Another Big Boy Model

[bogieman]

There's been quite a few Union Pacific Big Boy locomotives done but I had to try to build one for my home layout. Most recently, Berthil graciously posted this thread and free instructions for his model:

I look for inspiration in models other have built and was especially intrigued by MorningStrummer's model he sells plans for on Rebrickable: 

https://rebrickable.com/mocs/MOC-89126/morningstrummer/4014-big-boy-version-2/#details

I particularly liked the motor arrangement he developed putting the motors on the two driver "bogies" directly rather than in the boiler and running shafts down to the driver axles. I then learned thru a build video on YouTube that MorningStrummer's model was being sold as an authorized kit by Letbricks: 

So I purchased that and assembled it to see how well it worked.

Being a retired mechanical engineer, I just can't leave well enough alone. I found two major items that I felt would improve the model in my application. First, it is advertised to be at 1:40 scale whereas everything I have built to date is 1:48 scale - I found it to be too big relative to my other cars and locomotives. Second, it uses Lego steam drivers 85489a&b (size L per the Brick Train Depot wheel chart) which I feel are too small to get the "right" look yet are the only option available to keep it all Lego. At 1:48 scale, these wheels scale to 57 inches versus 68 inches that the Big Boy used. So I decided to re-scale MorningStrummer's design to 1:48 scale and use Big Ben's XL drivers. I ended up changing a lot.

The larger drivers require a spacing of 5 studs, versus 4 for the L size wheels; after much work on stretching the technic driver bogies I ended up scrapping that design and building with technic bricks instead. I had bought some Circuit Cubes Cubit motors to try out a while ago and decided to try them here since they are so small (2x4x2 high) and fit easily. They exceeded my wildest expectations for their power. Each driver bogie has two Cubit motors for 4 total, no driven axles are in the tender. This is the trail driver bogie before I made some other changes that shows how nice the Cubit motors work:

It's hard to see but I milled a small recess in the rear of the Cubit motor case that allows a Bar 4L slightly shortened to fit between the technic axle 1L with pin (3749) that keeps the pins aligned better to prevent them wobbling in the technic beam hole; the side rods keep the wheels synchronized.

On my first steam locomotive, built from Tony Sava's Southern Pacific Daylight GS-4 instructions, I experimented with a Seuthe smoke generator before switching to a water mist generator I designed and 3D printed. Based on that system, I designed and printed a two stack mist generator with a large water reservoir for the Big Boy. To get more realism, I thought about how I could create a puffing of the steam synchronized to the driver rotation which would be especially evident at low speed. I found a cheap inductive pickup on Amazon that I thought I could integrate into one of the driver bogies and created a mockup to test it out which can be seen in this video:

I was able to mill down the width and length of the pickup to fit in a 2x4 stud space without damaging it. It's simply wired to apply the 12V power to ultrasonic mist generator control board when the pickup detects metal. I ended up machining a trigger wheel that is on the lead axle of the trail driver bogie pictured here:

The mist generator uses two 16mm discs fed from a common reservoir. The assembly connects and supports the smoke box of the locomotive to maximize the water capacity which is enough for more than 1/2 hour. It's printed in 3 pieces as shown here: 

The driver arrangement is F-B-F-B in the lead driver set and B-F-B-F in the trail driver set. It negotiates R56 curves but struggles on R40 but that is not a problem on my layout. I placed the driver bogie pivots as far as I could away from the center of the loco to limit the swingout of the cab on curves but it still can't make my outer loop because the track is too close to the wall in few places that's not easily changed now. The video shows pulling a train around the level loop of the layout (pardon my grandkids play area).

The steam out the stack (mist) doesn't show up very well in the video particularly against a gray or white background. The Seuthe smoke showed up better but it leaves an oily residue that I did not like. Using distilled water, the mist leaves no trace.

With the modified driver spacing, this fits Zephyr's Trained Bricks rod set sold for the Brick Train Depot Big Boy model which is what is seen on the model.

For powering the model, I am using 3X 18650 Li-ion batteries powering an AirWire Convertr C-60 that gives wireless control to a Tsunami2 2200 Big Boy DCC board. The Tsunami board only powers one of the four Cubit motors but generates the sounds via a speaker in the boiler. There is a second Tsunami2 4400 board that drives the other 3 motors and controls the lights and mist generator which is wired in parallel from the AirWire board. One Tsunami2 4400 could control everything but only the 2200 is available with the Big Boy sounds. The batteries and AirWire receiver are in the tender, the rest of the electronics are in the boiler.

I made class lights for the front using Plate, modified with Light Attachment (4081b), by drilling a .09 inch hole in the ring, gluing two 0806 LED's to a bar milled on two sides at 90deg, on flat to pass the front LED wires, the other to mount the side LED seen here:

The model is now about 1/3 Lego parts, I will say the quality of the Letbricks parts is a step below real Lego parts but not terrible. Clutch is uneven, some are tighter, some looser.

I hope I haven't offended anyone with my part modifications, 3D printed parts and starting from non-Lego parts.

Dave

Edited January 29, 2023 by bogieman
added more detail

[Feuer Zug]

We're not offended in this forum if you 3-D print, use third party parts, or modify pieces. I think even the Kragle is allowed for some.

The 4000 class 4-8-8-4 model looks pretty good. Even at 1:48, that's a monster locomotive. Interesting how the motors are attached. Good work on all the electrical wiring. Adding lights, smoke, and sound is impressive. You have quite the layout as well.

[bogieman]

Thanks for your supportive comments.

[Shiva]

Nice :)

[Darkkostas25]

offended not showing it earlier :D (if it was possible) nice iteration and a good entry 
great build good ideas (and prints) 

[zephyr1934]

Okay, so you take a clone brand build of a great MOC and then you turn it up to 11, amazing. But then you go further and change the laws of physics?

So that entire massive train is being pulled by four tiny circuit cubes motors? That's insane! Do you know what voltage and current it takes? I assume you would need something with more power than the circuit cube controller to do this (you clearly show that you use your own batteries and controllers, I'm presuming that is a necessity rather than an option)

[Toastie]

"Another" big boy model ...

Yeah, sure. Another as in: "Look, this thing can fly to the Moon, return safely to Earth, as they did it before. The only subtle difference is: It is made of plastic bricks"

Dave - this isn't another big boy model - it is a new definition of a brick built big boy model. Man. Incredible.

With very best regards,
Thorsten

[bogieman]

Thanks Benn, now you see what I needed those rods for!

I was as surprised, as I expect most would be, that those little Cubit motors do such a great job in such a big locomotive. The Tsunami decoders allow you to set a 3 point volts versus throttle position curve (28 throttle steps). I have it set only with two points so it's linear from 0 to 7 volts, the Circuit Cube outputs 5V so I am allowing some overvoltage. What you see in the video though is the throttle set to about 80% of full so it's running at about 5.5 volts (I haven't tried yet to measure the current but I need to do that.) I do confess I first ran it with the full battery voltage, 11+V, the default setting of the decoder and after running about 20 minutes I turned a couple of the motors to bricks. All my freight cars have ball bearing axles (BrickTracks wheels and axles) and I also changed the locomotive and tender axles to ball bearings as well. The loco has pulled longer trains than in the video but I'm being a little more conservative now. With the 1:1 gearing the loco speed benefits from the XL drivers but it does load the motors more.

I should also note that MorningStrummer did an outstanding job on the tender 5 axle rear bogie design - axles 2 and 4 are fixed to the bogie frame and axles 1,3, and 5 slide laterally as required in curving, all very smoothly with not much rolling resistance.

 

Thanks so much for the kind words Thorsten!

Dave

Edited February 1, 2023 by bogieman
added some info

[Supplement_Creatif]

This is mind blowing! I have been getting use to seeing incredible locomotives on this forum with lights and sound, but now with smoke! Absolutely incredible!

First time I watched the video I was thinking to me myself ''those can't just be circuit cube motors look at that train its pulling!''. Not just mechanically impressive but on the electric side just awesome!

cheers!

[bogieman]

On 1/31/2023 at 6:17 PM, zephyr1934 said:

So that entire massive train is being pulled by four tiny circuit cubes motors? That's insane! Do you know what voltage and current it takes? 

I, too, wanted to know how much current the motors were drawing in operation so bought a cheap DC volt-amp meter on Amazon and wired it into one motor's power leads. I posted a video showing the meter while pulling the same train in the previous video. It shows at 3/4 throttle, the motor is drawing between 400-500 milli-amps at a voltage of about 5.2V ; at full throttle (28 on the controller) it's drawing about the same current at 6.1V. I'll eventually learn what the longevity of the motors are at these current levels. The video is here:

I think the slow speed performance is most impressive, at the start of the video the throttle is set to position 2 of 28 and the loco starts moving slowly and smoothly at 1.5 volts.

Dave

On 2/1/2023 at 12:57 AM, Supplement_Creatif said:

This is mind blowing! I have been getting use to seeing incredible locomotives on this forum with lights and sound, but now with smoke! Absolutely incredible!

First time I watched the video I was thinking to me myself ''those can't just be circuit cube motors look at that train its pulling!''. Not just mechanically impressive but on the electric side just awesome!

cheers!

Thanks so much!

[uImagine]

Wow, I'm impressed by the 3D printed parts, and even more impressed by the locomotive using steam. Just a phenomenal job of the engineering and it's not something you see everyday in the LEGO trains world!

Good job on all the hard work put inside of it!

Edited February 14, 2023 by uImagine

[BillytheKid]

Another model of BigBoy........ That's fine and the model of Berthil has it's issues too. Main problem is, the BigBoy is just too big and clumbsy at legotrack.

When using non-Lego pieces, sorry that's not moccing anymore in mine eyes. Then you can better buy a complete model of Marklin or something :( .

[bogieman]

8 hours ago, uImagine said:

Wow, I'm impressed by the 3D printed parts, and even more impressed by the locomotive using steam. Just a phenomenal job of the engineering and it's not something you see everyday in the LEGO trains world!

Good job on all the hard work put inside of it!

Thanks!

5 hours ago, BillytheKid said:

Another model of BigBoy........ That's fine and the model of Berthil has it's issues too. Main problem is, the BigBoy is just too big and clumbsy at legotrack.

When using non-Lego pieces, sorry that's not moccing anymore in mine eyes. Then you can better buy a complete model of Marklin or something :( .

There's many corners to this hobby, I'm in a different one than that.

[Pelzer117]

On 2/1/2023 at 12:43 AM, Toastie said:

"Another" big boy model ...

Yeah, sure. Another as in: "Look, this thing can fly to the Moon, return safely to Earth, as they did it before. The only subtle difference is: It is made of plastic bricks"

Dave - this isn't another big boy model - it is a new definition of a brick built big boy model. Man. Incredible.

With very best regards,
Thorsten

Thorsten, you have stolen my thoughts 😉

But yes, I fully agree! Incredible work! 
Dave, which parts did you have to change for the XL drivers? Sure, „normal ones“ without technic skills like me cant build such an incredible realistic train, but at least maybe I am allowed to modify it also with XL drivers and zephyrs rods 😅

[bogieman]

Thank you. As far as what I modified from Morningstrummer's model to fit the XL wheels, pretty much everything. The XL wheels require the wheels be spaced 5 studs apart, where his model using the Lego drivers has a spacing of 4 studs. I tried to make the change using his basic design for driver bogies made from all Technic liftarms but I wasn't happy with that so went with Technic bricks and ended up with bricks and plates but much of that was also due to substituting Circuit Cube Cubit motors for the Lego L motors. Zephyr does offer rods with either spacing, just have to be sure to get the right ones.

Dave