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NMRA car weight

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Posted by Guy Papillon on Saturday, April 4, 2015 6:20 AM

The greater benefits I saw to weighting cars to NMRA RP is to stop the "bubbleheads effect" and to help on coupling.

Guy

Modeling CNR in the 50's

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Posted by riogrande5761 on Saturday, April 4, 2015 8:23 AM

dknelson
 
riogrande5761

I picked up one of those old Front Range flat car kits based on the Southern flat cars built from old box car frames and converted to a 50' TOFC flat car.  The flat car kit has an open skeleton section on the end with the 3rd wheel hitch - there is no weight for the flat car and there isn't really any place to put weight either.  Yes, I've added metal wheels but the flat car floats on the trucks quite literally.  I will put weight in the truck trailer that rides on it but it's going to be fun trying to add weight to the flat car. 

 
One old trick was to wrap slender solder around axles.  Probably won't get the weight up to standards but it will help - and be where help is needed most.
Dave Nelson

 
I've heard of the wrapping axles.  The problem with that is the body is light as a feather and floating unstabley - adding weight to the axles won't help the body hunker down.  With a light body - it is an unstable platform for the trailer it carry's.  I need to somehow get weight into body.  It's going to mean what detail is in the underbody will have to be obscured - there isn't much space under there - especially with the open frame.  Ideally, the body would be cast metal, as some newer production models of similar type - but for now, the Front Range TOFC rebuilt from a box car flat car is the only game in HO that I know of.

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Posted by jecorbett on Saturday, April 4, 2015 9:50 AM

To me, the NMRA guideline is a minumum. I prefer heavier. Recently I read a post that suggested a higher standard of one ounce per 10 scale feet. I wish I knew who to credit for that because I tried it at it has made all the difference in the world in reducing derailments, particularly my 50 foot boxcars, most of which had given me trouble. It would be nice if we all had perfect trackwork with no trouble spots and we always operated under optimal conditions. In such a perfect world, the NMRA standards would be fine. My trackwork isn't perfect and I operate long freights and often perform switching moves which require shoving a long string of cars through turnouts and curves. Just yesterday I was shoving a long string around a curve and a pair of adjacent 40' BLI RTR boxcars buckled. I immediately took them to the scale and found they were 3.25 ounces. I put 3 quarter ounce lead weights in each of them and then repeated the switching move. This time they stayed on the track. I don't have all my rolling stock updated to this new standard but that is the goal. Each time I have a derailment I immediately check the weight and so far every time the car has weighed less than my new standard. Heavier is better plus this standard is so much simpler and easy to remember. If it turns out I need to use helpers to move a 25+ car train up a 1.75 degree grade, well that's not necessarily a bad thing.  

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Posted by maxman on Saturday, April 4, 2015 10:33 AM

jecorbett
Just yesterday I was shoving a long string around a curve and a pair of adjacent 40' BLI RTR boxcars buckled. I immediately took them to the scale and found they were 3.25 ounces. I put 3 quarter ounce lead weights in each of them and then repeated the switching move. This time they stayed on the track. I don't have all my rolling stock updated to this new standard but that is the goal.

Many seem to have their own opinions on this, and you are entitled to yours.  However, I see nothing that much different between your "new" standard and the NMRA recommended practice.

A 40 foot boxcar, assuming HO, is about 5-1/2 inches long.  The recommended weight for this car would be 1 ounce plus 1/2 ounce per inch of length, or 3.75 ounce.  I believe that your new weight totalled 4 ounces.  That 1/4 ounce is the tolerance I use for whatever my target weight is.

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Posted by jecorbett on Saturday, April 4, 2015 12:08 PM

maxman
 
jecorbett
Just yesterday I was shoving a long string around a curve and a pair of adjacent 40' BLI RTR boxcars buckled. I immediately took them to the scale and found they were 3.25 ounces. I put 3 quarter ounce lead weights in each of them and then repeated the switching move. This time they stayed on the track. I don't have all my rolling stock updated to this new standard but that is the goal.

 

Many seem to have their own opinions on this, and you are entitled to yours.  However, I see nothing that much different between your "new" standard and the NMRA recommended practice.

A 40 foot boxcar, assuming HO, is about 5-1/2 inches long.  The recommended weight for this car would be 1 ounce plus 1/2 ounce per inch of length, or 3.75 ounce.  I believe that your new weight totalled 4 ounces.  That 1/4 ounce is the tolerance I use for whatever my target weight is.

 

As I stated before, the biggest improvement has been in the performance of the 50 footers. Those are 7 inches which by the NMRA standard would be 4.5 ounces. I now have a full 5 ounces in them and the difference has been night and day over when they were only at the NMRA RP. The BLI 40 footers that derailed were a half ounce underweight even by NMRA standards. I went a quarter ounce better than the NMRA recommends. The benefits far outweigh whatever downside there might be, not that I have noticed any. My F7 AB set had no trouble pulling a 29 car train up a 1.75 grade. That's as long a train as I will ever run. Some of my lighter steamers might need a helper, but those have been relegated to the secondary trains anyway. If I run a helper, it will probably be just for show, not because it's really needed.

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Posted by TomLutman on Saturday, April 4, 2015 7:08 PM

I'm going to start putting in some lead a batch at a time until all of them are up to weight. I have several that need some weathering and a few that still need metal wheels on them. I've not had a derail problem yet, but then again, I haven't had to push cars through curves and switches yet. In general, 50ft'ers will be the big cars, but I do have some branchline heavyweights that I haven't really run yet either. I am currently building the switchwork for the yard area, and no5 frogs are the norm due to space constraints. If I get to close to the woodburner, weighting the cars will be a moot point

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Posted by farrellaa on Saturday, April 4, 2015 8:05 PM

I don't know what the 'scale' weight should be, but if an HO tank car model of a 10,000 lb prototype weighs 1/87 of that, it would be around 1840 ounces or 115 lb!

What method would be used to arrive at a 'scale weight'?? I am comparing this to the 'fast (scale) clock' that many use in running their layouts? Just letting my mind wander here?

   -Bob

Life is what happens while you are making other plans!

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Posted by dknelson on Saturday, April 4, 2015 9:27 PM

farrellaa

I don't know what the 'scale' weight should be, but if an HO tank car model of a 10,000 lb prototype weighs 1/87 of that, it would be around 1840 ounces or 115 lb!

What method would be used to arrive at a 'scale weight'?? I am comparing this to the 'fast (scale) clock' that many use in running their layouts? Just letting my mind wander here?

   -Bob

 

 
Scale weight would not be 1/87 because we are dealing with three dimensions so in theory it would be 1/87 x 1/87 x 1/87.  But the physics of our trains, with our sharp curves and such, need their own weight standards.
Dave Nelson 
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Posted by maxman on Saturday, April 4, 2015 9:31 PM

farrellaa
I don't know what the 'scale' weight should be, but if an HO tank car model of a 10,000 lb prototype weighs 1/87 of that, it would be around 1840 ounces or 115 lb!

I believe that this has been discussed before.  Assuming a 200,000 pound loaded coal car, you would need to divide 200,000 pounds by 87 three times, since you are dealing with a volume not a single dimension.  So 200,000#/87 = 2299#; divided by 87 = 26#; divided by 87 = 0.3#; or about 4.9 ounces.

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Posted by BRAKIE on Sunday, April 5, 2015 4:10 AM

maxman
A 40 foot boxcar, assuming HO, is about 5-1/2 inches long. The recommended weight for this car would be 1 ounce plus 1/2 ounce per inch of length, or 3.75 ounce. I believe that your new weight totalled 4 ounces. That 1/4 ounce is the tolerance I use for whatever my target weight is.

At a Prototype Modelers meet a small group of us discussed what should the weight recommendation / standard be of a 12" car compared to a 7 or 8" car? What weight 4 or 5 unit well car?

To be sure that was one of the most mind boggling discussions I ever took part in.

Larry

Conductor.

Summerset Ry.


"Stay Alert, Don't get hurt  Safety First!"

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Posted by jecorbett on Sunday, April 5, 2015 7:41 AM

farrellaa

I don't know what the 'scale' weight should be, but if an HO tank car model of a 10,000 lb prototype weighs 1/87 of that, it would be around 1840 ounces or 115 lb!

What method would be used to arrive at a 'scale weight'?? I am comparing this to the 'fast (scale) clock' that many use in running their layouts? Just letting my mind wander here?

   -Bob

 

Weight doesn't scale down because when you scale down, you do it in three dimensions. Suppose you had a single weight on a HO flat car that weighed 1 ounce and was one cubic centimeter in size. For simplicity sake I will multiply by 87 instead of 87.1. If you scale that up, it would be 87 centimeters long, 87 wide, and 87 high. That's 87X87X87 or 658,503 cubic centimeters and the same number of ounces.

Edit: I guess I should have read the further posts because several have already explained this.

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Posted by farrellaa on Sunday, April 5, 2015 8:00 AM

maxman
 
farrellaa
I don't know what the 'scale' weight should be, but if an HO tank car model of a 10,000 lb prototype weighs 1/87 of that, it would be around 1840 ounces or 115 lb!

 

I believe that this has been discussed before.  Assuming a 200,000 pound loaded coal car, you would need to divide 200,000 pounds by 87 three times, since you are dealing with a volume not a single dimension.  So 200,000#/87 = 2299#; divided by 87 = 26#; divided by 87 = 0.3#; or about 4.9 ounces.

 

Thanks for the explanation, I was posting the question because I didn't know if/what/how this was determined. Now it makes sense.

   -Bob

Life is what happens while you are making other plans!

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Posted by jecorbett on Sunday, April 5, 2015 8:10 AM

One of the biggest challenges regarding weight is what to do with empty flats, gondolas, and hoppers. Where do you put the added weight where it won't be obvious. To be weighted properly, they would need more weight when empty than when carrying a load.

I haven't figured out a solution to this dilemma so I'm going to try to be judicious as to where in the train they get placed. I'm still experimenting with that but my thinking is near the front would be the best place for an underweighted car. Any other thoughts?

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Posted by gregc on Sunday, April 5, 2015 8:23 AM

some kits come with metal plates to weight them.

Lead is convenient for additional weight and is 44% denser than Iron.  It is malleable and can easily be melted into a form.

But tungsten is 70% denser than lead.  Unfortunately it's hard even to machine, but may be an alternative if found in an appropriate shape to provide weight in a small space.

greg - Philadelphia & Reading / Reading

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Posted by Soo Line fan on Sunday, April 5, 2015 10:25 AM

I only weigh the rare car which is causing a problem. If a car with the stock weight tracks well and does not derail, what exactly is being accomplished.

Jim

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Posted by TomLutman on Sunday, April 5, 2015 10:54 AM

jecorbett, I would think if you were to run the light cars in the front and weighted cars to the rear, you would increase the chances of stringlining. It's just because of those weighted cars acting like an anchor, and the loco trying to straighten the line out.

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Posted by dknelson on Sunday, April 5, 2015 11:22 AM

riogrande5761
The problem with that is the body is light as a feather and floating unstabley - adding weight to the axles won't help the body hunker down.  With a light body - it is an unstable platform for the trailer it carry's.  I need to somehow get weight into body.  It's going to mean what detail is in the underbody will have to be obscured - there isn't much space under there - especially with the open frame.  Ideally, the body would be cast metal, as some newer production models of similar type - but for now, the Front Range TOFC rebuilt from a box car flat car is the only game in HO that I know of. 

Hmmm.  OK I see the problem now - and the same issue exists with an older generation of wood kits and some plastic models which had no provision for a place to "hide" weights.  The thought does strike me that given such a light car, part of the problem might be our nearly scale sized bolsters both on car frame and truck, and that a broader and wider bolster such as you see on the mountings of some locomotive trucks onto frames might address the wobble issue.

For one super-light Varney gondola I carefully cut sheet lead and in essence thickened the sides and ends, then painted and weathered to look like the floor of the car.  Some guys put in false lead bottoms into their underweight gondolas, and I would think that a false deck of lead could be added to a flat car.   It would come at the cost of total scale appearance, but then, so does the wobble you describe.  I wonder if a thin sheet of lead fitted to the top deck of the flat car would look OK enough to work.

Dave Nelson

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Posted by doctorwayne on Sunday, April 5, 2015 1:48 PM

jecorbett

One of the biggest challenges regarding weight is what to do with empty flats, gondolas, and hoppers. Where do you put the added weight where it won't be obvious. To be weighted properly, they would need more weight when empty than when carrying a load.

I haven't figured out a solution to this dilemma so I'm going to try to be judicious as to where in the train they get placed. I'm still experimenting with that but my thinking is near the front would be the best place for an underweighted car. Any other thoughts?

 
Athearn 50' flatcar with bulkhead ends from Walthers:
 
 
...but even empty, this car can be used at the front of a long train:
 
 
This car is a knock-off of the Athearn car, with the same external modifications, but a plastic underbody:
 
 
...the load is hollow, but with some added weight:
 
 
Both weigh 8oz.
 
This is the Athearn 40' pulpwood flat, lengthened to 53' and with sides built from sheet and strip styrene:
 
 
It weighs only 5oz., but could easily accommodate a larger weight:
 

This is a re-worked ConCor (Revell) all-welded 53'6" gondola. 

While these cars had a cast metal fishbelly underframe and were of a decent weight, the cars rode much too high.  I removed the weight, modified the underfloor, then added a new weight, bringing the LT.WT. to 7oz.:

Incidentally, with a few cosmetic modifications, this car is a good representation of a Pennsy G-31:

The low-riding GSC cars from Walthers are the backbone of my flatcar fleet, but because these cars are really just a deck on an underframe, I couldn't really eliminate the frame:
 
 
Instead, I made moulds from sheet aluminum (four required for the different-shaped cavities), and poured weights in lead:
 
 
Empty, these cars weigh 6.5oz. (the load of plate steel shown is negligible, as it's made from Plastruct ABS, with styrene stakes and blocking).
I've run one of these as the first car in a 71 car freight, and had no issues with derailments, despite the fact that my layout is mostly curves and grades, often in the same locations.
 
Wayne
 

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