Micro gradients

[47137]

I am sketching up a small zig-zag style model, much in the style of a classic design 'Gumstumping', and wanting to put a point on a gradient. The textbooks usually say this is a big no-no but it seems to be possible within some constraints. The photo shows my test rig.

 

 

I am looking at one- or two-wagon trains being propelled of hauled up either route through the point. In simple terms, at 1:10 the train slides down the slope under gravity. At 1:15 the loco would manage itself, but not its train. But at 1:17, it seems to be just fine. The plan for the layout is dictating 1:22 in the space available. That's with a 1:18 on another gradient without a point. It seems, these will work. I know, the geometry of curves on gradients implies a twist, and so logically the point needs to be shimmed up at the frog. But the point seems to work in its flat state, and so the twisting of the formation might begin a few inches (like: a wagon's length) away from the frog. The main point is clearly to keep a constant gradient through the point.

 

The trouble with ideas like this is they can seem just great on a workbench and then show up an ugly side on a layout. Any warnings or support from people who have tried to do this would be very welcome.

 

- Richard.

[Lisa]

There is no problem in having a point on a gradient, but as in your experiment the point MUST be on a plain.

 

Lisa

[olivegreen]

I've been there, done it, got it very wrong and have had to throw away Peco Streamline points that I fouled up by trying to make them work all bendy. Be assured, they don't like it, nor do the point motors - and everything derails eventually.

 

Whatever may be real railway practice, for us I support Lisa in saying that the points themselves MUST be secured to a flat base, even if the lines to them are not. 

That flat base for the point need not itself be exactly horizontal, but I would make every effort to make it so.

 

I have a zig-zag transfer siding arrangement on my layout that works well in this way - points are flat and horizontal but the lines joining them are quite steep.

 

Hope this helps

[Lisa]

The other important considerations are allowing a distance from the point crossing of the length of the driving wheels or bogie before changing gradient or cant. Finally making the transition using a transition curve.

 

 

The easiest way of achieving this is to use a tongue. Like yours it is linked to the board,from which you are transitioning from at one end and is free to be bent up or down etc. as required at the other end. You will need to experiment as to who quick the transition can be and not have derailment problems. From the end of the tongue you use another piece of board to carry the track onwards.

 

A material such a plywood will naturally form itself when bent into a transition curve.

 

Lisa

 

PS a tongue can start in the middle of a board too.

[47137]

Thanks both for all of this.

 

My track bed is going to be two pieces of 6mm birch ply, both shaped with a jig saw to suit the locations of the track. If the ply won't flex enough at the transitions, I'll cut parallel slots into it. Definitely, transitions must begin more than the wheelbase of the longest vehicle away from the point frogs.

 

I suspect the key to success is the use of 00 gauge with its tolerant wheel/rail relationship. It would be a nightmare in one of the finer scales.

 

Here is the current track plan set on a grid of two-inch squares ... if I can pull this off I think it will be a very satisfying little layout. Baseboard length is set by the domestic location and also by having bought the ply frame for another project. Another six inches on the length would ease things a lot, but then it wouldn't be quite so 'at the limit'.

 

- Richard.