REA chair types and designations in plug track

[Martin Wynne]

.
It's now quite a while since I finished enough chairs for a full turnout, so it's time I wrote an explanation of the REA chair designs and how they are designated in Templot.

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REA chairs come in S , M and L. That's Short, Medium and Long. This refers to the length of the rail seat supporting the rail. Or in other words it is the sideways dimension that we normally refer to as the width of a chair.

And in two sizes:

Size 1 chairs are for BS-95R 95lb/yd bullhead rail (95 pounds per yard). This corresponds to code75 BH rail in 4mm/ft scale and code131 BH rail in 7mm/ft scale.

Smaller size 2 chairs are for the lighter BS-85R 85lb/yd bullhead rail. This corresponds to code125 BH rail in 7mm/ft scale. As far as I know there is no corresponding code72 BH rail available for 4mm/ft scale.

So for 95lb rail we have prototype size 1 chair designations such as S1, L1, M1, etc. (M1 bridge chairs not yet done for plug track -- but available in brass from DCC Concepts if you need some in 4mm/ft scale).

BS-95R 95lb rail was intended and used for main running lines. It is still in use and is by far the most common size of bullhead rail.

BS-85R 85lb rail was intended for branch lines, loops, sidings and yards. In practice not much is found because such lines very often use serviceable used 95lb rail cascaded down from running lines. I haven't yet done any size 2 chairs (S2, L2, M2, etc.) in plug track but I will do eventually, mostly for modellers in 7mm/ft scale where 85lb rail (code125 BH) is very commonly used (why?).

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1. Switch chairs

(to be continued shortly. I shall edit this post rather than posting replies, with the aim of eventually transferring it to a Companion page. I'm too tired to write it all in one go.)

Martin.

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2. V-crossing chairs

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3. V-crossing chairs - more

 

[Hayfield]

I don't know if this is just coincidence but the Exactoscale range has M1 chairs, from memory they are only used in slips, certainly none are used in the old turnout and diamond crossing kits they sold. They had no kits or plans for 3 ways or tandems.

A pack of 100 lasts years, unless of course you build slips. However I have noticed some abnormalities in some Exactoscale plans and with turnouts Exactoscale provided a limited range

 

[Phil O]

There were 10 panels of 85R on the ESR, there was very little visual difference to it compared with 95R, in fact on a couple of occasions we got worn 95R to sit in 85lbs chairs. The difference is only a couple of mm.

 

[S-Club-7]

...for modellers in 7mm/ft scale where 85lb rail (code125 BH) is very commonly used (why?)...

Because until fairly recently that's all that was available from the trade

And it measures approx 1/8 by 1/16 inch so perhaps (i.m.o.) before the trade got involved that size of plain bar was all that was available?

 

[Martin Wynne]

Because until fairly recently that's all that was available from the trade

@S-Club-7

Hi David,

Not so. At one time code 131 BH rail was available from both Slater's and C&L, before C&L's many changes of owner. Slater's track-building handbook even mentions their "Code 131 bullhead rail". They now deny ever supplying such a thing, despite the fact that somewhere I have an invoice showing that they sold me some back in the 1980s. When I find it I shall send them a copy.

I suspect the reason is that at some stage the rail-drawing tool needed replacement, someone was drawing up a new tool for the rail, and measured a bit of 85lb rail not realising what it was.

cheers,

Martin

 

[Martin Wynne]

The difference is only a couple of mm.

@Phil O

Hi Phil,

It's a bit more than that. The height difference between BS-95R and BS-85R is 1/4" = 6.35mm.

But I agree it's not much, and if the 95 rail is worn probably no difference at all.

cheers,

Martin.

 

[Steve_Cornford]

Hi Martin,
In your diagram - "3. V-crossing chairs - more" you have labelled two ZY chairs but they have different sizes.
Also 2 occurences of DD.
Was that your intention?
Steve

 

[Martin Wynne]

Hi Martin,
In your diagram - "3. V-crossing chairs - more" you have labelled two ZY chairs but they have different sizes.
Also 2 occurences of DD.
Was that your intention?
Steve

@Steve_Cornford

Hi Steve,

Yes, that's correct. ZY chairs are not interchangeable for the very reason that they are not all the same size or angle.

ZY is the type designation, not a specific size. ZY chairs are the standard-width 8" wide chairs which fill the wing rail front space where there is not enough room for 2 L1 chairs on the timber, and before you reach the knuckle. How many depends on the V-crossing angle and the model flangeway gap. If there is more than one they will differ in size as the rails get closer together. They will also differ fractionally in rail angle, which means, at least in theory, that the loose jaws are not interchangeable between them.

Likewise DD chairs are not interchangeable and vary in size. On the prototype they should have inside keys on the gauge side of the rail. We can't do that in models because of the deeper flanges for 00/EM etc. In plug track, but not the prototype, they have a fiddly slide-in central locking jaw because there isn't room for two pin-type loose jaws to flex past each other when inserted.

There is so much of this stuff that I have to keep writing and it's wearing me out. Thanks for helping.

I was trying to write all this stuff and more earlier when my phone system bit the dust being changed over to digital internet. It's been a difficult day, and Firefox isn't helping.

I will get back to describing all the other chair types as soon as I can.

cheers,

Martin.

 

[Stephen Freeman]

Because until fairly recently that's all that was available from the trade

And it measures approx 1/8 by 1/16 inch so perhaps (i.m.o.) before the trade got involved that size of plain bar was all that was available?

Just a thought, perhaps it was a desire to be "more compatible" with code 124, a sort of a version of bullhead sold by a company in the UK. On second thoughts perhaps because most 7mm scale modellers actually model Branch Lines. Very few main lines.

 

[Lancastrian]

@S-Club-7

Hi David,

Not so. At one time code 131 BH rail was available from both Slater's and C&L, before C&L's many changes of owner. Slater's track-building handbook even mentions their "Code 131 bullhead rail". They now deny ever supplying such a thing, despite the fact that somewhere I have an invoice showing that they sold me some back in the 1980s. When I find it I shall send them a copy.

I suspect the reason is that at some stage the rail-drawing tool needed replacement, someone was drawing up a new tool for the rail, and measured a bit of 85lb rail not realising what it was.

cheers,

Martin

Martin,

From "Track Construction Without Tears" by Slaters' (Plastikard) Ltd.

Not even Code 131 according to them.