Home > Military > Tsar Tank

Tsar Tank

November 10th, 2022 Leave a comment Go to comments

A WWI experimental tank model. Features drive, steering, motorized turrets and side sponsons.


Completion date: 09/11/2022
Power: electric (CaDa brick)
Remote control: CaDa brick
Dimensions: length 51 studs / width 34 studs / height 31 studs
Weight: 0.942 kg
Suspension: none
Propulsion: 2 x PF M motor geared 21:1
Motors: 2 x PF M, 1 x PF Servo, 1 x Micromotor

Here’s a model of quite possibly the most unusual take on the tank design. Invented during WWI as means to break through trenches, it was built thanks to the marketing skills of the inventor who managed to get an audition with tsar Nicholas II and presented him with a spring-propelled wooden scale model of his project. The tsar apparently loved the model so much that he granted budget and resources to build a full-scale prototype. The prototype was built in 1914-1915, with giant 9-meters wheels propelled by two captured Maybach engines rated at 240 HP each (most likely the Maybach HSLu (Mb IV) engines, originally designed to propel Zeppelin airships). The armament was located in two turrets – ventral and dorsal one – as well as in two side sponsons. Unfortunately the weight of the prototype (approx. 30 tons) far exceeded the original estimations, and the poor weight distribution put too much load on the rear wheels and not enough load on the front ones. As a result, the rear wheels got stuck in the mud and the front wheels couldn’t get enough traction to pull them out. The prototype was abandoned in a forest where it stood for 6 years before being dismantled for scrap.

My model was built and scaled around LEGO Hailfire Droid wheels. There were no significant challenges to the build except for the usual “trying to squeeze a lot of things in” and for structural integrity, as the chassis is under a lot of stress, being thin and supported only on its extreme ends. I have, in fact, cheated a little to fit all the stuff in – the drive motors were sticking out of the hull between the wheels, and the CaDa brick, which powers the model and provides remote control, was hidden in a box in front of the hull, which isn’t present in the real tank. I have used a PF Servo motor to rotate the turrets because there wasn’t enough space for a different motor with gearing, so the turrets could only rotate 180 degrees forth and back. Additionally, while the side sponsons were independent, I had to control their motors from the same output because making them independent would require four outputs and the CaDa brick has four.

The worst part of the model were the wheel spokes, which didn’t rotate with the wheels. The problem was that it’s quite difficult to connect any LEGO pieces to the Hailfire Droind wheels, and the wheels are driven using teeth on their inner side, so their inner side has to remain out of contact with the spokes, or they would collide with the gears driving the wheels. The spokes and the axle that connects then can actually rotate and I was looking for a way to drive them with the drive motors, but this would realistically require a long rubber band connected to one of the drive motors, resulting in spokes that rotate 21 times faster than the wheels do, are all coupled to one wheel instead of being coupled to both wheels independently, and then we would have an exposed yellow rubber band ruining the look of the model. In the end I’ve kept the spokes free from any connection to the drivetrain, so they look wrong when the model drives but fine when it’s stationary.

The scale of the model was relatively small despite giant wheels and there was little room for fancy details, especially given the limited and sometimes contradictory documentation of the real tank. The model wasn’t great at driving, it tended to veer to a side while driving straight and it struggled with pulling the rear wheels over difficult terrain. I’ve actually made the rear wheels bigger than they originally were, but the problem that affected the real tank was present in my model as well.


01.JPG IMG_0389.JPG IMG_0396.JPG IMG_0398.JPG IMG_0402.JPG IMG_0408.JPG IMG_0413.JPG


Media coverage:

The Lego Car Blog

Categories: Military Tags: ,
  1. No comments yet.
  1. No trackbacks yet.