A simple buggy. Features 2-speed remotely controlled gearbox, live rear axle and lights.

Datasheet:

Completion date: 23/11/2008
Power: electric (Power Functions)
Dimensions:  length 47 studs / width 25 studs / height 25 studs
Weight:  1.08 kg
Suspension:  front: independent with shock absorbers / rear: live axle on shock absorbers
Motors: 2 x PF Medium

A simple sandrail (subcategory of buggies), built basically to test my live axle concept. A live axle is an axle that has no fixed attachment to the frame of the vehicle. Instead, it is connected by a system of links and supported by shock absorbers. Live axle suspensions are usually complex, but offer very good stability and excellent performance, comparable to those of a typical independent suspension. And just like the independent suspension, live axle does not let the vehicle’s weight affect the drivetrain, which means that it performs better in heavy vehicles that the pendular suspension does, because the weight doesn’t generate extra friction on the drivetrain components (except wheels, of course).

In Lego, a very complex live axle systems exist, with probably the most extreme example available here. Therefore my goal was rather to create something as simple as possible. I ended up with an axle suspended on 4 links and a driveshaft only – a solution that turned out to blend simplicity with reliability pretty well. It had two minor drawbacks: it was slightly affected by the driveshaft’s torque, just like the pendular suspensions are, and the driveshaft could be theoretically affected by the vehicle’s weight to some extent while maing a turn or climbing certain obstacles. Despite that, this suspension system worked far better that I could expect.

Another noteable feature was the use of the direction sensitive gearbox I have developed earlier. It was braced by liftarms here, and allowed the vehicle to be driven only forwards. It did work as expected, but the liftarmic frame turned out to be somewhat loose, and did not deliver the kind of performance that traditional bricks could.

The model was built with minimal attention to the aesthetic side, I just wanted it to look realistic, not pretty.  Therefore I’ve used rather unusual palette of colours, and did not intend to film the vehicle. The LUGPol community, however, showed much interest in the suspension concept, and persuaded me into filming it, so I’ve eventually published a video titled Live Axle, to emphasize the fact that it was the suspension concept that was important, not the actual car.

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Small, simple lightweight buggy. Features full suspension and rear axle drive.

Datasheet:

Completion date: 20/01/2008
Power: electric (Power Functions)
Dimensions: length 37 studs / width 22 studs / height 26 studs
Weight: 0.86 kg
Suspension: front – independent / rear – dragged axle
Motors: 1 x PF Medium, 1 x PF XL

This project was intended to test what speed can be achieved with a PF XL motor, and additionally I was hoping it could drift a bit. There is a differential with 4 bevel gears in the rear axle (a technique developed by LUGPol user Aro_kal), and the gear ratio accelerates motor’s output speed almost twice. The buggy proved to be fast and manoeuvrable, but a bit too slow and to heavy for drifting (probably in part because of the battery box over the rear axle), unless it was given rear wheels without tires and placed on some tiles instead of a regular floor.

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Small, fully suspended buggy. Very good power-to-weight ratio.

Datasheet:

Completion date: 09/05/2007
Power: electric (wire-controlled)
Dimensions: unknown
Weight: 0.65 kg
Suspension: dragged axles on shock absorbers
Motors: 1 x RC, 1 x 2838

Briefly inspired by the vehicle from Batman Begins the movie, called Tumbler. The only real reference is the rear axle actually, with two wheels on each side.

The drivetrain, consisting of a single RC motor, few bevel gears and a chain, turned out to be surprisingly effective. It’s been most likely thanks to the lightweight body,  low center of gravity and the advantage of bevel gears and chain over the traditional gears, as they generate much smaller backlash and thus much less energy is lost. The buggy is very manouverable too, with a very good steering lock and a well-calibrated speed of steering. I have been testing a version with kinda ‘off-road’ wheels, but the wheels with the flat tires offered a considerably better performance on the floor. Simple as it was, this car turned out to  provide lots of fun while driving around.

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