MAZ-535
Model of a Russian military truck. Features drive, steering, remotely controlled transmission, V12 piston engine, opening doors and hatch, lights, UV headlamp and custom stickers.
Datasheet:
Completion date: 29/10/2019
Power: electric (Power Functions)
Remote control: SBrick
Dimensions: length 74 studs / width 23 studs / height 28 studs
Weight: 3.405 kg
Suspension: pendular axles
Propulsion: 4 x PF XL motor via a remotely controlled 2-speed transmission with ratio 5.4:1 / 8.64:1
Motors: 4 x PF XL motor, 1 x PF L motor, 1 x PF M motor
Like many LEGO Technic builders, I have a soft spot for the giant Russian military trucks. And I consider MAZ-535 to be one of the best-looking one of these monsters. I’ve had my eye on it for a while, but the problem was always the chassis’ width. The real MAZ-535 has really enormous wheels and a relatively narrow chassis, which translates into limited room between a LEGO model’s wheels, even if you go with really big LEGO wheels – in this case, popular LEGO 107 x 44R wheels translate into just 12 studs of space between left and right wheels. I used to think this isn’t enough to add some proper gear reduction near wheels, necessary to prevent the weight of a large LEGO model from damaging the drivetrain. But then LEGO has released the 42099 set with its brilliant planetary wheel hubs which solved the problem of sufficient gear reduction.
The model was rather simple, but it came with its own set of challenges. Even with gear reduction solved by the planetary wheel hubs, the chassis was still narrow and the body was quite front-heavy, so instead of trying to somehow fit an independent suspension in there (which would be sagging under cabin’s weight anyway) I have used pendular axles with shock absorbers for stability. This created sturdy unsprung suspension, but resulted in a severly complicated drivetrain and steering system. The two front axles were steered at various radii using a PF L motor with a worm gear (for maximum torque when steering in rough terrain) and the steering was transferred over the driveshaft using empty differentials. All wheels were driven by 4 hard-coupled PF XL motors via a very simple 2-speed transmission shifted using a small pneumatic cylinder, which was controlled remotely using my compact motorized compressor/valve unit. There was also a V12 piston engine driven by these motors directly, bypassing the transmission. There were two LEGO 8878 batteries in the model along with two SBricks, each powering and controlling two of the PF XL motors. So in order to prevent accidentally turning only one battery on instead of two, which would result in driving with half of the motors stopped (risking damage to the drivetrain), I have connected the tail lights to one 8878 battery and the headlights to the other. This way, it was possible to easily see from the outside whether one or two batteries were turned on.
Speaking of the headlights, I found that the reason why the real MAZ-535 had three headlights was because the middle one was actually an IR lamp that was supposed to help the driver see using night vision goggles. I didn’t have an IR lamp, but I had an UV LED from Brickstuff.com, which I have installed in the middle. It had no real practical application, but it still looked cool.
The body was another challenge. I’ve built dozens of military vehicles in dark bluish gray color and I really didn’t feel like using it again, especially since I really liked the real truck’s dark green color. So, at a serious expense (the flatbed alone required over 300 dark green pieces, costing 60 EU with shipping included) I’ve started gathering dark green pieces, building on a collection I’ve previously prepared for my ORP OrzeĊ project. I was actually slowed down by having to wait for my salary to afford some of these pieces, and it took some creativity to work around the lack of certain pieces in this color. On one hand, the MAZ-535 body is basically a simple box, but on the other LEGO hasn’t released a surprising number of basic pieces in dark green – the 2×2 plate, for instance, or any bars/antennas. The only way to build a dark green hinge was to combine a 2×1 plate with a handle, which was rare, with a 1×1 tile with a clip, which was even more rare and sold for as much as 2.5 EU per piece. All in all, the model was a serious expense, but I was hoping that this investment that would allow me to use dark green more often in the future. My only regret was the complete lack of any bars and antennas, which would make for some nice details on this truck.
The finished model performed well and had plenty of torque, but was somewhat hindered by the pneumatically operated transmission, which often required the compressor to keep going to prevent the transmission from disengaging under stress. The steering system and the drivetrain turned out to be quite complicated, and the use of pendular axles has used up plenty of room in the chassis and compromised its integrity somewhat. In a hindsight, independent suspension built using drivetrain pieces from the 42099 might have been a better solution – it would certainly simplify the drivetrain and resulted in a roomier, more robust chassis. But it would still be difficult to fit it in a model of this width, and I didn’t want to use a Tatra suspension system here.
