P4 vs S4 - Pro's and con's

Discuss the prototype and how to model it.
Julian Roberts
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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sat May 13, 2017 12:21 am

I was not expecting to provoke any thoughts of changes to P4 dimensions which seem to have worked fine for many years. The reason I've been asking questions about the prototype is to try to understand this:

Russ Elliott wrote:
andrew jukes wrote:An S4 wheelset with a 17.87mm BB running through a turnout built to P4 standards i.e. using a check gauge of 18.15mm violates condition 2 of the Digest: BB (17.87mm) + EF (0.38mm) = 18.25mm i.e. >18.15mm, so the wheelset is likely to conflict with the crossing nose.

Hmmm. 'Conflict' with the crossing nose is a spectrum, and, as the Digest condition 2 points out, a problem is likely to occur only where the value of BB plus a small proportion of EF starts to approach the CG value. My view is that the shape of the flange front, together with dressing of the crossing nose, makes it unlikely that a P4 CG of 18.15mm would give rise to any significant problem. That said, I do agree with you that using a CG of 18.25mm is a more sensible approach if using wheel BBs above 17.82mm.


which conflicts with Martin's repeated insistence that BB+EF must not be greater than CG - to an insistence that even a 0.01 excess is unacceptable.

While I understood the prototype to exceed the CG by 1/32" it seemed plausible that what Russ' words here describe could occur at full size; if not, I could not see how, Russ, you could be promoting this idea, which you have before, and which seems so contrary to Martin's prohibition, viz:

not less than 17.57mm,
not more than 18.15mm minus the effective flange thickness.
With the best results if you get as close as possible to the latter dimension without ever exceeding it.
In other words 17.75mm works only if you can rely on the effective flange thickness not exceeding 0.40mm.


However I now see the source of your approach Russ - this famous Clause 2, (the new bit of which I will have to have explained in very simple terms if I need to understand it...)



Capture Clause 2.JPG


I think what the new bit of Clause 2 is about is what all this was about (though the discussion today has left me behind completely), how to get the checking down to the same amount as the prototype. I am sure I'm on a completely naff level compared with you guys, practically, as well as intellectually; however, here, from my bargain basement perspective, is a loco being checked on the outside road of a curving turnout (without switch rails). The checking is occurring about 2 seconds into the video. This must be about as bad as it gets - 600mm curve and some ridiculous crossing angle. I don't see what the problem is really. These wheels were set on the 17.67 artefact and came out slightly less than that, around 17.64. I already showed on the previous page (Sun Apr 30, 2017 10:33 am) the "turnout" and a train of wagons zipping through it as though nothing was there at all, at a crazy speed for such a bend, with not the slightest sign of derailment on many repetitions - nor buffer locking, AJ uncoupling problems...I do understand however the latter problems reduce as sideplay decreases.

[youtube] lrXkgC5vph8 [/youtube] (have I done it right this time I wonder?....)

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Martin Wynne
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Re: P4 vs S4 - Pro's and con's

Postby Martin Wynne » Sat May 13, 2017 5:33 am

Julian Roberts wrote:


(have I done it right this time I wonder?....)

Hi Julian,

No, you included extra spaces between the youtube tags. There should be only the video ID number between the tags (11 characters for YouTube). I have corrected it above.

If the phpBB programmers had done their job correctly they would have trimmed white space from the ID before using it, because it is entirely predictable that folks would add extra spaces -- they are conditioned from an early age to think in terms of space-separated words and not character strings. This is why it is next to impossible to get folks not to include spaces in file names, even though it can create lots of problems on the internet.

Code: Select all

[youtube]lrXkgC5vph8[/youtube]

regards,

Martin.
39 years developing Templot. And counting ...

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Martin Wynne
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Re: P4 vs S4 - Pro's and con's

Postby Martin Wynne » Sat May 13, 2017 6:16 am

Julian Roberts wrote:While I understood the prototype to exceed the CG by 1/32"

Hi Julian,

It doesn't, and I have never seen any evidence to suggest otherwise.

which conflicts with Martin's repeated insistence that BB+EF must not be greater than CG - to an insistence that even a 0.01 excess is unacceptable.

I'm sticking to that, to the extent of regarding some of the stuff in the Scalefour Digest as barmy. I think you are tending to place far too much reliance on the words and numbers in the Digest as if they are the Holy Grail.

For example: "the check rail will ensure that the wheel cannot take the wrong route through the crossing".

Take the wrong route? !!!   For that much to happen something must have gone disastrously wrong.

It is not a binary choice for the wheel -- the vee nose is not a knife edge (it wouldn't last 5 minutes in service if it was). The vee nose is a blunt object 3/4" wide in the path of the wheel flange. That scales to 0.25mm wide, or 10 thou, on our models. If the checking is even a fraction deficient the wheel flange will hit it. Resulting at the very least in a click sound, more likely a visible bump, and in many cases a derailment.

It's true that if the vee nose is rounded and lowered in the style of the prototype, many wheels would likely survive flange contact with it. Unfortunately it takes very little encouragement to derail a P4 wheel -- it is not supporting several tons load as is a prototype wheel.

regards,

Martin.
39 years developing Templot. And counting ...

Julian Roberts
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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sat May 13, 2017 9:34 am

Thanks for correcting the you tube thingy, again!, Martin. What I didn't say is the amount of checking the video shows, (shock, horror?): - it's the approx + 0.11 of the below the ideal 17.75 BB of the rear wheelset of this loco, + approx 0.25 from the gauge widening (given by the Society Triangular Tool).......... so 0.36 or so. (Err...the less the BB the more the checking)

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Martin Wynne
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Re: P4 vs S4 - Pro's and con's

Postby Martin Wynne » Sat May 13, 2017 10:50 am

Julian Roberts wrote:+ approx 0.25 from the gauge widening (given by the Society Triangular Tool).......... so 0.36 or so. (Err...the less the BB the more the checking)

Hi Julian,

Gauge widening does not affect the checking. The check gauge remains the same, and the check rail flangeway increases by the same amount as the gauge widening. The prototype makes special widened check rail chairs for this purpose.

regards,

Martin.
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Russ Elliott
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Re: P4 vs S4 - Pro's and con's

Postby Russ Elliott » Sat May 13, 2017 3:03 pm

Martin - is there not a danger, in using the 4-SF tool, that it could leave the check gap at 16.2 - 15.4 = 0.8, which presumably would not be approved of because it would trap a 0.8 EF, and it would leave BC (at say 14.4) as non-compliant, and would foul a 14.3 BBmin wheelset? I suppose another way of asking the question is whether the 0.2 gap was intentional, or whether the 0.8 tool flange was merely a convenient one.

4-sf-check-detail-2.png
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btw, sorry for the facetious level crossing pic - even with 2" flangeways, I just wanted to show that no Check Gauges were used in its construction...

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Russ Elliott
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Re: P4 vs S4 - Pro's and con's

Postby Russ Elliott » Sat May 13, 2017 3:25 pm

Regarding the parenthesis wording under condition 2, I accept it is a bit naff. (It is not incorrect though.)

Julian - I do not condone BB+EF being greater than CG, but as Martin says, the vee does not present a binary choice for the wheel. Deficient checking will cause a nudge from a sharp nose, but less so from a dressed one. It isn't possible to check the accuracy of a Check Gauge - all we know is that they are (hopefully) between 18.15 and 18.2. If nose nibbling is detected, then the check can be eased out. (It is, after all, a minimum setting.)

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Russ Elliott
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Re: P4 vs S4 - Pro's and con's

Postby Russ Elliott » Sat May 13, 2017 3:36 pm

Martin Wynne wrote:The dimension relates to the track, not necessarily a gauge tool. In the case of problems you might want to measure the check span, and know what max it should be. I didn't say a check span tool would be superfluous, merely that it is not very practical to use one when building model track. It could be useful in testing finished track if problems arise.

Yes, it is useful to know what BCmax should be, but in practice, everyone just slips in a CF shim to check any tightness. (Or, an appropriate size of drill shank in an area where GW is present.)

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Martin Wynne
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Re: P4 vs S4 - Pro's and con's

Postby Martin Wynne » Sat May 13, 2017 6:46 pm

Russ Elliott wrote:Martin - is there not a danger, in using the 4-SF tool, that it could leave the check gap at 16.2 - 15.4 = 0.8, which presumably would not be approved of because it would trap a 0.8 EF, and it would leave BC (at say 14.4) as non-compliant, and would foul a 14.3 BBmin wheelset? I suppose another way of asking the question is whether the 0.2 gap was intentional, or whether the 0.8 tool flange was merely a convenient one.

Hi Russ,

incorrect_use_of_check_gauge.png
incorrect_use_of_check_gauge.png (6.52 KiB) Viewed 2387 times

The 0.2mm gap was intentional. That drawing shows the position of the flat on the roller gauge so that it can be used over a vee. The remainder of the tool circumference has a slot to locate on a full running rail where possible, such as at the wing rail front.

Image

The instructions with the gauge make clear that it should held firm against the vee when being used with the flat portion. The differing design of the two ends of the gauge makes clear which way round it is to be used -- thick end on the crossing, thin end on the check rail.

It is available (in pairs) from C&L.

regards,

Martin.
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Russ Elliott
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Re: P4 vs S4 - Pro's and con's

Postby Russ Elliott » Sat May 13, 2017 7:16 pm

Thanks, Martin. I've now located the instructions. http://4-sf.uk/#gauge_tools

Julian Roberts
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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sat May 13, 2017 7:34 pm

Martin Wynne wrote:
Julian Roberts wrote:+ approx 0.25 from the gauge widening (given by the Society Triangular Tool).......... so 0.36 or so. (Err...the less the BB the more the checking)

Hi Julian,

Gauge widening does not affect the checking. The check gauge remains the same, and the check rail flangeway increases by the same amount as the gauge widening. The prototype makes special widened check rail chairs for this purpose.

regards,

Martin.


Martin I am surprised you did not see my point! - the first turnout at 2 secs is the outside road of a curved turnout therefore the checking is being done by the knuckle rail just before where it becomes a wing rail. The wing rail is gauged from the inside running rail by the Crossing Flangeway gauge. The check rail is opposite by the outside running rail gauged with the Check Gauge but has no function except for inside pair of wheels of 0-6-0 and similar vehicles!!!! At least I think that is the case though you will know better!

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Martin Wynne
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Re: P4 vs S4 - Pro's and con's

Postby Martin Wynne » Sat May 13, 2017 8:24 pm

Julian Roberts wrote:Martin I am surprised you did not see my point! - the first turnout at 2 secs is the outside road of a curved turnout therefore the checking is being done by the knuckle rail just before where it becomes a wing rail.

Hi Julian,

I did mention earlier that in the case of the outer road of a curved turnout, any gauge widening is ineffective over the length of the wing rail. The wheelset will be pulled way from the stock rail by the wing rail. That's why there is a flare angle on the wing rail end and a radius at the knuckle.

However in practice the problem would not normally arise -- if the outer radius is sharp enough to need gauge widening, the inner radius would be impossibly tight. So such a turnout is not practical for anything other than industrial sidings -- where no gauge widening is needed because used only by short 4-wheel wagons and short 4-coupled shunting engines.

Without gauge widening and with optimum back-to-back the wheel back should just kiss the wing rail with the opposite flange running against the stock rail.

regards,

Martin.
39 years developing Templot. And counting ...

Julian Roberts
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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sat May 13, 2017 9:49 pm

Martin Wynne wrote:
However in practice the problem would not normally arise -- if the outer radius is sharp enough to need gauge widening, the inner radius would be impossibly tight.
.


Yes Martin but this shunting plank is just an exercise to test out what actually happens in taking things to an extreme. The curved turnout outside road will show the effect of the smaller than prototype BB. You can see how greatly it knocks into this gauge widened one. But my point is that it doesn't matter!!!! Even with this absurd checking nothing derails, couplings and buffers still work, etc. My conclusion is that we are looking so much for utter perfection with the checking being the smooth running protypical "kiss" that we may lose sight of the fact that to get that close to 17.75 we may be going over it and likely to derail at a V. The test plank also has an ordinary turnout to test this aspect.

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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sun May 14, 2017 5:20 pm

Russ Elliott wrote:It isn't possible to check the accuracy of a Check Gauge )


Russ my check gauge disassembles unlike the brass one above. The exact thickness of the rail will be the question mark I suppose. You quoted it earlier at 0.92 ish, give or take 0.03 either way. So converting 0.678 into new money and add 0.92 gives me 18.14...of course, my technique in the way I handle it will be the bigger question mark as to its accuracy...
Attachments
20170514_103638.jpg

Julian Roberts
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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sun May 14, 2017 11:11 pm

Martin Wynne wrote:
The prototype production and tolerancing is meaningless at a reduction of 1:76.2

Martin.


Russ Elliott wrote:....where the min of 4' 5 19/32" came from. No matter, it all ends up at 17.8x, where x is approximately 7, and unmeasurable to us........most modern stuff scales out at 17.84 to 17.87mm


Just going back to before you were revising all the
track dimension figures Martin, when we were talking about the tolerance of prototype wheels.
[1360min to 1362max for steam loco wheels] I think you both agree that such a tolerance is meaningless or unmeasurable in 4mm scale. But, and I am sure it's been said here before, if the "official" recommendation is to regard 17.75 as our minimum, yet as Martin has repeatedly said,
that is our maximum and then only with a compliant EF of 0.4, are we not expecting a zero tolerance, a perfection that is even beyond the prototype.

As you admit, Russ

I don't think I can set a BB to an accuracy
greater than 0.1mm anyway,


which I assume means 0.05 either way? What I take from that is that Philip's 17.70 BB gauge (i.e. artefact) is
the maximum realistic one. Personally I doubt I can be as accurate, and am happy with the 0.08 a traditional 17.67 gauge gives me, and !hang! the greater checking than the prototype.

You later said

I do not condone BB+EF being greater than CG, but as Martin says, the vee does not present a binary choice for the wheel. Deficient checking will cause a nudge from a sharp nose, but less so from a dressed one. It isn't possible to check the accuracy of a Check Gauge - all we know is that they are (hopefully) between 18.15 and 18.2. If nose nibbling is detected, then the check can be eased out. (It is, after all, a minimum setting.)


Well on my own railway I could do that, but I can't go round to the club or a friend's and expect the checks to be adjusted for my errant stock, can I?!
I wonder if you or anyone can tell me exactly what the K crossing problem is in P4 with a narrower than max BB so that I can put in a test on my shunting plank? It is frequently referred to but I haven't seen any drawing to precisely describe the issue.

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Russ Elliott
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Re: P4 vs S4 - Pro's and con's

Postby Russ Elliott » Mon May 15, 2017 12:28 pm

Julian Roberts wrote:which I assume means 0.05 either way?

That is a way of describing it, yes. Although I can make a BB gauge face to within 0.02 say, the real problem, in setting, is always the runout.

For C&W, I use a round thing, rotating it (with finger and thumb of right hand) around the circumference of the flange face, the pinpoints being loosely held with finger and thumb of left hand. The runout is judged by eye and by the feel of the gauge.

setting-bb-2.png
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I wonder if you or anyone can tell me exactly what the K crossing problem is in P4 with a narrower than max BB so that I can put in a test on my shunting plank? It is frequently referred to but I haven't seen any drawing to precisely describe the issue.

At shallow diamonds with fixed Ks, there is a discontinuity of the checking at the crossing. The BB question is therefore the compromise value that would both minimise the likelihood of a flange back taking the wrong route through the crossing and the flange front not hitting the closure rail nose. (For a 1:8, the length of discontinuity is in the region of 15mm.)

Len Newman found that he had to tighten the CFs to approx 0.6mm to improve the reliability of K crossings in the Exactoscale products. Check clearance was maintained, but it was uncomfortably close with P4 BBmin.
k-crossing.png
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grovenor-2685
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Re: P4 vs S4 - Pro's and con's

Postby grovenor-2685 » Mon May 15, 2017 6:39 pm

Julian Roberts wrote:I wonder if you or anyone can tell me exactly what the K crossing problem is in P4 with a narrower than max BB so that I can put in a test on my shunting plank? It is frequently referred to but I haven't seen any drawing to precisely describe the issue.

Also, go to the link in this post and check out Appendix C.
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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Wed May 17, 2017 6:16 am

Thanks Russ and Keith. I had had the impression that in S4 there weren't the problems with obtuse crossings that there are in P4. But a brief read of Appendix C gives the impression that obtuse crossings are problematic on the prototype too, is it right to say, depending on the angle and wheel size? For making a test crossing, and assuming wagons are being used for the testing, is there an angle that might show up where P4 is problematic, where S4 is not?

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Noel
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Re: P4 vs S4 - Pro's and con's

Postby Noel » Wed May 17, 2017 10:22 am

Julian Roberts wrote:Appendix C gives the impression that obtuse crossings are problematic on the prototype too


Hence, with higher speeds, switched diamonds, ladder junctions and single lead junctions. Two steps forward, one step back... https://en.wikipedia.org/wiki/Double_junction
Noel

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Russ Elliott
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Re: P4 vs S4 - Pro's and con's

Postby Russ Elliott » Wed May 17, 2017 12:09 pm

Julian Roberts wrote:Thanks Russ and Keith. I had had the impression that in S4 there weren't the problems with obtuse crossings that there are in P4. But a brief read of Appendix C gives the impression that obtuse crossings are problematic on the prototype too, is it right to say, depending on the angle and wheel size? For making a test crossing, and assuming wagons are being used for the testing, is there an angle that might show up where P4 is problematic, where S4 is not?

Yes, unswitched Ks are and always have been a problem on the prototype. Angle and wheel size will have an influence. My sketch above showed the typical area of flange below the railhead for a 3'-ish wheel (flange length approx 5mm). Tighter CFs will mean shorter unchecked lengths, which will help. There is probably a good argument for not blunting the nose of the model point/closure rail, which will also help reduce the space a wheel can wiggle in.

'P4 v S4' settings aside, the key issue is any sideways force on a wheelset. If a wheelset is proceeding in an orderly straight direction over a K, and is not undergoing any appreciable checking (= sideways force) in the traverse, it is unlikely to want to change its course. Buffing and coupling forces will influence the situation. Unrestrained pony trucks are particularly vulnerable, as are freely-yawing coach bogies. Needless to say, curved diamonds are asking for trouble. Here's a contrary flexured outside slip, and even though the Ks are not 'shallow', it still needs to be traversed very cautiously:

http://www.clag.org.uk/pics/track/track010.jpg

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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Fri May 19, 2017 6:53 pm

Well that's a rather nice bit of trackwork Russ. I wonder what scale speed might be meant by your "very cautiously" - without wishing to ignite a "speed can't be scaled" debate... Thanks for your helpful comments, and to Noel too.

I was going to take Noel's link suggestion of 1:8 crossings as a guide to what angle to try. I've just looked to see if Keith has a photo guide to making obtuse crossings, but it would appear not, so I'm going to be guided by Tony Wilkins at https://www.scalefour.org/members/digests/#23. Here he says that 1:8 is the shallowest angle used in the prototype (unswitched) so that seems a good reason to choose that angle. I seem to remember reading Martin Goodall has some 1:10 crossings for his EM wheels to contend with apparently more successfully than his P4 wheels, but if that is unprototypical there seems no reason to attempt it.

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Re: P4 vs S4 - Pro's and con's

Postby grovenor-2685 » Fri May 19, 2017 9:19 pm

IIRC Martin Goodall was referring to standard vee crossings, not obtuse crossings.
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Re: P4 vs S4 - Pro's and con's

Postby Tony Wilkins » Fri May 19, 2017 11:33 pm

Hi Julian.
The outside slip on Green Street is in the goods yard where typically the scale speed would be about 10 MPH.
Obtuse crossings are difficult to build accurately at the best of times as there are so many interrelated dimensions to control. Trying to build a 1:8 diamond in both P4 and S4 for comparison is likely to be fraught with difficulty. You are dealing with probability envelopes and tolerances that are difficult to control to the degree of accuracy required I think. Although I have built many obtuse crossings over the years, they don't seem to get any easier. Trying to produce one expecting a 100% derailment result seems rather futile. The best one can hope to demonstrate is that there is or isn't a situation where a wheelset can be moved sideways just before the point rail of the obtuse crossing is reached as the checking of the opposite wheel ends too soon. As the distance between the point rail tips increases as the angle gets flatter, this is most likely to occur in a 1:8 obtuse crossing. Widening the flangeway increases the effect and with a 1mm flangeway in 4mm scale, it is a certainty. As has already been mentioned, there are ways to mitigate against this by lengthening the point rail by filing the end to a finer point, but such things need to be undertaken with care.
Regards
Tony.

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Re: P4 vs S4 - Pro's and con's

Postby Julian Roberts » Sat May 20, 2017 9:03 am

Hi Tony, thanks - I just need to clarify, I'm not intending to make a crossing in both S4 and P4, just one in P4, and hoping to find out whether or how I can get it 100% derailmentproof, or whether it is an impossibility - though if I can't do it, it would beg the question, would I be able to do it in S4 as it is problematic even on the prototype and not particularly easy for you with many years experience. Anyway I'm wanting to see if I get the same problem in P4 as Ray Hammond where he says in Snooze 11:

Capture Ray Hammond article Snooze 11.JPG
Capture Ray Hammond article Snooze 11.JPG (53.01 KiB) Viewed 1914 times


I'm wanting to find out the truth about certain P4 myths - at least "the" truth as far as I can demonstrate them to myself.

The shunting plank (600mm reverse curve) was made to prove whether the myth I had created in my own mind that the triangular gauge gave insufficient gauge widening was true. It proved the opposite, it works perfectly well for trains suitable to go round such a curve, though in practice (at least as done by me) it gives more widening than in theory. Then I thought, I could test out some other myths, first of all what is the problem with gauge widening the curving road of turnouts? As far as I'm concerned, this plank with added dummy turnouts proves there is no big problem there. It also proves that, if checking of around 0.36mm is no big problem, the checking of around 0.08 from a BB of 17.67 as opposed to the perfect "kiss" from 17.75 is just so piffling as to be not worth bothering about.

Yes the checking from a 17.67 BB is not perfectly prototypical, but, it seems to me, it is good enough and far preferable to a derailment resulting from taking this (from the Digest)
(In practice, because of
the shape of the root of the flange, the likelihood of
wheel A taking the wrong route increases only as
BBmax approaches the value of CGmin.)

exactly literally. But I get the idea from Russ that it is the wider BB that makes a diamond more likely to work and the question becomes, is it preferable to have a derailment at a turnout or a diamond? - in that on most turnouts the crossing itself is straight so a flange is unlikely to be hard up against the V on the diverging road. But in writing this I may be showing I still have not understood adequately what the Digest is saying.

Also I must say I rather think that Ray's conclusion, why not use prototype standards, is a logical step rather than the complexity of the above trade off. Andrew Jukes uses S4 track dimensions with a 17.82 BB. If Martin Wynne's 0.1 minimum clearance over the Check Span holds good for S4 that 17.82 BB could be reduced to 17.77 giving that much more practicality for a modeller....maybe? - not that I'm going S4-wards myself.

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Re: P4 vs S4 - Pro's and con's

Postby Martin Wynne » Sat May 20, 2017 10:15 am

Julian Roberts wrote:and hoping to find out whether or how I can get it 100% derailmentproof

Hi Julian,

It is very easy to make a diamond-crossing derailment-proof -- just build it as a switch-diamond (i.e. with movable K-crossings). It's not only 100% reliable, it is easier to build because there are no K-crossing check rails to fit. Which makes slips very much easier. The only downside is the need for two extra point motors (or one with a rocking crank arrangement).

The prototype allows fixed K-crossings up to 1:8 -- but only if all 4 legs are straight. If there is any curving the restrictions are tighter. Here are some prototype notes extracted from Templot:

Code: Select all

In radius down to:   the flattest angle for a fixed K-crossing is:

60 chains (3960ft)......1:8
30 chains (1980ft)......1:7.75
20 chains (1320ft)......1:7.5
15 chains ( 990ft)......1:7.25
12 chains ( 792ft)......1:7
10 chains ( 660ft)......1:6.5
below 10 chains.........1:6

This information is dated 1943 for the GWR, and similar rules can be assumed for other companies.

It is interesting that fixed K-crossings can be more reliable in EM than in P4 because of the deeper flange and higher ratio of flange thickness to flangeway gap. Using RTR wheels at 16.4mm back-to-back in EM (RP25/110 profile, flanges 0.8mm thick in 1.0mm flangeway), fixed K-crossings work very well. Likewise in 4-SF (00-SF) at 14.4mm back-to-back.

regards,

Martin.
39 years developing Templot. And counting ...


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