OS 4-8-8-4 BIG BOY locomotive

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I have just started on modeling a recreation of my favorite locomotive in the world ALC 4000 class 4-8-8-4 Big Boy. I was able to get the source files of thing 259005 the big boy by Makerbot. I am scaling it down and modifying it to integrate an electric drive-train. The modeler hired by Makerbot also recently released the tender car for the big boy here. I also plan to include that as part of the whole project as the housing for the control electronics and battery compartment. I have a few questions that I'm trying to answer for myself that some of you may be able to help with. Sense the front have of the engine drive-train pivots, this portion of the system must run on its own motor. What drive-train should I go with for transmitting the motor power to all four sets of driving wheels. More questions to follow as I make progress

Since these models are mostly plastic, you could get away with motorizing one set of wheels (rear) while the front simply freewheels. Or house the motors in the tender, letting the engine freewheel entirely. Those seem to be the easiest and most-used designs I see in the model railroading world.

But if you want to power both sets of drivers, try mounting two sets of gears and motors in each end.

Thanks irab

My previous plan of attack was to make a separate drive-train with the front and rear sets of wheels being powered by their own motors and having a set of gears that distributes the motor power to each axle of the driving wheels via a worm gear system. Late yesterday after reading your comments I had the idea of just sending motor power to one axle via a worm gear then allow the main linkage on the driving wheels to distribute the power among the rest of the wheels.

What are your thoughts on this method?

P.S. At this Scale what would be an appropriate speed for this locomotive? I currently Im looking at getting an output of 400 rpm with the drive wheels gives about 1.8 mph full scale speed not scaled mph

Hi Tris4200,
any progress on the 4000 series model?

Will you build it more in Märklin 1 scale (1:32), or more like Lehmann LGB II scale (1:22,5) ?
Or maybe even something in between like a few OS-Railroaders do (1:29 +/-)?

If I were you, I'd give a motor for each 4 axles, so 2 Motors for the locomotive. That thing might
be heavy, and if realistic, you'd want to pull at least 10 or 12 coaches.
Don't think about powering the tender, that's even harder since all wheels have to give to sideways
forces when you go thru corners. Hard to accomplish, but I have an idea in mind, I'll gladly explain,
if you'd like to hear it.

Since both, purchased model train tracks, as well as OS-Railway tracks can have quite narrow turns,
the wheels need to be able to move to the left or right while still transmitting moving force to the tracks.
I had this in mind since I'd like to design a locomotive that has a 3-axle bogie at both ends, meaning
that the middle axle needs to be able to move sideways, otherwise it can't go thru the narrow turns.
Also, of course, both driven wheel quartets (bogies) need to be able to move to almost 45% angles
to get around these unrealistic turns you get when scaling a railroad that in original stretches thru
a continent needs to be able to fit on a dining table.
Also it needs to be able to cope with uneven tracks, when those grand railroads end up in a rather
humble garden, often seen especially in under- and overpasses.

Good luck! You've chosen the hardest locomotive to build, but in my opinion, it's the most interesting
steam locomotive ever built. I can't wait to print your model.

With my limited knowledge, I'll gladly help you wherever I can.

Hello DJHcom

Sadly the project has stalled for the most part, though seeing your interest is definitely is a kick in the pants to restart working on this. I work as a mechanical designer working in cad software all day so its often hard to have energy to get back on cad software again. I really do love this locomotive as it always blows my mind as it is the pinnacle in american steam power. Also how the engineers back in the day were able to design and build this all using pen and paper. No 3d CAD

in terms of scale I'm working a 1:45 scale as that is the scale of the rail tracks. This loco is going to still be around 2 ft long still at this scale. turning will definitely be a challenge with this locomotive. the tender will be un-powered though I had planned on using it as the home for all the controlling electronics and batteries.

Oh, very interesting. Besides Cinema 4D class and an afternoon SketchUp lesson I'm new to CAD.
Hard to start, and another class I can't afford, since it is only a hobby.

And yes, I admire those engineers who had no help in form of a computer, or even a calculator.
I still use a drawing board from time to time, since my lack of knowledge in CAD.

I got the scale mixed up, I had 1:32 in mind, not 1:45 (0 gauge).
I guess I'd have to scale it up to around 150% and it will fit my LGB tracks.
This would mean it's going to be a 3ft locomotive. I can't wait!

As for the tender, I suggest to only use it to house batteries. That way, you'd only need to connect two terminals to the locomotive,
as it is housing all the electronics. This magnetic quick connector comes to mind: https://www.thingiverse.com/thing:1023944

Good luck, and hopefully hear you soon again.

Magnetic electrical connector for LGB Carriages and Trains