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This is my Fourth LEGO RC MOC. It was completed on 1/18/2014. Other than drive and steering, it features boom elevation and boom extension.
About this creation

Because my Road Grader model was successful, I have decided to fix the minor mistakes I made in the drivetrain and reinforced it, and I started the MOC from there. It used the same wheels, and I have even tried to fit a V4 Piston Engine in there, which did not work because of limited space. Putting the battery in the back would make the model rear-heavy, so it ended up on the side, but I knew that batteries cannot be replaced because it also helped reinforce the model. The IR Receivers were located in the rear.

One of the challenges is to make the bevel gears' reinforcement not come apart on the 2 Linear Actuators that lift the boom. I used as much reinforcement as I can, but it eventually caused some friction and I had to locate the L Motor that lifts it in the front, which is quite far from the LAs. The motor did not have enough torque, although it had a 1:25:1 reduction. It was impossible to fit more gear reduction because of limited space, although I could've used a z12 gear meshing a z20 gear near the motor's output instead of knob wheels for more gear reduction, but because the clutches in the Large LAs take a lot of force to slip, those gears' teeth would then slip. Another problem was the large steering lock, and because the 90 degree rotation the servo motor makes, it can be too large for some steering systems. Gearing it down makes it impossible for the axle to point forward unless you use many gears, because of the gears' teeth, which I discovered on my Street Buggy. Yes, using a M-Motor with gear reduction could work better, but in my opinion the M-Motor is simply not the motor for steering, as most RC Cars have Return-to-Center steering. At the end, the steering lock was large and the motor driving the LAs had to stall when fully extended because of the lack of gear reduction and friction.

Building the model's body was pretty straightforward, which had a black colored body. The cab was on the side, and because the battery cannot be taken out, I have created a door that can access the switch on the battery box, and there were lights on top of the cab. However, because there cannot be a lot of reinforcements for the body because of the wires under it, it wasn't very sturdy.

The boom was the most challenging part. It was built the way that's usually done on Technic sets, such as the 8053 and 8295, but it's bending, especially when the extendable part is out, and a complex boom like the one on the 42009 would be too heavy, so I used as much reinforcement as possible. The extendable section used a rack-and-pinion mechanism with the 1x4 plate type of rack, as that type of rack is the only rack that can be placed next to each other and make a rack of any length. The boom extension worked very well and can extend about 28 studs.

Overall, I think it was as good as the Road Grader, although it took longer to finish and did not have much use. For some of my future Construction Vehicles, I plan to combine my EV3 supplies with Power Functions supplies to create something with a lot more functions


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By Justin (ctw100s)
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Added January 23, 2014

LEGO models my own creation MOCpages toys shop TelehandlerTechnic

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