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Derailment at Point on Curve
Richo who models HO would like suggestions:
“My loco has a habit of coming of the track at a point on the beginning of a curve. It doesn’t derail anywhere else. I ran my eye over the track and it looks okay. What else should I try please?”
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7 Responses to Derailment at Point on Curve
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Try elevating slightly the outside part of the turn where the train goes off the track. Shim the track of board
If you have a track gauge then run this over the problem area to make sure it’s still in gauge and also check the wheels on the loco as well as they may be a bit tight.
Long steam locos will have problems with tighter curves. Manufacturers specify a recommended minimum curve radius for their locos. If it is a modern model, this info should be on their website or in the instruction manual.
Please tell us the make and model of locomotive and the curve radius you are using.
If you check that the two rails are lined up correctly in the fishplate. If it’s not a smooth transition the flange of the wheel can hit the protuding head of the rail at the joint and derail.
Curves can be deceiving. Lay the curve again and try this trick. Place a template of your minimal track at the centre of the length of the curve, screw or nail it down just inside where you think it ought to go. Then lay flex track in the normal way. You will notice that the new track doesn’t follow your template exactly, but is wider or broader by about 0.25″ towards its outer ends where it joins the the straight (tangent) track. What you have created is an easement and what it does is “ease” your train into the curve rather than belting from straight to curve track. This jerk will sometimes (often?) derail a train.
Full size railways have complicated formulae for working out easements, but we modellers can get away with “fudging” it. Derailing locos have many causes, wheels not in gauge, wheel back to back out of whack, long rigid wheelbases trying to go round corners instead of curves, but more often than not, on model railroads it’s the track geometry. If you bend a piece of Lathe or stiff wire into what looks like a quarter of a circle, and then measure it carefully you will discover that it too has created an “easing” of the cure from the end towards the middle – this is the effect we are trying to create.
if HO they make curved track gauges that fit between the rails. obtain the one for your curve radius and place it at your rail joint. The slightest kink can become the biggest pain for some engines and cars.
If you’ve checked the gauge of the track & wheels of the loco, and shimmed up the outside of the beginning of the curve, you could try using a transition curve. This is really easy with flextrack. From the beginning of the curve, start with a very gradual curve coming from the straight, and gradually increase the amount of curve until you get to the desired radius. Do this at both ends of the curve. Your locomotive & cars will transition into the curve. That’s the complicated formula prototype RR’s use but if you’re using flex track, this is an easy way to smooth out the entrance onto a curve. It’s harder if you’re hand laying track & not feasible if you’re using rigid curved track (although you could use a small piece of flextrack just for the transition curve). If your space is limited this could make the radius at the apex of the curve tighter but I find it improves tracking all over the layout. It can ease a train into the tighter curve.