Turnout construction - Question here please.

[Martin Wynne]

Shame Tim's film doesn't show this part of the process!

Hi Julian,

It does show knuckle bends being made, at around 6 minutes 30 seconds in.

Here is another old film about junction renewal:



cheers,

Martin.

[Julian Roberts]

+1 ......not least, for the great music sound track!

[TEZBEDZ]

I built 11 turnouts on my layout Llanfyllin, but, 1 is giving me a lot of grief.
One turnout refuses to work properly. I dont know the correct terms but when used as a trailing point all vehicles pass through correctly without detailing.
When vehicles go through as a facing point all weighted wagons go straight on, none will turn. However I have a plastic box van without weight which turns.
The switch blade fits flush up against the straight rail and the wagons dont derail. I have checked their back to back and also the gauge through the turnout
Any ideas why?

[Will L]

Are your wagons rigid, compensated or sprung. If a mix does the type of suspension make any difference?

The next step is to get your eyes down to tack level and watch what happens as the wheels go through the point.

[Winander]

I have looked in the digests and the turnout construction thread accompanying this questions thread and cannot find the answer to the following:

What distance apart do I fix the switch blades when fixing the stretcher? Or phrased another way, how much gap do I leave between the outside of the switch blade and the stock rail? I assume the check gauge comes into play, but suspect a little more is allowed on the model (which means the prototype dimension is not useful).

Thanks in anticipation....

[Winander]

Are your wagons rigid, compensated or sprung. If a mix does the type of suspension make any difference?

Also test your wagons by rolling them down a glass (or as flat a thing as you can get) incline. If they don't roll straight, the axles are not parallel.

As Will says, we need some more details of the wagons used such as wheelbase and weight.

[davebradwell]

Winnander - Blades on the prototype open to give a 4 1/4" gap to the stock rail - it's far more than the check gap and scales at 1.4mm. A drill shank makes a good gauge. If the rails are joggled, the opening should be measured to the bit that is to gauge ie away from the joggle. It is a very common error to provide inadequate opening and can result in a wheel catching the end of the "not open enough" blade. This dimension is from an LNER turnout but is unlikely to vary between companies.

With troublesome pointwork, try holding a rigid wagon and just pushing it through very slowly. You can bias it towards the closed blade and feel for it catching the blade which must then be fettled until the wagon passes the end of the blade without a detectable step. There's been plenty on teh forum about blade end shapes.

DaveB

[Winander]

Thanks Dave, the tip to use a drill is also helpful.

[Tony Wilkins]

Certainly the nominal distance for the blade opening is usually quoted as 4 1/4" although I am sure I have seen 4 1/2" quoted in some instances.
4 1/4" or 1.4mm scale should be adequate for our purpose. I do sometimes use 1.5mm for P4 blades for luck.
However my feeling is that the fault is most likely due to the fit of the closed switch blade against the stock rail. P4 flanges being so fine can pick up on remarkably small projections from the true line. Run your finger along the running edge and see if you can feel any step or corner at the start of the switch blade as this should feel smooth.
Something else to look out for is the finish of the top of the switch blade. If this is flat at the very tip then it is possible for the flange to ride up and run along the head of the switch rail instead of being deflected sideways by the face of the flange.
Regards
Tony.

[TEZBEDZ]

Are your wagons rigid, compensated or sprung. If a mix does the type of suspension make any difference?

The next step is to get your eyes down to tack level and watch what happens as the wheels go through the point.

Thanks. Looking at track level helped and I discovered that the gauge narrowed a tiny amount about 2mm before the joggle on the curved stock rail. This tiny amount was enough to lift the wheel above the switch rail.

[Terry Bendall]

Thanks. Looking at track level helped and I discovered that the gauge narrowed a tiny amount about 2mm before the joggle on the curved stock rail

There is always a reason - the trick is finding what it is. The lack of weight would not have helped. When looking for faults I sometimes put a piece of lead or something of similar mass on top of the errant vehicle and see if it makes any difference. If everything else runs through the problem is usually with the vehicle.

Terry Bendall

[bécasse]

There is always a reason - the trick is finding what it is................. If everything else runs through the problem is usually with the vehicle.

........ but not always.

I can go back some 49 years when we found at our first exhibition that some wagons (uncompensated in those days of course but well weighted) didn't like being propelled into the goods siding. We couldn't find anything wrong with wagons concerned and checks quickly showed that the point was spot on for gauge. It wasn't long before the tongues started to wag "we always said that this finescale stuff may look very nice but it clearly doesn't work".

It wasn't until one of our group, a pw engineer, found an old plan buried in the railway's archives that the mystery was solved - because written in pencil on that plan was a list of wagons, real 304,8mm to the foot ones, known to have derailed on the prototype point. Our track work was built to the precise plans of the real thing, fortuitously recorded by the same engineer before the track was lifted, and in doing so we had managed to replicate the point's faulty geometry - and derailments! The geometry of secondary track work, which used available secondhand materials, was often "bodged", usually without too many ill effects.

[Winander]

Is the track gauge listed in the stores as "Track gauge, Type 'A', Brook Smith" the one in the picture below (stolen from Tony's construction thread)?

Q Book Smith Gauge.jpg (143.39 KiB) Viewed 3689 times

Also, can anyone please supply photos of gauges TGS4/1 and TGS4/2 that Alan Gibson sells? Listed in the catalogue as follows:
TGS4 Set of four Scalefour track gauges
TGS4/1 Scalefour track gauge - actually holds running rails
TGS4/2 Scalefour Rolling gauge for checking for tight spots
TGS4/3 Scalefour Crossing flangway spacer
TGS4/4 Scalefour Check rail gauge
TGS4/5 Scalefour three point track gauge (not above set)

(From the blurb in the catalogue TGS4 is a set of four of the gauges listed after it.)

I am only interested in TGS4/1 Scalefour track gauge - actually holds running rails and TGS4/2 Scalefour Rolling gauge .

If TSG4/1 is not the 'traditional' three point gauge (TSG4/5) then what is it?

Thanks

[stephenfreeman]

I wasn't aware that Alan Gibson supplies the gauges, I bought mine from the stores. Assuming these are the same, you have posted a picture of the first gauge you are interested in. I'll try and post a photo of the other one but expect to be beaten to it.

[stephenfreeman]

hope this helps

gauge.jpg (231.21 KiB) Viewed 3623 times

[Tony Wilkins]

Hi Richard.
Yes, the track gauge pictured is a Brook Smith track gauge and was part of a set then available.
It also contained one as pictured above.
I thought the picture looked familiar.
Regards
Tony.

[CornCrake]

Picture of Brook Smith Type "A" received from stores last week:-

Brook_Smith_Type_A.jpg (73.42 KiB) Viewed 3502 times

Steve

[Winander]

Thanks very much for all the responses.

I had reached the conclusion that the picture I posted when posing the question was the Brook Smith type A, but thanks to Steve, not the case!

[CornCrake]

Hi Richard,

Thought you might like to see the component parts:-

The important part is the "bobbin" which looks very similar to the "bobbin" part depicted in the first photo that you posted from Tony's track building thread.

Steve

[Winander]

Hi Steve,

Thanks for this, I had concluded that being described as Brook Smith, and from the look of it, it might grip the rails vertically and cause gauge problems if using plastic chair construction rather than rivets. It's documented elsewhere on the forum as a problem with some triangular gauges that have the 'legs' too long - when the rail is released they spring into the 1:20 inclination imposed by the chairs and result under gauge.

Your latest picture is really useful and I do see the similarity - thanks very much for taking the time to post it, it looks just what I need.

best wishes

[stephenfreeman]

Ah! the ones based on the nut and bolt were, if memory serves me right the original Alan Gibson product from when he used to sell the range for Len Newman. To avoid any possibility of the gauge narrowing effect best to not have the nut adjusted too tightly. The current 3 point gauges available from the stores only sit on the head so should be OK. By turning up a suitable sleeve you can adapt the original gauges to suit other gauges to P4 standards. As well as having a Society 3 point gauge for IrishP4 this adds a couple of extra gauges when I need them.

I wasn't aware that the nut and bolt gauge was still available, so useful to know. In fact the design seems to have changed in that instead of the "bobbin" there used to be 2 shouldered washers and a spacer tube. The new design obviously doesn't lend itself to the Irish mod above.

[grovenor-2685]

The original bolt together guages were the Protofour Mk II, as illustrated here
https://www.scalefour.org/history/protofoursociety/manual/4.1.5-gauges
I have a set but still use the Mk 1 more often.

[Martin Wynne]

Hi Tony,

In your latest post on your construction topic: viewtopic.php?p=77214#p77214 you say:

The hardest part (of the vee) to bend is where the point and splice rail are physically soldered together, but it can be done.

It's not prototypical to bend the splice area*, otherwise it won't fit properly in the A and B chairs and the through bolts won't line up. What happens in effect is that the length from the knuckle to the end of the splice is left straight, as a chord across the ruling curve, with a resulting fractional dog-leg bend at each end. If you do the maths at a typical railway radius, you find that the resulting gauge error is tiny, and soon worn away by traffic. Of course on models we tend to use much sharper curves than the prototype, so we may have no choice but to bend the splice a bit. Also in 00, EM and P4 (not S4) the wider than scale flangeways increase the distance from the knuckle.

*unless manufactured curved as a special order in the crossing shop.

However a closer examination of the fit of the inner switch blade leaves something to be desired. The blade is not a snug fit against the stock rail.

It's quite tricky to do, but the curving in the turnout-side stock rail over the length of the planing needs to be at the same radius as the opposite (main-side) stock rail, not at the same turnout radius as the remaining section of the rail. It needs an accurate set angle and frequent checking of the stock gauge when fixing the stock rail (at the end of the planing -- should be the track gauge plus one rail-width between the stock rails).

cheers,

Martin.

[Tony Wilkins]

Hi Tony,

In your latest post on your construction topic: viewtopic.php?p=77214#p77214 you say:

The hardest part (of the vee) to bend is where the point and splice rail are physically soldered together, but it can be done.

It's not prototypical to bend the splice area*, otherwise it won't fit properly in the A and B chairs and the through bolts won't line up. What happens in effect is that the length from the knuckle to the end of the splice is left straight, as a chord across the ruling curve, with a resulting fractional dog-leg bend at each end. If you do the maths at a typical railway radius, you find that the resulting gauge error is tiny, and soon worn away by traffic. Of course on models we tend to use much sharper curves than the prototype, so we may have no choice but to bend the splice a bit. Also in 00, EM and P4 (not S4) the wider than scale flangeways increase the distance from the knuckle.

*unless manufactured curved as a special order in the crossing shop.

Agreed. Most crossings are effectively straight from the knuckle through the splice as many photos show and I often don't bother to bend this part of the crossing as the error is so small, but for those who wish to approximate a curved crossing, I would suggest that this method is somewhat easier for model purposes than trying to form one from pre-shaped rails. The main problem is holding the point and splice rails together correctly whilst soldering and being able to check the accuracy after, since our jigs are for straight vees and there are an infinite number of radii. But I am sure there will be someone who has.

However a closer examination of the fit of the inner switch blade leaves something to be desired. The blade is not a snug fit against the stock rail.

It's quite tricky to do, but the curving in the turnout-side stock rail over the length of the planing needs to be at the same radius as the opposite (main-side) stock rail, not at the same turnout radius as the remaining section of the rail. It needs an accurate set angle and frequent checking of the stock gauge when fixing the stock rail (at the end of the planing -- should be the track gauge plus one rail-width between the stock rails).

cheers,

Martin.

Indeed. It is actually more complex than that in most cases as the curved switch rail will require three different radius curves if done accurately. The planed length must match the stock rail radius, then the remainder of the switch rail length must match the switch radius plus or minus (depending on the direction of flexure) the curving radius and the rest must match the new closure rail radius. In this case, as the turnout is a C-10, which is a natural turnout, only two radii were required as the switch and closure rail radii are the same.
As always, the best advise I can give is try to match the template as accurately as you can.
Tony.

[TEZBEDZ]

Hopefully this topic covers chairs used on a turnout.

I am just starting an extension to my model of Llanfyllin which requires more turnouts being built, I completed my last ones at least 6 years ago using exactoscale products.

I have just purchased some chairs for turnouts but in the pack of chairs for the common crossing 4CH 502A 4mm scale chairs 1:5 6 7 8 and 10 common crossing (1 set) there appears to be 4 chairs which will act as P1 and P2 (L & R) which of the other pieces do I use to make P3 and P4 (L & R)

Apologies if I have missed some instructions somewhere