Sub 4ft radius curves

Discuss the prototype and how to model it.
User avatar
the fatadder
Posts: 53
Joined: Sat Jul 26, 2008 6:07 pm

Sub 4ft radius curves

Postby the fatadder » Mon Dec 23, 2013 11:42 am

With my first child being expected in January, my layouts current location has become unavailable. As a result I have spent the last couple of weekends insulating and putting up plasterboard to convert the garage into a new home for the layout. As a result I now have a fair bit more space to play with…

My plan was to design a continuous run fiddleyard which could be used with both my Kites Croft and Blackcombe layouts. However, the overall width of the converted garage is only 7ft11 inches which prevents the use of 4ft radius curves that I understand are the generally accepted minimum.

Now for bogie diesel stock I don’t really see an issue with this, however I am much more concerned about how my stem stock will perform. In particular, 8 coupled 2800 and 4200 class along with various GW 4-6-0s.
The majority of which will have sprung (I think I have 3 rigid chassised Hornby locos which will remain so unless Brassmasters were to release a replacement) Rolling stock is all based on sprung chassis, with smiths couplings and (for the moment at least) solid buffers.


Having done some quick calculations and I think that the maximum radius I can manage is going to be 3ft6, and ideally I would also like to have a second track inside this (though I realise that is going to be really pushing the running quality for large locos, the main reason for the second track is going to be the diesel layout.)

I know of layouts which have gone for tighter radius curves (iirc Clutton is around the 3ft mark)
So I would be interested to hear experiences of larger steam locos on sub 4ft radius curves, and what I need to keep in mind both for track and chassis construction to ensure reliable running on these curves.

Thanks for the help
Rich

martin goodall
Posts: 886
Joined: Fri Oct 02, 2009 6:20 pm

Re: Sub 4ft radius curves

Postby martin goodall » Mon Dec 23, 2013 1:36 pm

The main line curve on "The Burford Branch" is 3-foot radius (and the carriage siding, being an after-thought, has a radius of no more than abvout 2' 10").

What determines whether locos will go round the curves is not the overall size of the loco but the amount of sideplay allowed for the middle axle. However, a big 4-6-0 might look a bit silly going around a curve of that radius, even though it may be possible to achieve it by suitable adjustment of the frames and hornblocks/hornguides.

I can tell you from experience that you can get a six-coupled P4 loco (such as a Dean Goods or a Pannier) round a 2-foot curve if it has sufficient sideplay on the middle axle. We tried it once on my old "Crichel Down" layout. A Pannier and a Dean Goods which both had plenty of sideplay in the middle axle coped with the 2-foot curves on that layout without difficulty, but another Pannier which had little or no sideplay in the middle axle fell off.

My own experience has taught me that locomotives (and other rolling stock) should be built specifically for the layout on which they are intended to run and adjusted accordingly.

Philip Hall
Posts: 1125
Joined: Mon Aug 10, 2009 7:49 pm

Re: Sub 4ft radius curves

Postby Philip Hall » Mon Dec 23, 2013 1:55 pm

I have converted a few 4-6-0s and 2-8-0s to P4 and all have been quite happy at 2'6"radius although I wouldn't expect to hurtle around at that speed. 3'0" to 3'6" is quite practicable, and indeed was going to be my own ruling radius until the possibility of a larger space came up. As Martin says, build for the layout the engines are going to run on. With a 4-6-0, I tend to allow sideplay on the middle axle, hardly any on the front behind the slidebars, and a little bit on the rear axle.

2-8-0s, such as the Hornby 28XX and the Bachmann ROD 2-8-0, need a slightly different approach: here the front and third axles have very little sideplay (slidebars again), with some play on the second axle (care behind the connecting rods) and quite a bit on the rear axle. The tender coupling should prevent the rear of the engine swinging around too much. An interesting point about these two particular engines is that the front and third axles have a little bit of upward play, so that the engine actually rests on only two axles, the second and third. I am talking about only a few thou here, and have only recently been able to check this with some test wheels and a surface plate which I obtained in order to check the truth of another kind of Bachmann engine. It may well be that Hornby and Bachmann have deliberately done this to assist with transit around sharp curves, but whatever, it helps us in P4 as well. I have found no need to introduce any kind of downward springing, the weight of the wheelsets seems to be enough to keep things on the rails.

This upward play is also apparent on some six coupled engines, and does not affect running adversely on these either.

Philip
Last edited by Philip Hall on Mon Dec 23, 2013 4:06 pm, edited 1 time in total.

User avatar
Andy W
Posts: 811
Joined: Thu May 21, 2009 8:11 am

Re: Sub 4ft radius curves

Postby Andy W » Mon Dec 23, 2013 2:18 pm

Congratulations Rich. I hope all goes well with the birth. You may have more space for playing trains - but will you have any time?
Make Worcestershire great again.
Build a wall along the Herefordshire border and make them pay for it.

User avatar
the fatadder
Posts: 53
Joined: Sat Jul 26, 2008 6:07 pm

Re: Sub 4ft radius curves

Postby the fatadder » Mon Dec 23, 2013 3:19 pm

Thanks for the advice, I will take that into consideration when i get on with my conversions.

I think I will look at building the layout with a double track curve in this case with the outer track being 3ft 6 and the inner slightly less

Will find time somehow post arrival, at any rate she can nap in the train room with me (hopefully)....

User avatar
Paul Townsend
Posts: 654
Joined: Mon Sep 14, 2009 6:09 pm

Re: Sub 4ft radius curves

Postby Paul Townsend » Mon Dec 23, 2013 8:00 pm

the fatadder wrote:
Will find time somehow post arrival, at any rate she can nap in the train room with me (hopefully)....


So speak many a proto-parent :)
I got four of the tee-shirts so gently suggest you may be a tad over-optimistic :D
The first few weeks may well go by the book and then it all falls apart!

Never mind, take the long view.......

User avatar
Ian Everett
Posts: 378
Joined: Tue Jul 21, 2009 9:43 pm

Re: Sub 4ft radius curves

Postby Ian Everett » Tue Dec 24, 2013 9:31 am

The Bradford North Western Branch has a 3'6"curve and my Bachman WD and Hornby Black 5 romp round it. The G5 0-4-4T is a little less happy!

I'm sure you will succeed if you follow the advice above.

Ian

DougN
Posts: 849
Joined: Wed Sep 01, 2010 9:57 am

Re: Sub 4ft radius curves

Postby DougN » Tue Dec 24, 2013 10:03 am

Oh don't say that Ian, I have one that is almost complete, a G5 that is, I was hoping to get it to match my other locos that I set to go around a 1metre radius. I want to have a look at that over the Christmas holidays :D but I think I may run out to of time as it is only 3 weeks and the list is rather long.


Merry Christmas to all! :thumb
Doug
Still not doing enough modelling

User avatar
Simon_S
Posts: 81
Joined: Wed Aug 06, 2008 7:32 am

Re: Sub 4ft radius curves

Postby Simon_S » Thu Dec 26, 2013 9:26 am

Congratulations Rich but don't expect much modelling time when the little one arrives! Sub 4' radius no problem in Brio railways though :D

User avatar
Ian Everett
Posts: 378
Joined: Tue Jul 21, 2009 9:43 pm

Re: Sub 4ft radius curves

Postby Ian Everett » Thu Dec 26, 2013 11:31 am

DougN wrote:Oh don't say that Ian, I have one that is almost complete, a G5 that is...


I built the G5 mainly for Humber Dock, the main line of which is virtually straight and the 3'6" curve on BNW is temporary. The G5 does get round it but with a lot of flange grinding. I'm sure that with a bit more side play than I have given her she would be fine. (At present she runs so well elsewhere that I'm loth to take her apart. Chance plays a large part in my modelling success or otherwise...)

Ian

User avatar
steamraiser
Posts: 336
Joined: Thu Dec 31, 2009 4:49 pm

Re: Sub 4ft radius curves

Postby steamraiser » Thu Dec 26, 2013 6:23 pm

Tim Venton's (Of this parish) Clutton layout runs with 180 degree 3ft radius ends in P4.
The locos do need a touch more sideplay, but generally run fine.

Gordon A
Bristol

DougN
Posts: 849
Joined: Wed Sep 01, 2010 9:57 am

Re: Sub 4ft radius curves

Postby DougN » Thu Dec 26, 2013 9:16 pm

Thanks Ian, I have one part built and waiting for me to complete the chassis. I thought that due to the bogie having such limited swing it was causing the problems. I will have to look further into the entire mech.

All the best
Doug
Still not doing enough modelling

steves17
Posts: 86
Joined: Thu Nov 28, 2013 12:00 am

Re: Sub 4ft radius curves

Postby steves17 » Sat Jan 25, 2014 10:41 pm

Its a relief to find this thread. I decided to abandon Peco 100 at the eleventh hour. Talking at the P4 stand at the NEC was the tipping point otherwise i would be on 'toy track ' now. One thing i didn't bank on was the increased curvature. Four foot is huge - 8 ft plus for U-turns. I've been able to get up to 3ft radius or so as a minimum with massive re-planning and some heavily altered boards but if sub 3ft can be done with some tweaking them i'm at a little more ease.

Knuckles
Posts: 1127
Joined: Fri Nov 18, 2011 9:15 pm

Re: Sub 4ft radius curves

Postby Knuckles » Tue Feb 02, 2016 8:23 pm

steves17 wrote:Its a relief to find this thread. I decided to abandon Peco 100 at the eleventh hour. Talking at the P4 stand at the NEC was the tipping point otherwise i would be on 'toy track ' now. One thing i didn't bank on was the increased curvature. Four foot is huge - 8 ft plus for U-turns. I've been able to get up to 3ft radius or so as a minimum with massive re-planning and some heavily altered boards but if sub 3ft can be done with some tweaking them i'm at a little more ease.


But you fell and went back to 00!! :D


Just read the whole thread and am thinking is it worth redesigning my layout slightly? I don't really care if engines will look silly going around a tighter than desirable curve as long as they go around it.

I designed my layout with 4' curves on the outside and the immediate inner ones a wee less and the branch again a little less.

I'd like to get those 4' curves don to 3'6" or even 3" if at all possible as the track is basically almost hugging the roof eves and I could do with an extra 6" -1' for scenery and back scene but as I plan to run a couple of Pacifics and 10-Wheelers I do worry if things will manage.

What do you guys think? Resurrecting old threads can be good. :shock:
“He who dares not offend cannot be honest.” Thomas Paine

http://www.shapeways.com/shops/sparksho ... eationsscc
Mostly offering Loco kits & bits in 4mm.

Philip Hall
Posts: 1125
Joined: Mon Aug 10, 2009 7:49 pm

Re: Sub 4ft radius curves

Postby Philip Hall » Tue Feb 02, 2016 11:42 pm

My only reservation about fairly tight curves is not that engines cannot be built to run around them, merely that big engines will look a bit daft when they do. This is much less obvious if you are viewing from the inside, which is what I was planning to do a few years ago when I was restricted to a space 15'6" x 10'6". My new building will be at least 21'6" x 19'6" inside so 4'6" radius minimum suddenly became possible. I still intend to go below that on parts of the hidden yards and at the ends of sidings, but the main running lines will be able to be generously curved.

I would say that if you get a more workable and visually pleasing railway by reducing the radius a little, and you're viewing it from inside, go for it.

Philip

Knuckles
Posts: 1127
Joined: Fri Nov 18, 2011 9:15 pm

Re: Sub 4ft radius curves

Postby Knuckles » Wed Feb 03, 2016 12:58 am

It is viewable from inside only pretty much. I could do with bringing the curves in a bit from the edge so the backscene scenery can be built up a bit more as the track is almost going into the crook of the roof eves.

17.5ft x 11ft is the max space I got.

Bottom of the page is the plan...

viewtopic.php?f=9&t=2133&start=75

Unless I redo it in Templot first so I can put some transition curves in and redesign the turnout geometry to fit. But currently I still haven't got past the 2nd tutorial.of building a single slip, exasperated because Bullguard keeps jamming it up and quarranting files.




I'm more bothered about running than visuals as it is a compromise I actually need due to the usual.issue of having less space than really needed for a given plan.

I just fear building 3' or 3'6" curves then finding out getting a pacific or black 5 around it is next to impossible.
“He who dares not offend cannot be honest.” Thomas Paine

http://www.shapeways.com/shops/sparksho ... eationsscc
Mostly offering Loco kits & bits in 4mm.

User avatar
John Donnelly
Posts: 581
Joined: Fri Mar 16, 2012 7:03 pm

Re: Sub 4ft radius curves

Postby John Donnelly » Wed Feb 03, 2016 9:02 am

Knuckles wrote:I just fear building 3' or 3'6" curves then finding out getting a pacific or black 5 around it is next to impossible.


Dave Bradwell's 9F chassis will go round a 3' radius curve so you should be in with a good chance with a Pacific...

John

Philip Hall
Posts: 1125
Joined: Mon Aug 10, 2009 7:49 pm

Re: Sub 4ft radius curves

Postby Philip Hall » Wed Feb 03, 2016 9:31 am

I would go for 3'6" as a minimum then, with maybe 3'0" in yards and sidings where big engines will not go.

Philip

SHurst
Posts: 55
Joined: Wed Sep 09, 2009 7:30 pm

Re: Sub 4ft radius curves

Postby SHurst » Wed Feb 03, 2016 4:31 pm

Dave Bradwell's 9F chassis will go round a 3' radius curve so you should be in with a good chance with a Pacific...


I think you will find that in his instructions for the 9F Chassis, Dave states:

"My own model will run around 1 metre radius, laid accurately with a template"
"The limit on radius is probably set by the brake hangers which trap the wheel flanges between inner and outer parts and so restrict the allowable side play. This will be more of a problem in EM and OO with thicker flanges than with P4"

Not so sure about a 3 ft radius therefore- but may be wrong - will ask Dave next time we operate Derwenthough !

Simon

Knuckles
Posts: 1127
Joined: Fri Nov 18, 2011 9:15 pm

Re: Sub 4ft radius curves

Postby Knuckles » Wed Feb 03, 2016 5:00 pm

This is all pretty promising. To get a 9F around a 3' curve seems phenomenal.
You can always bodge the brake hangars and file them back a little so the flanges are not in the way, I find this is sometimes a good idea.

Thing is, in P4 the frame width as I understand it is supposed to be 16mm's so that leaves less than 1mm of play either side. Is that considered generous? Seems restrictive to me.

Maybe instead of publishing the minimum radius as 4' it should be stated that 4' is the minimum radius where things still look ok and then a smaller minimum for running but worse visuals? I've seen that suggested before but can't remember where.

I may try to redesign the layout with 3'6" then, (Maybe 3'??) and see how it looks.
“He who dares not offend cannot be honest.” Thomas Paine

http://www.shapeways.com/shops/sparksho ... eationsscc
Mostly offering Loco kits & bits in 4mm.

User avatar
John Donnelly
Posts: 581
Joined: Fri Mar 16, 2012 7:03 pm

Re: Sub 4ft radius curves

Postby John Donnelly » Wed Feb 03, 2016 5:31 pm

SHurst wrote:
Dave Bradwell's 9F chassis will go round a 3' radius curve so you should be in with a good chance with a Pacific...


I think you will find that in his instructions for the 9F Chassis, Dave states:

"My own model will run around 1 metre radius, laid accurately with a template"
"The limit on radius is probably set by the brake hangers which trap the wheel flanges between inner and outer parts and so restrict the allowable side play. This will be more of a problem in EM and OO with thicker flanges than with P4"

Not so sure about a 3 ft radius therefore- but may be wrong - will ask Dave next time we operate Derwenthough !

Simon


Thanks for that, I was taking the 3' from one of his MRJ articles and a brief chat at S4N last year. Derwenthaugh - now that's a layout I'd like to have a go on especially as the real place is just 10 minutes from my house...

John

Enigma
Posts: 183
Joined: Tue Aug 13, 2013 2:49 pm

Re: Sub 4ft radius curves

Postby Enigma » Fri Feb 05, 2016 9:30 am

Try and build in transitions so that the radius gradually reduces and then increases which should help to guide the locos through the smallest radius section. Done carefully, the overall 'average' radius can still be 3' or whatever else you can manage to fit into your available space.

(Don't tell anyone but I've done this with Peco Setrack on my US HO layout using gradually decreasing then increasing 'number' curves in the 180' curves at each end. It certainly helps the Mallets get round! But don't worry - I'm P4'ing again now :) )


Return to “Track and Turnouts”

Who is online

Users browsing this forum: No registered users and 2 guests