Minimum radius for Scale 7 curves/point work

[MarcD]

I have been thinking of building a scale 7 industrial micro layout I have some waverley 5ft/8ft point kits an I was I was wondering if I could use them? What would people think the minimum curve radius would be?

 

Marc 

[Simond]

Recent discussion on Phil C’s new topic, Smoke Steam & new 0 Gauge layout.

 

I clipped a Google Earth screendump of a dockside track formation in Birkenhead docks into my cad, and measured the curve at 180 feet, so around 4’ to scale.

 

The limiting radius of your stock will depend on wheelbase, and any gauge widening you apply. The limiting radius for a train will depend on couplings and buffers too, and will be larger than your smallest loco will traverse.

 

In 0F you’ll almost certainly get a pug around a 2’ radius, but probably not in S7

 

Best

Simon

[MarcD]

The idea is to have some small 0-4-0STs shunting a few wagons. Hoping for something in the 8ft region including fiddle yard area, I would settle for an inglenook. I have noticed C&L have both A4 and A5 point kits Do they equate to 4ft and 5ft radius points?

 

Marc  

[Simond]

Marc,

 

not an expert here, but I do not believe so.  The letter refers to the switch planing length;  see http://www.finescale.org.uk/index.php?route=information/faq

 

Might be worth having a look at Templot - you can create a piece of track and it will tell you the minimum curve.  I don't have a copy at work or I'd do it for you!

 

best

Simon

[Ian Kirk]

Marc,

The average short wheelbase wagon had a design radius of one chain (66ft) so around 18 inches in O gauge. Small industrial pugs were similar. The attached photographs of Kirkcaldy harbour had bits of two chain. This was worked by short wheelbase J88 0-6-0T. If the full size could manage then presumably S7 could too.

 

best wishes,

 

Ian

[bécasse]

The normal minimum radius on the real railway was 3 chains (or 198 feet), which equates near enough to 4 feet 6 inches in 7mm scale, and this was only considered practical for short-wheelbase locos and wagons, even so, as Ian Kirk points out, there were situations where much tighter radii were found in industrial premises and, notably, docks. The minimum radius they I know of on a goods running line was Gotham Curve on the erstwhile Cromford and High Peak line which was 140 feet, 98 cm (or 3 feet 2.5 inches in 7mm scale) and which incorporated no less than 9 inches of superelevation.

 

In practice, even in Scale7, you can work with model curves that are tighter than the real thing scaled down, but as you reduce the radius so you increase the propensity to derail. Note that is always easier to pull wagons round a tight radius than to propel them.

[railwayrod]

Marc.

 

If you have not already done so It would be worthwhile contacting the S7 society. They put out a great deal of info regarding track and wheel standards. If the prototype does it so will S7 as it is scaled directly from the real thing (given manufacturing tolerances etc).The Groups website is www.scaleseven.org.uk

 

Hopr this is useful.

 

Rod

[MarcD]

I will drop them a email. I like the photos of Kirkcaldy harbour I was think of something along those lines, if you pardon the pun.

 

Marc

[Dungrange]

The idea is to have some small 0-4-0STs shunting a few wagons. Hoping for something in the 8ft region including fiddle yard area, I would settle for an inglenook. I have noticed C&L have both A4 and A5 point kits Do they equate to 4ft and 5ft radius points?

 

Marc  

 

No, the letter is the length of the planing on the switch and the number relates to the angle at which the tracks diverge (eg an A5 diverges at 1:5).  If you look at the C&L website at http://www.finescale.org.uk/index.php?route=information/faq and go the last of the frequently asked questions, you will find that an A5 turnout has a radius of approximately 6' 8" in S7.  That assumes that the straight road is straight.  The radius of the diverging road will increase or decrease if you curve the 'straight' road, depending on whether you aim for a 'Y' or 'curved' point (ie whether the radii are of opposing on the same hand).

[Sturminster_Newton]

Minimum radius is about your size of stock and locomotion and the kind of line you wish to represent.

 

As one with knowledge of smert-two, 30" is a feasible radius and the nice elves at Peco have bent their rails to suit.

 

At the end of the day it is personal preference and how true to life you wish to be.

 

Or whether you can live with a compromise, whilst I am not suggesting that your line should be constructed with smerty-two, as the rail profile is a bit forth bridge in section many of the modern 0-4-0 will traverse 30" radius as long as the buffing suits the radius of operation.

 

There are those reading this who will be crossing themselves and reaching for the yeastvites at the idea of the 'new' Peco O-gauge set track which in some quarters has been rubbished as not fit for purpose, which does no-one any favours.

 

The only thing you may be certain about is the Peco set track will be reliably traversed by most of the smaller and medium sized r-t-r locomotives and constructed to good accurate standards using professionally made jigs and bending tools.

 

The declared 1082mm radius is listed as R2 in the catalogue; so one assumes that a range of curves will appear over the next century or so

 

The production of R3 curves would allow double or triple track. The 752mm and 958mm are declared for Smerty-two so it would in theory be possibly to produce R0 and R1 if it was not for the rail section.

 

Most muddlers are well aware that smaller rolling stock will pass around curves that would be impractical in 12" scale.

 

Best advice would be to put together a test track using your chosen radius to see what is feasible and what stock looks most comfortable being hauled and propelled.

 

This will allow you to work out what you have in mind, and it will give the thumbs up to that rewarding build process.

[brack]

http://www.rmweb.co.uk/community/uploads/monthly_08_2015/post-7071-0-75171900-1441047113.jpg

 

35' in real life, so about 9.6" in scaleseven then. That's got to be pretty near the minimum...

[Donw]

In addition to getting stuff round tight curves there are other issues that arise on tight curves one is couplings.  Another is buffer locking and a third is clearances for platforms etc. For an industrial setting the clearances will probably not be a problem if there are no coaches and no platforms. Buffer locking can be a problem on tight curves especially with coaches and long wheelbase wagons. With really tight curves even 4 wheel wagons may suffer with buffer locking. You can increase the size of the buffer heads but it seems rather out of step with S7. An auto coupling which includes a buffing action can be an answer but again seems out of step with S7. Finally the first one couplings, you may find on tight curves the couplings need to be longer than scale this will give an excessive gap on straight track but without it the couplings ,may pull stuff off the rails. I adopt the policy of lightly sprungs buffers and somewhat stronger sprung couplings so that on a curve the buffers on the inside will compress easily and the couplings will only extend if that isn't sufficient.

BTW locos with frames at underscale width with the thinner S7 wheels will give more sideplay again it is not quite the S7 ethic to keep the frames at 0F width but it can help to squeeze round tight curves. Jointed rods on 6 coupled locos makes sense too.

 

On the question of turnouts I would suggest using a 9ft straight switch either 1:5 or 1:5.5 these would be correct anyway for industrial settings a 6ft 1:4 could be used I cannot remember the effective radii offhand.

 

Don

[MarcD]

Its a long term plan. I have a 0-21 Narrow gauge layout to build first. but my intentions is to go industrial 0-4-0T or short WB 0-6-0T, 4 wheel wagon 9ft or smaller WB. Thinking of going pre 1900 so might have a few dead buffered wagons.

 

Marc

[ian@stenochs]

Industrial pugs will go round very sharp curves.  Scale 7 models will do likewise.

 

On my old S7 Layout, Auchlin, I ran industrial pugs with short trains round an S curve of 24" radius on a gradient of 1 in 12 to get the colliery branch under the main line.  It did have a check rail on the visible part but not on the reverse which was on the operators side.  The trains were restricted to 3 loaded wagons, but that was fine from an operating point of view, and kept the action moving for the spectator.  At the exchange sidings there was a loop used to run round and permit the wagons to be left for the main line locos to remove.  The industrial sidings were very tight, turnouts were A switches curved to suit the restricted space. Wagons were pushed and pulled without buffer locking problems.

 

On the 'straight' sections of the industrial line each length of track was joined with a kink just like so many real life pit lines.  This never gave us any trouble but did look good.  We never had any problems throughout the 10 years or so the layout was on the show circuit and we used to run at prototypical speeds, quite fast actually.  Most of the pugs were 4 coupled but there was a 6 coupled diesel which worked just as well.  

 

I regret that I took so few pictures, it was just at the start of the digital photo revolution, but here are a couple of views which have been scanned from rather poor prints, the colour looks a bit washed out too.

 

 

This shows one end of the run round loop and the Tally mans hut.  The turnout under the Barclay has been curved to fit and is a Y.

 

 

The Barclay on the curved gradient just coming out of the underbridge with 3 loaded wagons. You can just see how sharp this curve was.

 

Regrettably I no longer have the layout having sold it on.

 

Ian.