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I'm happy to hear that you enjoy the construction. I should make a video with working mechanisms in a few days.

Hello everybody. I would like to show how a hotel porter push his luggage cart. That’s my first LEGO Technic MOC over 2000 pieces and I hadn’t any experience in building such a big structure. First of all let’s look at some pictures. link to my short gallery at bricksafe There are three mechanisms in my MOC, all of them are stimulated with the only one L motor. * the hotel porter breathes as long as the motor is on, the porter’s chest moves up and down; * the first option in the gearbox located in a blue suitcase: the hotel porter walks (by moving his legs in hips and in knees); * the second option in the gearbox located in the blue suitcase: the hotel porter speaks. The standard bbox is hidden in a dark bluish grey suitcase and I have to push a black handle to switch it on. Of course there is only one possible rotation. Moreover, a luggage cart has the steering mechanism with the Ackermann geometry. I added it into my MOC because I feared that independently rotating wheels wouldn’t let to move. Let’s watch a few scenes from hotel porter’s life and then read about mechanisms, if you wish. Steering mechanism with Ackermann geometry: When the hotel porter breathes, his one-stud-thick chest moves up and down in a one-stud-thick gap. The chest is connected to two red panels located in two sides of the body. Ten gears lead from the main axle upwards and the rotation is changed into the vibration of light bluish gray seven-stud-long beam, which is connected to the body by the pin marked with purple colour. Majority of place in my MOC is taken by a walking mechanism. At the beginning of building I stated that legs must move by means of four linear actuators (LA). All the fun was to change the rotation of a L motor to the sequence of the leg movement: 1) lowering a leg in a hip; 2) straightening a leg in a knee; 3) waiting; 4) raising a leg in a hip and bending it in a knee. The sequence for the other leg stays two activities behind the first one. If you want to change one extreme position of a small LA to another, you have to do about 19 rotations. So the whole sequence is equal to about 80 rotations of the axle in a LA small. According to LEGO Technic gears, 72 rotations was the optimal value and I made it by two conjugations: 8/24 and worm/24. Linear actuators don’t reach their extreme positions. One may consider it as a disadvantage. Surprisingly, I discovered that it’s impossible to prepare the mechanism that leads each linear actuator going back and forth between two exact positions. Therefore, after every step the position of linear actuator changes a bit and the reserve is sufficient. Purple axles turn 72 times slower than the gears with 16 teeth near the red gearboxes. That mentioned gears turn all the time (poor L motor): each line of six gears produce the rotation in another direction (something like in 42042, blue crawler crane). Blades installed on the purple axles switch red changeovers and make linear actuators move forward, backward or stay. It’s very difficult to prepare the blades because gears in Lego Technic have even number of teeth. Consequently, the first and the fourth gear wouldn’t stay vertical simultaneously: Honestly, I admit that the L motor has troubles with this mechanism. When leg is lowered too much the motor can even stop during straightening the leg in a knee while the bbox is still working. A few experiments let me to prepare all the things (blades and linear actuators) and hotel porter makes that few steps in the movie. Number of pieces: about 3900. Weight: 3017 grams. I would be grateful for any comments or ideas concerning this MOC.

I'm trying to make an image which is a link to the other image. Therefore I can use smaller image in my article and bigger would wait in a link. It works! Clicking the signature of Vincent van Gogh leads to his portait.