Pre-group and a 3' radius turnout

Discuss the prototype and how to model it.
William A

Pre-group and a 3' radius turnout

Postby William A » Tue Jan 11, 2022 12:30 pm

I have put together what I think is an achievable layout plan which is properly limited in scope, and I would be as happy as larry were it not for one problem: I'm aware that a 4' radius is minimal desirable, and that a 3' radius is really a hard minimum. My space however, is constrained unfortunately such that I don't think I can avoid them. If I may illustrate...

Here's a rough plan:
Image

    Specs:
  • The exit from the throat and the turnouts there are on a 6' radius, narrowing transitionally to 3'5" at the entrance to the traverser. However, the biggest pinch point is the left hand exit of the tandem turnout, which has a radius of 3'.
  • My standard train length is 3'6" to account for a tender loco, station pilot loco, and five six wheeled coaches with a little breathing room.
  • My platform clearance and traverser road length is nominally 4'
  • I am looking primarily to run 19th century locomotives and six wheeled coaches on this layout. A longest fixed wheelbase 0-6-0 is 32mm + 29mm on a tender goods loco. I would plan to use cleminson underframes for the 6w coaches

The traverser is exactly 4' long and butts up into the corner of the room, so cannot be moved.

I would dearly like to avoid having the platform lines running parallel with the layout borders, but at this point I'm just not sure whether realistically with appropriate gauge widening it will be a non-issue with the stock I am running? This will be traversed by all shunting moves from the arrivals platform into the departures road, and all shunting moves into the goods yard - so it's important that it works properly within the scope of the layout.

I have made a version of the layout which adheres to a 4' radius on all the pointwork, but now almost every single turnout is a Y of some form, and it no longer fits in the space I have available :(
Image

I am happy to get some track laid to these radii and try it out myself when I have accumulated the relevant stock, though if someone has material experience that can avoid the wait and the hours spent to do that, I would gladly appreciated it. Any thoughts or opinions gladly taken.

Many thanks,
William
Last edited by William A on Tue Jan 11, 2022 1:08 pm, edited 3 times in total.

petermeyer
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Re: Pre-group and a 3' radius turnout

Postby petermeyer » Tue Jan 11, 2022 12:37 pm

William

The turnout in my goods yard is down to a minimal radius of 1000mm as defined in Templot. My pre-group 0-6-0T’s and 0-6-0 tender engines seem to cope with it.

garethashenden
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Re: Pre-group and a 3' radius turnout

Postby garethashenden » Tue Jan 11, 2022 12:57 pm

I’d be inclined to test it. Build it as plain track and see how things behave on it. If you have the stock to hand.

William A

Re: Pre-group and a 3' radius turnout

Postby William A » Tue Jan 11, 2022 1:10 pm

Peter, that is good to know, and Gareth - appreciated. I don't have the stock to hand I'm afraid but I can hold off doing anything layout-wise until I do.

It may require more fiddling with templot but between the two plans I have posted I feel like there must be a way to make that tandem behave...

davebradwell
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Re: Pre-group and a 3' radius turnout

Postby davebradwell » Tue Jan 11, 2022 3:16 pm

Does a separate crossover fit, especially on the first version? Perhaps it's too long. It would also eliminate a rather tricky looking curved slip. Your biggest problem will be the 6 wheelers and a simple drawing will show the offset required and whether you need to widen the solebars to accommodate the movement of the axleguards. In practice you'll need rather less movement because of the clearance between wheelset and rails. Remember, though, that you're propelling stock round the curve and that's always a worry with sharp bends. The reverse curves from my suggested crossover will only be an advantage if you can get a decent radius through.

DaveB

William A

Re: Pre-group and a 3' radius turnout

Postby William A » Tue Jan 11, 2022 3:30 pm

Hi David,

It may do, but I only have 8' x 2' to work with, and would rather not have trackwork on the removable section (denoted by the diagonal slashes). I have re-drawn the plan and managed to get everything into a >4' radius except the turnout in the yard. The yard turnout would work geometrically as a C9, but would straddle a board joint, so a wye B7 with a minimum radius of 3'6" was supplanted:

Image

Clearly not as ideal, but if the only thing going through that turnout are a couple of wagons I should be OK, right?

davebradwell
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Re: Pre-group and a 3' radius turnout

Postby davebradwell » Tue Jan 11, 2022 4:44 pm

There's no harm in straddling a board joint with a turnout, as long as the cut is clear of switch and crossing. Your 3ft radius will probably be fine, subject to a few checks first but it seems wise to move yourself as far away from potential troublesome situations as possible. You'd be amazed at how many wagons you can end up pushing just to drop a couple in a siding.

I have a hidden 180 degreee 3ft curve and large 0-6-0s go round it - 8cpld engines have shorter wheelbase. I've just noticed the WD has gone down there at last session despite limited swing on pony to avoid front steps. Reversing unsprung 12ft w/b hoppers round it isn't a good idea, though.

DaveB

William A

Re: Pre-group and a 3' radius turnout

Postby William A » Wed Jan 12, 2022 8:19 am

Hi DaveB, thanks for the validation on the 3' curve - I would unfortunately be propelling 8-9' wheelbase wagons around the curve into the yard, but in that direction there would be a fairly generous transition from the mainline, across the tandem and slip?

Either way, if I can replace the turnout in the yard from a B7 to a C9 and gain an extra 6" effective radius (and it will make such a difference) then it's worth considering. The join would be between the vee and the closure rails - but I've not the foggiest how I would build such a turnout. Presumably laid in-situ with the boards bolted together, a fair amount of copperclad around the joint area and then sliced through with a piercing saw? It sounds hairy!

Terry Bendall
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Re: Pre-group and a 3' radius turnout

Postby Terry Bendall » Wed Jan 12, 2022 9:14 am

Someone I know had problems with sharp curves but he was trying to run 6 wheel pre-grouping coaches round a 4 foot radius curve.

William A wrote: I would unfortunately be propelling 8-9' wheelbase wagons around the curve into the yard,
Wagons with that length of wheelbase shoud run OK.
i
One way to proceed is to obtain some flexible track, build a turnout and lay it down temprorarily, perhaps with drawing pins, wire it up and see how things run. If it works, proceed.

William A wrote:The join would be between the vee and the closure rails - but I've not the foggiest how I would build such a turnout.


I did just this many years ago on Staverton with a turnout built using rivetted wooden sleepers. Build the turnout as usual. Lay it across the joint and when the glue is dry, make the cut in the required place. It worked very well. From memory the joint was a bit futher toward the heel of the tunout than the usual place for the join between the ends of the vee and the closure rails. All I did was to make the rails of the vee a little longer than usual. The relevent part of the layout was subsequently dismantelled so I no longer have the turnout to show.

Terry Bendall

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Winander
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Re: Pre-group and a 3' radius turnout

Postby Winander » Wed Jan 12, 2022 10:29 am

William A wrote:if I can replace the turnout in the yard from a B7 to a C9

You shouldn't be laying any B7/C9 turnouts. those are way later in permanent way development. You should be looking at loose heeled turnouts viewtopic.php?f=5&t=6257

These are my notes from Tables and Diagrams of Switches & Crossings : A Handy Platelayers Guide. Published 1895 by Thomas Summerson & Sons
p13 These are made of various lengths to suit the situation for which they are intended; the usual lengths for the standard gauge on main lines being 12 ft., with a proportion of 15 ft. and 18 ft., whilst about sidings the lengths run principally 9 ft. down to as low as 6 ft. The principal object in long switches is to make an easy turn off; they have also the advantage of additional stability as compared with short ones, for, being secured only at one end, switches are liable to rock and jump when heavy loads are passing over them. The lengths of switches should in a measure be adapted to the radius of the curve, for obviously there is no advantage in making the angle at the point less than the angle at the heel. This will more readily be understood by reference to the figure below, which shows a pair of long switches (a) applied to a short curve, where the abruptness of the angle of the turnout is met at the heel of the Switches (H) instead of the point (P).
Screenshot 2022-01-12 at 10.22.01.png

In general practice, for the standard gauge it will be found that there is nothing gained by making the switches longer than twice the angle of the crossing in feet; that is to say, 9ft is a better length of switch to work with crossings 1 in 4.5 than 12ft., and longer switches than 12ft. can only be applied to with advantage to crossings above 1 in 6.


I have a free pdf digitised by Google but don't recall where I found it. I can supply a copy if you PM me.
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Richard Hodgson
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davebradwell
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Re: Pre-group and a 3' radius turnout

Postby davebradwell » Wed Jan 12, 2022 10:45 am

The other place of concern is the K crossings in the slip - have you checked the angle. Julian had quite a bit of fun with some 1 in 8s on here a little while ago. These are the flattest used on the prototype without switch blades (someone said). There is, of course, a danger that when you try a longer point it will flatten the slip.

Although I said the 3ft would likely work, I was hoping to give the impression that I would try everything else first, including encroaching on the sacred territory on the right. One day someone is going to propel your 6 wheelers round there, or a visiting loco won't make it. Having said that, I have most of an LNER BZ 6 wheeler (10' 6" + 10' 6") with centre wheels on a carriage suspended on swing links, scale width solebars, all sprung, of course, and that went round the 3' very easily, although I suspect your coaches will be longer. Mark Tatlow has since come up with a very simple arrangement for the sliding centre axle.

When sawing track in situ I hold the rails with a specially slotted piece of wood. Sawing isn't the most gentle of processes.

DAveB

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Guy Rixon
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Re: Pre-group and a 3' radius turnout

Postby Guy Rixon » Wed Jan 12, 2022 2:37 pm

Since the station is spec'd for six-wheeled coaches, they may limit the radius more than the locos and other stock. If the stock already exists, it would be sensible to test it thoroughly, both hauled and propelled, on plain line around the limiting radius. If the stock is yet to be built, I'd guess that Cleminson arrangements might be necessary.

Philip Hall
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Re: Pre-group and a 3' radius turnout

Postby Philip Hall » Wed Jan 12, 2022 5:20 pm

I once had a long curved turnout built across a baseboard joint and it didn’t give any problems. I laid it in the usual way (in a bed of Copydex on cork underlay) and cut through at the joint once set. If anything did get out of alignment the Copydex allowed for a bit of heaving to true things up again.

That layout also had some fearful bends and generally 3ft radius gave no problems. I used to always say that I could get most things around 3ft radius but with the (very fortunate) minimum of 4ft 6ins on the new layout I now don’t have to.

Philip

William A

Re: Pre-group and a 3' radius turnout

Postby William A » Fri Jan 14, 2022 9:08 pm

Thanks for the tips, I've managed to ease the curve into the station lines to get everything above 4' even with a B7 turnout.

I'm aware that I should be modelling loose heel turnouts, and no doubt I will re-draw the layout again with those. I don't have any SER permanent way drawings I'm afraid, so SECR will have to do. Given that everything will be covered in ballast, I'm not sure how fussed I am about getting the correct timber spacing :)

The K-crossing on the slip is a 1:9 and includes a switched diamond. Probably another pain to address!

davebradwell
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Re: Pre-group and a 3' radius turnout

Postby davebradwell » Fri Jan 14, 2022 9:59 pm

Hmmm, that's rather terrifying! Was the slip any more co-operative with the 3ft curve? Beyond that it's a separate crossover which you didn't fancy.

DaveB


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