Templot Club Archive 2007-2020                             

topic: 235C+L track and P4 gauges
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posted: 13 Nov 2007 03:43

from:

mattots
 
United Kingdom

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I just received my copy of the Scalefour Digest in the post today, having just joined the Scalefour Society (yep, I've finally decided to go down the P4 route).

One interesting point that I stumbled across while flicking through it is on the sheet covering turnout construction using C&L components (23.6.4). It says that you "do not want a track gauge that has a firm grip on the running head and holds the rail upright" since as soon as you remove the gauge the chairs will tilt the rail inwards (as they are supposed to) therefore making the track under-gauge.

I've never seen this mentioned anywhere before. Can anyone expand on this? Do the gauges produced by the Scalefour Society have this problem with track constructed using C&L chairs and if so how do people get around it? The digest sheet recommends turning down the flanges on roller gauges so that only the top of the rail head is engaged. Is this necessary? How is it done? What about the other types of gauges? Or is this digest sheet referring to older types of gauges no longer available? I presume there are plenty of people out there building P4 track with C&L components!

Matt

posted: 13 Nov 2007 12:55

from:

Paul Boyd
 
Loughborough - United Kingdom

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The original K&L chairs did have this feature, and it allowed for automatic gauge widening on curves as well as giving the prototypical 1:20 cant.  At the time this was widely advertised as a selling point.  As far as I know, the current C&L chairs have the same feature although there was some confusion over this point a little while ago on either P4_talk or E4um.  If you use roller gauges with this type of chair, you will neatly undo the automatic gauge widening, apart from the fact that roller gauges give no gauge widening anyway.

Not that I've built miles of P4 track, but I find the gauges don't actually grip that tightly, or maybe the design has been modified, but I don't really find it an issue.  From memory, none of the gauges I have hold the rail over the full height.   At critical points, such as crossings, you'll be using check rail gauges anyway - the rails are upright through crossings and the Exactoscale check rail chairs achieve this nicely.

I only use roller gauges to roughly hold rails in alignment.  They're nasty, horrible things :)  The ones to use are triangular gauges for plain track, and various block and check rail gauges for crossings.  All available from either the Scalefour or EM Gauge Societies.

posted: 13 Nov 2007 13:54

from:

mattots
 
United Kingdom

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Paul Boyd wrote:
At critical points, such as crossings, you'll be using check rail gauges anyway - the rails are upright through crossings and the Exactoscale check rail chairs achieve this nicely.
So would you suggest not using C&L chairs on the crossing part of turnouts?
Matt

posted: 13 Nov 2007 15:15

from:

Paul Boyd
 
Loughborough - United Kingdom

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So would you suggest not using C&L chairs on the crossing part of turnouts?
For the check rail area, I use the Exactoscale check rail chairs which hold the stock rail vertically together with the check rail itself.  On the vee, you can try C&L crossing nose chairs which look really nice, and then further back up the vee you can revert to standard C&L chairs (where the rail prototypically cants back over).  On the wing rails again use C&L or Exactoscale chairs leading up to the vee, but then I only use plastic chairs cosmetically - the wing rails and the V are soldered to a thin strip of brass or nickel-silver strip.  Exactoscale do some quite nice bridge chairs which need to be scattered about here and there!

Really, it's just a case of using the parts from the two manufacturers to suit your needs.  There's nothing to choose between them in terms of quality, but they both do different parts.  Personally I tend to use C&L wherever possible, and Exactoscale for the bits that C&L don't do.

I should mention that this is for GWR trackwork.  If you're into modelling LNER (or early BR, I think), then you might want to look at the Exactoscale turnout kits.  I've never used them but they do look really nice.

posted: 14 Nov 2007 02:48

from:

mattots
 
United Kingdom

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Paul Boyd wrote:
I should mention that this is for GWR trackwork.

I am modelling GWR trackwork. As you may have seen in a recent post I raised the issue of the lack of availability of 2-bolt slide chairs. I'm certainly no expert on prototype track but from what I can gather from the various sources I've been scouring recently the check and bridge chairs should also really be 2-bolt for GWR track. I'm assuming that you just accept the fact that some of the chairs will be slightly incorrect, or do you 'doctor' them in any way to replicate the correct bolt detail? (As an aside, I did have a go at filing off the bolt detail on a C&L plastic slide chair with a view to trying the wire-in-hole method of replicating a single central bolt but I'm not sure I can bring myself to go to such lengths, even for the small layout I have planned. I am very surprised that neither Exactoscale or C&L have produced appropriate versions of these chairs yet.)

Also, what is the difference in useage between the two types of checkrail chairs produced by Exactoscale (0.68mm and 0.8mm flangeway)?

Matt

posted: 14 Nov 2007 04:12

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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mattots wrote:
I'm certainly no expert on prototype track but from what I can gather from the various sources I've been scouring recently the check and bridge chairs should also really be 2-bolt for GWR track.
Hi Matt,

Well strictly "2-screw" when they are used in pointwork. Only GWR plain track sleepers have bolted chairs (bolts inserted from below). For pointwork on timbers, the chairs are fixed from above with chair screws. The bridge chairs (L1) have the screws on 2 diagonally opposed corners.
Also, what is the difference in useage between the two types of checkrail chairs produced by Exactoscale (0.68mm and 0.8mm flangeway)?
The latter are for use where you have 0.12mm of gauge-widening, in order to preserve the correct check gauge. Mainly intended for continuous check rails in curved plain track, rather than pointwork. If you have some other amount of gauge-widening, you shouldn't use them -- prototype steam-era gauge widening is up to 3/4" max, which scales to 0.25mm.

In pointwork the check gauge is so important that I would prefer to use a soldered construction for crossing check rails and add the chairing detail as cosmetic half-chairs only.

regards,

Martin.

posted: 14 Nov 2007 12:53

from:

Paul Boyd
 
Loughborough - United Kingdom

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Matt wrote:
I am modelling GWR trackwork
Ah - do you have "The Bible"?  This is the "GWR SWITCH AND CROSSING PRACTICE - A Design Guide for 4mm Modellers" published by the Great Western Study Group.  Essential reading!
I'm assuming that you just accept the fact that some of the chairs will be slightly incorrect, or do you 'doctor' them in any way to replicate the correct bolt detail?
I'm afraid life's too short :) I just accept them as they are, but I too am surprised that these aren't available.  I take the view that what we do have available is a massive improvement on what was around years ago and take what I can get!

posted: 14 Nov 2007 13:34

from:

Alan Turner
 
Dudley - United Kingdom

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mattots wrote:
Also, what is the difference in useage between the two types of checkrail chairs produced by Exactoscale (0.68mm and 0.8mm flangeway)?

The 0.68mm is for crossings, the 0.8mm is for check-rail.

Alan

posted: 14 Nov 2007 13:43

from:

Alan Turner
 
Dudley - United Kingdom

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mattots wrote:
One interesting point that I stumbled across while flicking through it is on the sheet covering turnout construction using C&L components (23.6.4). It says that you "do not want a track gauge that has a firm grip on the running head and holds the rail upright" since as soon as you remove the gauge the chairs will tilt the rail inwards (as they are supposed to) therefore making the track under-gauge.

I would suggest that you do not use "Roller Gauges" to construct "Scale" trackwork (ie with a 1:20 cant). You should use the EM or P4 type three point type. The Roller Gauge is only suitable for rail soldered to copperclad where the rail is upright.

Alan

posted: 14 Nov 2007 17:10

from:

Brian Lewis
 
United Kingdom

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Alan Turner wrote:
I would sugest that you do not use "Roller Gauges" to construct "Scale" trackwork (ie with a 1:20 cant). You should use the EM or P4 type three point type. The Roller Gauge is only suitable for rail soldered to copperclad where the rail is upright.
Not so Alan, a roller gauge is designed to do no more than 'kiss' the top of the rail. Properly used they will not interfere with the cant.

As to what type of gauge you use, this is very much down to individual preference. At one time, I built trackwork for others, but sadly had to give up due to lack of time. I remember that I built 36 turnouts in various arrays in the month I stopped and this was typical of a month's output. In all the construction I ever did, I used nothing more than 6 roller gauges and a pocket mirror.

Regards

Brian Lewis

Carrs -- C+L Finescale

posted: 14 Nov 2007 17:35

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Alan, Matt,

I agree with Brian. Roller gauges are fine, and far and away the easiest type to make (assuming you have a lathe, of course :) ). The trick is not to have them too large in diameter, so that they fit between two adjacent rail fixings without getting in the way. A roller gauge turned from 6mm or 8mm bar is plenty large enough (1/4" or 5/16" dia) in 4mm scale.

For use with canted rail in chairs it's important not to make the gauge slots deeper than the rail head. The radiused corners on the rail head easily allow a few degrees of twist to accommodate the cant.

For use with soldered construction on rivets or copper laminate, you don't have the chairs to hold the rail upright. So in that case it helps to make the slots the full depth of the rail so that the gauge also serves to hold the rail vertical.

This means that a roller gauge for glued chaired construction is not so good for soldered construction, and vice versa. Ideally you need a gauge tool specific for each. If you have a gauge with deep slots, it can be converted for use with canted rail by winding 0.9mm soft copper wire into the slots.

regards,

Martin.

posted: 14 Nov 2007 17:49

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Alan Turner wrote:
The 0.68mm is for crossings, the 0.8mm is for check-rail.
Hi Alan,

Only Exactoscale can say in detail what their components are intended for, but the standard flangeway gap for P4 is 0.68mm. So the smaller size should be used for all pointwork, except very short turnouts where some gauge-widening has been introduced through curviform-type crossings. In that case, and assuming the widening is exactly 0.12mm (to 18.95mm gauge), the 0.8mm chairs will give the correct check gauge.

On track laid to 18.83mm gauge, the 0.8mm chairs will produce a non-functional cosmetic check rail, where required.

regards,

Martin.

posted: 14 Nov 2007 20:27

from:

Bruce Boldner
 
 

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Matt,

I also use the Scalefour Society triangular 3 point gauge. In fact you should always use it when laying curves (with the apex of the gauge on the inner rail and the two claws of the wide side of the triangle on the outer rail). This fractionally widens the gauge throughout the curve.

However, I also use the triangular gauge for laying straight track. I find it the handiest of all the gauges. I have filed down the outer leg of each of the three claws which clamp onto the rails. I've left just enough of these outer legs remaining so that they just stand proud of the indentation that the railheads seat in. I've left the inner legs of each claw untouched. Modifying the gauge in this way allows the rails to be held in gauge but not forcibly held vertically upright. If the gauge isn't modified, the rails snap back under gauge when the gauge is removed, as the seat of the chairs cants them inward as per the prototype. Just be careful not to file the outer claws below the depth of the indentation that holds the rails. You must still have that slight recess to hold the head of the rail in gauge.

I haven't tried to modify any of the roller gauges, but just use them as is. I use the roller gauges for building common crossings, as the rails should be vertical in these anyway.

Regards,

Bruce Boldner.

posted: 14 Nov 2007 20:35

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Bruce Boldner wrote:
I use the roller gauges for building common crossings, as the rails should be vertical in these anyway.
Hi Bruce,

I've seen this stated elsewhere, and I'm not sure where it comes from. I know the V-crossings in the Exactoscale kits have all vertical rails for ease of manufacture, but that doesn't make it prototypically correct.

For all bullhead track, and flat-bottom track prior to about 1970, only the nose ends of the vee point and vee splice rails are vertical. For the common sizes we use, 1:6 to 1:9, there is a twist in the rail between the C and D chairs* (3rd and 4th from the nose) to return the rails to a 1:20 cant for the remainder of their length.

All the other rails in the V-crossing, including the wing and check*** rails, are canted at 1:20.

From about 1970 to 2000, flat-bottom turnouts used vertical rails throughout, not just the V-crossings (and the track gauge was reduced to 1432mm).

* below 1:6 the twist is between the B and C chairs.
* for 1.9.5 to 1:13 the twist is between the D and E chairs.

*** correction. GWR check rails are vertical, and possibly other companies' too. See later in this topic.

regards,

Martin.

posted: 15 Nov 2007 08:52

from:

Bruce Boldner
 
 

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Hi Martin,

Thanks for your advice.  Yes, I did get the information about the rails being vertical  through the common crossing from the information sheet supplied with an Exactoscale turnout that I purchased. I'm always happy to be corrected, as I hate to be misinformed. 

Apart from that one commercial turnout, I have constructed all others on my layout  using a home made modified version of a jig designed by Paul Kehoe. This jig was featured in the Scalefour news back around 2002 (I don't know which issue.)

Whilst held in the jig,  point, splice, wing and check rails are held vertical whilst being soldered to PCB strips. However, the common crossing unit is then secured to the wooden sleepers  on the layout with C & L plastic chairs.  So the rails forming the central part of the crossing are vertical, whilst these same rails, as they approach the  outer extremities of the crossing are twisted back towards the 1:20 cant by the chairs. 

This twisting must occur, as I have never noticed a difference in angle between the rails emanating from a common crossing and adjoining sections of plain track.

So that being the case, it appears my turnouts, even if inadvertently, reasonably conform with the prototype!
 
Regards,

Bruce Boldner.

posted: 15 Nov 2007 11:33

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Bruce Boldner wrote:
This twisting must occur, as I have never noticed a difference in angle between the rails emanating from a common crossing and adjoining sections of plain track.

So that being the case, it appears my turnouts, even if inadvertently, reasonably conform with the prototype!
Hi Bruce,

The prototype twist is not as simple as it might seem, and is extremely difficult to replicate properly in model form. The running face of the rail must remain in a straight line, so what you have in effect is a sideways joggle in the foot of the rail.

I now need to correct myself. I have now read in David Smith's GWR book that GWR check rails are vertical to reduce wear on the rail head, and so better maintain the check gauge. I looked at the Paddington chair drawings and they confirm this. However, other bullhead check chair drawings show inclined check rails, so I'm not sure if this is purely a GWR practice or more widespread. Apologies for the error.

However all bullhead wing rails are inclined.

regards,

Martin.

posted: 15 Nov 2007 17:44

from:

Bruce Boldner
 
 

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Martin,

Well, I model the Midland, not 'God's Wonderful Railway', so I guess the jury is still out on whether the former may also have had vertically oriented rails in it's  crossings.

All very interesting. However I have found the most important aspect of a common crossing in order to achieve successful running  by rolling stock (apart of course from getting the crossing to stock rail gauge right) is to have the point and splice rails in perfect alignment with their respective closure rails.

By the way, for P4, what gap would you recommend between the tip of each switch blade and it's adjacent stock rail?  I've been using the same gauge I use for the flangeway gap in the common crossing, ie .68mm, but have been told this is too fine.  My thinking has been that the swich blade tip currently not resting against it's stock rail can act as a check rail and stop the wheels floating across and riding up over the switch blade on the opposite side.  But I've been told wheels should not need to be checked at this section of the turnout. I can see this should be so for straight turnouts, but what about curved ones?

Anyway, all of the 35 operating turnouts on my layout have been built with just a .68mm gap at the blade tips and 99% of the time they work OK. Now again a piece of rolling stock rides up over the opposite switch blade however, and I do wonder. But if the switch blade to stock rail gap was increased, surely this would allow more latitude for the wheels to float over to the other side.

I must say that P4 trackwork can be incredibly frustrating to achieve consistently reliable running. I have constructed all my turnouts to the very best of my ability, using all the society gauges, filed the switch blades sharp as razors, notched the stock rails and recessed the blades in some cases, just put a set in the stock rail with no notching in other cases.

But then it is necessary to fine tune all the rolling stock. Getting the wheel back to back gauge is the most obvious and easiest to achieve. Then comes getting the vehicles sufficiently weighted. I tried MJT compensated bogies on my Ratio coaches, but found that the extra flexibility made them more liable to ride up over switch/closure rails. I found that with enough weight, the more limited flex of the plastic Ratio bogies made for the most reliable running. But if the two axles in each bogie frame aren't exactly parallel with each other, they will ride up and over turnouts when that turnout is set in the direction of the crooked axle.

Then there are the 4 wheel goods wagons. So far, I've stuck with rigid wheel mounting. But non parallel axles create the same derailment problems. But how do you achieve parallel axles when using pin point axle bearings which allow the axle point to float around in the bearing?

I spent around 11 hours fine tuning the suspension of an Alan Gibson framed Midland 0-6-0T.

All 6 wheels are sprung and I endlessly fiddled with spring tension and freedom of movement of each axle box, then found that there was insufficient side play on the centre axle in one direction as it was hitting the gearbox, etc etc.

The locomotive runs pretty well everywhere without problems now, but it was yet another time when 0 gauge was looking very attractive.  Unfortunately 0 gauge takes up too much room and is just too expensive for me. So I soldier on with 4mm, although must say that when things finally work, one does feel a very definite sense of achievement (and relief!)

Sorry, perhaps I have digressed! But I think I was just trying to say that getting the trackwork right is only one part of the equation in achieving reliable running.

Regards,

Bruce.

posted: 15 Nov 2007 18:48

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Bruce Boldner wrote:
By the way, for P4, what gap would you recommend between the tip of each switch blade and it's adjacent stock rail? I've been using the same gauge I use for the flangeway gap in the common crossing, ie .68mm, but have been told this is too fine.  My thinking has been that the swich blade tip currently not resting against it's stock rail can act as a check rail and stop the wheels floating across and riding up over the switch blade on the opposite side. But I've been told wheels should not need to be checked at this section of the turnout. I can see this should be so for straight turnouts, but what about curved ones?
Hi Bruce,

I'm afraid you are making a big error, although it seems a common one which I see on a lot of EM and P4 layouts. Hopefully I won't be seeing it also on 00-SF layouts soon. It makes the switches look very wrong to anyone familiar with the prototype. :(

The prototype switch opening is 4.1/4", which scales to 1.42mm -- more than double the flangeway gap*!

Only by opening the switch tips by this much can you be sure that there is the required 2" minimum clearance (again more than the flangeway gap) all along behind the open blade. On the prototype it is very important that the backs of wheels do not hit the open blade, because this can damage the stretcher bars, and the detection gear for the signalling.

Under no circumstances should an open switch blade be acting as a check rail! Proper check rails experience a significant side force from traffic travelling at speed. An open switch blade has no means to resist such forces and is not designed to do so. In fact without the support of the stock rail, an open switch blade is quite delicate at the tip and easily damaged.

If you are having trouble with wheels riding up over switch blades it suggests that you have not got them profiled correctly, or maybe the switch is under-gauge at the tips? This often happens if folks don't get a sharp enough set in the stock rail. For some notes and diagrams about this, and how to check the "stock gauge", see:

http://www.templot.com/martweb/gs_realtrack.htm#set

http://www.templot.com/martweb/gs_realtrack.htm#split_switch

Sometimes for curved switches a proper check rail is provided immediately in front of the inner switch tips, as shown in this picture (linked from RMweb, thanks to Adrian Marks):

41_horseboxes_1.jpg41_horseboxes_1.jpg

This prevents the wheel flanges from running hard against the outer rail as they approach the tip of the switch.

In photographs you can often estimate such matters by comparison with the rail width. Most modern UK rails are 2.3/4" wide, which is significantly more than the flangeway gap of 1.3/4" and significantly less than the switch opening of 4.1/4". Even in this picture you can see that the switch opening is more than a rail width.

For P4 I suggest a slightly overscale switch opening of 1.5mm (which allows for the slightly overscale flangeway gap clearance needed behind the blade).

For EM and 00-SF 1.5mm opening may not be enough to create a 1mm flangeway all along behind the open blade, and I suggest 1.6 or 1.7mm opening (or a bit of trial and error). :)

Matters can be eased for a flexible switch by leaving the blade free to flex for a longer length than the prototype.

*Where a switch occurs in a roadway the switch opening is sometimes reduced to 3" (still more than the flangeway) for the safety of road traffic and pedestrians, and additional drive connections may be needed to maintain the 2" clearance.

regards,

Martin.

posted: 15 Nov 2007 18:57

from:

rodney_hills
 
United Kingdom

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Bruce,

0.68mm at 1:76.2 represents about 51.8mm full-size, ie 2.04 inches.

I notice that in Iain Rice's 'Finescale Track' book there are drawings on page 71 of a NER switch and a GWR switch, with switch blade travels of 4.1/4" and 3.3/4" respectively. So your travel is about 50% UNDERscale!

Interestingly, the switch blades get CLOSER to the stock rails as they progress along towards the final slide chair, presumably the gap is allowed to be down to the "0.68" FW dimension ?

Regards,

Rodney Hills

posted: 15 Nov 2007 20:20

from:

Russ E
 
 

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rodney_hills wrote:
Interestingly, the switch blades get CLOSER to the stock rails as they progress along towards the final slide chair, presumably the gap is allowed to be down to the "0.68" FW dimension ?

Functionally, the gap limit could be as low as 0.4mm (EFmax); this would still allow a flange to squeeze through it. In practice, this is not a good idea. As Martin notes, an open switch rail should not act as a check. A prototype open switch rail is not strong enough to act as a check. A model open switch rail will be strong enough, but we don't need any checking at that area, nor do we want want any checking at that area because of the friction that could be imposed on the backface of a tyre. In short switches (A or B), there is usually no difficulty in maintaining a generous gap (see pic below), but in longer switches (C and above), there can be a difficulty in maintaining a gap in excess of 0.7mm throughout the length of the blade if only one stretcher bar is used. I'm inclined to think that two stretchers are desirable for C-switches, and certainly necessary for anything longer than a C.

trac003.jpgtrac003.jpg

Russ

posted: 15 Nov 2007 20:38

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Russ,

Welcome to Templot Club. :)

I like your sparking conductor rail logo, but I think the novelty will soon wear off, and it will become a distraction while trying to read the messages.

Please folks, don't let's go mad with animated gifs. Please? :)

We don't want Templot Club to end up looking like a page from RMweb, where you have to fight through a visual barrage to read a few lines text. That's one reason why I disabled the signature feature.

regards,

Martin.

posted: 15 Nov 2007 21:27

from:

Russ E
 
 

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Sorry my avatar is distracting you, Martin. I do agree about not going mad with animated gifs, but at 1950 bytes, I think mine is a modest novelty. Does Templot Club have a recommended avatar size limit?

And there was me thinking it might be time for some seasonal chill:

snow2ani.gifsnow2ani.gif

(a whopping 11k)

Russ
Last edited on 15 Nov 2007 21:28 by Russ E
posted: 15 Nov 2007 22:03

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Russ E wrote:
I do agree about not going mad with animated gifs, but at 1950 bytes, I think mine is a modest novelty. Does Templot Club have a recommended avatar size limit?
Hi Russ,

The current limits for the logos are 128 pixels square and 15KB file size.

I'm not too bothered about either limit and I'm happy to increase them if anyone thinks it necessary.

I'm more concerned about the visual distraction of having something moving in the corner of your eye while trying to read the text.

And there was me thinking it might be time for some seasonal chill:

snow2ani.gifsnow2ani.gif
Very seasonal. Merry Christmas to you too. :)

Martin.

posted: 15 Nov 2007 22:37

from:

Russ E
 
 

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Martin Wynne wrote:
I'm more concerned about the visual distraction of having something moving in the corner of your eye while trying to read the text.

Ok. Avatar now replaced with non-animated version.

Russ

posted: 15 Nov 2007 22:45

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Russ E wrote:
Ok. Avatar now replaced with non-animated version.
Thanks Russ.

p.s. I've now been watching the snow falling for over an hour and it hasn't got any thicker. I think you should ask for your money back. :)

Martin.

posted: 15 Nov 2007 23:46

from:

Nigel Brown
 
 

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Bruce Boldner wrote:
I must say that P4 trackwork can be incredibly frustrating to achieve consistently reliable running. I have constructed all my turnouts to the very best of my ability, using all the society gauges, filed the switch blades sharp as razors, notched the stock rails and recessed the blades in some cases, just put a set in the stock rail with no notching in other cases.
Just a couple of thoughts:-

(1) Have you tried putting a radius at the top on the end of the switch blade (i.e. so that it is curved rather than angled)? Also, making sure that that corner is extra thin may help without reducing the strength.

(2) Could the switch blades be riding up a bit at the end, relative to the stock rail?

I find the most common cause of poor running at the end of the switches is when I haven't filed enough metal from the switch or stock rail, further along from the switch tip, so that the two meet before the tip of the switch is able to reach its intended position.

Nigel

posted: 16 Nov 2007 00:21

from:

Keith Norgrove
 
 

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Bruce Boldner wrote:
By the way, for P4, what gap would you recommend between the tip of each switch blade and it's adjacent stock rail?  I've been using the same gauge I use for the flangeway gap in the common crossing, ie .68mm, but have been told this is too fine.
That is most certainly underscale and performance will be marginal as you found. In UK prototype the standard figure is 4.25 inches, which in 4mm scale gives you just under 1.5mm. in special circumstances such as track inlaid in pavement this can be reduced to the 2.5 to 3 inches found at the end of a checkrail flare but not down to the flangeway dimension unless the track is fully checked using tramway style rail.

Some railways increase the switch opening above 4.25 inches and most UK/US style point machines are designed to work up to 6 inches.

Other countries such as Germany where trailable points are used with independent locking for each swithblade may have switch openings up to 8 inches to suit the trailable mechanisms.

Keith

posted: 16 Nov 2007 01:00

from:

Richard Spratt
 
Stockton-upon-Tees - United Kingdom

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Bruce asked:
By the way, for P4, what gap would you recommend between the tip of each switch blade and it's adjacent stock rail? I've been using the same gauge I use for the flangeway gap in the common crossing, ie .68mm, but have been told this is too fine.
The Scalefour society used to sell "gauges" for turnout blades.  I've just measured mine and they measure 1.7mm for the blade tip and 0.84mm for the minimum spacing. There are photos of them:

http://www.scalefour.org/history/images/swbladegauges.jpg

fig-6.jpgfig-6.jpgThe whole article is: http://www.scalefour.org/history/mrc13.html

Regards

Richard

posted: 16 Nov 2007 16:28

from:

Bruce Boldner
 
 

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Martin,

Thanks very much for this very detailed and helpful information. My thanks also to Rodney Hills for  taking the time to  provide me with much useful advice in the same vein. The photos are also of assistance, illustrating what you both have said very clearly.

You've convinced me! I will endeavour to increase the switch blade clearance to 1.5mm wherever possible. I say where possible, because on my earliest turnouts there may be little room to maneouvre, having neither recessed the stock rails or even put a set in them.

How I wish I was aware of this information about 35 turnouts ago! I daresay this data is to be found somewhere within the Scalefour digests, although I never looked for it, as I assumed the crossing gauge would do for the switch blades.

 Regards,

Bruce.

Martin Wynne wrote:
Bruce Boldner wrote:
By the way, for P4, what gap would you recommend between the tip of each switch blade and it's adjacent stock rail? I've been using the same gauge I use for the flangeway gap in the common crossing, ie .68mm, but have been told this is too fine.  My thinking has been that the swich blade tip currently not resting against it's stock rail can act as a check rail and stop the wheels floating across and riding up over the switch blade on the opposite side. But I've been told wheels should not need to be checked at this section of the turnout. I can see this should be so for straight turnouts, but what about curved ones?
Hi Bruce,

I'm afraid you are making a big error, although it seems a common one which I see on a lot of EM and P4 layouts. Hopefully I won't be seeing it also on 00-SF layouts soon. It makes the switches look very wrong to anyone familiar with the prototype. :(

The prototype switch opening is 4.1/4", which scales to 1.42mm -- more than double the flangeway gap*!

Only by opening the switch tips by this much can you be sure that there is the required 2" minimum clearance (again more than the flangeway gap) all along behind the open blade. On the prototype it is very important that the backs of wheels do not hit the open blade, because this can damage the stretcher bars, and the detection gear for the signalling.

Under no circumstances should an open switch blade be acting as a check rail! Proper check rails experience a significant side force from traffic travelling at speed. An open switch blade has no means to resist such forces and is not designed to do so. In fact without the support of the stock rail, an open switch blade is quite delicate at the tip and easily damaged.

If you are having trouble with wheels riding up over switch blades it suggests that you have not got them profiled correctly, or maybe the switch is under-gauge at the tips? This often happens if folks don't get a sharp enough set in the stock rail. For some notes and diagrams about this, and how to check the "stock gauge", see:

http://www.templot.com/martweb/gs_realtrack.htm#set

http://www.templot.com/martweb/gs_realtrack.htm#split_switch

Sometimes for curved switches a proper check rail is provided immediately in front of the inner switch tips, as shown in this picture (linked from RMweb, thanks to Adrian Marks):

41_horseboxes_1.jpg41_horseboxes_1.jpg

This prevents the wheel flanges from running hard against the outer rail as they approach the tip of the switch.

In photographs you can often estimate such matters by comparison with the rail width. Most modern UK rails are 2.3/4" wide, which is significantly more than the flangeway gap of 1.3/4" and significantly less than the switch opening of 4.1/4". Even in this picture you can see that the switch opening is more than a rail width.

For P4 I suggest a slightly overscale switch opening of 1.5mm (which allows for the slightly overscale flangeway gap clearance needed behind the blade).

For EM and 00-SF 1.5mm opening may not be enough to create a 1mm flangeway all along behind the open blade, and I suggest 1.6 or 1.7mm opening (or a bit of trial and error). :)

Matters can be eased for a flexible switch by leaving the blade free to flex for a longer length than the prototype.

*Where a switch occurs in a roadway the switch opening is sometimes reduced to 3" (still more than the flangeway) for the safety of road traffic and pedestrians, and additional drive connections may be needed to maintain the 2" clearance.

regards,

Martin.


posted: 16 Nov 2007 17:05

from:

rodney_hills
 
United Kingdom

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Bruce Boldner wrote (snipped)

How I wish I was aware of this information about 35 turnouts ago! I daresay this data is to be found somewhere within the Scalefour digests, although I never looked for it, as I assumed the crossing gauge would do for the switch blades.

Bruce,

Opened my printed copy of "Digest Sheets",

The first digest is 1.2 "P4 Track and Wheel Standards" by Russ Elliott,

Page 4 - 'Recommended dimensions at turnout switches':

1.5mm minimum at end of switch blade, 1mm minimum further along blade.

Regards,

Rodney

posted: 16 Nov 2007 18:26

from:

Bruce Boldner
 
 

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Hi Nigel,

Thanks for your comments. Yes, I have found that radiusing the top of the switch  blade tips and ensuring that they don't protrude above their adjacent stock rails are essential contributing factors towards reliable running. And I agree that if part of the switch blade meets the stock rail before its tip, then the tip will never seat sufficiently.

Having made those adjustments to the best of my ability, I am now of the assumption that my underscale switch blade/stock rail gaps may be the major cause of derailments.

I should add that my turnouts aren't a total shambles. Ninety percent of my rolling stock and locomotives run through 90% of my turnouts consistently with no derailments. It's just that I can't leave a train roaring around at supersonic speeds whilst I go to the kitchen for a cup of coffee and KNOW that nothing will derail, as I did with my old 00 layout consisting of Peco flex track and two foot curves!

Regards,

Bruce.
Nigel Brown wrote:
Bruce Boldner wrote:
I must say that P4 trackwork can be incredibly frustrating to achieve consistently reliable running. I have constructed all my turnouts to the very best of my ability, using all the society gauges, filed the switch blades sharp as razors, notched the stock rails and recessed the blades in some cases, just put a set in the stock rail with no notching in other cases.
Just a couple of thoughts:-

(1) Have you tried putting a radius at the top on the end of the switch blade (i.e. so that it is curved rather than angled)? Also, making sure that that corner is extra thin may help without reducing the strength.

(2) Could the switch blades be riding up a bit at the end, relative to the stock rail?

I find the most common cause of poor running at the end of the switches is when I haven't filed enough metal from the switch or stock rail, further along from the switch tip, so that the two meet before the tip of the switch is able to reach its intended position.

Nigel


posted: 16 Nov 2007 18:47

from:

Bruce Boldner
 
 

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Hello Richard,

Many thanks for the excellent article, which I had not seen before and have taken the liberty of printing out so I can read it at length. There are many good tips in there.

One aspect of the article which I take slight issue with, is where it advises to keep the crossings and switch blades straight, even in a curved turnout.

I've printed out a D9 and a D7.5 curved turnout for my layout using Templot and plan to curve the common crossings and my one piece switch blade/closure rails to conform with the 4' radius of the "straight road" of each  turnout respectively.

It would appear to me that to maintain the radius through the turnout,  to that of the plain track both leading into and departing from the "straight road" of the turnout would better ensure smooth running of rolling stock. Better that, than have the wheels have to conform to a brief straight section through the common crossing, only to have to turn into the original radius once again on the exit from the turnout. Do you disagree?  I've been proved wrong on a number of issues in the last few email exchanges, so won't be surprised if I'm wrong again!

As for those switch blade gauges, I assume they are no longer available from the Scalefour Society. No matter, I'm sure  a strip of metal 1.5mm thick will suffice. And I already have similar clamps to those in the photo, to clamp the rails to the gauge.

Regards,

Bruce.

posted: 16 Nov 2007 18:55

from:

Bruce Boldner
 
 

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Keith,

Thanks for your comments.  Everyone except me on this list  appears to have been well aware that the switch blade gap in P4 should be around 1.5mm.

I'm just a poor colonial boy thousands of miles away in the Southern Hemisphere, so shall use that as an excuse for my ignorance.

That said, it's probably the practice here in Oz to use identical clearances. Although I'm only slightly ashamed to admit that I wouldn't have any idea.

Regards,

Bruce.
Keith Norgrove wrote:
Bruce Boldner wrote:
By the way, for P4, what gap would you recommend between the tip of each switch blade and it's adjacent stock rail?  I've been using the same gauge I use for the flangeway gap in the common crossing, ie .68mm, but have been told this is too fine.
That is most certainly underscale and performance will be marginal as you found. In UK prototype the standard figure is 4.25 inches, which in 4mm scale gives you just under 1.5mm. in special circumstances such as track inlaid in pavement this can be reduced to the 2.5 to 3 inches found at the end of a checkrail flare but not down to the flangeway dimension unless the track is fully checked using tramway style rail.

Some railways increase the switch opening above 4.25 inches and most UK/US style point machines are designed to work up to 6 inches.

Other countries such as Germany where trailable points are used with independent locking for each swithblade may have switch openings up to 8 inches to suit the trailable mechanisms.

Keith


posted: posted: 16 Nov 2007 19:03

from:

Paul Boyd
 
Loughborough - United Kingdom

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Bruce wrote:
Yes, I have found that radiusing the top of the switch blade tips and ensuring that they don't protrude above their adjacent stock rails are essential contributing factors towards reliable running.
One little trick I picked up somewhere is to twist the switch blade slightly so that the head of the blade is fractionally closer to the stock rail than the foot.  Not enough to be noticeable, but enough to be sure that the head contacts first.

Oh, by the way, the switch rail gap at the tip should be around 1.5mm :)

16 Nov 2007 19:03

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Bruce Boldner wrote:
switch  blade tips and ensuring that they don't protrude above their adjacent stock rails are essential contributing factors towards reliable running.
Hi Bruce,

On the prototype this is one of the essential functions of the stretcher bar. It runs under* the stock rail at a clearance of 1/8", so preventing the blade tip from lifting above the correct level. This essential function of the stretcher bar seems to have been missed from many of the model designs and "turnout operating units" which I see published. Without something to hold it down onto the slide chair, a blade tip can very easily lift up as traffic runs over it.

*or in some old pre-grouping designs, through a hole in the stock rail.

You mentioned that some of your turnouts have neither a joggle nor a set in the turnout-side stock rail? In that case it is almost inevitable that the switch will be under-gauge, which I have found to be the greatest single cause of wheels riding up over switch blades.

regards,

Martin.

posted: 16 Nov 2007 19:10

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Bruce Boldner wrote:
One aspect of the article which I take slight issue with, is where it advises to keep the crossings and switch blades straight, even in a curved turnout.
Hi Bruce,

You are quite right to take issue. Please ignore this nonsense and use the Templot templates as curved throughout. Apart from looking and running ten times better, it also matches prototype practice.

I'm so weary of arguing this case time and again over the years that it makes me bad-tempered every time I see it. Whoever wrote it in the first place should be taken out and shot. :(

Martin.

posted: 16 Nov 2007 19:28

from:

Roger Henry
 
Brisbane - Australia

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  This myth has also been perpetuated by one of the 'glossy' UK magazines (BRILL, Steam Days, hopefully not Backtrack) which, some years ago, published an article on trackwork and stated that there was ALWAYS a straight section through the crossing and that it was a common modelling 'error' to incorporate a curve/s. The article then included a number of pictures of various curved turnouts which showed, or appeared to show, that this was the case.

Roger,

Brisbane

posted: 16 Nov 2007 19:37

from:

Paul Boyd
 
Loughborough - United Kingdom

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Martin wrote:
Please ignore this nonsense and use the Templot templates as curved throughout. Apart from looking and running ten times better, it also matches prototype practice.
Er, so why is that when you curve a template the crossing stays straight? :)  I must admit that often one of the first things I do is to change each crossing to 'Curved' because it looks and runs ten times better!  Perhaps that should be the default action.

posted: 16 Nov 2007 21:21

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Paul Boyd wrote:
Martin wrote:
Please ignore this nonsense and use the Templot templates as curved throughout. Apart from looking and running ten times better, it also matches prototype practice.
Er, so why is that when you curve a template the crossing stays straight? :)  I must admit that often one of the first things I do is to change each crossing to 'Curved' because it looks and runs ten times better!  Perhaps that should be the default action.
Oh, Paul, the crossing doesn't stay straight!

For the regular, generic, and parallel types of V-crossings, both roads through the crossing are curved to the same radius, matching the curving radius in the main road of the turnout. Use this type of curved crossing in crossovers.

For the curved/curviform type of V-crossing, the turnout-road side is curved to a different radius from the main-road side, matching and continuing the actual turnout radius. Use this type of crossing where there is contraflexure in yards and sidings, and sometimes in curved double junctions.

regards,

Martin.

posted: 17 Nov 2007 02:28

from:

Keith Norgrove
 
 

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Martin Wynne wrote:
I'm so weary of arguing this case time and again over the years that it makes me bad-tempered every time I see it. Whoever wrote it in the first place should be taken out and shot. :(
Like most things to do with railways, it's right some of the time! Some railways use curved crossings some don't, and some use both straight and curved as suits the need. Just about any dogmatic statement will turn out to be wrong some of the time.

Keith

posted: 17 Nov 2007 02:43

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Keith Norgrove wrote: 
Just about any dogmatic statement will turn out to be wrong some of the time.
Hi Keith,

Well I did say I was being bad-tempered. :)

And so would you be, to receive endless emails saying "you do realise Templot is completely wrong? Because according to **** curved turnouts should always have straight bits in them" or similar.

Even after I have pointed to an image such as this:

http://bristol-rail.co.uk/w/images/0/03/Filton_Abbey_Wood92.jpg

From the excellent Bristol Rail web site for more of the same.

regards,

Martin.
Last edited on 12 Feb 2012 11:44 by Martin Wynne
posted: 17 Nov 2007 02:56

from:

rodney_hills
 
United Kingdom

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Keith Norgrove wrote:
Like most things to do with railways, it's right some of the time! Some railways use curved crossings some don't, and some use both straight and curved as suits the need.

This Hungarian firm will sell you 12"/ft (or is it 1000mm/meter?) scale 'turnouts' in either style:

http://www.vamav.hu/tech_los_e.html  - 'Technical solutions'

http://www.vamav.hu/index_e.html  - select 'Introducing' for company profile.

Regards,

Rodney Hills

posted: 17 Nov 2007 03:20

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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rodney_hills wrote:
This Hungarian firm will sell you 12"/ft (or is it 1000mm/meter?) scale 'turnouts' in either style:

http://www.vamav.hu/tech_los_e.html  - 'Technical solutions'
Hi Rodney,

Sorry to labour this but those are straight turnouts. This discussion is about curved turnouts!

Templot already offers the two styles shown there, for both straight and curved turnouts. See:

http://www.templot.com/martweb/gs_realtrack.htm#xing_types

The style there called "curved" is now called "curviform" in later versions of Templot in an attempt to reduce the confusion. Some hope! :(

regards,

Martin.

posted: 17 Nov 2007 03:38

from:

rodney_hills
 
United Kingdom

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Martin,

Sorry for being dense. This one thread covers an awful lot of sub-topics!

Regards,

Rodney

posted: 17 Nov 2007 04:02

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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rodney_hills wrote:
This one thread covers an awful lot of sub-topics!
Hi Rodney,

It sure does. :) Unfortunately the forum software doesn't provide any means to split a topic into new topics, and if you change the topic title it changes it for the whole topic, including the first messages for which the original title is ok. :(

Martin.

posted: 17 Nov 2007 09:06

from:

Bruce Boldner
 
 

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OK. Thanks again, Rodney.

Bruce.
rodney_hills wrote:

Bruce Boldner wrote (snipped)

How I wish I was aware of this information about 35 turnouts ago! I daresay this data is to be found somewhere within the Scalefour digests, although I never looked for it, as I assumed the crossing gauge would do for the switch blades.

Bruce,

Opened my printed copy of "Digest Sheets",

The first digest is 1.2 "P4 Track and Wheel Standards" by Russ Elliott,

Page 4 - 'Recommended dimensions at turnout switches':

1.5mm minimum at end of switch blade, 1mm minimum further along blade.

Regards,

Rodney


posted: 17 Nov 2007 09:08

from:

Bruce Boldner
 
 

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OK. Thanks for the tip about twisting the rail, Paul. I'll try everything!

Bruce.
Paul Boyd wrote:
Bruce wrote:
Yes, I have found that radiusing the top of the switch blade tips and ensuring that they don't protrude above their adjacent stock rails are essential contributing factors towards reliable running.
One little trick I picked up somewhere is to twist the switch blade slightly so that the head of the blade is fractionally closer to the stock rail than the foot.  Not enough to be noticeable, but enough to be sure that the head contacts first.

Oh, by the way, the switch rail gap at the tip should be around 1.5mm :)


posted: 17 Nov 2007 09:20

from:

Bruce Boldner
 
 

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Thanks Martin. I'm glad I got something right!

Bruce.
Martin Wynne wrote:
Bruce Boldner wrote:
One aspect of the article which I take slight issue with, is where it advises to keep the crossings and switch blades straight, even in a curved turnout.
Hi Bruce,

You are quite right to take issue. Please ignore this nonsense and use the Templot templates as curved throughout. Apart from looking and running ten times better, it also matches prototype practice.

I'm so weary of arguing this case time and again over the years that it makes me bad-tempered every time I see it. Whoever wrote it in the first place should be taken out and shot. :(

Martin.


posted: 9 Dec 2007 07:52

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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I wrote:
Bruce Boldner wrote:
One aspect of the article which I take slight issue with, is where it advises to keep the crossings and switch blades straight, even in a curved turnout.
You are quite right to take issue. Please ignore this nonsense and use the Templot templates as curved throughout. Apart from looking and running ten times better, it also matches prototype practice.
As a further follow up to that, this linked image has been posted today on RMweb:

2NOL_1829_Lewes_16-3-58_s.jpg2NOL_1829_Lewes_16-3-58_s.jpg

Many thanks to Robert C on RMweb.

regards,

Martin.

posted: 12 Feb 2012 11:38

from:

Jerry
 
Mansfield, Notts - United Kingdom

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Just a note to anyone who has tried the Scalefour Society links will find these yield an error.

The society is at http://www.scalefour.org/

Hope this helps

Jerry

posted: 12 Feb 2012 23:28

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Thanks Jerry.

I have updated the links.

The Scalefour Society have made available online the original Protofour articles in MRN and MRC magazines. It's now nearly half a century ago -- this stuff was meat and drink to many of us at the time:

  http://www.scalefour.org/history/history.html

They also have much of the original Protofour Manual online:

  http://www.scalefour.org/history/p4pub.html

regards,

Martin.



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