Sariel.pl

My first racing truck. Features full suspension, dual motor drive, and lifted cabin.

Datasheet:

Completion date: 16/08/2008
Power: electric (Power Functions)
Dimensions:  length 47 studs / width 18 studs / height 26 studs
Weight: 1.92 kg
Suspension: front independent / rear pendular with shock absorbers
Motors: 1 x PF Medium, 2 x PF XL

In August 2008, I’ve come across the European truck racing, and this sport appeared to me as very potent in the terms of a LEGO Technic competition. To try out some assumptions of such a competition, and demonstrate my idea, I have built an exemplary truck.

The assumptions of the LEGO Truck Trial competition were as follows:
– trucks scaled to the 62.4 x 20 S wheels, or different wheels of similar size
– maximum width of a vehicle: 19 studs, exluding side mirrors
– full suspension on all axles
– at least one axle driven, at least one axle steered
– must refer to an existing racing truck; therefore I’ve assumed that truck with more than 3 axles won’t be used, as there are no such trucks in the real sport
– no weight limits, and unlimited number of motors used to drive

The idea, presented at LugPOL, prompted several builders to build their own racing trucks, most of which did not comply with the assumed rules (a lot of people complained about the suspension system requirement, which I have viewed as crucial for realism). As of the end of 2008, not a single contest took place.

The truck was driven by two PF XL motors connected by an adder. The rear axle was driven via the new type of differential from the 8297 set, and had pendular suspension stabilized by shock absorbers. The front axle was not driven, and had an independent suspension based on the components from the 8435 set, with very hard shock absorbers (to support the weight of the cabin and to improve stability of the truck, which could rely on the rear axle only). The dimensions and the look of the truck have been to a large extent based on layout of Scania R 340. The battery box was located above the front axle, and the cabin could be lifted to access the box. The truck was equipped with a large array of lights, both front and rear. The IR receiver was located in the chassis and well exposed.

For the lack of any official contest, the truck went through a lot of test-driving. It performed well, with a drivetrain which provided speed below my expectation, but proved entirely capable of handling all the torque involved in driving such a heavy vehicle. Because of the large accelerating gear ratio in the drivetrain, the truck suffered from a large inertia while stopping. I have assumed that a braking manoeuvre must be used to eliminate that, namely the motors were switched to reverse to stop the truck. Again, the drivetrain endured a huge torque generated while stopping truck this way, and since that time, I required all my racing trucks to be able to endure such a manoeuvre.

The disadvantages of the truck was a significant weight, and a tall center of gravity, which did not cause any trouble here, but I have anticipated that it would, if the truck was faster. Moreover, there was a noticeable part wear in the front suspension, which resulted probably from the large weight of the vehicle, located mainly on the front axle.

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