This discussion is starting up, off-topic, in the detailed-RTR-operating-model thread. It deserves its own named thread for discussion.
Some of the discussion thus far is as follows:
ATLANTIC CENTRAL Lastspikemike Yes, thanks, I've actually previously book marked that extensively detailed description. [This is the link to big blue trains.com on improving adhesion for light models.] Thanks. The disparity in pulling power for these steam locomotives has me pondering coefficients of friction on nickel silver... However, I noted an extensive thread on locomotive drawbar force as it may relate to the coefficient of friction of steel on steel as well as steel on sanded steel comparing prototype to HO. In light of the significant disagreements evident there I decided not to make my own contribution. The topic seems surprisingly controversial, given that the physics have been well understood for over 100 years. Interestingly, diesel models seem quite predictably uniform in their pulling power and roughly correspond to prototype patterns: bigger and heavier pull proportionately better. This is not the case for steam locomotive models which is frankly a bit weird. It is not weird at all. Model steam locos, even with spring drivers suffer from a lack of even weight distribution on the drivers, as well as other traction losses on our sharp curves, etc. This problem increases with the number of driven axles. The physics of the prototype does not scale down. The flexibility of diesel trucks solves this problem. Sheldon
Lastspikemike Yes, thanks, I've actually previously book marked that extensively detailed description. [This is the link to big blue trains.com on improving adhesion for light models.] Thanks. The disparity in pulling power for these steam locomotives has me pondering coefficients of friction on nickel silver... However, I noted an extensive thread on locomotive drawbar force as it may relate to the coefficient of friction of steel on steel as well as steel on sanded steel comparing prototype to HO. In light of the significant disagreements evident there I decided not to make my own contribution. The topic seems surprisingly controversial, given that the physics have been well understood for over 100 years. Interestingly, diesel models seem quite predictably uniform in their pulling power and roughly correspond to prototype patterns: bigger and heavier pull proportionately better. This is not the case for steam locomotive models which is frankly a bit weird.
Yes, thanks, I've actually previously book marked that extensively detailed description. [This is the link to big blue trains.com on improving adhesion for light models.] Thanks.
The disparity in pulling power for these steam locomotives has me pondering coefficients of friction on nickel silver...
However, I noted an extensive thread on locomotive drawbar force as it may relate to the coefficient of friction of steel on steel as well as steel on sanded steel comparing prototype to HO.
In light of the significant disagreements evident there I decided not to make my own contribution. The topic seems surprisingly controversial, given that the physics have been well understood for over 100 years.
Interestingly, diesel models seem quite predictably uniform in their pulling power and roughly correspond to prototype patterns: bigger and heavier pull proportionately better. This is not the case for steam locomotive models which is frankly a bit weird.
It is not weird at all. Model steam locos, even with spring drivers suffer from a lack of even weight distribution on the drivers, as well as other traction losses on our sharp curves, etc. This problem increases with the number of driven axles.
The physics of the prototype does not scale down.
The flexibility of diesel trucks solves this problem.
Sheldon
I am sure there is wide and rich experience with both the practical and esthetic aspects of improving adhesion, some of it since the last coverage of the subject here or in books...
Roughly, model diesel locomotives have about 25% adhesion (just like the real thing historically, not counting modern traction controls). That means if a loco weighs in at 16oz., it should have about 4oz. in tractive effort, more or less.
At my club, we test all registered locos using a spring scale that measures force in 1/4oz. increments. Right now, we have about 2000 engines on the roster, and since I test most of them, I have a lot of experience in measuring tractive effort.
Things that make an engine pull less:Less weight on drivers VibrationClean wheelsClean trackUnbalanced on driversNickel-Silver wheelsNickel-Silver trackLess powerful motor
Things that make an engine pull more:More weight on drivers (up to a point)SmoothnessDirty wheelsDirty trackBalanced on driversSintered wheelsSteel trackMore powerful motor
my understanding is that prototypical adhesion is ~25% of the balanced weight on the drivers and this is also roughly true for models: 20-30%. Of course wetness, leaves, dirt, frost, ... can affect this.
my understanding of friction is that it depends primarily on weight and less to do with surface area.
i don't understand why the value is as small as it is if the coefficeint of steel-on-steel is ~0.74-0.8.
"balanced" refers to the desire to have an equal amount of weight on each driver. since friction depends on weight, the first driver to start slipping will be the one with the least weight. Once it slips, all the force is now imposed on the non-slipping drivers which very likely will exceed their friction limit and also slip.
balancing the weight on drivers appears to be easier with diesels than steam.
greg - Philadelphia & Reading / Reading
Other minor things that are technically covered in the list, but could be expanded upon:
more traction can come from:
1. weaker/no springs on the leading/trailing trucks
2. even springs on wheels*
3. less blind drivers
4. a more rigid wheelbase**
5. drawbar on engine should be (ideally) at the height at which the centers of axles on the drivers are***
Many of these have minimal effect, only apply to certain engines, and potentially hurt the operating characteristics in other ways(for ex sprung leading/trailing truck helps tracking) but they do contribute to pulling power.
The most common cuprits are usually unbalanced drivers, and a general lack of weight.
This is a very interesting thread, I will be keeping track of it.
Charles
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*often times on brass engines, the wheel with the gearbox has stiffer suspension than the rest, creating a sort of seesaw effect, where not all wheels are putting equal force on the track.
**=flanges scraping against sides of track will provide more traction,thats why engines pull more on curves. rigid wheelbase=more horizontal force on flanges against track.
***=too high and the load will pull the front of the engine up.
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Modeling the PRR & NYC in HO
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Lastspikemike Interestingly, diesel models seem quite predictably uniform in their pulling power and roughly correspond to prototype patterns: bigger and heavier pull proportionately better. This is not the case for steam locomotive models which is frankly a bit weird
Interestingly, diesel models seem quite predictably uniform in their pulling power and roughly correspond to prototype patterns: bigger and heavier pull proportionately better. This is not the case for steam locomotive models which is frankly a bit weird
That's why I model steam!
I assume it has to do with having enough weight with the correct distribution to have the steam power appropriately transferred to the rails (not totally unlike like getting a car engine's torque/hp transferred to the tires) in order to get the maximum pulling power.
In the prototype the design reality of the innards were pretty consistent from producer to producer compared to our models....IMO, and the bigger the loco the more it weighed proportionally to a smaller loco.
Adding ballast mattered some, but the weight of the mechanicals and "shell" of the prototype alone was proportionally heavier than the weight of the mechanical innards and shells of our models.
With the models, weight (or added ballast) is a much larger component of the overall weight of the loco...IMO... and with different producers have different innards, there has to be enough space to add the weight in the right spots.
Probably not consistent from producer to producer, or even small loco to large.
- Douglas
I have little mechanical engineering in me, only personal experience with my locomotives.I totally agree with the blind drivers being less adhesive. My Bachmann and Bowser 4-8-4s are not good pullers, run and look good but puny drawbar for such a large locomotive. All have stock weight and motors.My Rivarossi articulateds have very nice drawbar, 5.8 to 6 oz. Most have 8 to 10 ounces of added weight and at least one new can motor, many have dual can motors. They weigh in at 19 to 20 oz. each or around 30% traction, more wheels higher percentage?? Dual motors don’t have any effect on drawbar they just run better. The original Rivarossi drive locking the two driver assemblies cause them to have a slight wobble, the dual motor floating driver assemblies don’t wobble.Most of my diesel fleet are Athearn three axle truck, a few Proto 2K three axle truck and a few Model Power E-7s, again three axle trucks most with a lot of added weight. My Athearn E-7s have Cary metal shells on SD40-2 frames with can motors, weighing almost two pounds each and have 8 oz drawbar or 25% as mentioned above.If someone wants to up the drawbar on their locomotives they can add weight but make sure the motor will handle the higher current. A single can motor in a 4-8-8-2 with the added weight is around 560ma at wheel slip, with dual can motors they run about 275ma each.My remotored E-7s draw a bit over 800ma at wheel slip, 8 oz drawbar, a pair will pull your sox off.Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
LastspikemikeFriction is a coefficient.
friction is a force (lbf). the coefficient of friction is a scalar
LastspikemikeI suspect but don't know that nickel silver alloy (mostly copper actually) has a pretty poor coefficient of friction.
the coefficient of friction depends on both metals. No need to hypothesize, there are tables: friction and friction coefficients
LastspikemikeAs for weight distribution on the drivers that is not relevant to total tractive force because friction is a coefficient.
LastspikemikeThe locomotive will develop the same tractive effort whether the drive wheels are equally loaded or wildly different loading, until the rail gives.
doesn't matter until one wheel starts slipping and all the rest follow. max tractive effort therefore depends on the max force of the wheel with the least weight
LastspikemikeThe drive wheels are all locked together. They can't slip just because one wheel develops less tractive force. They all slip as if they were one big wheel.
the force applied by the cylinders is evenly distributed on all wheels because they are locked together, but the friction on each wheel depends on the weight.
when the force exceeds the friction on that one wheel, the force then shifts to the remaining wheels which usually exceeds the friction on those wheel and they immediately slip.
LastspikemikeWhen we speak of friction we are actually speaking about the coefficient and not the force.
huh? the coefficent of friction will be the same on different types and sizes of locomotives but the friction determining the max tractive effort of a specific locomotive depends on the weight of the locomotive and the number of drivers.
Well, the list of variables here is pretty long, and lots of people have touched on many of them.
And, with steam loco models, what is a major factor for one model may be of no concern for another.
I have a pretty good sized steam fleet, I pull long trains, I have done some testing. And I have added weight and made other modifications with considerable success in most cases.
I am not going to try and offer all my thoughts on this topic in one post.
In this converstation some will try to rely completely on known prototype engineering theory, some of that has already come up. I wish it was that simple....
A few basic observations based on my 53 years at this:
Balance of weight on drivers does matter.
Springs on leading or trailing trucks will often reduce tractive force.
Sprung drivers sometimes help, sometimes not.
Vertical curves in track are a problem........
Sharp radius curves are a problem.......
More axles mean more potential losses and problems.
Yes, drawbars can complicate the issues, in several ways.
Now, example one:
Bachmann Spectrum USRA Heavy 4-8-2 vs Bachmann Spectrum USRA Light 2-10-2
These two locos share the same boiler, just like their prototypes.
The 4-8-2 is driven by the second driver, and has a sprung third driver, all others fixed with minimal vertical play. This puts most of the weight on the second and forth drivers, with the others more "floating". These locos pull well, mine will pull 35 of my 5 oz piggyback flats on level track.
The 2-10-2, same basic weight, same cast boiler, is driven from the third driver, and has no driver springing. Driver three is blind, like the prototype. The first and second driver have minimal vertical play. Drivers 3 thru 5 have noticable vertical play. This has the effect of putting most of the weight on drivers 2 and 5 on level track, but potentially shifting that weight to drivers 2-4 on some vertical curves.
This loco also pulls well, but not quite as well as the 4-8-2. It handles about 30-32 my piggies comfortably.
So in both cases, due to rigid wheelbase length, the engineers at Bachmann decided to purposely take the weight off some drivers and focus it on others to allow the loco to track better in vertical curves with less shifting of weight from driver to driver.
I have observed this design principle in other brands and models.
That is enough for tonight. Next we can consider my kit bashed Mikados, built from Bachmann 2-8-4's and with added weight.
LastspikemikeAs long as the weight is within the driver wheelbase it shouldn't matter where it goes. Adding weight outside that wheelbase gets you into possible leverage effects which should not matter in most situations but it might in some.
The added weight doesn't all need to be within the drivers' wheelbase. As long as the additional weight is balanced at the mid-point of the driver wheelbase, it will be effective in increasing traction.
Wayne
Lastspikemike Friction is a coefficient. Unless steel on steel develops the same coefficient as whatever model drivers are made of on nickel silver the model cannot match the prototype.
Friction is a coefficient. Unless steel on steel develops the same coefficient as whatever model drivers are made of on nickel silver the model cannot match the prototype.
I agree with greg. friction is not a coefficient, but rather a force. In modeling, we generally are less worried about that, but rather the coefficent of friction, which determines how much the weight affects friction, and is different for all materials/situations.
Lastspikemike The nickel silver part is a constant. Bronze rails likely would be stickier, as used in G gauge, but that's just a guess. What is the ideal metal for drivers though?
The nickel silver part is a constant. Bronze rails likely would be stickier, as used in G gauge, but that's just a guess. What is the ideal metal for drivers though?
I believe friction between metals is likely more due to how soft each metal is. Even so, I'd argue that the finish on the metal is more important than the metal itself. In theory if you were to put diamond tread on a steel engine wheel, and placed it on a track that has a similar finish, that will run the sh!t out of any nickel silver plated wheel.
Lastspikemike As for weight distribution on the drivers that is not relevant to total tractive force because friction is a coefficient. Uneven weight produces proportionally differing traction force for each driver but the total is the same (not the case for pneumatic tired vehicles just btw, but air filled rubber tires are really weird structures) . For prototypes weight distribution matters only because of rail carrying capacity, not a concern for our models.
As for weight distribution on the drivers that is not relevant to total tractive force because friction is a coefficient. Uneven weight produces proportionally differing traction force for each driver but the total is the same (not the case for pneumatic tired vehicles just btw, but air filled rubber tires are really weird structures) . For prototypes weight distribution matters only because of rail carrying capacity, not a concern for our models.
weight distribution is most certainly relevant. I may not know the math behind it all, but I know from experience that if the center of balance for the weight of an engine is off, that it will pull less than one with proper weight distribution.
In fact, I presume that's why Sheldon placed additional weights near the front of his Bachmann 2-8-4. I dont have one of these engines, but I will soon. I recall from various reviews that the center of balance is between the third and fourth driving wheel, which allowed it to pull a less-than-satisfatory amount of cars(<20). The common solution is to place more weights near the front.
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In fact, that is why so many MTH steamers perform so pitifully without their stock traction tires. Because they cram a huge smoke unit into the front of the boiler, the center of balance of the engine is so off that it ends up requiring traction tires.
An MTH USRA 2-8-2 pulls only 9 bluebox 40' cars(theyre under weight) before it slips.
An MTH K4 pulls literally 3 bachmann P70 coaches with walthers oiled trucks, and still slips occasionally.
With traction tires, performance is satisfactory. Still, that's a compromise I would rather not take.
Any actual physics involving friction will note it as a force, with units of a force, and in vector analysis corresponding to a force even though the mechanics that produce it are acting at a substantial angle. The reason we use coefficients is that they are dimensionless numbers; see Cd in streamlining for a comparable example.
There certainly were tables carefully comparing the coefficients of different materials at different surface finishes (which is an important characteristic so far missing from the present discussion). As I recall ASTM has standards for how to conduct meaningful research in 'undocumented' combinations and perhaps geometries, and it would be relatively simple for someone with, say, access to a college lab to do careful analysis of various materials on nickel-silver (perhaps even against nickel-silver rail of various states of 'gleam') as part of the investigation I keep hoping to see.
There are some other concerns here. In the prototype, there is clear deformation and surface-welding in the contact patch, less deformation and wear in the wheeltread than in the railhead by design. I very much doubt anything of the kind occurs in nickel silver rail, particularly that which is extruded with a sharp shoulder in the contact patch/gauge corner area as so much commercial product is. On the other hand I have never read an analytic discussion of model wheel wear, which is an obvious effect and often noted as an obvious problem -- I'm sure there are experienced people on this list who can tell us the operative mechanisms that produce it on both driven and non-driven wheels. In my slim experience with steam-locomotive models that have severely worn wheels, the drivers appear to be little if any more deeply worn than the 'carrying' wheels in the trucks, which I expect to be significant in appraising the various wear mechanisms.
Note that wheels ought to be both precisely machined and tread-hardened (as all good modern wheels have been since the days of chilled-iron tread) so that sacrificial distortion and wear is as much as possible seen in the railhead (where it can be dealt with effectively with magic-wear-rate techniques). It occurs to me that a case could be made for hard coatings and even superfinishing of model treads, both for rolling and for traction. This would particularly involve steam-locomotive driver tires, where hard coating is compromised by soft substrate and perhaps improper plating techniques. Remember this is rolling friction, not laterally engaging friction (so for example we can expect vertical engagement of asperities, but not sliding surface welding or upsetting), and a little review of why creep control is important in achieving 'best' full-scale adhesion numbers ought to be done even if 'it turns out' there is no comparable effect practically to be achieved at model scale.
As a personal prejudice: I have never understood why people think that power transfer through typical primitive model side rods, with ridiculous bearing clearances and no particular attention to tribology, is going to produce particularly equalized or steady torque at the wheelrims. I suspect that very careful precision quartering (in models, for sameness and not precise 90-degree, but you almost need the same quartering-machine pin-grinding precision for either...) followed by some sort of acetal bearing accurately pressed to dimension in the rods, would give the proper combination of running freedom and consistent force transfer when loaded to 'share the torque' with the motored driver pair(s).
I won't get into the theories of slip in steam locomotives as expressed so far, except to note they don't particularly jibe with either observations in practice or actual theory for locomotive design.
I don't know much, but I do know some things from experience. I run short trains (6 to 12 freight cars), so pulling power really does not mean much to me.
This I know: My Oriental Powerhouse Light Mikados would pull a 12 car freight train around my layout, but the Athearn Genesis Light Mikado would not even pull a six car train around the 24 inch radius curves.
Physical experimentation and real world experience mean more to me than theory. Any model locomotive that does not live up to my needs must be a total lemon in the drawbar pull department.
The Athearn Light Mikado was junked and its nicer-looking tender is now coupled to one of the Powerhouse locomotives.
-Kevin
Living the dream.
SeeYou190Physical experimentation and real world experience mean more to me than theory.
Part of the issue, though, is that you have nothing but black magic and trial-and-error to account for why the stuff you do works -- you cannot, for example, account for why some locomotives appear 'slippery' while others don't. One of the great trends in engineering becoming an actual profession is developing the models that can actually serve as good predictors for performance ... or to explain anomalous or seemingly-mysterious results (or achievements) in reproduceable terms.
There is very little objective reason to junk a model as a 'lemon' when you can't even tell me why it doesn't do what its wheels, and basic physics, say it should. Not that there aren't plenty of people who do, and not just in models -- and not necessarily for expedience as in the likely case of the PRR T1s... in a world where practice matters, and time is valuable, we have come to specialize design engineering and proof testing as a profession, as nobody else has the time to waste learning to re-invent the watch before learning to build it when the object is to know the time. (Fortunately or unfortunately, someone will need to know a great deal about how watches are designed and constructed if they have a timepiece that is observed 'not to be keeping time' and it is then important to have watchmakers instead of 'parts changers' finding correct solutions to guide and inform practice.
OvermodThere is very little objective reason to junk a model as a 'lemon' when you can't even tell me why it doesn't do what its wheels, and basic physics, say it should
Certainly not what you would consider an objective reason, but in my world, tools and equipment that do not meet my needs are unceremoniously disposed of and something that meets my needs is obtained.
I will not waste my time and energy fixing what a manufacturer should have done right in the first place. Especially if there is something else available that will get the job done.
Why it does not work does not interest me. The designers should have a keen interest in that, not kick the can to the consumer to deal with.
My needs for pulling power are so low, that this should be a non-issue for me.
Overmod Part of the issue, though, is that you have nothing but black magic and trial-and-error to account for why the stuff you do works -- you cannot, for example, account for why some locomotives appear 'slippery' while others don't.
Part of the issue, though, is that you have nothing but black magic and trial-and-error to account for why the stuff you do works -- you cannot, for example, account for why some locomotives appear 'slippery' while others don't.
There are professional baseball players who are paid tens of millions of dollars a year for their skills, knowledge, and judgement. You'd be shocked (and/or amazed and/or amused) at the empirical data they rely on or the reasons they give for changing bats.
Robert
LINK to SNSR Blog
LastspikemikeObserve a locomotive with blind drivers that don't touch the rails. It will still move and pull a train.
if a driver isn't making contact then the friction on the remaining wheels will be greater and the cylinder force will be distributed over fewer drivers
LastspikemikeI doubt there is a published table comparing the coefficient of friction of those two materials to that of steel on steel, for example.
do you look at the links posted in comments?
here's a partial table, previously posted, Friction and Friction Coefficients (click the link?)
SeeYou190Certainly not what you would consider an objective reason, but in my world, tools and equipment that do not meet my needs are unceremoniously disposed of and something that meets my needs is obtained.
The discussion here is more about mistaken theories that lead to throwing engines that might be relatively easily salvaged out because the problem with them was misunderstood or mischaracterized. That might not be important to many people, but some (particularly those who had to scrimp to afford the engine in question) may not have the luxury of 'letting it go' -- and for those, if you have a slipping engine it may be valuable to understand something about what you can do and where to put the effort.
ROBERT PETRICKYou'd be shocked (and/or amazed and/or amused) at the empirical data they rely on or the reasons they give for changing bats.
That this is somewhat unlikely is a major point of what I've been trying to say here.
Couple more thoughts:
Adding weight to the extreme front and rear of the loco will improve the tractive effort of the loco....as long as the weight is equidistant from the midpoint of the drivers....or in the case of our models, equidistant from the driver(s) that actually does the work.
If the nickel silver drivers of our models are so slippery, why don't they make the drivers out of the sintered metal that Athearn made for their old BB diesel trucks? Electrical pickup problems? Certainly those BB trucks picked up track power decent enough.
DoughlessIf the nickel silver drivers of our models are so slippery, why don't they make the drivers out of the sintered metal that Athearn made for their old BB diesel trucks?
Doughless Couple more thoughts: Adding weight to the extreme front and rear of the loco will improve the tractive effort of the loco....as long as the weight is equidistant from the midpoint of the drivers....or in the case of our models, equidistant from the driver(s) that actually does the work. If the nickel silver drivers of our models are so slippery, why don't they make the drivers out of the sintered metal that Athearn made for their old BB diesel trucks? Electrical pickup problems? Certainly those BB trucks picked up track power decent enough.
There's a trade off. The more "texture" you have on wheels, the more traction it may have, but the easier it will pick up dirt from the track.
Those old BB wheels needed a wheel clean after a few hours of running.
Also I prefer the look of nickel plated wheels.
Just thinking that they could do something other than traction tires with those rubber inserts.
OvermodDon't like iDrive?
Had to look this up. Down here "I-Drive" is International Drive in Orlando. One of the most fun streets in the entire World. I was thinking... who doesn't like I-Drive?
Trainman440There's a trade off. The more "texture" you have on wheels, the more traction it may have, but the easier it will pick up dirt from the track. Those old BB wheels needed a wheel clean after a few hours of running...
While I do agree that those wheels tended to accumulate a lot of dirt, I don't recall ever having to manually clean them. Instead, I'd simply couple the locos to a heavy train and send them up a decent grade. Once the wheels started to slip, the crud flew-off in chunks, faster than your cat sheds on a new custom-made suit.
Gary
SeeYou190The Athearn Light Mikado was junked
I hope that the word "junked" was not literal, as despite the poor pulling power, the Athearn Mikados were otherwise very smooth runners.
SeeYou190...This I know: My Oriental Powerhouse Light Mikados would pull a 12 car freight train around my layout, but the Athearn Genesis Light Mikado would not even pull a six car train around the 24 inch radius curves...
In Overmod's initial post in this thread, there's a sub-quote from Lastspikemike referring to my link to another Forum, where a thread showing a method of increasing the pulling power could be viewed.
While the procedure might not have been all that simple for beginners, it certainly wasn't complicated nor did it require much in the way of special tools or materials, and I think that it was fairly well-illustrated, too.After seeing some of the great work that you do, I don't doubt that had you known of that thread, you could have easily made your Athearn Mike into a decent puller.
A half hour-or-so ago, I grabbed one of my modified Athearn Mikados, then coupled 20 Accurail boxcars, and a TrueLine caboose to its tender. It left the staging yard easily, and then proceeded down a fairly steep grade, and into a similar up-bound grade....
With much of the trailing train still coming downhill, the loco made it onto level track again...
...but once the cars were all now heading uphill, the loco slipped its drivers, and I had to put the 0-5-0 helper into service. This took the locomotive to a downhill run, but with some of the last trailing cars still heading uphill, the loco struggled until all but the last 3 or 4 cars were on level track...
The loco and train then proceeded down a 2.5% grade, and then through a small town on level "ground"....
From there, it entered a fairly wide curve (34" or 36" radius) on a slight downgrade ...
and then onto the longest stretch of level track on the lowest portion of the layout with one major curve of about 34" radius...
Granted, my track curves are at somewhat larger radii than yours, but on this portion of the layout the locomotive handled the train without issue. Total trailing weight (tender not included) was 84oz. or 5.25lbs.
In normal operations, the train would be, at most, 15 or 16 cars, and would have 2 such locomotives.
I"ve worked on a couple of those Powerhouse locos, for a friend, but if they were mine, I would have simply created floors for the tenders, and mounted the trucks in a manner similar to that used on most tenders and freight cars.
doctorwayneI hope that the word "junked" was not literal, as despite the poor pulling power, the Athearn Mikados were otherwise very smooth runners.
I used the tender on one of my Oriental Powerhouse Light Mikados. The Powerhouse models have terrible tenders, so the Athearn Genesis tender was an upgrade.
The resulting Hybrid model is something I am quite happy with. I hope to find another tender from an Athearn Light Mikado for my last one.
The third Powerhouse Light Mikado I own was upgraded with a Tenshodo brass tender.
I had three steam locomotives I was not happy with. A Mantua 2-6-6-2, a Bachmann 4-8-2, and the Athearn Mikado. I have plans to revive the Mantua and Bachmann, but since I have 5 other USRA Mikados (3 Powerhouse and 2 Sunset Heavies) for my smallish layout, I saw no reason to put effort into fixing the culprit. The tender was put to good use.
I decided to resolve some of this by looking up actual research, for example the Maine On2 FAQ discussion very specifically related to the present topic. What I've found so far has mostly been a methodological hash, with most of the actual historical work dancing infuriatingly around what is actually needed to advance fundamental knowledge. I regrettably conclude that some basic research -- actual scientifically-principled research, not calculating 'coefficients of friction by the inclined slope method' by someone claiming nearly a quarter century in the 'friction-reducing business' by putting a scale on model railroad stock rolling downhill -- is going to be required on both the actual alloy composition and the effect of drawing (and then surface prep) before anything better than the current state of anecdotal and empirical research, often full of wack assumptions, can be developed. When I have done some more research, I will put at least a proposed methodology for review here; in the meantime look up the Maine On2 reference and list the issues or concerns you have with their analysis and references...
... and somebody tell me the specific alloy composition of popular brands of track. B10 is about 13.38% nickel, probably the lowest proportion that gives a reasonably 'white' appearance. Conductance still goes down markedly with increasing nickel n this range of nickel concentrations, so the 'less' nickel the better from that perspective. I have the suspicion that at least some rail is actually a nickel brass, or contains additional effective alloying agents at small concentrations, rather than being a binary alloy.