Scale Weight

[Eryalen]

Does anyone add weight to their engins / rolling stock? Is this done to scale or is that out of the question?
Best regards - Erik

[RAM]

You only want to add enought weight to your engines / rolling stock to have good operation.  More weight than needed will only shorten the life of your rolling stock.

[Conrail Quality]

If weight our equipment according to the prototype, they would be much too light to operate reliably. We overweight our equipment a bit so that they perform decently.

How much easier life would be for us modelers if physics could be scaled down...

Timothy

[Santa Fe buff]

Enough so it doesn't fly off at high speeds and  doesn't reduce your power too much.

[Yampa Bob]

Erik
Your question contains 2 elements, so 2 different answers.

Rolling Stock: Based on length. The NMRA recommended practice for rolling stock is one ounce, plus 1/2 ounce for each inch of length.  A car 6 inches long should weigh about 4 ounces.  If a car is properly tuned, easy rolling and tracks well, there is no benefit to adding additional weight, except to compensate for poor trackwork. 

Locomotives: Based on weight. A 200 ton locomotive in HO scale would only weigh 9.7 ounces, a 100 ton only 4.85 ounces.  In both cases this would be too light for adequate traction.  I like my locos to weigh from 10 to 16 ounces depending on their prototype.  Many modelers weight their locos a bit more for increased traction on steep grades, or to pull more cars.   

As mentioned, adding a lot of extra weight to pull an excessive number of cars might put a strain on the motor and drive system. The best way to monitor loco performance is by testing the current draw with a DC ammeter on a DC powered track, under various conditions.  My thread on current testing might be of interest to you.

http://www.bachmanntrains.com/home-usa/board/index.php/topic,6229.0.html

You might also want to know how to determine HO scale.  For length, just divide by 87.  So a 50 foot car would be about 7 inches, or multiply the 7 inches by 87 gives you 50 foot full scale.

Weight is determined by volume or cubic function.  For a 200 ton locomotive:
200 X 2000 X 16 = 6,400,000 ounces.  Dividing by 87 three times (cubed) yields 9.7 ounces.  Here is an excellent page about model train scale.

http://www.spec2000.net/rr_site_pages/rr_scale_dfn.htm

[Jim Banner]

Let's take Bob's calculation one step further.  According to the NMRA RP, a 6" car should weigh in at 4 ounces.  That would correspond to a real world car weighing

4 x 87 x 87 x 87 /32,000 = 82 tons.

That is nicely between 50 tons (typical empty weight) and 100 tons (typical loaded weight) for a 40 foot car.  Close enough to scale weight for me.

There is more on this at the link below:
http://www.geocities.com/budb3/arts/tech/wght.html

[Yampa Bob]

I agree with "Bud" on his weight page, that the NMRA RP for car weight is a bit excessive, (in some cases) and here is an example.

I recently received some Bachmann J&S open excursion cars. Length is about 6.5 inches, and they weigh only 2 ounces.  Before considering adding weight, I tried them on the layout and they tracked beautifully. The only adjustments were  loosening the truck screws a bit to reduce flange rubbing and "picking" on my 18" curves, and reaming the journals. Of course, I run these cars at very slow speeds, typical of excursions, and my trackwork is as near perfect as possible. 

Depending on who does the testing and formula used, there are conflicting figures regarding the required drawbar pull of an "easy rolling" car.  MR magazine uses a factor of .071 ounce per car, possibly to enhance the performance of reviewed locomotives.  This implies that a loco with drawbar pull of only 3.55 ounces should pull 50 cars.  Other sources state .2 ounce, or only 18 cars for the same loco. Frankly, all that leaves me cold, I use my own ramp method for testing car weight and tuning. I mentioned this in another post, but will repeat it here.

I have a 3' flex track mounted on a 1 X 4.  I prop up one end 3/4 inch, representing a 2% grade.  My cars must roll quickly down the grade by themselves. For the "acid test", I use a 1/2 inch prop, a 1.4% grade. The car must roll slowly to the bottom, with just a gentle nudge to get it rolling. Some of my cars will coast down a .5% grade.

So...in regard to car weight and other factors, should I expect my locos to only pull 18 cars, or 50? Well, since I rarely pull more than 15 cars on my small layout, it's not a big concern for me.

If an out of the box freight car tracks well after tuning, (at 60 mph) I don't add any weight. 

[rogertra]

Just keep in kind folks, you cannot scale weight (Mass) nor friction both of which effect the rolling ability of rolling stock.

However, I add as much weight as I can to steam locos in particular in order to increase their pulling power.  The acid test is that the wheels must still spin when the weight of the train stalls the locomotive or I can hold onto to tender coupler and the loco will still spin its wheels.

Traction tire fans please note, this prevents motor burnout.   Traction tires will stall and the motor may burn out.

[Eryalen]

Let's take Bob's calculation one step further.  According to the NMRA RP, a 6" car should weigh in at 4 ounces.  That would correspond to a real world car weighing

4 x 87 x 87 x 87 /32,000 = 82 tons.

That is nicely between 50 tons (typical empty weight) and 100 tons (typical loaded weight) for a 40 foot car.  Close enough to scale weight for me.

There is more on this at the link below:
http://www.geocities.com/budb3/arts/tech/wght.html

Thanx to all for the info.