Author Topic: Scales to weigh N scale rolling stock  (Read 972 times)

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robert3985

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Re: Scales to weigh N scale rolling stock
« Reply #15 on: December 06, 2018, 12:34:22 PM »
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Bob,
Scales designed for reloading are not really that great for weighing N scale rolling stock.  Because gun powder charge weights must be reliably weighed to 0.1 grain, and a grain is only 1/7,000 of a pound, they are both more sensitive than necessary and also typically don't have a very high maximum weight. For instance, the one in your link only goes to 750 grains or 50 grams, which is 1.71 or 1.75 ounces.  Although that is theoretically good for the NMRA weight of a car up to 8.3" long in N scale, it certainly won't work for locomotives.  And, at least my reloading scale is pretty "touchy", compared to my wife's cooking scale - I need to support the weighing platform whenever I put it away.  And florescent lights can affect the reading if they are nearby, at least to the point of affecting powder charges at the 0.1 grain level.

I never have weighed a locomotive.  Is there an NMRA recommended practice for this?  Some of my brass light Mikes and FEF's are filled with low-melt metal and they seem to weigh a couple of pounds, but...I've never weighed 'em...but they'll pull over 70 cars.

I didn't take too long looking for a scale for the OP, but I assume there may be a reloading digital scale that will be in his price range and meet his precision requirements, plus provide a brass weight "standard" to calibrate his scale...which kitchen scales don't do...unless "zeroing" them does the same thing.

Of course I know about "grains" since I am an avid reloader and shooter, but most digital scales have the capability to change between imperial, metric or "grains" (whatever standard that is???)  and since accuracy seems to be important to the OP, it's better to have more of it than less.

Fluorescent lights affecting accuracy???  That's weird.  I wonder what that's all about?????

In any case, it give the OP another avenue to maybe find what fits his needs.  :)

Cheerio!
Bob Gilmore

Maletrain

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Re: Scales to weigh N scale rolling stock
« Reply #16 on: December 06, 2018, 02:07:12 PM »
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I don't see any real need to accurately calibrate a scale used for N scale rolling stock.  (On the other hand, I definitely calibrate my reloading scale, or at least check it every use with a calibration weight in the range of the powder charge I intend to weigh - there is a safety issue involved with reloading that isn't a problem with model railroading.)

Most scales come with a "zero" button that sets the current reading to zero and gives the difference between that and subsequent readings.  This allows setting a "tare" weight to zero, and should not be confused with a calibration.  This "zero" function is useful when you need to put something on the scale to support the item being weighed (such as a jewel case lid to support all wheels of a steam locomotive), or perhaps to keep the item from making the scale's platform messy (such as when weighing food). 

But, even though the tare weight has been "zeroed" out of the reading, if the scale is not properly calibrated, then the reading of the object will still be off by the amount that the scale is out-of-calibration.  With electronic scales, the calibration error may not even be the same fraction of the reading over the entire range of possible weights.  My reloading scale came with a "calibration" function that uses 2 weights and uses a mathematical function to make the calibration apply more closely over the whole range, base on the 2 weights provided.  Even greater accuracy can be had by using more calibration weights and a more complex mathematical calibration curve.  A scale that has a calibration function comes with the appropriate weights for whatever math it uses to do the calibration over its range.  Of course, it is up to the user to make sure those calibration weights don't change by getting worn (lose weight), getting dirty or corroded (gain weight), etc.

But, this complexity is driven by need for particular applications.  For model railroading, I don't see a need to be very accurate.  Today, most electronic scales are going to be well within 1% accuracy in the middle of their design ranges, and I would not care if I weighed a 3" long car that should (according to NMRA) weigh 0.95 ounce, but my scale is 1% off, so it only really weighs 0.94 ounce.  That NMRA recommended weight is only based on a mathematical approximation of the collective results of some testing that was somewhat subjective, anyway. 

Weighing really just puts your cars "in the suggested ballpark" for smooth operation.  Even without a scale, you could just add weight to cars that are sting-lining and reduce weight to cars that your loco can't pull up your grade (or shorten your trains or add more locomotives to the rear, etc.) and probably arrive at approximately the NMRA recommendations after a lot of futzing (and cursing).

peteski

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Re: Scales to weigh N scale rolling stock
« Reply #17 on: December 06, 2018, 03:05:46 PM »
+1
As with everything else in the Interwebs, everybody here has an opinion, idea, or recommendation.  There are plenty (too many actually) choices already presented here for someone to make a decent choice of scales for weighting N scale cars.  Both from the accuracy standpoint and price.  If Bob wants to have accuracy to 1 femto-gram, so be it. Others might be satisified with less accurate scale. And yet some people, like our own Cody, remove as much weight from their rolling stock as possible.  Different strokes . . .

As for Bob, I think he is confusing NMRA with NRA.  Yes, I  made a joke.  :D
--- Peteski de Snarkski
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Maletrain

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Re: Scales to weigh N scale rolling stock
« Reply #18 on: December 06, 2018, 03:19:48 PM »
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As for Bob, I think he is confusing NMRA with NRA.  Yes, I  made a joke.  :D

If there was a National Model Rifle Association, I am sure they would recommend calibration for femto-gram accuracy for reloading ammo for N scale rifles! 

Seriously, the OP is looking for criteria for choosing a scale, and that is what he is getting various opinions about - which is what makes this forum great.

But, when Peteski feels he has to make sure we know he is joking, are things getting that serious?


mmagliaro

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Re: Scales to weigh N scale rolling stock
« Reply #19 on: December 06, 2018, 04:11:41 PM »
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Get a German-designed scale. Most scales are built in China, so you need to check out where each one was designed. 

http://myweigh.com/

30 year guarantee.

I assumed all these cheap scales on eBay were made in China.   What I did NOT assume was that a good, calibratable scale from Germany or the US (like the myweigh you cited) would be available for a tolerable price.  But actually, balances.com carries MyWeigh, and there are plenty of good options there for scales in the $20 - $50 range that would be perfect for weighing N Scale rolling stock and engines.

peteski

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Re: Scales to weigh N scale rolling stock
« Reply #20 on: December 06, 2018, 04:58:15 PM »
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But, when Peteski feels he has to make sure we know he is joking, are things getting that serious?

It is not me - it is the world around me that has changed.  :facepalm:  I had few bad experiences by having something humorous being interpreted in a way I did not intend, so I just want to make sure to show my intentions (to reinforce the emoticon I also used).

I'm pretty sure, in this instance, that Bob would understand the humor, but some others here might get their knickers in a twist.
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peteski

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Re: Scales to weigh N scale rolling stock
« Reply #21 on: December 06, 2018, 05:09:23 PM »
+1
I assumed all these cheap scales on eBay were made in China.   What I did NOT assume was that a good, calibratable scale from Germany or the US (like the myweigh you cited) would be available for a tolerable price.  But actually, balances.com carries MyWeigh, and there are plenty of good options there for scales in the $20 - $50 range that would be perfect for weighing N Scale rolling stock and engines.

I think that most (if not all) digital scales use the same Chinese-made off-the-shelf components (like the strain gauge and other electronics) inside those scales, so  it is not all that important where the scale was designed.  I suspect that most use the same pre-canned design using the same controller integrated circuits.

Kitchen scales are also pre-calibrated (since there is really no need to calibrate those for extreme accuracy). Plus in order to calibrate a scale one needs a precision reference weight set (which most mortals do not own), so the calibration is a moot point.   And strain gauges are quite sturdy, eliminating need for periodic calibration (at least for what we use them).  A model train car will still work, even if it is' mass is slightly out of spec.  You won't see any difference in car's trackign whether the car is 1.200 or 1.205 oz.  BTW, the specs themselves are just recommendations (not absolute rules).  I'm all for accuracy and precision where it *REALLY* makes a difference, but here we are *REALLY* overthinking this thing.
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muktown128

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Re: Scales to weigh N scale rolling stock
« Reply #22 on: December 06, 2018, 07:51:26 PM »
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We verify scales weekly where I work using 2 different reference weights (100 g and 1000 g) and track the results to determine if the scale is drifting over time.  The verification weights are stored in a plastic case to protect them.  We also have a company come in once a year to calibrate our scales using standards that are traceable.

If you are concerned with scales drifting over time and losing accuracy, I would get a couple of brass weights of different mass amounts 50-100 grams and 500-1000 grams and record the mass of each weight 3-5 times to determine an average weight.

You can then check the mass of these weights weekly or monthly to see if there are changes over time.  This will help determine if your scale is drifting out of calibration.  The verification weights should be stored in a case or box to protect from damage.  You also want to make sure your scale is level.  Do any of the scales have a bubble to determine if it is level?  I didn't check any of the links to look at the scales. 

Cajonpassfan

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Re: Scales to weigh N scale rolling stock
« Reply #23 on: December 06, 2018, 08:15:10 PM »
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If I were to succeed in getting my rolling stock to within a whole gram :o of whatever weight standard I deem optimal, I'd be quite happy with myself. I'd do a dance... Going beyond that is silly, imho, unless one is dealing with munitions or precious metals and such. YMMV. And yes, I do weigh my locomotives; tracking, tractive effort, and electrical conductivity are all a function of weight (and weight added).
Otto K.

Angus Shops

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Re: Scales to weigh N scale rolling stock
« Reply #24 on: December 06, 2018, 08:38:49 PM »
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For my resin castings projects I use a little digital scale I purchased a local full service drug store (London Drugs). I don't remember the price, maybe $40.00 Cdn. It measures to 1/100 of gram or in oz's, and it can be 'zero'd' as required for additive  weighing. It's about 2 1/2 X 3 1/2" and is battery powered, which are replaceable, but seem to last forever. I managed to mess one up with spattered resin long before the battery died. It would be great stocking stuffer for a loved one, and then you can use it as required without having to dip into the hobby funds.
Geoff

Maletrain

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Re: Scales to weigh N scale rolling stock
« Reply #25 on: December 06, 2018, 09:02:14 PM »
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One reason it might pay to measure car weight fairly accurately (or maybe I should say precisely), would be to conduct tests on freeness of rolling.  I am planning to do that with a rig that allows me to change grade under a car to better than 0.1% (grade) precision, to see what force makes it starts to roll, and what force will barely not keep it rolling.  Because the force that makes the car roll is provided by gravity, making all of the test cars the same weight is useful for making the results comparable for different cars.  I plan to use bird shot for weight adjustment.  One #8 pellet weighs 0.07 grams (1.09 grains), so I am only interested in the scale distinguishing weight difference to a little less than that level.  Of course, that is only about a quarter of one percent of the recommended weight for a 3" N scale car.  But, when looking for thresholds against  force, I want to make sure that the force is well known so that it does not introduce any more variation in the results than I am already going to have to contend with from other parameters.

The idea is to make all the cars weigh the same for the test, no matter what length, so they all have the same gravitational force pushing on their trucks when they are at the same grade angle.  That way, I can make sure that the trucks meet a standard for free rolling (once I decide what value to establish as a standard).  Of course, when the test is over, I would return the cars to whatever weight I decide works best for me.  Because I want some long trains, I may decide that car weights less than NMRA recommendations are better, provided they run reliably in my operations on my layout.  If I was running them on a bunch of different layouts, I might decide to use the NMRA recommendations.
« Last Edit: December 06, 2018, 09:07:07 PM by Maletrain »

Mike Madonna

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Re: Scales to weigh N scale rolling stock
« Reply #26 on: December 06, 2018, 09:47:55 PM »
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I never have weighed a locomotive.  Is there an NMRA recommended practice for this?  Some of my brass light Mikes and FEF's are filled with low-melt metal and they seem to weigh a couple of pounds, but...I've never weighed 'em...but they'll pull over 70 cars.

I didn't take too long looking for a scale for the OP, but I assume there may be a reloading digital scale that will be in his price range and meet his precision requirements, plus provide a brass weight "standard" to calibrate his scale...which kitchen scales don't do...unless "zeroing" them does the same thing.

Of course I know about "grains" since I am an avid reloader and shooter, but most digital scales have the capability to change between imperial, metric or "grains" (whatever standard that is???)  and since accuracy seems to be important to the OP, it's better to have more of it than less.

Fluorescent lights affecting accuracy???  That's weird.  I wonder what that's all about?????

In any case, it give the OP another avenue to maybe find what fits his needs.  :)

Cheerio!
Bob Gilmore

Hey Bob,

I was wondering what you use when you say "low melt metal"?

Thanks!
Mike
SOUTHERN PACIFIC Coast Division 1953
Santa Margarita Sub

robert3985

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Re: Scales to weigh N scale rolling stock
« Reply #27 on: December 06, 2018, 10:41:22 PM »
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...As for Bob, I think he is confusing NMRA with NRA.  Yes, I  made a joke.  :D


HAHAHA...thanks for letting us know Peter!   :trollface:

Cheerio!
Bob Gilmore

robert3985

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Re: Scales to weigh N scale rolling stock
« Reply #28 on: December 07, 2018, 12:15:42 AM »
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Hey Bob,

I was wondering what you use when you say "low melt metal"?

Thanks!

I use low melt-temperature metal to add weight to both brass and plastic locomotives sometimes to increase their pulling capacity.  I also use these casting metals to cast up parts in RTV molds sometimes.

I buy them at MicroMark here: https://www.micromark.com/search?keywords=casting

I use the Type 160 and Type 280, which are categorized by their melting temperature in deg. F

You can read on MicroMark's page the composition of each of these alloys.

I melt the Type 160 by putting a chunk of it in an aluminum cup and then setting the cup in a shallow pan of boiling water.  I use a silicon heat-resistant kitchen glove to hold the cup while I'm pouring it.  I've added weight to several plastic and brass locomotives and to all of my highly kitbashed cabooses.

I melt the Type 280 with a propane torch, being careful to not apply too much heat as I don't want the melted metal to get much hotter than its melt temperature.  I use an aluminum cup for this too, holding the cup with long-nose Vice Grips, and wearing silicone heat resistant gloves for protection.  I generally use this higher temperature metal to cast parts in RTV molds because my logic says that it will be more durable than the lower temperature alloy.  However, I have cast parts using Type 160 as well, and I haven't had a durability problem with either alloy. Some of the models that have parts on them I cast using these alloys are over 20 years old nowadays, so I guess my assumption about durability doesn't matter as either alloy evidently holds up over time.

Cheerio!
Bob Gilmore


peteski

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Re: Scales to weigh N scale rolling stock
« Reply #29 on: December 07, 2018, 12:43:57 AM »
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I use low melt-temperature metal to add weight to both brass and plastic locomotives sometimes to increase their pulling capacity.  I also use these casting metals to cast up parts in RTV molds sometimes.

 I generally use this higher temperature metal to cast parts in RTV molds because my logic says that it will be more durable than the lower temperature alloy.  However, I have cast parts using Type 160 as well, and I haven't had a durability problem with either alloy. Some of the models that have parts on them I cast using these alloys are over 20 years old nowadays, so I guess my assumption about durability doesn't matter as either alloy evidently holds up over time.

Cheerio!
Bob Gilmore

Not sure about your reasoning.  You thought that just because a metal alloy has low melting temperature, it would somehow degrade over time (even if kept in temperatures under its melting point)?  What sort of degradation did you expect?  Crumbling or flowing maybe?  Used as weight, it is not really subjected to any stress or even strain.
--- Peteski de Snarkski
--- Honorary Resident Curmudgeon