First steps in track building and P4.

Help and advice for those starting in, or converting to P4 standards. A place to share modelling as a beginner in P4.
seanmcs
Posts: 34
Joined: Wed Dec 10, 2008 12:57 am

Re: First steps in track building and P4.

Postby seanmcs » Fri Sep 11, 2020 9:07 am

Well, we had this conversation about a year ago. There seems to be no doubt that the current die used by some if not all rail vendors has a thicker web than the previous iterations. Hence the current crop of plastic chairs are always splayed. Particularly if you want to preserve the inward tilt of the rail in the chairs, something needs to give. Whether it is the rail die, or the chair moulds, I do not know. How about the P4 leadership acceptinhg a challenge?

Sean in Sydney

User avatar
David Thorpe
Posts: 931
Joined: Tue Oct 21, 2008 11:13 pm

Re: First steps in track building and P4.

Postby David Thorpe » Fri Sep 11, 2020 9:35 am

Terry Bendall wrote:
Noel wrote:but have come across suggestions that they can hold the rail head vertical, which results in instant gauge narrowing when you remove them, as the chairs adopt their designed 1:20 inclination,


I have to say that I have never found this. If the chairs are glued to the sleepers and the gauges left in place whilst the glue dries then the top of the rail should be in gauge when the gauges are removed. It does of course mean that you either need quite a lot of gauges and progress will be slow. I always use the triangular gauge when making track.


I did find it the hard way. I built quite a number of points using the usual gauges with plastic chairs and ply sleepers, and ended up having to adjust or rebuild many of them because the rails canted inwards after construction, thereby effectively narrowing the gauge. Some I remedied by doing as Philip suggests, ie "soldered upright rail on the pointwork. Ply sleepers, rivets every two or three sleepers, with plastic chairs cut in half and glued either side of the rail. The rivets will hold the rail very securely and the plastic chairs glued either side won’t let the rail go anywhere either. Being cut in half means that they can’t force the rail out of gauge", and that's what I'll do from the start next time I have to build some points. I believe the problem can be helped by use of the Society's Mint gauge, though I haven't as yet tried one myself. If someone was to offer plastic chairs that held the rail upright instead of this business of a prototype cant that might be fine in the prototype but is not in 4mm, I'd be in the queue to buy them.

DT
Last edited by David Thorpe on Fri Sep 11, 2020 2:57 pm, edited 1 time in total.

User avatar
John Donnelly
Web Team
Posts: 758
Joined: Fri Mar 16, 2012 7:03 pm

Re: First steps in track building and P4.

Postby John Donnelly » Fri Sep 11, 2020 9:38 am

seanmcs wrote:Well, we had this conversation about a year ago.


And here it is: viewtopic.php?f=40&t=6083&hilit=chairs

John

JFS
Posts: 729
Joined: Wed Dec 16, 2009 3:47 pm

Re: First steps in track building and P4.

Postby JFS » Fri Sep 11, 2020 11:58 am

Terry Bendall wrote:
Noel wrote:but have come across suggestions that they can hold the rail head vertical, which results in instant gauge narrowing when you remove them, as the chairs adopt their designed 1:20 inclination,


I have to say that I have never found this. If the chairs are glued to the sleepers and the gauges left in place whilst the glue dries then the top of the rail should be in gauge when the gauges are removed. It does of course mean that you either need quite a lot of gauges and progress will be slow. I always use the triangular gauge when making track.

Terry Bendall


You have definitely been 'lucky' here Terry as the effect is very real, and the principle which Noel describes is the cuase - any guage which holds the rail vertically whilst 1:20 chairs are glued will result in guage narrowing due to the rail springing to 1:20. And it is not insignificant.

I think it actually depends on the particular type of Guage(s) used (and how worn they are!). Not all guages of any particular type will cause the effect and indeed, the thickness of the rail head is also very far from a constant factor. (Compare the DDC Stainless steel rail - which is excellent - with C&L rail and you will find a measurable difference, and the old Studiolith rail is the narrowest of the lot)

I think the worst culprits are the types of guages which use powerful springs to grip the rails (The 'C&L' Guage is of this type though I would not wish to single it out for vilification!). Most of these guages have a means of reducong the spring pressure which is a big help - though then it is easy to go over-guage though this is less of a problem within reason. It is also probably true that the affect is much less pronounced when a hybrid chair/solder construction is used - an approach which has merits in my view.

Some years ago, I did a track demo at the 101 Not Out event and I had several people ask about why they ended up with narrow guage track and this turned out to be the common factor between them all - it was quite learning point for me - and since then I have always pointed it out whenever the discussion turns round to plastic chaired track.

Best Wishes,

CornCrake
Posts: 112
Joined: Sat Dec 05, 2015 2:03 pm

Re: First steps in track building and P4.

Postby CornCrake » Fri Sep 11, 2020 2:27 pm

I recently purchased 2 tri-angular gauges from P4 stores.
I had to return one of them because it was impossible to fit the rail head into one of the legs.
Jeremy Suter very promptly replaced it.

So I now have 2 gauges that work, but there are differences.
The two legs at the "pointy" end of the triangle on both gauges allow the rail head to rotate slightly.
On one gauge the two legs on the "long" side of the triangle also allow the rail head to rotate slightly.
However on the other gauge the two legs on the "long" side hold the rail head very firmly so no rotation is possible.
In fact one leg on the "tight" gauge was very tight.
Same bit of rail for these tests, so I inferred that on this "tight" gauge the slots were narrower.
So there seems to be some manufacturing inconsistency.
Scalefour stores supply Alan Gibson tri-angular gauges.

This was code 75 rail that I had purchased from the stores at one of the Scaleforum shows at Aylesbury.
I then decided to measure the thickness of this rail head,
Of course my cheap digital vernier gauge might not be that accurate, and I might not be using it properly but it does look as though this rail is more code 85 than 75.
Upon checking the digest it appears that the standards for P4 are to use code 85R.
Perhaps the Alan Gibson P4 gauges have slots for code 75 rather than code 85.

Would this be where the problem lies?

User avatar
grovenor-2685
Forum Team
Posts: 3371
Joined: Sun Jun 29, 2008 8:02 pm

Re: First steps in track building and P4.

Postby grovenor-2685 » Fri Sep 11, 2020 2:43 pm

The code 75 is the height of the rail, not the head width. The width does vary between makes, largely dependent, I think on the age of the die. I suppose the height will similarly vary as the tool ages, but should not get anywhere near code 85.
A prototype 95lb bull head rail when new is 145.26 mm high by 69.85 mm wide. Hence scaled at 1:76.2 should be 1.91 mm high by 0.92 mm wide, or 0.075 in by 0.036 in. Code 75 means 0.075 in high.
For fitting chairs the web thickness is also important and all model 95BH rails are overscale here, by variable amounts which causes most of the problems.
Regards
Keith
Grovenor Sidings

User avatar
Martin Wynne
Posts: 897
Joined: Mon May 14, 2012 4:27 pm

Re: First steps in track building and P4.

Postby Martin Wynne » Sat Sep 12, 2020 1:01 am

JFS wrote:any guage which holds the rail vertically whilst 1:20 chairs are glued will result in guage narrowing due to the rail springing to 1:20. And it is not insignificant.

Only if the track is straight or very nearly straight.

Curved model rail cannot be canted at 1:20.

If it were so, it would mean that the head of the rail is following a larger or smaller radius than the foot of the rail.

In order to do that the head of the rail would need to be longer or shorter than the foot. Not by much, but enough to require significant stress in the rail way beyond anything a plastic chair could impart. It needs a heavy lump of cast iron, a hardwood wedge, and a big hammer.

And since in the entire history of 4mm model railways, no-one has ever been able to see whether the rail on a layout is vertical or canted, the sensible approach is to build it vertical and avoid any gauging or other problems.

You might think that you could see it canted by looking at the ends of the check rails. Not so -- prototype bullhead check rails are always vertical (except for some early pre-group designs).

Martin.
40+ years developing Templot. And counting ...

JFS
Posts: 729
Joined: Wed Dec 16, 2009 3:47 pm

Re: First steps in track building and P4.

Postby JFS » Sat Sep 12, 2020 7:11 pm

Martin Wynne wrote:
JFS wrote:any guage which holds the rail vertically whilst 1:20 chairs are glued will result in guage narrowing due to the rail springing to 1:20. And it is not insignificant.

Only if the track is straight or very nearly straight.

Curved model rail cannot be canted at 1:20.

If it were so, it would mean that the head of the rail is following a larger or smaller radius than the foot of the rail.



Hello Martin,

Good point - I agree - at least in theory!

And I would confirm that the discussions at "101 Not Out" related to straight track - people simply could not understand why, in the most basic stiuation, they were in trouble.

It was a new one on me as I have no straight track on the layout! (well, just a bit in the platform roads). And I only use Exactoscale guages which do not create the problem.

Martin Wynne wrote: the sensible approach is to build it vertical and avoid any gauging or other problems.
.


but here I think, you miss a point - if you use 1:20 chairs functionally, you *cannot* build vertically.


Best Wishes,

C_FORD_97
Posts: 7
Joined: Mon Aug 31, 2020 2:58 pm

Re: First steps in track building and P4.

Postby C_FORD_97 » Sun Sep 13, 2020 7:25 pm

Hi all,

I managed to have a few hours on the test track today and successfully managed to get the chairs onto a length of rail with the thanks to the suggestions made here.
Rail with chairs.png

Ive laid a length of the Exactoscale concrete bases, which im very impressed with and will hopefully feature some on my future layout.
Exactoscale concrete track.jpg

Cut up some 12" timbers for the turnout and hope to get a start next week on laying them and making a start on the various rail's.
Turnout timbers.jpg

Connor

C_FORD_97
Posts: 7
Joined: Mon Aug 31, 2020 2:58 pm

Re: First steps in track building and P4.

Postby C_FORD_97 » Thu Oct 01, 2020 1:39 pm

Made some progress on the test plank last night, managed to get a length of timber track layed.
IMG_20200930_200858.jpg

IMG_20200930_211316.jpg
IMG_20200930_211805.jpg
IMG_20200930_215649.jpg

Overall I'm happy with the results so hopefully have the next couple bits layed soon.

Connor


Return to “Starting in P4”

Who is online

Users browsing this forum: No registered users and 5 guests