42028 Bulldozer – Remote Controlled

Hi all, here we are for a new mod !

42028_A42028 is a nice small bulldozer with 2 functions, a blade on the front and a ripper on the rear. With its chains, it’s very realistic, but as usual with technic chains, totally unplayable on a smooth ground. The front blade is manoeuvrable thanks to the exhaust pipe. This is a good idea because it’s so much discreet than the traditional hand-of-god gears. The rear ripper has no real use, it’s just a mechanism added to complete the model, you can’t play with it at all, point.

My son was playing with it, when i realized that it would be much more fun if it was fully remote controlled. I started with the tracks, the more elegant would have been to add a subtractor, but the lack of space led me to install two motors, one on each side and driving its own track. I chose to gear down a lot to increase torque, lowering speed, after all, this is a construction equipment, not a race car !
The front blade received also it’s own motor, and lots of gearing down, it’s heavy and the mechanism requires also lots of torque.

The main challenge was the battery box. Firstly I wanted to use a traditional PF battery, but it’s so huge that i could not find a place for it without altering severely the overall look of the bulldozer, mainly by modifying the cabin. Another point is that the new Lego tracks are wide and there’s not much space between them under the cabin.
I remembered then that my son has Lego trains, a quick raid in his bedroom and I stole him a battery box. They’re smaller, less powerful although, but smaller, which was the reason why I took it. I decided to install it in place of the ripper, it’s useless, so, let’s force ourselves to use it ! Another good reason to put it at the rear is that it equilibrates the weight of the bulldozer and improves the contact between the chains and the floor. Last thing, the 2 Power Function infrared receivers, the last free space was behind the cabin, it’s just wide enough, easy choice. This is not very handsome, but it’s my choice. Another possibility was to place them on each sides of the bulldozer, but the infrared signal is weak and I prefer to have them located high over the model than on its sides.

The rests of the modifications were more easy. The tracks are a bit shorter, 30 links instead of 32.

The summary of changes is as follows:
– Removal of the fake motor
– Removal of the rear ripper
– Adding of a motorization of the 2 tracks
– Adding of a motorization of the front blade

Instructions are available for free as a PDF file, you won’t need the original booklets and the part list is in the file. Feel free to download them, experiment and report your comments here !

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