Radius - Circumference

[Crisis Rail]

Tight of baseboard Garage space so does anyone know what is the minimum dimensions in imperial for a roundy. 

To run 00 stock? Mainly Class 26 60 and 68. 

 

40 and 45 preferably but chassis issues may be a problem. 

[The Johnster]

Setrack standard curves are as follows:-

 

1st radius - 14.6 inches

2nd    "      - 17.24  "

3rd.    "      - 19.9    "

4th.    "      -  22.5   "

 

That equates to the diameter plus 2" for clearance in terms of layout baseboard width, so 1st radius would need at least 2'and 7", 2nd would need just over 3', 3rd needs 3'6", and 4th needs 3'11".   Your next move is to find out from the manufacturers what the minimum radii recommended for those classes of loco are; I'm guessing 2nd for the Bo-Bos and 3rd for 40 and 45.  Claseses 26, 40, and 45 seem incompatible period wise with 60 and 68.

[DCB]

My old Dining room table layout board is 38" wide, 37" inside the 1/2" wide sides which stand 1/2" proud of the surface and it had 2nd radius curves.  The Hattons 14XX struggles with 2nd radius, the Bachmann 64XX refused which is odd as I thought they were designed for 2nd radius,   You should be pretty safe with 3rd radius, Only my all wheels flanged Romford wheeled Hornby locos jib at them (Jibbed, they are now defunct)

The 1 coco 1 locos usualy use a 2-4-2 + 2-4-2 or 1B1 1B1 chassis and are easier to get round curves than a steam 0-60 though the end throw is horrific.

3rd Radius should get round in 42"  4th in 46" If you use flexi track below about 2ft radius you have to be extremely careful to avoid kinks at rail joints,

 

Bekra models in Newton Abbott get a 00 scale class 47 and Mk2 coaches round 12" radius curves on their display layout.  They did a few mods but it can be done.  I think they used a single 40" piece of flexi for the 12" radius  curve, I didn't see any joins and a 180 degree 12" radius turn  is just within the circumference allowed by 40" of track .

However their workmanship is superb.  If we still have the Lock down when I've done all the jobs the wife has found me my next layout will be a 24" X 5ft 00 roundy roundy!  Very ight railway/ Industrial.

For high speed you need very large radius curves, my 00 garden layout has a 6ft radius curve and runaways often derail there, mind you its a 1 in 14 ruling grade and they are doing about 10 mph as they approach, that's a scale Mach 1!

Edited March 26, 2020 by DavidCBroad

[PatB]

I have an old Mainline Peak which grinds and growls its way around  a 1st radius oval. I wouldn't call it happy, but it doesn't fall off or stick. I wouldn't like to say what it might do if there was any pointwork to confuse its wobbly bogies though.

[Il Grifone]

Since the radii are measured to the centre of the track, I would allow at least 2" clearance on the radius, rounded up to the nearest inch (i.e. 34" for 1st radius . The overhang, especially on locomotives, is quite considerable on sharp radii.

[knitpick]

Note that Settrack points are 2nd radius.  So all commercial stock currently can manage that radius with some short wheelbase and most older locos capable of managing 1st radius.  As noted, a single track circle of 2nd radius is a tad over 3ft diameter.  If you are planning a double track then you will also need to go for 3rd radius giving 3ft 6inch diameter.  If you can manage 4ft baseboard width then use 3rd and 4th radii.

 

[Note, I tend to use 2ft Tracksetter and Peco flexitrack as a minimum with Peco 2ft radius points.  But have been known to use Settrack when absolutely essential.]

[The Johnster]

I don’t recommend flexible track for radii less than 2’.  It is very difficult to lay accurately to sharper radii, due to it’s tendency to form transition curves meaning that the middle part of the arc may be very tight, and you risk pulling the rails out of gauge, or even tearing them out of the chairs. 
 

Bear in mind that if your roundy includes curves close to a back wall, the stock may well foul on it because of end throw, so close attention must be paid to clearances here. 

[Bill Radford]

I'm sure 4th radius is 24 inches.

 

I use 4th radius in my fiddle yard, 4 turns of 90 degrees. I have had problems on one turn with some of my Bachmann 66s (not all). I have cured this problem by using flexible track and a tracksetta of the same radius - 24inches.

[nswgr1855]

Its best to stick with the AMRA minimum radius standard for better appearance and improved tracking. https://amra.asn.au/standards/

 

[Bochi]

15 minutes ago, Bill Radford said:

I'm sure 4th radius is 24 inches.

 

I use 4th radius in my fiddle yard, 4 turns of 90 degrees. I have had problems on one turn with some of my Bachmann 66s (not all). I have cured this problem by using flexible track and a tracksetta of the same radius - 24inches.

 

4th radius is defined at 57.2 cms which rounds to 22.5" which may be why you fared better with Tracksetta. I have just this morning finished converting an old CJ Freezer plan to Anyrail to see if I can make it fit with a 2ft ruling radius but needed to go down to 4th Radius setrack inner curves at the station approach (it's a looped eight with a central peninsula terminus, a lovely arrangement but challenging in the space). 

Hopefully, given that trains entering and leaving the station will not be at full speed, it will be OK.

[Guest Half-full]

My friends budding layout has curves down to 19" and all his stock runs fine on it, all steam from 0-6-0's to 9f's, but he has supe-relevated the trackwork, with appropriate run-ups, I guess that must help?

[Crisis Rail]

Thanks Chaps

 

The curves are not aesthetic as they will hidden with scenic breaks

So therefore what will dimension "x" be in the below graphic?

David "B" recommends  38" which hopefully will be all good.

 

Johnster - as regards 26 to go with 68 it's a dual era concept but that would be.....refreshing.

 

On 25/03/2020 at 04:21, PatB said:

I have an old Mainline Peak which grinds and growls its way around  a 1st radius oval. I wouldn't call it happy, but it doesn't fall off or stick. I wouldn't like to say what it might do if there was any pointwork to confuse its wobbly bogies though.

 

Like

 

 

Ian

[The Johnster]

You need to find out what the minimum manufacturer’s recommended radius is for your locos.  Most will be fine on 2nd radius, but I wouldn’t like to state that 40s or 45s will manage.  3rd rad is much more likely, but 2” over your 38” spec even without allowing for a back wall

if there is one. 
 

Suggest you assemble a few 2nd rad curves on a table top or hard floor temporarily, wire up, and try the big locos’ running on them before you commit to building baseboard. 

 

[legin]

If you can go bigger than 2nd radius, I would.  I have an inner circuit of Peco 2nd radius and an outer of about 3rd radius flexitrack. I have a whole variety of locos from new to 30 years old.

Although my Hornby 2P is said to be ok for 2nd radius and above, it has repeatedly shed its traction tyres on second radius, particularly the inner tyre. My Airfix Royal Scot, 30 years old, is jumping slightly when traversing the 2nd radius. My Mainline class 4  also seems to be grinding slightly on the inner curves. All of these locos are fine on the outer radius. So whereas the manufacturers might say that your locos are fine on second radius, maybe they should say that they are sort of fine.

I know what has been said above about flexitrack and second radius and broadly I agree. However, if you use this and have space for lets say a 2.5 radius, it might make all the difference. A Tracksetta would be fairly essential. 

[zarniwhoop]

1 hour ago, legin said:

A Tracksetta would be fairly essential. 

Tracksettas are great, but only if your desired radius is a multiple of 3 inches.

[DCB]

On 26/03/2020 at 17:22, legin said:

I know what has been said above about flexitrack and second radius and broadly I agree. However, if you use this and have space for lets say a 2.5 radius, it might make all the difference. A Tracksetta would be fairly essential. 

The alternative is to treat set track like flexi and cut the webs between sleepers and ease the radius out by an inch or so.   Being notoriously tight fisted I have eased 2nd radius out to 3rd radius in the past to avoid buying more track and it works fine. It stays put, keeps curved and does not try to straighten out like Flexi does.  Obviously you have to cut it like flexi as 4 and a bit 2nd rad eased out to 3rd is needed to curve 180  degrees..  Likewise I use set track straights where track needs to be straight and mix and match streamline points with set track 

[knitpick]

Just a thought - Peco do a track laying gauge.  It is double sided - one side for Settrack spacing and one for Peco flexitrack and associated points.  So if using 1st or 2nd radius Settrack curves or equivalent (or if using Settrack points) use the Settrack spacing.  This should ensure sufficient clearances on curves.  At larger radii, the Peco flexitrack spacing should be sufficient.  You can then use a Tracksetter for one curve radius and lay the other curve with the Peco track laying gauge.  That way you avoid the implied 3 inch spacing from only using Tracksetters.