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Hello Lego train fans, (I repost here the work I have done on a pneumatic locomotive. I really don't know where to post since my MOC belongs to Technic category and Train category. So I post it here too. Of course here maybe we can talk more about the design and reproduction of the details of the locomotive. If this other post is too much, I am sorry that I posted in two places (and moderators could remove it), but I think it's understandable why I did this. Anyways !) I am glad to introduce you my last big project : a pneumatic steam locomotive ! I think it's one of the firsts pneumatic locomotives, using only Lego parts. I love trains as much as you do on this forum probably, so I hope some steam lovers will enjoy the model ;) The model is based on a Mikado type locomotive, from the mid 20th century. It especially copy the design of 141R french locomotives (even they were apparently built in USA, for France). First of all, the YouTube video and some photos: The idea with this model is to replace the steam of a real Locomotive by compressed air, and this for as much functions as possible. Here are the main functions : Movement of the train : Using 4 pistons, 2 on the sides, and 2 inside, the train can move forward. It works like a classic LPE, with 2 pistons shifted 90° from the others. 4 pistons consume a lot of air, but they guarantee enough power to move the whole train. To make the rotation smooth, a free wheel is hidden inside the boiler part of the locomotive. Its rotation is 25 times faster than the wheels of the train (40t/8t x2). The train isn't moving very fast because the pneumatic elements aren't modified. However, it's fast enough to make it interesting to look at the connecting rods and wheels moving. The breaks : On a real locomotive, compressed air is produced by a compressor (powered by steam) and is used to press some brake shoes against the wheels. Here, the same technique is used : a small piston is filled with compressed air, and thanks to some rods, brakes shoes are pressed against the wheels. It's cool but...it's not enough. Plastic against plastic isn't very efficient to stop the train's movement. Therefore, another rod is connected to the brake system and press another brake shoe against the free wheel. Because its rotation is faster (and therefore, with a low torque), it's is way easier to stop it. The Whistle : A system that I love in this locomotive is the whistle. Currently there isn't any whistle produced by Lego that could be used in the locomotive, so I had to think a little for finding something working. I can give you more details if you want but I used some lego parts that are empty inside and have a small aperture. By blowing air on these parts, we can produce a noise that is a little similar to a whistle noise. This whistle is activated by a switch in the cabin. The Cabin : Nothing much to say except that in contains 3 switches for the 3 main functions (whistle, wheel movement and brakes). There is also a pressure gauge showing the pressure coming from pumps. The train moves with a minimum of 1 bar. A 2-2.5 bars, the movement is faster. The air supply : There are several possibilities for the train : we can directly pump with Lego pumps, or store the air into 6 to 8 airtanks or produce the air with Lego motors and small pumps. For instance I use 4 pumps side by side, linked to some air tanks, but I don't what the final model should work. Maybe some motors and pumps could be cool ? The design : The hard part was to make the boiler of the locomotive. It's a little hard to make cylinders with Lego technic parts but, with flex axles passing through Technic beams, I managed to make something satisfying. Some details are visible on the locomotive, I tried to make it look a little crowded like a real locomotive with fake air/sand tanks, fake compressors and mechanical elements. It's probably possible to make it look better, but for instance I am happy with it. The rails are "homemade" with Lego bricks. The locomotive is too big of course to work on Lego railtracks. The wheels aren't perfectly flat so the train is "blocked" in position inside the rails. Therefore, the train can move foward cur cannot go out of the railtracks (which is great for a train). Finally, as a bonus functions, there are some bumpers at the front and back of the locomotive to imitate the real bumpers used to absorb small chocs on a Locomotive. That's it for now, I hope the model is interesting to you and if that's the case, don't hesitate to support it on Lego Ideas ! Click here to support on Lego Ideas If you have any question or comment, please reply to the post, I'll be glad to discuss with you !