[MOC] 42099 alternate 'Jeepy'

gyenesvi · January 14, 2021

Hi All,

I'd like to introduce my alternate model for 42099. It was inspired by the recently released Jeep Wrangler, in that it has a small turntable based suspension on both wheels. Since 42099 has the two large turntables, I thought I'd try and build a similar suspension. Also, since it has yellow-ish parts, I thought I'd build a body with Jeep-like features. Of course, not enough yellow parts for a full body, so I focused on the front (hood and the grill to be somewhat Jeep-like) and used to rest to make a consistent body at least.

Building instructions are available from Rebrickable: https://rebrickable.com/mocs/MOC-62435/gyenesvi/42099-c-model-jeepy

Some details

I have opted for a simple suspension design by moving the turntables as close to the two axles as possible. The drivetrain is also very simple, putting the drive immediately to the differentials, resulting in slow speed but high torque on the wheels.

The left and right arms holding the wheels are fixed, the whole front and rear axles are rotating and are damped by the springs. Due to the large turntables, a single pivot point is enough to hold the axles at both ends. Naturally, the size of the turntables is a bit of a problem for ground clearance (about 3.5 studs in the front and 4 studs in the back), but not as much as I expected (see below).

A major challenge was to mount the steering motor on the front axle in a small space under the hood and to create a strong enough steering rig using only one side on the front of the axle (as opposed to the two-sided rig in the original model). The next challenge was to create a chassis rigid enough to hold the end points of the springs in a small pivoting mount to enable the lengthening of one side when the other one shrinks. Naturally, the arched pieces available in the model are useful for this purpose, with further reinforcements later on.

The battery is placed in the middle of the chassis, providing a low center of gravity with easy access to turn it on. It is not a structural part of the model, so it can be taken out easily after removing a few body panels. Also, there's plenty of empty space inside the chassis to hide the cables.

On the outside, I wanted to replicate some Jeep-like features with the few available yellow-ish panels. I decided to focus on the front, creating an arched hood with a massive front grill and lights. I wanted a consistent yellow body, so I used all yellow pieces for doors and hoods, and none were left for a roof, so I decided to build just a frame. Luckily, the curved corner pieces and the long black axles available could be pieced together for a consistent frame, that matches the style of the front grill. I think the overall proportions of the model came out quite well. I was also able to include a quite clean interior.

As for actual performance on real terrain, see the video for my own off-road tests. Surprisingly, the large turntables are less often a problem in terms of ground clearance as I expected. I suspect it might be because with the fixed-arm pendular suspension, as one wheel is lifted, it also lifts the turntable half-way, so it is less likely to hit something on the ground. Also, with locked differentials it can climb quite well. Be careful however, on real rocks, it is possible to scratch the bottom of it, including the motors.

The model can be controlled with the Control+ App just like to original model.

More pictures