Remote Control Beach Buggy Jeep

Overview

The following is my version of the Lego beach buggy designed with or without Power Function (PF) motorisation.

There is a working 4 stroke piston engine, working driver and hand-of-god steering, 4 independent suspension and sprung front bumper.

The size is 29 studs long by 17 studs wide (about 1:10 scale), and weighs 600g with PF, which was as small as I could make it to contain the battery box and ‘pinon’ steering rack.

The 400 brick pieces came from Lego set 8048 (apart from 4 smaller wheels, and 3 extra suspension).

Design (talking)

Small as physically possible using the currently available Lego Power Function (PF) servo, large motors, lights, receiver and battery box. This was mainly to reduce the brick count as much as possible to keep it as light as possible for greater speed, increase the likeness to a buggy rather than a supercar, and make an affordable commercial Lego set.

Keep the working 4 stroke piston engine when motorised, and pistons clearly visible to watch them moving.

To make suspension for all 4 wheels, plus double spring shock absorber for the front bumper (as found on toy RC cars).

Similar to the Lego 8048 buggy the driver’s steering wheel to also be able to turn the wheels and also rotate during hand-of-god steering.

Working LED front lights, positioned to give a bright beam.

The side doors and rear boot should also open.

Finally, I still wanted the option of playing un-motorized, where I could un-pin all the PF units to use on my other MODs or pin back in afterwards, with no rebuilding of the body or paneling (which may be a first for a Lego RC car) except adding back the seats and hand-of-god steering.

Build (making)

The difficult part was I did not want the standard integrated design of placing the power functions back to back, as starting from a 16 stud length would eventually create a very long 40 stud supercar or monster truck. So instead to keep unintegrated and the square ‘buggy’ shape they are placed side by side, with the 8 stud battery box determining the minimum length possible between the wheel axels. After taking account steering and support beams the total length was 29 studs.  I haven’t seen this unintegrated PF configuration used by Lego before.

It soon became apparent that the large motor would need to take precedence in the center to allow minimal additional gearing with the differential and avoid using any Lego universal connectors. The motor moves with the suspension (so is connected only to the rear half by 4 pins), which is the approach taken in RC cars rather than a fixed motor with only wheel suspension. This avoids using any universal connectors at the suspension pivot which requires a lot more space, and creates a lot of strain on the motor.

To go 50% faster than the previous version the drive gear has being increased from 32 teeth to 48 teeth. Possibly could even try a 60 teeth gear, but may put too much strain on the motor with the differential.

The servo is forced to one side with numerous medium gears but this was needed anyway for the driver’s steering wheel to rotate (which is the same axle as used by the servo). The servo is only connected by 4 pins to the front half to allow the rear suspension to move and easy removal. I haven’t seen this ability to easily unpin the PF’s used by Lego before.

As the buggy is symmetric, left and right hand driver steering are both possible (as in Lego Chassis 8860), by swapping the gearing, servo and battery box around.

As there is rear suspension, the model is pivoted and consists of two separate parts held together with pins at the pivot, which was difficult to build strong enough to compress the suspension springs, especially with the battery box preventing any connections.  So from the underneath photo you can see that there is additional bracing with L beams around the rear wheels making extremely tough, as well as using the panels to provide an external skeleton.

Review (look & play)

From the photos I like the why the tubular axels, bumper and panels give that feeling that this is a ‘kit car’, with the prominent engine pistons showing off the customised engine. The angular nature of the frame throws you back to the 1970 and 80’s, further emphasized by the impression of fake red leather seats popular at the time. These are best seen with the doors fully open, which are the usual half height ‘kit car’ doors.

Further ideas

The buggy is limited to indoor flat ground, for uneven ground or outdoors not too difficult to raise the clearance with larger wheels and build a monster truck or jeep using the same PF layout.

As an alternative to black, the panels are also available in red from the Lego customised truck 42029 and Lego Supercar 8070, with a matching red battery box (only available) from Lego red cargo train 3677. It would be cool to see it in this colour and any other colour, say blue, if you have the panels please attach a photo with your comments.

Please comment if you would prefer with PF as a good way of obtaining RC motorization for this and other MODs, or a cheaper non PF version with a supplementary PF box. This is essentially how my interest in motorizing Lego sets started with Lego sets 870 and 872 when I was a kid.