Sariel.pl

My second model of an actual tank. Features a drivetrain with a subtractor, pendular suspension with possibility to tilt the hull pneumatically, pneumatic front dozer blade, detachable side skirts and rear fuel tanks.

Datasheet:

Completion date: 08/03/2008
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions: length 58 studs / width 25 studs / height 20 studs
Weight: 2.0 kg
Suspension: pendular bogies
Motors: 1 x PF XL, 2 x PF Medium,
Pneumatics: two circuits with one autovalve and one manual valve

This tank, again, has been inspired by someone else’s work. It was Mrutek’s smaller model that drew my attention to the Swedish Strv 103 tank. The tank is so unusual, that I just had to create a model of it. Since the scale is entirely different, I did not rely on Mrutek’s work, I have just learned of the original tank’s existence from him.

The look of the model is not actually very accurate, it’s slightly too large and out of proportion, and the suspension system looks  entirely different. It maintains, however, the characteristic silhouette, which apparently makes up for it.

The space inside the hull is utilized down to the last stud: rear and middle part of the chassis are occupied by the classic subtractor, used in my several previous tanks. The front part of the chassis houses a horizontal battery box and the entire pneumatic system, that is two circuits, one used to elevate hull on the suspension, and the other one used to control the front dozer blade. The first circuit is controlled by an autovalve I have designed earlier, which allows to use a single motor to drive the compressor and to switch the pneumatic valve. The second circuit is attached directly to the compressor via a manual valve. When the valve is opened, the compressor feeds the second circuit exclusively, without affecting the first one. It is possible thanks to the pressure principle – second circuits needs less pressure to operate, so if the compressor feeds both circuits at once, the second one utilizes all the air provided, thus not letting the pressure to reach the level needed to operate the first circuit.

The chassis, probably the tank’s most noteable feature, is not very complex. On each side of the tank, there are two stringers, one above the other. The upper stringer is entirely attached to the hull, while the lower stringer has only two points of attachment. One of them is a central transverse axle that connects it to the upper stringer. The other one is the top of a pneumatic cylinder which connects it to the front part of  the hull, thus controlling the hull’s tilt. I have, in fact, tried a number of purely mechanical solutions before relying on pneumatics. Given the hull’s weight, however, each mechanical solution turned out to generate a significant backlash, and the linear actuators were not yet available at that time.

I have put a lot of effort in the construction of the chassis, which has been test-driven in a huge variety of conditions. That resulted in a very good off-road performance of the tank, additionally supported by the use of a subtractor. I believe that the weight of 2 kilograms was pretty close to the limit of capability of a single PF XL motor driving the model over multiple obstacles, and if the model was a little heavier, it would have to be fitted with a second PF XL motor – which would result either in much larger size of the model, either in removal of the subtractor to gain space for the second motor.

The response to the model, both local and worldwide, has by far exceeded any of my expectations. Some people, who are familiar with my later work, still consider it my best, or one of my best creations, while in my personal opinion it could be significantly improved. Note that this was the first case of a good quality video, as I have paid little attention to the video materials earlier.

Photos:

Videos:

Media reference:

Brick Blogue, TechnicBRICKs