I woke up this morning suddenly confused by something that was obvious to me six months ago. Under the Recommended Practice in the title, NMRA suggests one ounce plus and additional half ounce for each inch of the particular car. I've always assumed that the first ounce is the initial, base weight to be installed, not a representation of the weight of the car itself before any weights are added. So, a 5.5" Intermountain reefer kit should get 1 + 2.5 ounces suitably fixed to the floor of car body (throwing out the exta half inch). Hope this is clear. Is this correct?
Thanks.
John
The weight is for total weight so that car should weigh 3.75 oz if I did my math right. Now in this age you can choose which way to go. Some people over weight their cars for max drag, others under weight for max cars in a train, still others mix it up tp be more relistic and you have to know proper placement tp avoid a problem, your choise.The things available when the NMRA came up with this were a lot different than today and were ment for smooth operation at a time that the drag from trucks would always be be an important item to consider. This is still true of those who run sprung trucks ect. Some trucks you can get today you can easily blow down a length of track. I have some cars that will roll away on a very slight grade and others that just sit there based on the trucks and wheels they have.
rrebellSome people over weight their cars for max drag, others under weight for max cars in a train, still others mix it up tp be more relistic and you have to know proper placement tp avoid a problem, your choice.
I find the NMRA Recommended Practice way too complicated.
My system is simpler by far for freight cars:
Less than 50 feet: 4 ounces
50 feet: 5 ounces
More than 50 feet: 6 ounces
I have had no problems with derailments or operational problems, ever.
If I ever do get passenger car modelling underway, I will ask the experience available in here what is best to do for excellent operation.
-Kevin
Living the dream.
I've never seriously bothered with the NMRA's standards (not that I question them), but I prefer to make my own assumptions.
This Athearn 2-bay hopper...
weighs 2 ounces when empty...
...and 7.2 oz. loaded...
...while this much re-worked Athearn boxcar (one of eight)...
also weighs 7.2oz.
In the past, I have added extra weight into a number of Rivarossi passenger cars, to make them track better, but soon discovered that the "new" 15oz. total weight of each car, while making them track much better, also made short work of damaging both the plastic journal boxes and the axle-tips of the Kadee wheelsets.
If I'm running a train with a number of those lightweight empty hoppers, they're always at the back of the train...but if there are enough of them, derailments will still occur.
Wayne
For HO, the NMRA recommended weight for all cars is one ounce plus another 1/2 and ounce for every inch of the car length. If the car weight meets this spec, no additional weight is required (or wanted). There is no concept of "base weight". Weight is weight. NMRA weight has always worked for me. I have had RTR cars that derailed all the time. Weighting them up to the NMRA recommended weight fixed that. In addition, you want all the cars in a train weighing about the same, give or take a bit for length. Other wise heavy cars will pull lighter cars off the track on curves. And longer cars need more weight. I'm cheap, I use a cheap kitchen spring scale to weigh my cars. The postal scales are more accurate but cost more. You can use anything for weights. I like sheet lead which I get from the lumberyead, they sell it as flashing for chimneys and such. Acrylic caulking compound will stick any kind of weight down good and hard. For lead weights, soak the lead in vinegar for 5 or 10 minutes to etch the surface and give the adhesive something to grab onto.
David Starr www.newsnorthwoods.blogspot.com
RP20.1 is not complicated if you pull out a sheet of graph paper and chart total weight on one axis and total length on the other. Calculate the weight for your most common car type and draw a slope from the O/O point in the bottom left corner.
Our layout has 30" minimum radius curves with easements and grades of less than 2 percent. We get good results with a NMRA RP+1 ounce formula, and don't weight anything more than 9 ounces. We don't run much in the way of passenger cars but do have TOFC and autorack traffic.
Hello All,
Attuvian1Under the Recommended Practice in the title, NMRA suggests one ounce plus and additional half ounce for each inch of the particular car.
Whether or not you subscribe and/or adhere to NMRA RP-20.1 is not what the OP is questioning.
rrebellThe weight is for total weight so that car should weigh 3.75 oz. ...
The RP is for the total weight of the car, which for the OPs example is indeed 3.75 oz.
This can get tricky with flat cars and open-topped hoppers where the load(s) are added or removed- -thus increasing or decreasing the car's total weight.
In my opinion, this is where personal experience and preferences come into play with car weight.
Keep in mind this is a Recommended Practice and not a Standard; which all manufacturers need to follow for interoperability.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
what I have done to make the calculation easier, I made a ruler marked off in inches however labeled each mark in "ounces" taking into consideration the 1+1/2 ounce per inch formula.
For example:: the 1" mark is labeled "1.5oz" 2" mark "2oz" 3" mark "2.5oz" all the way up to the 12" mark being "7 oz"
then all you have to do is place this ruler against a car and it will instantly tell you what the car should weigh according to the recommended practice
as others have stated, that is the "finished" weight the car should weigh not how much to add...The amount to be added is the difference between the original weight of the car and the recommended weight of the car
wt ruler by Paul John, on Flickr
dbduck . . . that is the "finished" weight the car should weigh not how much to add...The amount to be added is the difference between the original weight of the car and the recommended weight of the car
. . . that is the "finished" weight the car should weigh not how much to add...The amount to be added is the difference between the original weight of the car and the recommended weight of the car
You are welcome, I hope my description of my "Weight Ruler" made sense as well
It did.
SeeYou190 rrebell Some people over weight their cars for max drag, others under weight for max cars in a train, still others mix it up tp be more relistic and you have to know proper placement tp avoid a problem, your choice. I find the NMRA Recommended Practice way too complicated. My system is simpler by far for freight cars: Less than 50 feet: 4 ounces 50 feet: 5 ounces More than 50 feet: 6 ounces I have had no problems with derailments or operational problems, ever. If I ever do get passenger car modelling underway, I will ask the experience available in here what is best to do for excellent operation. -Kevin
rrebell Some people over weight their cars for max drag, others under weight for max cars in a train, still others mix it up tp be more relistic and you have to know proper placement tp avoid a problem, your choice.
I use a similar system somebody on this forum suggested a number of years ago. One ounce of weight for every 10 scale feet. That translates well to my passenger car fleet. I have 72 footers which are weighted to 7 ounces and 80+ footers which are weighted to 8 ounces.
This system produces a slightly heavier car which I think reduces derailments. A 40 foot boxcar is 480 inches which in HO scale rounds out to 5.5 inches. The NMRA formula would call for a weight of 1 oz. + 2.75 oz. for a total weight of 3.75 oz. or .25 oz. less than the system I use. I find it works well for all lengths of cars. An 80 foot passenger car is 11 inches in HO scale so the recommended NMRA weight is 1 oz. + 5.5 oz. for a total of 6.5 oz., a full ounce and a half less than my system. My locos are powerful enough to pull my trains up the one grade on my mainline which is about 1.75%. Sometimes I add a helper for operational interest even though it's not really needed.
rrebell The weight is for total weight so that car should weigh 3.75 oz if I did my math right. Now in this age you can choose which way to go. Some people over weight their cars for max drag, others under weight for max cars in a train, still others mix it up tp be more relistic and you have to know proper placement tp avoid a problem, your choise.The things available when the NMRA came up with this were a lot different than today and were ment for smooth operation at a time that the drag from trucks would always be be an important item to consider. This is still true of those who run sprung trucks ect. Some trucks you can get today you can easily blow down a length of track. I have some cars that will roll away on a very slight grade and others that just sit there based on the trucks and wheels they have.
Not sure I understand the sprung truck comment? I run sprung trucks on most of my freight cars and a percentage of my passenger cars.
Did many sprung trucks back in the day have poor rolling qualities? Sure. That was then.
I consider equalization particularly important for 4 wheel trucks.
I conducted consderable testing years ago to find a free rolling equalized/sprung truck.
The result, Kadee sprung trucks refitted with Intermountain wheelsets proved more free rolling than ANY rigid frame plastic truck. No matter truck turner tuneups, different wheel sets, the Kadee/Intermountain setup beats them all.
Car weight - I make sure my cars are at or slightly below the NMRA RP.
The Kadee metal trucks lower the center of gravity of the cars.
Lower center of gravity, and equalization work together for much better tracking with long trains, without making cars into heavy sleds.
A prime example of the benefit of metal trucks and metal wheelsets are my Athearn 50' piggybacks.
By simply adding the Kadee/Intermountain truck setup, the stock Athearn flat car and vans comes out at 4.3 oz, within .14 oz of the NMRA RP.
Sheldon
What is the car length of this model? Is the basis for the RP20.1 just experience (a rule of thumb)?
Kadee 50' PS-1 Cushion Underframe boxcar 9' P-S door stock#6312 (Product without coupler trip pins) 1196
BN7150What is the car length of this model? Is the basis for the RP20.1 just experience (a rule of thumb)?
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
For HO scale, RP-20.1 is easy to calculate:
Measure the length of the car in inches. Divide by 2. Add 1. That's the recommended weight, in ounces.
--Steven Otte, Model Railroader senior associate editorsotte@kalmbach.com
Steven OtteFor HO scale, RP-20.1 is easy to calculate:
SeeYou190I find the NMRA Recommended Practice way too complicated.
There are two very different points of view.
If you calculate it once, and create a chart with length on the horizontal axis and weight on the vertical axis, you will never need calculate it again.
use a "ruler" marked in Ounces...
crude but it works
dbduck what I have done to make the calculation easier, I made a ruler marked off in inches however labeled each mark in "ounces" taking into consideration the 1+1/2 ounce per inch formula. For example:: the 1" mark is labeled "1.5oz" 2" mark "2oz" 3" mark "2.5oz" all the way up to the 12" mark being "7 oz" then all you have to do is place this ruler against a car and it will instantly tell you what the car should weigh according to the recommended practice as others have stated, that is the "finished" weight the car should weigh not how much to add...The amount to be added is the difference between the original weight of the car and the recommended weight of the car wt ruler by Paul John, on Flickr
As long as this topic has been revived, I'll ask the question I meant to ask 6 months ago:
According to your ruler description of 1/2oz. per inch, the boxcar in the photo is 8 inches long. If that's an HO car, and it looks to be a 40-footer, it should be 5.5" long, as others have already said. So what am I missing here?
hmm - if that was a S-scale car, that length would be about right. But then S-scale has a different weight formula... Actually, don't get me started on the NMRA S-scale weight RP - that formula has been wrong since the beginning...
It is a 60 foot HO box car
60' x12 = 720 prototype inches
divided by 87
720÷87=8.275 inches
hey dbduck - apologies - i didn't look close enough, I'm a transition-era modeler and just assumed a box car would be 40 feet - oops!
I wonder if anyone will pick up on my S-scale weight comment...
gerhard_k hey dbduck - apologies - i didn't look close enough, I'm a transition-era modeler and just assumed a box car would be 40 feet - oops! I wonder if anyone will pick up on my S-scale weight comment...
no problem, I saw the S scale comment but since I have never dealt with that scale not sure what you were referring to
gerhard_k hmm - if that was a S-scale car, that length would be about right. But then S-scale has a different weight formula... Actually, don't get me started on the NMRA S-scale weight RP - that formula has been wrong since the beginning...
Just as a musing I did a bit of multiplying using the scale ratios and other math figurings. I noted that S is almost exactly in the middle between HO and O. Using that idea, I almost wonder if something closer to a 2.5 or 3 oz start with 3/4 ounce for every inch would be more in line. Disclaimer: I model HO so I don't know anything about S scale other than the numbers. Just my humble opinion.
So just to put more mud in the waters of this discussion, how does the coupler length factor in to this weight equation? Should the length measurement only be the body of the car or include some portion of the couplers? When models have the longer cushioned couplers shouldn't that have some effect on car weight? I would think so since the idea is to have the weight evenly spaced throughout the length of the train to prevent tracking issues and clothes lining.
Good Luck, Morpar
Never mind.
Since weight does not scale down with our models, how does the NMRA address weight of cars for switching layouts? Or do the standards ignore them and focus on layouts that operate many trains over grades and long mainline runs...to maximize train length.
I find that the standard weight of a car is way too light....and its wheels way too free rolling...to provide sufficient resistance when coupling. That realistic clunk-look of two heavy objects striking each other....competing inertias so to speak.... is hard to represent. Excessively floppy coupler springs is not the answer. IMO.
I'm skeptical that any standardized answer for what a car should weigh would not capture the diversity in our hobby.
Modern free rolling cars need more weight added to them...and maybe their axle journals stuffed with tacky glue...in order to provide the realism needed when switching...and staying put on a slight grade. Heavier, poor-ish rolling models should still make little challenge for a modern loco to pull a 7 car train.
- Douglas
The HO standard I use is 1 oz. for ever ten scale feet of car body length. It's not that the NMRA standard is hard to calculate. I could never remember it. This standard is both easy to calculate and easy to remember. It yields a slightly heavier car than the NMRA standard but I prefer that. A 40' boxcar is 4 oz. I think by the NMRA standard it would be 3.75 oz.
"So just to put more mud in the waters of this discussion, how does the coupler length factor in to this weight equation?"
We measure the length of the car from one end sill to the other. Couplers don't enter into it.
Doughless Since weight does not scale down with our models, how does the NMRA address weight of cars for switching layouts? Or do the standards ignore them and focus on layouts that operate many trains over grades and long mainline runs...to maximize train length. I find that the standard weight of a car is way too light....and its wheels way too free rolling...to provide sufficient resistance when coupling. That realistic clunk-look of two heavy objects striking each other....competing inertias so to speak.... is hard to represent. Excessively floppy coupler springs is not the answer. IMO. I'm skeptical that any standardized answer for what a car should weigh would not capture the diversity in our hobby. Modern free rolling cars need more weight added to them...and maybe their axle journals stuffed with tacky glue...in order to provide the realism needed when switching...and staying put on a slight grade. Heavier, poor-ish rolling models should still make little challenge for a modern loco to pull a 7 car train.
Interesting thought.
But my free rolling metal sprung truck cars equiped with code 110 wheels and Kadee original head couplers couple easily with a feather touch, without causing the stationary car to roll.
The Kadee semi scale coupler requires more coupling force even when perfectly aligned. And because it is smaller, it is not always as well aligned, causing it to require even more force.
While my old layout and my new layout have lots of mainline running, I also have plenty of industrial areas requiring switching. I have never had the kind of problem you are describing to any degree that would cause me to over weight cars.
In fact, many of my cars are just under NMRA RP by a 1/2 oz or so.
Again, this situation is related to the semi scale wheel and coupler issue - the degrade the performance of coupling and uncoupling.