When The Lego Company put out their 8 x 8 airport fire truck, set 8454, I thought I could build it much better. I decided to use the tires from the big Lego Technic Jeep set and it would be easy. After a lot of frustration trying to build the drives and a few questions to Eric Sophie on how to build the drives, I think they work ok. The truck is FULLY Lego Radio Controlled using four of the black RC electric motors, one for each set of wheels. There is no differential so this makes it very hard to steer. The wheels are geared through a worm gear so the truck can not roll without power. The steering is driven by one geared electric motor. The wheels are connected to walking beam, which allows then to have a great deal of forward and side-to-side movement. Since the truck is now about 22lbs, with the radio it, the suspension has been changed from the independent suspension used on the real truck.
The truck was also to carry its own water tank but due to the weight increase, an external tank is used. A GMC windshield washer tank and electric washer pump are used to pump the water through the truck and out the two nozzles. The hose coming from the pump is split through a valve so two water lines enter the side of the truck connecting to a brass fitting. The hose lines can be both operating or one can be turned off at a time. The hose lines are run through the truck, one to the front of the cab to a movable nozzle and the other run up to the boom end nozzle.
The Snozzle Boom is motorized so it can turn left or right. The boom works off two sets of pneumatic rams. Since the boom is so heavy, the boom was also modified to work a little differently from the original truck. CLICK the “UP” button to see more pictures of the boom working in the pictures of the 6x6. All of the pneumatic switches are mounted as parts of the details. The motor for both the boom and the compressor run off two knobs on the side of the truck. The hose connection is hidden under the two gray caps with the chain on them.
Real truck: You can see this truck at http://www.e-one.com/arff.asp .
Length: 98 cm
Width: 26 cm
Weight: 22 lbs
Any comments are welcome.
Thanks for reading