12-30-2010, 08:51 PM
I don't have any experience with Peco Code 83 track. I do understand, that unlike their other lines, the Code 83 track is deliberately made to NMRA standards.
In attempting to set semi-scale standards or RPs, the NMRA committees found that to avoid frog drop, the wheel width should be at least twice the flangeway width. NMRA specs for HO are flangeways 0.040" to 0.050". Semi-scale wheels are code 88 or 0.088" wide; regular HO wheels are code 110. FWIW, Proto87 uses a wheel width of 0.064". Theoretically, semi-scale wheels should work just fine if the flangeways are set to the narrow end of the range. And they do.
The hitch is that by studying the gauge diagrams, one realizes that to achieve 0.040" flangeways, the track gauge must be at the minimum value of 0.649". The track gauge at the frog is 2 times the flangeway width plus the check gauge (the distance between the outer corner of the guard rails). The check gauge has to be accurate, and consistent with the back-to-back wheel gauge for the guard rails to do their job. No commercial turnout manufacturer is going to use minimum flangeways and minimum track gauge for several reasons:
I have not measured Peco code 83 flangeways. I suggest you do. If they are close to 0.050" as I suspect (still meets NMRA standards), then you will likely experience wheel drop with sprung trucks and code 88 wheels. The larger the frog #, the more likely the drop will occur. Some rigid frame trucks will escape wheel drop because the truck frame will hold the wheel in the air when it would otherwise drop. Great for not having wheel drop at frogs, not so great for tracking over any other vertical irregularities. But then I prefer sprung trucks.
The only way I know of to completely avoid wheel drop with code 88 wheels is to hand lay your own turnouts with the smaller flangeway and track gauge. I will eventually hand lay all my turnouts to semi-scale specs (which work just fine with code 110 wheels, since the flange width is the same). In the meantime, I used a few #4 Atlas and Shinohara turnouts to get my layout started - and yes, my code 88 wheels in the sprung trucks do rattle around and sometimes drop at the frog.
my thoughts, your choices
Fred W
In attempting to set semi-scale standards or RPs, the NMRA committees found that to avoid frog drop, the wheel width should be at least twice the flangeway width. NMRA specs for HO are flangeways 0.040" to 0.050". Semi-scale wheels are code 88 or 0.088" wide; regular HO wheels are code 110. FWIW, Proto87 uses a wheel width of 0.064". Theoretically, semi-scale wheels should work just fine if the flangeways are set to the narrow end of the range. And they do.
The hitch is that by studying the gauge diagrams, one realizes that to achieve 0.040" flangeways, the track gauge must be at the minimum value of 0.649". The track gauge at the frog is 2 times the flangeway width plus the check gauge (the distance between the outer corner of the guard rails). The check gauge has to be accurate, and consistent with the back-to-back wheel gauge for the guard rails to do their job. No commercial turnout manufacturer is going to use minimum flangeways and minimum track gauge for several reasons:
- - minimum track gauge pushes up minimum radius requirements. Gauge widening is used on our tight model curves to allow the rigid wheel base to fit around a tighter curve than would otherwise be possible. The result is locomotives and rolling stock that will barely go through a #4 or #5 will need a #5 or #6 turnout.
- wider flangeways will allow a wheel set that is gauged slightly wide to transit the frog without riding up on or picking the frog point. As a result, a wider variety of unchecked rolling stock will go through the turnout without derailing
- manufacturing tolerances are much tighter. Gauge and flangeway can only vary by a couple of thousandths, instead of 10 thousandths. This pushes up manufacturing costs.
I have not measured Peco code 83 flangeways. I suggest you do. If they are close to 0.050" as I suspect (still meets NMRA standards), then you will likely experience wheel drop with sprung trucks and code 88 wheels. The larger the frog #, the more likely the drop will occur. Some rigid frame trucks will escape wheel drop because the truck frame will hold the wheel in the air when it would otherwise drop. Great for not having wheel drop at frogs, not so great for tracking over any other vertical irregularities. But then I prefer sprung trucks.
The only way I know of to completely avoid wheel drop with code 88 wheels is to hand lay your own turnouts with the smaller flangeway and track gauge. I will eventually hand lay all my turnouts to semi-scale specs (which work just fine with code 110 wheels, since the flange width is the same). In the meantime, I used a few #4 Atlas and Shinohara turnouts to get my layout started - and yes, my code 88 wheels in the sprung trucks do rattle around and sometimes drop at the frog.
my thoughts, your choices
Fred W