EM Gauge 90 degree Radius 2 curve

[Rhobat Bryn JonesParticipant]

How much space is required in EM gauge for a Radius 2 curve going from a straight track to another straight track at 90 degrees to the original?

[Trade OfficerKeymaster]

The minimum recommended radius is 3ft. However it depends on what locos and stock you intend running. An 0-4-0 for instance could tolerate a smaller radius than a 6 or 8 coupled loco or a 6 wheeled rigid van. A 10 coupled loco may not get around a 3ft radius smoothly.

I have seen dockyard layouts with 2ft radii but they only have very short wheelbase stock. So it is somewhat dependent on the type of layout – very much like the prototype really

Gauge widening will help getting the larger wheelbase stock round the curve if space is a problem as will a little bit extra side play

 

 

john

[Rhobat Bryn JonesParticipant]

Many thanks.

 

Rhobat Bryn

[Bob AllisonParticipant]

Not sure of the meaning of “radius 2 curve” in the context of EM Gauge track. We talk radius in terms of feet, or millimeters.  Did you mean something that will take large main line stock, like pacific locos and BR Mk 1 coaches?

John has given you much guidance, but I would add…

• Exactoscale’s exhibition stand used to show a four wheeled tank loco running round a curve of about 7 inch radius, IIRC.  But buffing and coupling arrangements are crucial when considering extreme cases like this – there’s a reason why industrial locos had unusually large buffer heads.
• The limiting factor for main line stock is often side swing on bogies and pony trucks, rather than sideplay in the fixed wheelbase.  My Black 5 4-6-0 would go round a 3ft curve – usually – but the bogie wheels rubbed against the rear of the cylinders and would sometimes derail. Footsteps can also be a problem.

Bob

• This reply was modified 1 year ago by Bob Allison.

[Nick RidgwayParticipant]

It depends upon what is going round it.

A recent calculation in 12in scale suggests that the fixed wheelbase on a certain 6-wheel vintage coach will pass satisfactorily around a curve of 3.5 chains. My principal concern is that of buffer-locking, and the selection of a vehicle to propel it will be interesting. Convert this to 72mm wheelbase and 924mm radius in EM gauge – 36&3/8in rad.

I have an EM gauge class N7 0-6-2T, built a la Flexichas, that will just pass round 13in radius, which is 1.25 chains in 12in scale, whereas the prototype baulks at 4.2 chains and I had to design alterations to get that curve opened out to accommodate, which included gauge widening and providing a check rail. The model one has plenty of sideplay on all axles, with the pickups springing the axles back to something approximating straight. I’ve never tried propelling anything with it round such a curve as I know that buffer-locking would ensue.

I would have no qualms about 0-4-0T and a 9ft (36mm) wheelbase 16T mineral wagon on 2 chains (528mm) radius either in 12in or 4mm scales. I wouldn’t expect to get a Bulleid Pacific round such a curve in either scale.

The junction into the centre road at Waterloo on the Waterloo and City line appears to be something approaching an A&4 junction, which is 130ft/2chains radius off a straight (520mm in EM). The centre-couplers on tube coaching stock mean that buffer-locking is not a problem. How much gauge-widening there is through this particular junction is not known here.

One heritage railway’s track standard calls for the minimum radius for something to pass to be at least 20 times the fixed wheelbase of the vehicle. The reason for such a criterion is related to the angle of attack between the flanges of the leading wheelsets and the outside rail of the curve, and nothing to do with buffer-locking.

• This reply was modified 8 months ago by Nick Ridgway.
• This reply was modified 8 months ago by Nick Ridgway.
• This reply was modified 8 months ago by Nick Ridgway.
• This reply was modified 8 months ago by Nick Ridgway.
• This reply was modified 8 months ago by Nick Ridgway.

[Stuart FirthParticipant]

If you mean the equivalent to a RTR 2nd radius, i.e. about 18 inches, I would be very wary unless you are modelling something industrial. This curve on my layout is about that radius, and 4-coupled loco’s will traverse it, but no chance of coupling up on it unless you have sprung 3 links, which I mostly don’t. More importantly, in anything other than this kind of environment it will look wrong, and better realism, with track especially, is what sets EM apart from 00, in my view.

 

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