This model started almost 2 years ago with a new idea for a 4-speed remote controlled gearbox. After finishing the first version of this new gearbox, I needed a car to put it in. So I decided to build an American Truck around it. Both the truck and the gearbox went through numerous redesigns before the model worked to my satisfaction.
Of course I wanted to maximize the amount of technical features in this model. Allthough it’s a truck, it basically has all the functions you’d expect from a Lego Technic supercar.
- Full live-axle suspension on all axles
- Both rear-axles are driven
- Remote-controlled steering with working steering wheel inside the cabin
- PF-lights (OK, I went a bit overboard with those 8-)
- Openable hood and cabin doorsRemote controlled driving
- And the most important function of this model:
4-Speed remote-controlled gearbox
The main design goal for this gearbox was to have a reliable and comprehensive gearbox with more than 2 gears. One thing that was very important was that the gearbox had to be able to handle a lot of torque. It had to be able to drive large Lego Technic models. Another aspect was that switching gears had to be very easy. First, the transmission itself is a 2-way transmission, where one has a different gear ration compared to the other. Then I develloped a kind of switching-logic, where 1 M-motor would be able to switch 2 driving rings, each in either direction. For this I used differentials, 24z clutch gears and an inverter-mechanism which uses a sliding worm-wheel.
Full building instructions for the Truck are available.
The instructions for the gearbox can be downloaded here for free.
Go to the Kenworth W900 instructions-page to get them.