Williams Electric Trains

[chuck]

Isn't 3-4 cars for a 70 tonner about right?

The 45 ton GE industrial locomotive was rated to handle 20 fully loaded cars on level track with a top speed of 32 mph. It had twin diesel engines that were rated at 150 hp. The 70 ton units had a single engine rated at 600 hp but a top speed of 60 mph.

[rogruth]

OK but 3 or 4 would look better on most of our layouts.

[Rufus T. Firefly]

OK but 3 or 4 would look better on most of our layouts.

Scale that 20 cars down by 1/4 and how about 5,

[webenda]

Isn't 3-4 cars for a 70 tonner about right?

The 45 ton GE industrial locomotive was rated to handle 20 fully loaded cars on level track with a top speed of 32 mph. It had twin diesel engines that were rated at 150 hp. The 70 ton units had a single engine rated at 600 hp but a top speed of 60 mph.

Looking at videos of the GE 70 Tonner in action i don't see it pulling more than 6 cars at branch line speeds (30 mph?) on level ground.



The Pacific Southwest Railway Museum owns ex Southern Pacific GE 70 Tonner #5119.



To quote PSR, "The normal procedure for lighter trains at the museum is to use the museum's GE 80 Tonner, SD&A 7285, to pull them. 3 cars are well within the pulling capacity of 7285, so it was able to pull the morning train. However, the afternoon train had been chartered for 3 additional cars. The now 6 car train would be very heavy and raised concerns about 7285 not being able to pull the train up the hill. The solution was to put SP 5119 into service."

https://youtu.be/SneQrQbALQw

"The Hill" is six miles with a steady 1.3% grade. I had no idea the real 70 and 80 ton GE locomotives were so wimpy.

As a side note, the two electric motors in the Williams 70 tonner are rated at 0.005 combined horsepower.
Now if we scale that up 48 times 0.005 x 48^3 = 552.96‬ horsepower.

NOTE--Everyone is invited to challenge my math.

[Roy]

...the two electric motors in the Williams 70 tonner are rated at 0.005 combined horsepower.
Now if we scale that up 48 times 0.005 x 48^3 = 552.96‬ horsepower.

NOTE--Everyone is invited to challenge my math.

I'll bite. Why are you cubing the scale factor?

[Rufus T. Firefly]

...the two electric motors in the Williams 70 tonner are rated at 0.005 combined horsepower.
Now if we scale that up 48 times 0.005 x 48^3 = 552.96‬ horsepower.

NOTE--Everyone is invited to challenge my math.

I'll bite. Why are you cubing the scale factor?

Volume?

[chuck]

Weight/mass is non dimensional. We can debate what a railroad car would weigh if we shrunk it down to 1/48 size. I don't know how we are going to scale the atoms/mass since the car is just a replica. We aren't operating in 1/48 scale gravity either. Flying scale model planes aren't really "scale" because they are operating in 1:1 air. The wing chords are adjusted to get the model to fly and the air speed is the non scale (aka 1:1) real airspeed.

and raised concerns about 7285 not being able to pull the train up the hill.

aka HILL, aka NOT FLAT

From Wikipedia article on the GE 45 tonner:

The GE 45-ton was extremely versatile and many variants existed. It has a high weight to power ratio and has excellent traction, rated to be able to pull 20 loaded freight cars on level track.

Now theses were built in WW-2 and the size/loading of freight cars was considerably lower so the car count for modern equipment would be considerably less.

[webenda]

...the two electric motors in the Williams 70 tonner are rated at 0.005 combined horsepower.
Now if we scale that up 48 times 0.005 x 48^3 = 552.96‬ horsepower.

NOTE--Everyone is invited to challenge my math.

I'll bite. Why are you cubing the scale factor?

I would like my 70 tonner to grow big in three axis; x, y, and Z. It would look funny it it was 37 feet long, 10 feet wide but only 3.25 inches high. Might tip over if it was 37 feet long, 13 feet high but only 2.5 inches wide.

[Roy]

Wayne, even if you blew your toy up forty-eight times with your special scale sauce, it would still have only two powered axles, and a plastic shell. No prime mover or generator weight. It would probably be a shitty puller, compared to a real 70 tonner.

I think we can dispense with the scale sophistry. If you're happy with a $350 doorstop, fine. I'm curious why Bachmann didn't power both axles on each truck, and why they went with their completely under-floor drive design if, as seems to be the case, that necessitated under-powered motors, and undersized worm wheels.

[Roy]

The 45 ton GE industrial locomotive was rated to handle 20 fully loaded cars on level track with a top speed of 32 mph. It had twin diesel engines that were rated at 150 hp. The 70 ton units had a single engine rated at 600 hp but a top speed of 60 mph.

...From Wikipedia article on the GE 45 tonner:

"The GE 45-ton was extremely versatile and many variants existed. It has a high weight to power ratio and has excellent traction, rated to be able to pull 20 loaded freight cars on level track."

Now theses were built in WW-2 and the size/loading of freight cars was considerably lower so the car count for modern equipment would be considerably less.

Interesting. I really like 45 ton center cabs, with their rods and counterweights. I have no use for end cab switchers.

[webenda]

Chuck, you crammed a lot of information into a small post. It has taken some long thought (AKA Googling) to address each point.
Here we go...

Weight/mass is non dimensional.

Totally, totally mass is non dimensional but has nothing to do with what a scaled up version of what Williams 70 tonner would weigh. I haven’t weighed mine yet but when I do I might just have some fun comparing what it would weigh scaled up to the real GE 70 tonner.

We can debate what a railroad car would weigh if we shrunk it down to 1/48 size.

Why would any sane person want to do that when we can easily calculate the weight?

I don't know how we are going to scale the atoms/mass since the car is just a replica.

The size and mass of atoms is a constant. To make something bigger or smaller you do not scale the atoms, you add or subtract atoms to or from the item being made larger or smaller.

We aren't operating in 1/48 scale gravity either.

Well no, we are not operating in 1/48 gravity, gravity in any one location on earth is a constant, no matter what scale we make our trains. That is a good thing.

Flying scale model planes aren't really "scale" because they are operating in 1:1 air.

I thought we were talking about trains. Well, if you want to thread drift, fine. I fondly remember the time my Aerodynamics 101 teacher told the class that flying wings were unstable and used the crash of the Northrup YB-49 as proof. I immediately began making a paper model of the YB-49 at my desk. After class, I waited for the last student to leave before telling him the YB-49 flying wing was not unstable and showed him the reflexed airfoil of my model. I explained that the reflex served to stabilize the pitch of the wing just as the horizontal stabilizer stabilizes the pitch of a conventional aircraft. I then pitched the model at the back wall. I was a little shocked that on its first flight it flew straight over the desks and hit the back wall. I then said, “See, stable.” The teacher said that a paper model does not test the design of a real airplane and if I didn’t like the way he was teaching, GET OUT!”

The instructor made the same point you just did, and I understand, little trains will never behave like full size trains.

The wing chords are adjusted to get the model to fly and the air speed is the non scale (aka 1:1) real airspeed.

It is not necessary to adjust the wing chord to get a scaled down airplane to fly, adjusting the aircraft's weight works just as well. Both methods change the wing loading.

Getting back to toy trains, sometimes we adjust the length of our scale toys to get them to negotiate non-scale O-27 curves. I guess that would be equivalent to adjusting the chord of a model airplane.

and raised concerns about 7285 not being able to pull the train up the hill.

aka HILL, aka NOT FLAT

AKA. The definition of aka is an abbreviation that means also-known-as.
So, you say hill is also known as HILL and hill is also known as NOT FLAT. Very good Chuck. (FYI, I understand your point, we are talking about level track performance, not performance on grades.)

From Wikipedia article on the GE 45 tonner:

The GE 45-ton was extremely versatile and many variants existed. It has a high weight to power ratio and has excellent traction, rated to be able to pull 20 loaded freight cars on level track.

Now theses were built in WW-2 and the size/loading of freight cars was considerably lower so the car count for modern equipment would be considerably less.

I like your then and now information. Our toy trains are so scale like we have evolved easy rolling trucks to mimic improvements in real trains. As our old friend Pete once said, “Main advantage of modern trucks is reduced rolling resistence. The same engine will pull twice as many cars with modern trucks vs post war bar end or staple end trucks.”
Reference: https://ogrforum.ogaugerr.com/topic/rem ... ing-trucks 7/5/15, 9:26 PM.

Is any discussion of how many cars an engine will pull complete without bringing in THE DAVIS EQUATION?

The “Modified” Davis equation for Freight Cars published in AAR RP-548 takes the form:

R’ = 1.3 + 72.5/wn + 0.015v + 0.055v^2/wn (2)

Note the second term is a constant by the number of axles. In Davis’ work, when most
rollingstock had journal bearings, it was 29lb/axle. The constant in RP-548 is
based on 18lb/axle, for a four axle wagon with roller bearings, which is not immediately
obvious in the formula above.

Great! Frank Szanto worked the equation for us.
Reference: https://www.scribd.com/document/423130043/Szanto-Frank

Onward toy train soldiers...
GE 70 Tonner Tractive Effort (starting) 41,300 lbs @ 30%
Reference: https://www.thedieselshop.us/Data70-ton.HTML

Our Toy Train Mentality, "If it will start a train it will pull it at full speed," allows us to continue without regard to how hot our 0.0025 HP traction motors are going to get.

Old journal box cars
41,300 lbs / 29 lb / axle = 1,424 axles.
1,424 axles / 4 axles / car = 356 cars.

Scale the pulling power down by 1:48 and we get 356 / 48 = 7

New roller bearing box cars
41,300 lbs / 18 lb / axle = 2,294 axles.
2,294 axles / 4 axles / car = 573 cars.

Scale the pulling power down by 1:48 and we get 573 / 48 = 11 cars.

When I get around to testing my GE 70 Tonner I will report on how many cars it will pull (limited to my test track length of 127 inches.

[chuck]

You can build a scale model where all you intend to do is look at it and get the three dimensions 100% accurate. It isn't meant to do anything except look nice. If you want the thing to work/actually function you have to start making compromises in either scale fidelity or performance/behavior. If nothing else, the models are usually made of completely different materials and assembled in different ways.

We have to accept this with our toy trains if for no other reason that few of us have the real estate to support prototypical curves/grades. Trucks centers are adjusted to allow trains to run on non prototypical curves. The toy trains have completely different centers of gravity because the method of driving the wheels is nothing like the prototype. Fricative forces are higher/different because of these compromises.

If your 70 tonner pulls 8-11 cars, great. If it can pull more, all the better for you. If it pulls less than six, c'est la vie. At least it looks good doing it.

[rogruth]

Wonderful discussion.
But remember that most of us buy things we like for various reasons that have little to do with physics and/or math formulas.
Hey,I really did enjoy the disussion.

[chuck]

They are just toys. I don't see any problems with trying to get it as close to "right" as possible. I admire Waynes dedication in terms of his research and I do appreciate his skill at instruction/explanation.

Murph is an extremely talented modeler and I find his contributions to be very valuable. Rufus, Healey, George and several others are all outstanding modelers. I love seeing their work and I appreciate their posts.

Roger, you are way too hard on yourself. Your insight and instincts are also of great value. You got 90% right on the last Whatzit on the first try.

[bluelinec4]

Dont know about the pulling power the real thing but the Williams 70 tonner is a great little engine On the flat it was pulling 15 Atlas 55 ton hoppers without a problem As soon as it hit any type of grade it started burning rubber and spinning its wheels The engine pulled 5 of those hoppers reliably on any grade at the club With the double headed engines 11 hoppers were the max The paint scheme I chose is a NY City Transit owned railroad that hardly ever pulled more than ten cars and almost always had them double headed The Williams 70 tonner sells for $250 in most places but can be found cheaper if your patient and look around