Rokenbok ST440 Teardown



My teardown was of a broken Rokenbok ST440 remote control bulldozer. This is from a larger toy set that lets children build a miniature factory that sorts and moves plastic balls using lego like parts. Various types of RC trucks are capable of operating the factory once it is built:last-import-1-of-15

The treads and shovel came off easy, and screws underneath the body of the truck revealed a neatly stacked configuration of components. This is perhaps a testament to the Rokebok team who intentionally built these machines to be as hands on as they could:last-import-4-of-15

I was immediately surprised by how much grace there was. The steering mechanism that powered the treads and shovel was sitting in a pool of gelatinous oil:


If it was not clear before, this is a meticulously designed toy! Several of the exterior parts could only be removed after I had dug deep inside. I finally got the roll cage and chair off:


Next, I isolate the circuit board. This was the point of no return, since I had to break solder connections. Wires led to the circuit board, three motors, the antenna, and an LED light:


I tried to identify some of the parts. One was marked CFT455E. This component was widely available on websites like Alibaba from third party sellers. I found out that this particular part uses the piezoelectric ceramic effect to help keep fixed frequency communications devices tuned accurately. In other words, it keeps the truck connected to the remote control. I bet this is important because a Rokenbok remote is capable of controlling 15 toy trucks independently by toggling between frequencies. I removed all of the components by hand, just by bending them back and fourth.


And finally, the money shot:


For this tear down, all I needed was a screwdriver. The assembly was super simple sandwiched components, making extensive use of injection molding for the exterior parts (this was apparent from small tear lines from which the plastic structures were torn from the pour pipes. These are called the “drop”. There was some use of wire bending for support structures on the vehicle. For example, the apparatus that lifts the shovel is highly dependent on bent metal parts.

The electronics board, amazingly, looked to have been set by hand. This was the only place where glue was used; apparently hot glue to hold the components in place after they were arranged such that the board could be pressed onto a solder stencil to make the necessary connections. A few wires snaked through difficult parts of the machine, and these looked to have been hand fed through crevices in the assembly. Rokenbok was something of a boutique product, so perhaps the extent of the hand manufacture should not be surprising.

The design was genius in its simplicity. One aspect I particularly liked was the mechanism for transferring motor power from the treads to the bucket. It consisted of a gear shifting mechanism that apparently only activated the bucket when the mortars were both in reverse. As a child, I alway wondered why you could not simultaneously operate the bucket and the treads, and now I know why.


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