Kraz-255
Model of a Ukrainian heavy-duty military truck. Features 6×6 drive, steering, suspension and a piston engine.
Datasheet:
Completion date: 24/01/2024
Power: electric (BuWizz)
Remote control: BuWizz
Dimensions: length 50 studs / width 17 studs / height 19 studs
Weight: 1.308 kg
Suspension: pendular
Propulsion: 2 x PF L motor geared 3:1
Motors: 2 x PF L, 1 x PF Servo
The Kraz-255 is a known as a “Terminator” among off-road enthusiast because of its legendary cross-country capability. It was designed as an “extreme conditions” military truck, fitted with a powerful V8 engine, ultra-wide tires and it’s so enormous that it’s actually too large to be legally driven on roads. I’ve wanted to build a model of it for a long time, and eventually chose to build one as a proof of concept for a discussion about small-scale off-road LEGO trucks that I was having with the local Truck Trial people. Just to see what is possible, I’ve built a pendular front axle with drive and steering that was just 14 studs wide including wheels. Once this was completed, I had to build a model to test it in.
I’ve chosen to build the cabin is rare LEGO sand green color, following my feeling that such a color looks a little weathered and generally less toy-like than regular LEGO green. The model was initially equipped with LEGO 56 mm tractor tires, but the more I looked at the real truck, the less right they looked to me, until I eventually put 56 mm balloon tires instead. These weren’t perfect either, but I felt they were closer to what the real truck’s wheels look like.
I didn’t feel like building yet another truck with empty cargo bed, so I put over 300 of brown round bricks imitating a pile of lumber on the back. The pile was hollow inside, with opening top and the BuWizz unit hidden inside. The result was that the model’s center of gravity moved significantly backward, which I tried to mitigate by moving the motors and the BuWizz as far forward as I reasonably could. This is why the drive motors show between the cargo bed and the cabin and are visible inside the cabin, which hurts the aesthetics of the model. It also forced me to move the spare wheel higher than it should be, because the motors were right below it. There was plenty of room to put the motor under the “lumber”, but the model would be very rear-heavy if I did that.
The front suspension was a simple pendular axle stabilized with a pair of rubber bands, since there was no room for shock absorbers, and steered by a PF Servo that was blocked to rotate by 45 instead of 90 degrees each side. The two rear axles were also pendular, and connected by a longitudinal pendular unit, making them them able to not only oscillate sideways, but also go up and down. The resulting suspension unit proved too fragile for shock absorbers so I’ve stabilized it with two parallel axles, one above each pair of left/right wheels, which were connected to axles #2 and #3 at the ends, and able to oscillate just like they did. This kept the truck upright without stressing the axles, ensuring that if one wheel went up, the other went down, or in other words that the sum of distances between the wheels and the pivot of the stabilizing axle was always constant. Because the suspension unit holding axles #2 and #3 together was long and connected to the chassis only in the middle, it had a tendency to twist while turning, so I’ve added guides in front and behind it, which essentially acted like forks bracing parts of the suspension unit but still allowing them to go up and down.
I think I’ve spend roughly 1/3 of the total time spent on this model building the hood, so that it looked right, was only 1 stud thick and could be opened without falling apart. It was also challenging to fit a miniaturized V8 piston engine below it. Additionally, the sand green cabin and the “lumber” required a lot of shopping.
The completed model looked OK to me, but turned out to have high center of gravity and moderate sideways stability. On top of that, the front axle had very little ground clearance and few pieces actually protruded in front of the front wheels. This had a seriously negative impact on the model’s off-road performance and I saw no obvious solution to it. Perhaps building a live front axle would be a better option, but this would be difficult to pull off without creating a negative caster angle on it, and the structure required to brace and stabilize such axle would never fit under Kraz’s long, narrow hood. Perhaps it would be a viable option for a cab-over-wheels truck.
Work in progress photos:
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