4x4 X-treme Off-Roader (LEGO Technic 42099)

by ReDo.Bricks (@ReDo.Bricks)

4x4 X-treme Off-Roader (LEGO Technic 42099)

Description

LEGO Technic set 42099, the 4x4 X-treme Off-Roader from 2019, built in ReDo from LEGO Technic parts by their part numbers: 954 pieces, each one the real part in its real colour, every pin and axle joined into the holes it goes through as the set is built. Its two XL motors drive the front and rear differentials through their gear trains, and its L motor steers the front wheels through the steering rack and links; the Control+ hub sits on the chassis. The motors and the hub are placed without their cables.


## Where it comes from


Each piece is placed where the LDraw community's model of the set puts it: *42099 - 4x4 X-treme Off-Roader* by Philippe Hurbain [Philo], from LDraw's Official Model Repository, redistributable under CCAL 2.0 (CC BY 2.0). The parts are ReDo's own parametric LEGO parts and meshes made from LDraw's drawings, not LEGO's CAD.


## What is different from the box


- Some pieces are built as LEGO's current mould of the same part: the black friction pins (2780) as 61332, the blue 3L pins (6558) as 42924, the red towball pins (6628) as 66906, the tan 3L pins without friction (32556) as 39888, the pin connector hubs (87082, 48989, 15100) as 44874, 65489 and 65487, the yellow axle connectors (32039) as 42135, and the half-beams with a boss (33299a) as 33299b.
- The two rigid hoses are fitted to the model's LDCad paths and seated in the bar clips and angle connectors that hold them.
- The model paints the front XL motor and the steering L motor Light Bluish Gray; the set's motors are all Dark Bluish Gray, as here.
- The model leaves out pieces the set has, placed here where LEGO's own booklet puts them: the red Axle 2 in each rear steering link's cross block (steps 183 and 184), the two black 2 x 4 L-beams hanging from the back of the roof (step 293), and the second blue axle pin in each grille (steps 312 and 320). Three black friction pins the set lists are still missing: no step of the booklet places more pins than the model does, so they are most likely spares.
- The model draws every pair of gears tooth on tooth. Here each differential's inner bevel is turned half a tooth on its pin, each pinion axle half a tooth of its 20 tooth bevel, each drive shaft 14.4° and each motor's output axle a third of a degree, everything on an axle turning with it, so every pair meshes tooth in gap.
- Pieces the model draws a fraction of a millimetre into their neighbours are set where they belong: an Axle 2 in the front axle's stop-bush pin (0.8 mm too deep), the left curved panel and the front axle's left round connector (0.8 mm too far in), the rear differential's two side bevels (1.2 mm off their axles), the Axle 3 behind the front bumper (square while the connectors on it are turned 28.7°), the front steering links (level while the hub's towballs stand 0.8 mm higher), and the side bars' toggle joints (their pin holes drawn 0.66 mm apart, so each bar swings 0.18° on its door pin to line them up).
- The model draws each rear hub 0.55 mm nearer the differential than the front axle's 40 mm between CV balls. Here each rear CV joint's ball is slid along its axis into the hub's input, so the drive reaches the wheel, and the two CV joints on each rear drive shaft press 0.3 mm into each other over their Axle 2. Each rear toe link is likewise sprung over towballs 0.55 mm nearer than its length. Both are recorded as flexes, the give the real plastic takes up.
- A few faces LDraw draws touching come out a few hundredths to 0.2 mm into each other in ReDo's meshes: each wheel against its planetary hub's pin collars, two connectors against the front hubs, and each side bevel against its differential's inner tab. They are recorded as flexes too, until those meshes are made closer.
- The motors' cable clips stack on an Axle 3 on top of the hub, held in the set by the cables they grip, which are not modelled: they lift off the build here.
- The axle carrying the three motors' cable clips is drawn a module too high, through the roof's upright beam; it is lowered 8 mm with its clips, the least that clears the roof.
- The right grille is drawn as a copy of the left rather than its mirror image, reaching through the right headlight; each of its pieces is turned to mirror its left twin.
- The parts leave out what does not change how they fit: the hollows under a beam, the motors' and hub's moulded detail, the tyres' tread pattern.


## Try it


Run the motors in Simulation to drive the wheels and steer, take a wheel off its hub, or select any piece to see its part number.

Bill of materials

Licences

Open in the ReDo Playground