Picked up some metal wheelsets with scale width treads and narrow flanges to start converting my rolling stock but noticed they tend to drop into my turnout frogs which often results in a derailment. This got me to thinking, how do small-flanged wheelsets work at all in N scale, being that many N scale turnout frogs (at least mine) have big gaps between the rail and seem to rely on the wheel flange edges themselves riding up on the (built up) bottom surface of the frog area to traverse the frog without dropping into it? Small flanges would prevent this, it seems. I'm really scratching my head on this one as I have some MT wheelsets with narrow flanges that seem to do OK. Russ
I have a Peco double slip switch that has this problem. I remember reading a post about gluing a little styrene to the inside edge of the frog, haven't tried it, but it seems like an easy fix.
I've heard about that thrick too but don't understand how it would help in the situation I describe above, unless I misunderstand the actual issue completely. Seems to me the shim technique wouldn't resolve the wheel-dropping-into-the-frog problem, unless you shim the bottom of the frog to build it up some more. Regardless of how tight the frog is laterally on the section the wheel is riding on, it seems there would still be a relatively long span where there's no rail for the wheel to ride on top of. Unless you are supposed to shim the diverging section, effectively making the span where there's no rail shorter(?). Like I said, this one has me scratching my head! BTW, These are large-radius Peco insulfrog turnouts. I think the larger the radius, the longer the span is without any rail. Yet, something must be working for folks! Russ
Russ, The dimensions of your frogs and the tyre width and flange width of your wheels should be designed to match to avoid dropping in. The problem you have is that the normal N scale frog has quite large gaps between the frog and the wing rails and this matches the pizza cutter style wheels with large flanges and wide tyres. The width of the wheel tyre should be such that as a wheel rides off the nose of the frog, the outer part of the wheel tyre should be running on to the wing rail. With your finer scale wheels, this won't be happening and your wheel will drop into the gap. You could add packing in the gap between wing rails and frog to allow the smaller flanges to run on to prevent drop in, but that means that all your flanges should be the same depth so that you don't get rough running with deeper flanged wheels. The other thing you can do is try adding packing to the inside of the wing rails and level with the wing rail tops so that the effective gap at the frog nose is reduced to avoid the finer wheels dropping in. If you do this you might run in to problems with coarser standard wheels not running through the frogs since their back to back measurement might not be enough, or their flange width might be too much. If you want to move to finer wheel standards you should also look at changing your pointwork to match so that you get no problems. Frogs which are required to cope with old coarse standards and more modern finer standards are bound to be a compromise which can give poor results. I work with FS160 standards, which use the very fine standards of the UK 2mm Scale Association. But I can get them to run through Peco Code 55 pointwork by adding packing to the insides of the wing rails and the check rails. But that makes the pointwork unuseable for the coarser N scale standards. Jim.
Thanks for the help thus far! FVM 3301 33" wheels for MT trucks and Peco #8 (large radius) turnouts. I initially left this out as I didn't want this thread to be interpreted as my calling into question the quality of either product. This is not the case at all. Russ
