backup plan to make some much more robust ones on the morse-key principle.

 

I wouldn't worry unduly about the longevity of the microswitches, though they wont take well to very ham-fisted use.  I have used a number of home made combined bell/block instruments about the size of the old Hornby block instruments.  The tapper itself was also home-made - a flexible strip of copper or phosphor-bronze  with a  brass button soldered on the end as a knob and fastened at the other end with a few panel pins into the wooden base  contacting a fixed copper strip fastened in similar manner.  They have been in frequent use for half a century, worked by perhaps over a hundred different operators, some of whom would have been serving or retired BR signalmen.  Relatively little maintenance has been needed, though one or two tappers were too far gone to repair and have had to be replaced by microswitches which actually feel less positive than the home made ones.

[uax6]

The bells in use in the BR penguins were cast differently for different tones. You would often find that in a box that the tones would be similar, so unofficial mods would be made to the gongs to help change the tones more. One I've come across was the addition of chewing gum to deaden the sound, or the addition of a chain of paper clips on the clapper so that you could see which bell was being rung...

 

Andy G

[Claire RJ]

8 hours ago, uax6 said:

All four of our bells have different tones.

All four of our bells have different tones.