What is a good weight for a mainline diesel locomotive?

Model Railroader General Discussion (Model Railroader)
1

Hello everybody,

I was busy running trains in my layout room when I picked up some very light SD40-2’s from Kato and Intermountain when compared to the P2K SD45’s. So the following is a chart of how much the locomotives weigh:

P2k SD45 703 gram

Kato SD90/43 609 gram

Kato C44-9W 575 gram

Kato SD70Mac

2

Why are you weighing down your locos? How long of trains are you pulling?

I think it isnt a limitation, but rather an excuse to run more locos in a consist with lighter locos.

David B

3

There are several variables here, which I (as a non-modeler of US prototype) can’t answer personally.

  1. How much does the 1:1 scale prototype weigh? We don’t usually try to scale rolling stock weights, but the numbers would provide a proportion for comparison.
  2. Are any of the models fitted with traction tires, or have they been treated with Bullfrog Snot?
  3. Are you trying to handle longer trains, or is this just an exercise in standardization?

Back in the dark ages the standard was, “Add weight until the motor couldn’t spin the wheels at full thottle, then remove a little.” One result was that MR editor John Page found that his 0-4-0T Dockside could handle a train that maxed his passing sidings! So he selectively `de-weighted’ his locos so their model pulling power was proportioned to the tractive effort of the prototype, within the limitations of his layout. IIRC, Superdockside was cut back to where it could switch four cars, leaving the twelve car mainline freight for the heavy consolidation and the new F-3 A unit.

Chuck (Modeling Central Japan in September, 1964)

4

Let’s do a little math:

Let’s say a modern six-axle locomotive weighs approximately 200 tons. That’s 400,000 pounds. Or 181,436,948 grams. Now, divide that by 87 (three) times, since our models are three dimensional. You’ll end up with (approx) 275.5 grams for the model (or roughly 9.7 ounces for those of us using U.S. measurements).

By the same conversion, a car weighing 200,000 pounds (loaded), would scale out to about 138 grams, or roughly 4.8 ounces.

Hope this helps.

Brad

5

We don’t need math. And it doesn’t work anyway because you can’t scale mass nor friction.

Weight your locomotives has much as you can but only up to the point where, under full load, the wheels can still spin. This saves you from burning out motors.

Traction tire believers please note the foregoing comment. If you use traction tires [spit] the wheels will not spin under full load and you can burn out motors. Not that I’m biased against traction tires of course. [;)]

6

Hello,

thank you for all the replies. NMRA has weight guidelines for freight cars so I thought that maybe someone has come across something similar for locomotives.

On my current layout with the helix it is easy to get the engines to spin, so the extra weight would be a good thing being that it means more traction. My next layout, well I am not sure what that will be, time will tell. AS it is I enjoy running multiple lash up and also pusher service. That is where the really light engines come in handy. As for traction tires, I have one locomotive with them. It is a ROCO, and it was a surprise when I opened it up all the gears are about twice the size when compared to the gears from Kato, Atlas, P2K or Intermountain. Traction tires work very well but also must add a lot of extra stress to you engine drive line. So will definitely not use traction tires on any of my engines.

Again, thank you for the replies.

Frank