I am building a locomotive for a pulling contest. I am wondering what wheel sets would provide the maximum traction on nickel-silver track. While I have many chemistry and minerology classes under my belt none of them have been metallurgy related. I can find all sorts of information about steel on steel, nothing about NS.
I think my options for wheels are: NS, normal zinc based brass, the iron like Athearn BB locos, or steel. Does anyone know what “sticks” best to nickel-silver track?
Traction tires.
well that would be an addition after the fact I guess if I didn’t care about electrical pick up I could also add plastic to the list. But that doesn’t answer the fundamental question. There is also bull frog snot…
… and there is still weight! I don´t like traction tires on locos, as they appear to leave a gooey film on the track, hampering electrical pickup. Adding weight helps to improve traction.
I don’t know where the sintered wheels of Athearn BB fit in. I suspect they change with time as the polishing and smoothing reduces the adhesion of the rough (in comparison) surface.
Of the others, steel has the best adhesion on any common rail material. Steel on steel is better than steel on nickel silver. But steel on nickel silver is best, followed by brass, with nickel silver being the worst of the 3. Really high end model locomotives now have stainless steel tires (using a machinable alloy). Custom model locomotive builders used to use rolled steel for drivers but switched to stainless steel to avoid rust on a locomotive that would end up in a display case as often as it would be run.
my thoughts, your choices
Fred W
This implies that there may be a set of rules. Get them and read them.
If no mention of wheel material is in the rules, find someone who can make you rubber wheels or use traction tires. Add a car or other device in front of your locomotive for electrical pick-up. Add a lot of weight and a BIG motor. Who cares how it looks unless the rules say that it has to be a scale locomotive.
If there are no rules, then that suggests that you can do anything you want.
I agree with the weight. I would use a steam loco with nice large wheels which put more surface area on the rails. Also keep gear ratio low. Experimenting with the right decoder settings would be good as well.
If traction tires are allowed you can allow the tender to do the power pickup, allowing more bullfrog snot to be put on the Loco.
Well just a thought but like on the prototype you don’t want a smooth surface on a smooth surface so they drop sand on the rails correct, So your obviously not going to make sand feeders on this locomotive so I would think the next best thing would be to rough up the wheel surface. I would try experimenting with an air eraser to texture or roughen the surface of the wheels. I’m not sure if your familiar with one or not but for those who aren’t it works just like an airbrush but instead of spraying paint it sprays a fine silica material just like sand blasting. I just started cleaning a couple of corrugated metal building that I were in a lot of stuff I purchased and the builder did a nice job except when it came to the paint job.lIt looked like he slopped it on with a brush. The air eraser removed the paint in a flash and left behind a sort of satin finish to the metal.That little bit of texture might be the difference between you and the next guy.
Good Luck
A quick hit with 1000 grit sand paper might do the trick as well. It would be ashame though to screw with the wheels for a single contest. We still haven’t heard what the rules are.
Depending on the rules, I would suspect traction tires or other artificial means of altering the wheels would be prohibited.
I’ve found Athearn’s sintered iron wheels to work well. Use a full carbody-style locomotive, preferably with three axle trucks, and a good-sized motor, although it doesn’t have to be huge. The locos shown below are over-powered and would likely have been even better pullers with only a single motor and more weight in place of the second motor. While I no longer have these locos, there’s room for another 6 to 8 ounces of weight that could be hidden on the carbody, mainly under the end walkways and around the couplers. Each unit weighs just over 33 ounces and has a drawbar pull of 8.3 ounces. Viewed from trackside, their power potential isn’t noticeable, nor is it by their current draw.
This modified Akane USRA 2-10-2 weighs about the same (loco only) as one of the U-boats, but even though the weight is balanced at the centre of the driver wheelbase, it doesn’t pull anywhere near as well as one of the diesels.
Also, even though the motor is much larger, it’s at the upper limit of the amount of weight that can be added, as it’s just able to slip its drive
While this has gotten way off topic. I have been debating the multi-motor vs. more weight. I think the true answer is that it is dependent on the torque rating of the motor - two torquers would do better than more weight but a normal high speed motor would probably do better by itself with more weight and lower gears.
Actually back to topic - I was hoping someone would actually have the formula for calculating adhesion between two metals.
Back to the OP’s question:
When I was a member of the Penn State University Model RR Club, during the early 1990’s, some of the members were very serious about the pulling power of their locomotives.
They had found the Athearn sintered wheels to be the best for pulling power.
The members of the Penn State Model RR Club were adamant that the Athearn sintered wheels lose their pulling power as they wear in because they become polished–so they also replaced them periodically (we had been left with some severe layout grades by previous members).
In more recent times, the Athearn Genesis FP45/F45 has wheels that, to my eyes, seem to recall the sintered wheels of the past, but they are still smoother. With its high weight, the Athearn Genesis FP45/F45 is a real beastie when it comes to pulling a train.
My 2c.
John Mock
The only figure I know is that for dry steel on dry sanded steel on the prototype, the coefficient is about 25%. That means 25% of the locomotive’s weight on the driving wheels could be translated into drawbar pull.
The model case is always less (assuming no traction tires), due to vibration from gears, lack of sand, degree of polish, and different materials. From my experience, I would estimate nickel silver on nickel silver to be around 15-18%. From my reading, the best models achieve around 20-22%.
Motor torque beyond the ability to slip the driving wheels under power is wasted in extra motor space that could be used for additional weight.
Weight centered over the driving wheels is much more effective than off-balance weight at the ends. The center of gravity needs to be at the midpoint of the driving wheel base.
Equalized driving wheels will have a higher coefficient of adhesion than a rigid frame because every driving wheel remains in contact with the rail head.
Non-tapered wheel treads have more surface area contact than tapered wheel treads, and hence higher adhesion, but have lots more friction rounding curves. This obviously assumes rail heads are flat and level - the Brits mount their rail heads at an angle to match the wheel taper.
best of luck with the contest
Fred W
Well, the force goes F = a*G.
F=gliding force
a=coefficient for gliding for the two materials
G= weight of the engine
You have to drive all wheels. From this formula I think weight gives more than the material. Look here, so I think steel tires would be good at first point, but then comes weight! Compare with cast iron to copper and zinc.
Wolfgang
I agree with Wolfgang: the material used for the wheels will have a negligible effect compared to the overall weight of the locomotive.
Most good-quality locomotives available are overpowered for their weight, or, perhaps more correctly, underweight for their power. I mangaged to improve the pulling power of my Athearn Mikados (notoriously poor pullers due to their light and unbalanced weight) by adding about 4.25 oz. of balanced weight, which was all that could be concealed within the locos’ shells. However, the same locos were still able to slip their drivers with an additional 2 lb. “saddle” of sheet lead draped over the boiler. [:O] (I coulda made 'em all into saddle tankers, I suppose, but then they would’ve had clearance issues at several points around the layout.) [swg]
It would probably be useful if we knew the rules for this contest. An Athearn DD40X (or whatever it was called) with the original motor(s) and wheels (eight wheel trucks, I believe) along with its overly-wide hoods would be a good starting point. Remove the wiper-style current distribution and replace it with wires. Remove the flywheels, too, and don’t waste interior space on lighting and/or DCC circuitry. Fill all available space with lead, custom-cast or shaped to fill every nook and cranny. Don’t forget the space under the end walkways, cab roof and bottom of the fuel tank. (And, yes, I recall reading about the modeller who did this using depleted uranium). Another suitable candidate would be the original Athearn FP45 with similar modifications.
Wayne
Hey Zephyr,
Do you have the rules available to post?
This link here has a good explanation of friction forces. The coefficients you are talking about are generally found experimentally but uses the formula below (rearranged to find the coefficient of friction)
Usually you will use the static friction coefficient when the wheels are not slipping. the kinetic friction force is used when the wheels start slipping (spinning while not moving) on the rails.
Friction force =Weight*coefficient of friction
The friction force is how much of a load the locomotive can theoretically pull.the coefficients of friction are usually found experimentally and are generally in look up tables in most physics or statics textbooks.
if the load of the train exceeds the friction force the wheels will begin to slip.
Dirt.
If you make your wheels out of dirt you can even run the trains upside down and they’ll stay glued to the track. Its even better than magnetraction!
John
Easy…Find a Hobbytown RS3…Nothing made today can match its pulling power.
No, I do not. Unlike what most people seem to think, I am not asking for help on winning the contest. The design is already done except for which wheels to put into the trucks. So while the advise might be well intended it doesn’t address the question at hand.
I believe with the numbers I am estimating from the formulas given in the links from Charlie’s post and the coefficient numbers I already have access to. I am going to go with the Athearn iron wheels. Unfortunately I don’t have the time to experiment. Otherwise I would just buy a set of each and put them on the scale.
And oh by the way I have several Hobby Town locos including RS-3s both with and without the clutch. They don’t stand a chance.