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Busy putting together instructions, but I'm wondering about gearing. Lego's own trains that have been powered with L motors usually have 1:1 gearing (Emerald Night, Crocodile). Due to the low-mounted motor, this one is geared approximately 3:1 (three revolutions of the motor for one revolution of the driven wheels). This makes the model slower, but more powerful. Seeing as the original 1251 was mostly used for shunting duties, this seems appropriate. There is an alternate gearing solution I could implement, but that has two issues- It requires a 24z crown gear , which hasn't been in production since 2012 or so. The other gears are 8z gears - not really known for their sturdiness or reliability. So, does anyone here have a preference? The options as I see them are: A- Slow, steady, reliable, made from commonly available parts B- Faster but flimsier, made with out-of-production parts.

Technic Hub / Handle 1 x 1 : Part 424 | BrickLink

You're just making up random nonsense to get mad at.

Thanks for your suggestions! I did some fiddlin'. Well,as suggested- ditched the tender, moved both front and rear couplers inward. Boiler mounted 1 stud further to the rear, and one plate higher. Cab moved similarly. Ladder-entrance distance is shortened a bit. The now-inboard battery box compromises the look a bit, but since Circuit Cubes aren't my thing that can't be helped. Any other bits that can be improved?

Based on the Reading 1251 , which itself was a one-off prototype Frankensteined together from leftover parts of a I-2a class 2-8-0. The words "based on" are doing a lot of heavy lifting here. The proportions are slightly off, the colourscheme is all the way different, and the included coal tender doesn't really make sense for a shunter. And that's how we get to this topic. I've made trains with free instructions before, and may want to do so again. However, before I start wasting both my time and yours, I'd like to know if there's any interest in instructions for a train like this. I hear steam train fans are very realism-oriented. I'd like to give a rundown of the features, and I would love to hear if there's improvements I can make before I start the whole instructions thing. Starting off; the mechanism. My goal was to mount the motor as low to the ground as possible, to get more room for details. Gearing right now is 1:1 Also, the coupling rods assembly won't seize up. Trouble-free running ahoy! The battery tender is designed so switching batteries and minimizing wire length is as easy as possible. Transparent parts at the back allow for checking the status light. I still want to make some adjustments to the model before making instructions. On the to-do list are: Adjusting the proportions where possible. The front hangs over quite a bit, and I'm sure this can be improved. Making the model easier to construct. The front assembly has some math that while legal, might not be entirely Euclidean. Where possible, substitute expensive or hard-to-find parts. Structural integrity. Right now the model is pretty damn solid, but I still have some improvements in mind. So, how do you like the model? Would you be interested in instructions? Any improvements that would be welcome? I'd love to hear them.

This is just glorious. From the functionality to the excellent likeness to the original, I'm massively impressed.

What I'm looking for is a variation on a differential drive. Typical diff drive has two inputs, two outputs. 1- Powering input one means both outputs rotate the same direction 2- Powering input two means both outputs rotate different directions What I'm looking for is again a mechanism with two inputs and two outputs. 1- Powering input one means output 1 and output 2 rotate at the same speed 2- Powering input two means output 1 rotates, while output 2 remains stationary. Does anyone know of such a mechanism? Edit; nevermind. Powering one output of a differential with one motor and powering the differential itself with the other seems to do what I want. Now to fix the speed of the outputs.

https://www.bricklink.com/v2/catalog/catalogitem.page?P=80441pb01

In case people are interested; I've also published instructions for the tank cars seen in the video: https://rebrickable.com/mocs/MOC-179076/Mahj/green-tank-car/

Finally had some time to document my build: More pictures: https://flickr.com/photos/28134808@N02/albums/72177720315500612 IO file of the suspension: https://drive.google.com/file/d/1GSviTWD-voyIgLJKGDotRwY6L_854uuE/view

The mechanism to store energy in the springs and to release it at the right time was very fiddly. It had to be coupled to a steering axle that could withstand the weight of the car dropping onto the wheels continuously. Weight distribution was also very delicate. On top of that, it had to look good as well.

That -6 is because it's my own truck. As organiser, I'm not eligible to win any prizes. The other positive scores you see in that column are rewards for originality / looks.

Pretty much all it says on the tin- competitors are limited to wheels no larger than 56mm, max width is 17 studs (stickie-outie-bits like mirrors are OK), motors, power supplies etc should be 100& Lego, no 3D printed parts- very conventional. We found out during the trial that the obstacles may have been a bit too hardcore, but we intend to do it again with improved machines and gained knowledge. Edit: Phase 2 is now online- on to phase 3!

@UltraViolet definitely also take a look at this model: It uses those doors in a great way to cover up the battery box. The only downside I see is that they haven't produced 1x1 plates with clip in the right colour yet.