Minimum Radius?

[Brookers]

Just a quick question,

 

I'm currently planning a layout bassed on the CJF "diminishig dumbell" design from his book of "Track Plans for Various Locations" TP26 to fit in to my garage once I have reroofed and insulated it.

 

I'm planning on building it in oo with Peco Code 75 track work and I'm a little unsure what is the minimum radius curves I can use and be assured of good running on the hidden reverse curves with the currently produced ready to run locomotives including an 8F?

 

At the moment I have set the minimum radius in these curves as 18". Will this be ok or in your experience am I pushing my luck? I would like to get this right first time rather than finding out it doesnt work!

 

Many thanks,

 

Brookers

[Gruffalo]

I wouldn't go below 24", particularly with Code 75.

[Brookers]

I wouldn't go below 24", particularly with Code 75.

Thankyou for the quick reply!

 

Is that for running quality or for asthetics? these curves will hidden.

 

Thanks again.

 

Brookers

[Gruffalo]

Running quality. At that radius, multiple tracks need plenty of separation due to overhang between coach bogies and with them being hidden, you certainly don't want derailments. An 8F with flanged wheels would need a good bit of side-play to run smoothly round such tight curves and the friction will reduce the effective hauling power of your locos. 

[Brookers]

Running quality. At that radius, multiple tracks need plenty of separation due to overhang between coach bogies and with them being hidden, you certainly don't want derailments. An 8F with flanged wheels would need a good bit of side-play to run smoothly round such tight curves and the friction will reduce the effective hauling power of your locos.

That makes sense, thank you. Would I be better going to set track line seperation in these areas? Would switching to code 100 be of bennifit?

Is there anything I can do to cheat a smaller radius?

 

Brookers

[Joseph_Pestell]

Ultimately, no. The effects of physics are the same and tight radius curves will affect the haulage capacity of your locos.

 

It may however be worth going to Code 100 in these parts so that you can use sectional track. Laying flexible track to very tight radii can be difficult. I can't remember the detail of the plan concerned and therefore how many parallel curved sections you will require. Most sectional track systems only go up to about 22" radius. Shinohara has rather more but I don't know whether any UK stockist currently keeps these as a stock item (try ScaleLink).

 

With reverse loops, going to a greater radius will, of course, greatly impact on size: length as well as width. So unless you have a much bigger space than CJF designed the layout for, you are going to run into problems.

[ThePurplePrimer]

Interesting stuff that answers a few questions I have too.

 

Can I ask with the radius of a curve affects a locos pulling power please

[Silver Sidelines]

Good evening Brookers

 

It is not just the overhang / track spacing that you need to think about but also how close you want the stock to be coupled together.  If you want to close couple rakes of coaches you might need to consider curves of 30 or more inches (750mm?).  I would second the comments about the difficulties of using flexible track for small radii.  I had some success using G clamps to hold the track in place whilst cutting the surplus rail with mini cutting discs (with a Dremel type drill).

 

Regards

 

Ray 

[Gruffalo]

If you are going down the flexi track route, offset the rail ends to help keep the alignment by around 50-70 mm. Both rails joined at the same place on the curve will often produce a sharp step which the offset helps to overcome.

[Pacific231G]

I'm familiar with the Diminishing Dumbell plan as I looked at it as a possible way to get a main line terminus and fiddle yard into a too short space. I think I've got the original RM it was published in with rather more of CJF's notes so I'll try to dig it out.  Freezer's idea was that proprietary stock (of that era) would negotiate 15inch radius curves but looked very silly while doing so. By hiding the corners the visible parts of the layout would look convincing.

I think the catch may be that while a shortish train of main line coaches might be able to negotiate such a tight radius a full length train would be far more likely to come to grief especially if it was pushed rather than pulled as might well be the case with MU stock . Coupling units of the type that elongate on curves would help with the close coupling problem but the choice of couplers is also a factor.

OTOH out there in the world of model trains that most people inhabit, just about anything from the usual manufacturers is happily charging round 2nd radius curves (17 1/4 inch) on layouts whose owners probably think a transition curve is something to do with the economy.

I know people who've built roundy round layouts using main line stock in H0 and found that curves of less than 18 inch radius (or at least 2nd radius) do cause trouble but seem to be OK with that or above - carefully laid using set track pieces rather than flexible track- but their stock is all proprietary (Jouef mostly from before it was owned by Hornby ) so designed for fairly tight radii.

The diminishing dumbell will involve compromises but if it's the only way to get the type of operation you want apply rule one and maybe build a test loop for the minimum radius you've got in mind. It might be better to hide the reversing curves behind scenic breaks and backscenes rather than building scenery over them as you will want easy access to them without spoiling the visual effect.

[Pacific231G]

Update: I've just found the plan in RM that I'd thought was "Diminishing Dumbell"  and it was in fact "In Disguise". This was a shelf layout for a fairly comprehensive through station with two terminal platforms with storage loops behind it. The boards widened at each end to make room for the 15" minimum radius hidden return curves which gave the whole thing the shape of a dumbell. However, "Diminishing Dumbell"  was a series of much more complex folded dumbell schemes based on Exeter Central. It used the same principle of very tight (15inch) radius hidden return curves so the arguments about minimum radii would apply. 

I've had some experience of trying to run trains round very tight return curves on modular set ups and did find problems with flextrack curves laid too tightly with long passenger trains.

Though 15" or first radius curves are probably too extreme I still think that the "In Disguise" idea may have virtues for a semi permanent shelf layout along one wall of a room or garage used for other purposes. The front of the return curves could be made to fold out for operating sessions and stock could remain on the layout at other times but the return curves would have to be very carefully laid and reverse curves avoided. For a back bedroom with an unused chimney breast I can see definite possibilities and I just happen to have a back bedroom with an unused chimney breast that's just a bit too short for a main line terminus to fiddle yard with the trains I'd like to run.   

[Chimer]

For hidden curves at set-track radii, it makes sense to me to use set-track in order to avoid the risk of kinking while laying flexitrack.  This will also give the wider set-track spacing on parallel tracks and so reduce problems with overhangs.

[Brookers]

Ultimately, no. The effects of physics are the same and tight radius curves will affect the haulage capacity of your locos.

 

It may however be worth going to Code 100 in these parts so that you can use sectional track. Laying flexible track to very tight radii can be difficult. I can't remember the detail of the plan concerned and therefore how many parallel curved sections you will require. Most sectional track systems only go up to about 22" radius. Shinohara has rather more but I don't know whether any UK stockist currently keeps these as a stock item (try ScaleLink).

 

With reverse loops, going to a greater radius will, of course, greatly impact on size: length as well as width. So unless you have a much bigger space than CJF designed the layout for, you are going to run into problems.

 

Joseph, thank you for your reply. I'm aware of, how shall I put this? How ambitious CJF was with what could be fiited in to the space available, So I have picked a plan where I have more space available to me to allow me ease the radius of all the curves in the plan. I have at least 15'3" x 8'6" available to me. Probably more but untill I have refurbished and insulated the garage I wont know for certain.

 

Thanks for the suggestion of the Shinohara set track, I will have a look at that.

 

Good evening Brookers

 

It is not just the overhang / track spacing that you need to think about but also how close you want the stock to be coupled together.  If you want to close couple rakes of coaches you might need to consider curves of 30 or more inches (750mm?).  I would second the comments about the difficulties of using flexible track for small radii.  I had some success using G clamps to hold the track in place whilst cutting the surplus rail with mini cutting discs (with a Dremel type drill).

 

Regards

 

Ray 

 

Ray, Thank you for your reply, I havent given much consideration to couplings yet, for the moment I will use the tension locks but I have been looking at the Kadey couplings, I'm not sure if they will be better or worse? I think I need to spend some time researching this.

 

If you are going down the flexi track route, offset the rail ends to help keep the alignment by around 50-70 mm. Both rails joined at the same place on the curve will often produce a sharp step which the offset helps to overcome.

 

Gruffalo, thanks for the reminder about that technique, I will make sure I do as you suggest!

 

I'm familiar with the Diminishing Dumbell plan as I looked at it as a possible way to get a main line terminus and fiddle yard into a too short space. I think I've got the original RM it was published in with rather more of CJF's notes so I'll try to dig it out.  Freezer's idea was that proprietary stock (of that era) would negotiate 15inch radius curves but looked very silly while doing so. By hiding the corners the visible parts of the layout would look convincing.

 

I think the catch may be that while a shortish train of main line coaches might be able to negotiate such a tight radius a full length train would be far more likely to come to grief especially if it was pushed rather than pulled as might well be the case with MU stock . Coupling units of the type that elongate on curves would help with the close coupling problem but the choice of couplers is also a factor.

 

OTOH out there in the world of model trains that most people inhabit, just about anything from the usual manufacturers is happily charging round 2nd radius curves (17 1/4 inch) on layouts whose owners probably think a transition curve is something to do with the economy.

 

I know people who've built roundy round layouts using main line stock in H0 and found that curves of less than 18 inch radius (or at least 2nd radius) do cause trouble but seem to be OK with that or above - carefully laid using set track pieces rather than flexible track- but their stock is all proprietary (Jouef mostly from before it was owned by Hornby ) so designed for fairly tight radii.

 

The diminishing dumbell will involve compromises but if it's the only way to get the type of operation you want apply rule one and maybe build a test loop for the minimum radius you've got in mind. It might be better to hide the reversing curves behind scenic breaks and backscenes rather than building scenery over them as you will want easy access to them without spoiling the visual effect.

 

Update: I've just found the plan in RM that I'd thought was "Diminishing Dumbell"  and it was in fact "In Disguise". This was a shelf layout for a fairly comprehensive through station with two terminal platforms with storage loops behind it. The boards widened at each end to make room for the 15" minimum radius hidden return curves which gave the whole thing the shape of a dumbell. However, "Diminishing Dumbell"  was a series of much more complex folded dumbell schemes based on Exeter Central. It used the same principle of very tight (15inch) radius hidden return curves so the arguments about minimum radii would apply. 

I've had some experience of trying to run trains round very tight return curves on modular set ups and did find problems with flextrack curves laid too tightly with long passenger trains.

Though 15" or first radius curves are probably too extreme I still think that the "In Disguise" idea may have virtues for a semi permanent shelf layout along one wall of a room or garage used for other purposes. The front of the return curves could be made to fold out for operating sessions and stock could remain on the layout at other times but the return curves would have to be very carefully laid and reverse curves avoided. For a back bedroom with an unused chimney breast I can see definite possibilities and I just happen to have a back bedroom with an unused chimney breast that's just a bit too short for a main line terminus to fiddle yard with the trains I'd like to run.   

 

Pacific, Thanks for your reply, The idea of the plan is the return loops will be hidden behind a backseen rather than covered, I don't like the idea of track work thats covered as I'm sure it will cause problems. All stock should be pulled through the return loops as I can't see myself using anything other than a loco hauled train with the possible exception of and auto coach or single rail car. I'm thinking my maximim train length is likely to be six coach trains. Do you consider that to be a long passenger train?

 

The space I have availble is at least 15'3" x 8'6" for a permanent layout with no need for fold away sections or modular constuction and I'm happy to live with a duck under for access to avoid any lifting sections. I would like a through station with twin track main line running to watch the trains go by with a terminus to work. Any other suggestions of track plans I should consider? I do keep going back to the through terminus station idea?!

 

Thanks

 

Brookers

[34theletterbetweenB&D]

...At the moment I have set the minimum radius in these curves as 18". Will this be ok or in your experience am I pushing my luck? I would like to get this right first time rather than finding out it doesnt work...

 

What counts for long term operational enjoyment of a layout - in my opinion - is reliability, as in the trains stay on the track. Now, 'everything' in RTR from the larger makers will go around 2nd radius, just below 18", so you are good. (That radius is locked in due to the set track points, which are to this average radius on their curved route.) Well, sort of. What you need to know is whether the stock you plan to operate then works reliably on the layout you build including 18" radii. The individual pieces may go round the curves alright, but it may be a different matter for a train, especially as train length increases.

 

I'd build some test track at the minimum radius you want to use, and operate it with the longest train formations you are thinking of, and see what happens. Personally I found out that my OO set up had to go to 30" plain track minimum radius, 36" minimum radius on points, and I had to ensure consistency in wheel standards, rollability and couplers to get completely trouble free operation with full size trains running at scale speeds. But that may be somewhat down to my dodgy track base profiling and track laying skills; you may find you are able to employ a smaller radius.

[The Bigbee Line]

Roco radius 2 358mm radius http://www.conrad-electronic.co.uk/ce/en/product/214481/Roco-42422-H0-Track-bend-R2?ref=list

£17.99 for 12 pieces.  Probably as small as you want to go.  It's code 83 and quite sturdy.

 

They also do other radius curves.

 

Worth a look.  The only reservation is to change the joiners if pinning and ballasting.  Peco are fine for this.

[Pacific231G]

Pacific, Thanks for your reply, The idea of the plan is the return loops will be hidden behind a backseen rather than covered, I don't like the idea of track work thats covered as I'm sure it will cause problems. All stock should be pulled through the return loops as I can't see myself using anything other than a loco hauled train with the possible exception of and auto coach or single rail car. I'm thinking my maximim train length is likely to be six coach trains. Do you consider that to be a long passenger train?

 

The space I have availble is at least 15'3" x 8'6" for a permanent layout with no need for fold away sections or modular constuction and I'm happy to live with a duck under for access to avoid any lifting sections. I would like a through station with twin track main line running to watch the trains go by with a terminus to work. Any other suggestions of track plans I should consider? I do keep going back to the through terminus station idea?!

 

Thanks

 

Brookers

Hi Brookers

With as much space available as a large club exhibition layout I don't see why you'd even be thinking of going down to very small or even quite small radii. After all Peter Denny built the final Buckingham branch in a space of 14x14 and that had a main line junction, a main line terminus based on Marylebone, and a branch line terminus. I think he worked on a normal minimum radius of four feet with an absolute minimum of three foot and that was in EM .

 

With that space you could start looking at the trackplans of real stations rather than the compromised plans designed for space starved modellers. You'd still have to compress of course but not as much as most

You might think about a fairly important junction station with bays for local trains and parcels and a branch off it also capable of taking fairly substantial trains. I'm not thinking of a typically tiny BLT but something more substantial like a Minehead or even a Kingswear on single track or possibly even - if your tastes run that way- a small inner city terminus which would also be double track.

 

For the through station I'm sort of thinking of somewhere like Oxford. It had (and has) two through platforms with goods relief lines between them and three north facing bays.

 

I'd see the real downside of Freezer's Exeter Central Dumbell scheme being an awful lot of building to do before you get anything running. You might be better to start with the basic double track main line running around the garage with the appropriate points for the various loops and sidings that would come off it laid down.

 

Operationally that would allow you to feed the main station from storage loops so run normally it would be fiddle yard to station to fiddle yard and maybe with one side rather more extensive than the other for the trains coming from "London" that terminate at your main station. Some expresses could also be split with a section going up the branch while the rest continues on the main line. Local trains would also run between the terminus and bay platforms at the "Junction".

 

I've just been looking at H. Eric Fisher's classic Birkenhead Joint Railway in the October 1963 Railway Modeller. That was built in a substantially lengthened garage and though it was 38 feet long by 8 foot wide a lot of the length was used to give long main line runs while the main Chester Joint station - actually modelled on Newbury rather than the real Chester- had platforms eight feet long. "I spent about six months making plans but just could not avoid reducing the platforms to nine-coach length"!! The layout also included a busy city suburban station "Birkenhead Woodside" and a single track through station "Helsby"

I'm sure that with six coach trains, which would look substantial for an express, the basics of a layout like that would fit into your space. Looking at the track plan and his description 3ft 6ins to 4ft seems to be his normal mainline curve with some down to three feet and points of about three foot radius. I think you too could adopt three foot as your standard minimum and widen it wherever possible. three foot (Peco medium) is probably OK for points if you avoid reverse curves.

[imt]

I am a recipient of Pacific231G's sage advice - so I would encourage some thought on what he says.  I know of several who have started on something big, taken ages to produce the perfect layout and never really been able to operate it for years. Their advice to me was, if you must go big plan in stages that give some operating interest to provide encouragement to continue. I'd love a big layout with 6 or more coach trains but have no space.

 

I have copied the following so as not to have a huge reference:

 

You said "Ray, Thank you for your reply, I havent given much consideration to couplings yet, for the moment I will use the tension locks but I have been looking at the Kadey couplings, I'm not sure if they will be better or worse? I think I need to spend some time researching this."

 

I would suggest that you look at http://www.keen-systems.com/index.html - nothing to do with me I should add.  His carriage close coupling system was most interesting at the MRC Exhibition at Ally Pally, and will cope with just about anything.  I would endorse all the advice about as large radius as possible though.  I cannot do that because of space constraints. Kadee's are Nirvana as far as I am concerned - but again there are a wide variety including the beautifully named "Spratt & Winkle".

 

[Silver Sidelines]

Hi Brookers

 

"Ray, Thank you for your reply, I haven't given much consideration to couplings yet, for the moment I will use the tension locks but I have been looking at the Kadey couplings, I'm not sure if they will be better or worse? I think I need to spend some time researching this."

 

If you choose Bachmann Mk1 coaches for close coupling all you need to do is swap the Bachman couplings for Hornby (Roco) R8220 types.  Some people remove a little bit of plastic beneath the gangway - I don't believe in damaging the coach bodies so I pare away some of the nylon coupling.  This is a very cheap solution and results in rakes of coaches where the buffers are almost touching on the straight and yet will still negotiate Peco Medium Radius points (what ever radius that actually is!).  For a lot of older rolling stock fitted with tension lock couplings the gap between vehicles can be closed up considerably by substituting Bachmann Mini (long) couplings.

 

I have standardised on Peco Medium Radius points and 36 inch nominal radius curves for running lines.  I did buy a Peco Single Slip which gives better electrical running qualities than a straight diamond but I cannot use the actual slip because the radius is too tight for my close coupled rolling stock.

 

Regards

 

Ray

[Brookers]

Thank you all for your informative replys. Back to the the drawing board I think. I feel like I have almost too much space as I have so many options with the room available to me! As I'm most likely to be opperating on my own I'm mindfull that I dont want to go too complex.

 

I think I might look again at Wells Tucker street and see if I have room to do it justice.

 

Thanks again.

 

Brookers

[edcayton]

No connection, but I have been very impressed by the Keen close coupling display stand at exhibitions. IIrc they get round even first radius.

 

Ed

[Pacific231G]

If you choose Bachmann Mk1 coaches for close coupling all you need to do is swap the Bachman couplings for Hornby (Roco) R8220 types.  Some people remove a little bit of plastic beneath the gangway - I don't believe in damaging the coach bodies so I pare away some of the nylon coupling.  This is a very cheap solution and results in rakes of coaches where the buffers are almost touching on the straight and yet will still negotiate Peco Medium Radius points (what ever radius that actually is!).

 

I have standardised on Peco Medium Radius points and 36 inch nominal radius curves for running lines. 

 

Hi Ray

The Peco medium radius points are nominally three foot radius. Comparing one with an SMP three foot radius turnout the geometry does seem almost identical. I think Peco's points are based on adapting the fairly standard geometry of the the medium radius points to enable the small, nominal two foot radius, and large five foot radius points to have the same 12 degree divergence angle and the same track separation at the end of the unit. I've been looking at these and the V rails are identical for both small and medium radius  points. The large radius points do have a smaller crossing angle but the track continues to curve beyond the crossing. frog to give the same 12 degree divergence and track separation at the end of the point unit.

[Silver Sidelines]

Hello David

 

Thanks for that information.  I was aware that the medium radius points were advertised as being '3ft radius' however I am also aware that they do not fit smoothly within a 3ft radius curve because of the straight sections at iether end and for that reason the 3ft / 5ft curved points provide for smoother running.

 

Regards

 

Ray

Hi Ray

The Peco medium radius points are nominally three foot radius. ...