Reply To: EM Gauge 90 degree Radius 2 curve

Members Forum Track Scratch building track EM Gauge 90 degree Radius 2 curve Reply To: EM Gauge 90 degree Radius 2 curve

#247293
Nick Ridgway
Participant

    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.