not an A4 turnout

[John CutlerParticipant]

I have come across correspondence from Martin Wynne suggesting that a turnout with 1:24 loose-heeled switches saves space compared to an A4 turnout and has a larger effective radius.
I have to say that my limited experience of A4 turnouts is not good when it comes to anything bigger than an ordinary short wheelbase wagon.
As I was about to plunge into building an A4, I am reconsidering.
If I try and emulate a loose-heeled switch, is the planing length the same as for an A4?
It seems I could try using C&L A4 switch blades as these are apparently 1:24 or am I wrong?.
Does anyone have experience of this?
No, I am not competent to file my own switch blades!

Any comments are welcome.
John Cutler

[Nick RidgwayParticipant]

It is quite possible to use a ready-made A switch blade as a “9ft switch”. The blade is actually a scale 12ft long and the rail would need to be trimmed to this length to make the straight switch principle work. The planing length is exactly the same for an “A” and for a “9ft”: a scale 2&3/4in-wide rail comes out at a scale 5ft 6in for 1 in 24 planing. Loose heel fishplates were also a feature of this length of straight switch as they were intended to pivot rather than to flex.

Post-1923 A switches (the GWR didn’t adopt the A switch as a standard, BTW) are “natural” with a 1 in 7 crossing, as the A switch and the turnout curve radius are both a scale 482ft on an “A & 7”. A “9ft & 4” has a radius of a scale 151ft. Selecting a straight switch rather than an A switch takes the scale 482ft of the semi-curved switch heel out of the equation, making the lead of the junction somewhat shorter. However, don’t expect much other than a very small 0-4-0T and a short-wheelbase 4w wagon to get round this sort of junction if they have side buffers: the limiting factor will be end-throw of the vehicles and the prospect of buffer-locking as straight turns to curve and vice-versa.

I’ve just detailed-designed a “9ft & 4” in 12in scale from first principles and it is intended for things like Wickhams and Permaquip trolleys, where the side buffer coupling is out of the picture and it is only to be used by consenting adults rather than Customers.

I don’t yet know what the geometry of the junction leading from the centre shed road to both platforms at Waterloo, Waterloo & City Line, is. Next time you’re standing waiting for a train from Waterloo to Bank, look at how the train, which is fitted with centre couplings, negotiates the junction leading from the centre siding and arrives in the departure platform. The crossing has got to be in the range of 1 in 4 to 1 in 5 and the end throw is quite startling!

[John CutlerParticipant]

Thanks Nick

Martin Wynne actually suggests that a proper loose heel pivot or hinge is not necessary (although prototypical).
A flexible switch should work in practice; the geometry is correct.
So I hope!

The only way to find out is for me to try to build one!
Unfortunately that means I have to relearn Templot after a 5-year break.

I think that could take a while……..

[Paul WillisParticipant]

@John Cutler said:
Martin Wynne actually suggests that a proper loose heel pivot or hinge is not necessary (although prototypical).
A flexible switch should work in practice; the geometry is correct.
So I hope!

The only way to find out is for me to try to build one!
Unfortunately that means I have to relearn Templot after a 5-year break.

I think that could take a while……..  

If you’re only after a single turnout template, that is actually remarkably quick to achieve in the latest version of Templot. Almost all the configuration settings are in drop-down menus, and you just select what you want.

It’s when you want to design the trackplan for a whole layout it becomes more complex!

Cheers
Paul
(big fan of Templot)

[Stephen FreemanParticipant]

Hi,
Any problems let me know or ask on Templot Club, If you really really want an A4 turnout.

[Nick RidgwayParticipant]

I can do Templot too,as it has got simpler to use over the last few revisions. Any help needed?

[Nick RidgwayParticipant]

@John Cutler said:
Thanks Nick

Martin Wynne actually suggests that a proper loose heel pivot or hinge is not necessary (although prototypical).
A flexible switch should work in practice; the geometry is correct.
So I hope!

The only way to find out is for me to try to build one!
Unfortunately that means I have to relearn Templot after a 5-year break.

I think that could take a while……..  

Consider also how the switches are to be actuated. A pivoting switch in any scale is going to need less force to operate than a sprung one.

[Paul WillisParticipant]

@Nick Ridgway said:

Consider also how the switches are to be actuated. A pivoting switch in any scale is going to need less force to operate than a sprung one.  

One of the interesting recent developments in 4mm modelling is the Peco detailed bullhead fishplates. A simple google should produce plenty of examples, and suppliers.

Not only do they look reasonably convincing (more so if you have one of the pre-Grouping railways that ballasted well over the tops of the sleepers to hide the join at the bottom of the fishplate) but they are robust enough to use finctionally for pivoting straight switch blades. I certainly intend to try them out as a functional hinge when I next build some GER prototype pointwork.

The one thing extra that I will do is use wires to separately electrically bond the blade and rail, as I don’t trust the continued electrical continuity of a flexing hinge.

Cheers
Paul

[Nick RidgwayParticipant]

@Paul Willis said:

One of the interesting recent developments in 4mm modelling is the Peco detailed bullhead fishplates. A simple google should produce plenty of examples, and suppliers.

Not only do they look reasonably convincing (more so if you have one of the pre-Grouping railways that ballasted well over the tops of the sleepers to hide the join at the bottom of the fishplate) but they are robust enough to use finctionally for pivoting straight switch blades. I certainly intend to try them out as a functional hinge when I next build some GER prototype pointwork.

The one thing extra that I will do is use wires to separately electrically bond the blade and rail, as I don’t trust the continued electrical continuity of a flexing hinge.

Cheers
Paul  

I would recommend that the blade and the closure rail on short switches are bonded together electrically. Make the insulated joints for the crossing at the crossing front joint and not between the blade and the closure rail.

This is not a problem with the lettered post-1923 switch designs, as one can use the switch heel joint instead and there is no risk of the wheelset touching two rails of different potential; it is, however, a potential problem with short pre-grouping- and industrial-style switches, as a wheel flange might touch the stock rail and the closure rail, which could be at different potentials. Well worth avoiding.

[Andrew Bluett-DuncanParticipant]

Hello
You could hinge the switch on a loose heeled turnout with a nut soldered to the underside of the sleeper and bolt through from the top. Then solder the switch to the top of the bolt. There’s abit more detail on my post on Templot Forum Track Building Yeovil Pen Mill in EM.
Kind regards
Andrew

[Nick RidgwayParticipant]

@Andrew Bluett-Duncan said:
Hello
You could hinge the switch on a loose heeled turnout with a nut soldered to the underside of the sleeper and bolt through from the top. Then solder the switch to the top of the bolt. There’s abit more detail on my post on Templot Forum Track Building Yeovil Pen Mill in EM.
Kind regards
Andrew  

Absolutely.

Another possibility is to use a Brook-Smith-style rivet in the timber at the heel of the switch, and solder the switch rail to that.

[Nick RidgwayParticipant]

@Andrew Bluett-Duncan said:
Hello
You could hinge the switch on a loose heeled turnout with a nut soldered to the underside of the sleeper and bolt through from the top. Then solder the switch to the top of the bolt. There’s abit more detail on my post on Templot Forum Track Building Yeovil Pen Mill in EM.
Kind regards
Andrew  

Another way of doing it is to use a Brook-Smith-style rivet in the heel timber and solder the switch rail to that.

[John CutlerParticipant]

I finally undertook a (partial) relearning of Templot to produce a template for a loose-heeled straight 1 in 4 turnout.
This gives a radius of 19.6″ compared to 17.3″ for the A4.

Much more productive for me was to produce a template for a loose-heeled 1 in 5.
Compared to an A5, this saves approx 23mm on the length to the crossing nose.
It even saves c5mm on the length for an A4.
This enables me to replace the planned A4 with a loose-heeled 1 in 5 (Thanks Martin W!).
OK I have to curve the siding slightly to compensate in the restricted space available.
But this is well worth it; the turnout radius will be 30.8″ and should comfortably accommodate tender locos at low speed.
Before this I was contemplating a restriction to short wheel-base tank locos.

All I have to do now is build it!

Thanks for all the responses.
John Cutler

[John CutlerParticipant]

I finally built a 1 in 5 turnout to the loose-heeled template from Templot.
But as suggested by Martin Wynne, it is not loose-heeled.
So no complications with pivots.
This has resulted in the blades being a bit stiff.
However, I have tested with short-wheeled rolling stock and so far there are no problems.
It will be a while before I test under traction as I need to sort out actuation and wire everything up.
The real test comes with a tender loco.
But if it fails, it will be no worse than my previous efforts with an A4 (and an A5 come to that).

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