This truck is my attempt at building a fully functional RC Lego truck. The goal was to build all of the mechanical workings directly from Lego pieces with little to no modification. The drive train of this vehicle is a two speed manual transmission which drives the back wheels through two universal joints. By using universal joints, the truck is able to have full frontal suspension while keeping steering capabilities on the vehicle.
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Step 1: The Transmission and Motor
This step is about the design and building of the two speed manual transmission which drives the truck. The heart of the transmission is two separate gearings. The one gearing is geared to be exactly the same speed as the motor output. the other gearing is set by a small gear driving a medium to up the torque and pulling power of the truck. To select between the two gears I used a milk carton Lego piece to move a selector piece back and forth. The drive off of each gearing the grabs the selector which turns the output shaft.
Step 2: The Steering (Gearing)
Due to the high rotation speed of the small Power Functions motors, the steering requires a two stage gear box. the gear box gear design is higlighted in the photo. the gears used slow down the output and provide an immensely more powerful rotation to the rack and pinion. the output is transfered to the rack and pinion through universial joints which allows the suspenson to work properly. More info on suspension will be provided later. the final output before the universials goes through a slip gear to guard against binding and excess motor wear.
Step 3: The Steering (Rack & Pinion)
The rack and pinion on the truck is a simple design which utilizes a long geared piece coupled with a small rounded gear. The shaft from the gearing goes into the rack and pinion to directly drive the small gear, which turns the steering mechanism. The end pieces of the steering mechanism simply directly connect through axles to the wheels.
Step 4: The Rear Gear Drive
The rear gear-drive is what will take the power from your gear box, through the universal joints, and turns it at a 90 degree angle to power the wheels. In this situation, after having many problems with a custom design, I decided to use a pre-made lego worm gear assembly. By using this arrangement, I get a large amount of power, with the only drawback being the slow speed. The mounting that I chose to use is a system in which the worm gear uses arms which are sandwiched in place to hold it securely.
Step 5: Main Frame and Suspension
The main frame is mostly supported directly by the transmission in the middle of the truck. The design is centralized around the transmission so that there is a strong frame for the rest of the attachments. The suspension originally was going to be front and back, but due to complications with the gearing in the back of the truck, I decided to go with only front suspension. The front suspension is attached directly to the frame of the truck and then to the rack and pinion. The addition of universal joints on the steering mechanics allow the front to pivot up and down when needed.
Step 6: The Body
I could go into great detail on every piece specifically to build an exact clone of my truck body, but where is the fun in that! I feel that this part of the build has to be more of an art project and less of just a specific design. Ill lay out the basics through the provided photos, but the actual shape and final design will have to be up to you.
Step 7: Wiring and Power
The wiring on this truck is greatly simplified by using Power Functions equipment. The reciever is located in the cab of the truck to allow a good signal. The battery is located in the bed of the truck for ease of access in the future. The main drive motor and the optional headlights are connected to the red connector on the receiver. The steering motor is conncted to the blue connector. the wiring for the steering is run under the seats to keep it from getting caught in any of the moving parts. The wiring for the drive motor is simply run over the dash and into the cab of the truck.
Step 8: Other Options and Upgrades
Although the truck is very complete and ready to use on its own, adding other upgrades can greatly add to the realism. One of the upgrades that I chose to add to the truck is working headlights. The lights are from a Power Functions motor set and directly hook up to the main motor drive on the receiver. This allows the lights to come on when the truck is moving. The second upgrade that I added was a trailer hitch. The hitch not only allows a trailer to be added, but it makes the truck look even more realistic, even when a trailer isn't attached.
Step 9: Final Thoughts and Conclusion
I hope you enjoyed my instructable and that it helped you with your Lego projects! If you have any questions, I would be happy to help you with them. If you feel I need to add something to the instructions, leave a comment and I will do whatever I can to help. Also included in this step is a short video showing the different functions of the truck working.
Just a final reminder that this instructable is in the Lego building contest here on instructables. Your vote would be very helpful and is very much appreciated! Thanks!