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NMRA Weight Standards

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  • Member since
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NMRA Weight Standards
Posted by JOZ2 on Sunday, February 21, 2021 3:11 PM

Hello All,  I'm new to the forum, but a fairly long time model railroader.  I have recently kitbashed some n scale gondolas and am trying to get the weighting correct.  NMRA standards are for .5 oz plus .15 per inch.  When measuring the length, do you round up or down or just split the difference?  I cannot find that anywhere or in any archived weighting articles??  Thanks!

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Posted by mbinsewi on Monday, February 22, 2021 10:24 AM

Welcome!

I'm in HO scale, and I usually round up.

Mike.

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Posted by nealknows on Monday, February 22, 2021 4:16 PM

Welcome to the forum!Welcome

The NMRA weight reference you're referring to is not a 'standard' but a 'recommended practice'. I usually try to get a 'feel for the car and yes, I do reference the NMRA practice. I always round up..

Here's a copy..

https://www.nmra.org/sites/default/files/standards/sandrp/pdf/rp-20.1.pdf

Good luck and enjoy!

Neal

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Posted by John-NYBW on Wednesday, February 24, 2021 6:45 AM

One thing I've never seen stated with the NMRA recommendation is whether you measure coupler to coupler or the body length. 

I use a formula someone suggested several years ago that's a lot easier to figure. One ounce for every scale foot of body length. It makes for a slightly heavier car but I prefer that anyway. 

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Posted by richhotrain on Wednesday, February 24, 2021 7:02 AM

Shame on me, I guess, but I don't add weight to any of my rolling stock, freight or passenger. I do, however, add significant weight to the few dummy B-unit locomotives that I own to try to more closely match the weight of the A-units.

Rich

Alton Junction

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Posted by Overmod on Wednesday, February 24, 2021 7:09 AM

John-NYBW
One ounce for every scale foot of body length. It makes for a slightly heavier car but I prefer that anyway.

so a 40' boxcar is nearly 3 pounds?

You'd need depleted uranium to do 89' TTX flats... Big Smile

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Posted by richhotrain on Wednesday, February 24, 2021 7:37 AM

Overmod
 
John-NYBW
One ounce for every scale foot of body length. It makes for a slightly heavier car but I prefer that anyway. 

so a 40' boxcar is nearly 3 pounds? 

You'd need depleted uranium to do 89' TTX flats...  

The NMRA standard is 1 ounce of initial weight plus 1/2 ounce of weight for every 1 inch of body car length. So, a 40' prototype freight car would measure 5.5 inches in HO scale. Thus, you would add 3.75 ounces of weight.

Rich

Alton Junction

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Posted by John-NYBW on Wednesday, February 24, 2021 8:10 AM

Overmod

 

 
John-NYBW
One ounce for every scale foot of body length. It makes for a slightly heavier car but I prefer that anyway.

 

so a 40' boxcar is nearly 3 pounds?

 

You'd need depleted uranium to do 89' TTX flats... Big Smile

 

Sorry, typo. I meant to say one ounce for every TEN scale feet of body length. A 40 foot boxcar is 4 ounces. That's slighty higher than the NMRA recommendation which would work out to 3.75 ounces (1 + (.5 X 5.5)). For a 50 foot boxcar, it would be 5 ounces as opposed to 4.5 ounces by NMRA  recommendations. 

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Posted by mbinsewi on Wednesday, February 24, 2021 8:14 AM

Overmod
so a 40' boxcar is nearly 3 pounds? You'd need depleted uranium to do 89' TTX flats

Come on Rich, just having a little fun.  

So, a 40' box car would be 40 oz., or 2.5 lbs., a train of 10 cars would be 25 lbs. Surprise

Now, back to the draw bar pull thead, just how heavy would your HO scale locomotive have to be to pull that?

NOW I know why some modelers don't use foam, and nail the track to the plywood.  Laugh

Mike.

OOPS!  never mind, Laugh  I see John snuck a post in while I typed.

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Posted by richhotrain on Wednesday, February 24, 2021 8:19 AM

mbinsewi
 
Overmod
so a 40' boxcar is nearly 3 pounds? You'd need depleted uranium to do 89' TTX flats 

Come on Rich, just having a little fun. 

Oh, I knew that, Mike. Laugh

I just recited the standard for the sake of the less knowledgeable readers than you or I, recognizing our brilliance. Smile, Wink & Grin

Rich

Alton Junction

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Posted by davidmurray on Wednesday, February 24, 2021 8:59 AM

John-NYBW
One thing I've never seen stated with the NMRA recommendation is whether you measure coupler to coupler or the body length. I use a formula someone suggested several years ago that's a lot easier to figure. One ounce for every scale foot of body length. It makes for a slightly heavier car but I prefer that anyway.

This doen't seem right to me.  That would mean a forty ft boxcar would weight 40 ounces.  Just a tad heavy

 

David Murray from Oshawa, Ontario Canada
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Posted by richhotrain on Wednesday, February 24, 2021 9:03 AM

davidmurray
 
John-NYBW
One thing I've never seen stated with the NMRA recommendation is whether you measure coupler to coupler or the body length. I use a formula someone suggested several years ago that's a lot easier to figure. One ounce for every scale foot of body length. It makes for a slightly heavier car but I prefer that anyway.

John's calculation has been debunked in subsequent replies.

Rich

Alton Junction

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Posted by rrinker on Wednesday, February 24, 2021 9:06 AM

 Maybe 1 oz per TEN scale feet? 

                                         --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by rrinker on Wednesday, February 24, 2021 1:47 PM

 Whatever works. I just go by the NMRA standards. I already had a test track with a Kadee couple guage at the end - the old metal one with an actual coupler. So I stuck on a label graduated in half an inch incrememnts with the NMRA weights marked instead of inches. Stick a car on, couple it up - look at what the weight should be. Easy peasey.

 Many of my cars are heavier than standard though. Especially open hoppers with loads. Try as I might, it never causes a problem. Even putting an underweight long flat car or gon in front of at or over NMRA weight cars - still no stringlining. That's deliberately trying. If they don't come off the track under overly rough handling, then running them properly with smooth stops and starts is not going to be a problem.

                            --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by John-NYBW on Wednesday, February 24, 2021 2:12 PM

While we're on the subject, I'm curious as to how modelers add weight to their tank cars which are usually under weight whether RTR or kit built. Some are seriously too light. With some tank cars its easy to get inside the tank and add some weights but with others, especially some RTR, it's not that easy. I was thinking of drilling a hole in the bottom of the tank, dropping in enough BBs to bring it almost to weight and then pour Gorilla Glue into the hole. I would then plug the hole and turn the car right side up so the BBs and the glue would settle to the bottom. Does anyone have an easier way to do this. 

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Posted by SeeYou190 on Wednesday, February 24, 2021 2:21 PM

John-NYBW
I'm curious as to how modelers add weight to their tank cars

I use a couple of 1 ounce egg sinkers hammered into more of a cylinder shape and glued into the tank body.

-Kevin

Living the dream.

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