The Home Machinist!

Hello all,

Sizing springs for trucks with the proper flexibility looks like a math problem... and it appears that a freight car without a load is necessarily or consequently stiffer and more prone to derailments? Are springs in a truck with a given 'rate per inch' or ' maximum load' divided by the number of springs and the total expected load? Deflection amount expected or desired divided by the 'rate per inch' specification? Wouldn't that put the truck frame within the physically flexible area or the amount of movement or twist that the truck may require to negotiate rotten track.....?

Thanks ... I'm scratching....

BClemens

Dunno about your main question, but I read somewhere about putting a round-headed screw in the bolster where it would seat against the sideframe in order to create a pivot point when the car is running light and the springs are pushing the bolster up against the sideframe. Thus it won't matter if the springs are stiff; the truck will still flex. I've done that and it works great.

I bought some Roll Models 2-1/2" scale for 36" narrow gauge archbar trucks and had the same issue. I found softer springs from McMaster-Carr that fit inside the supplied coil springs. I ground off a coil or so of the heavier springs, so the empty car sits on the soft springs, yet settles onto the heavier coils when loaded. Fortunately, the inner springs were wound opposite-hand which is what you want to avoid interference!

Kimball McGinley wrote:dual.jpgI bought some Roll Models 2-1/2" scale for 36" narrow gauge archbar trucks and had the same issue. I found softer springs from McMaster-Carr that fit inside the supplied coil springs. I ground off a coil or so of the heavier springs, so the empty car sits on the soft springs, yet settles onto the heavier coils when loaded. Fortunately, the inner springs were wound opposite-hand which is what you want to avoid interference!

Kimball,
Were they too soft (or weak) when loaded? And they would they bottom out with a load?

I just placed an order for a number of different sets from McMaster-Carr of varying 'rates' and 'load-per-inch' for these trucks and I'm working with 2.5" scale 3' narrow gauge too. The thing is these are larger in diameter and height but the capacity of them should resemble 1.5" scale since the load will be much the same.

Good advice on the inner spring and we'll do that too but I'd like to get a handle on this spring set-up. A passenger flat car may carry two people, or only one person. The tender will vary a couple hundred pounds as a running day goes.... Maybe I worry too much but it would be nice to do a proper set-up to start with. Roll Models trucks would have been set up with correct springs - would seem anyhow...

BClemens

Greg Lewis, Thanks for that - good plan...
BClemens

BC - I felt they were too stiff for the empty weight of my all wood flatcars. The supplied springs are pre-loaded a little to keep them in place, so you need some amount to even begin to move the bolster.