Sariel.pl

Functional model of the APC from the James Cameron’s Aliens movie. Features 4×4 drive & steering, full suspension, remotely opened side slidedoor, manually opened driver’s door, remotely rotated turrets, lights and custom stickers.

Datasheet:

Completion date: 11/12/2008
Power: electric (Power Functions)
Dimensions:  length 61 studs / width 22 studs / height 19 studs
Weight:  2.49 kg
Suspension:  pendular with shock absorbers
Motors: 2 x 71427, 2 x PF Medium, 1 x PF XL

My first stricly movie-inspired model, preceded by a long period of a meticulous documentation. I’ve been planning to build it for over a year, and still had to do a lot of shopping before I started. Eventually, it turned out to be my most rare-parts-consuming project up to date.

The model can’t be described without an important point of reference – a model of the same vehicle built earlier by LUGPol user Havoc.  Havoc’s version was not functional, but had quite an accurate appearance, and featured full detailed  interior. My goal was to build a model of the same size, but fully functional. I did not’ however, rely much on the appearance of Havoc’s APC, and built many details in a different way, trying to introduce a number of my own improvements. Overall, my model had less and simplier small details, but better and more accurate silhouette. It was quite amusing to eventually learn that both versions had nearly identical weight.

I have started by choosing a different wheels than Havoc did. The 8448 set’s wheels were better suited in my opinion, because even though they lacked a military-style appearance, they looked very well with 8×8 dishes, and they offered a precious space for the suspension inside. I have used two identical suspension modules, partially based on my pendular steered & driven suspension module, but smaller and fitted with the 3-studs wide differentials. Each module was stabilized by a pair of shock absorbers, and the direction of driveshaft’s rotation was reverted in the middle of the hull, to neutralize the torque effect present in pendular suspensions. The steering lock was limited by the mudguards, but with both axles steered it sumed up very well. While the original vehicle was built from a pushback tug with the crab steering mode present, such a mode did not appear in the movie, and therefore I did not attempt to recreate it.

Full pendular suspension along with a longitudinal driveshaft and steering shaft crossing the middle of the hull has caused a major stability issue. Normally, a pendular suspension is fully stable as long as right and left sides of the vehicle have equal weights. Here, limited size of the hull and imposed location of internal mechanics did not allow me to place the heaviest internal components, that is the battery box plus drive and steering motors, in the middle of the hull. Instead, all internal components had to be moved to one of the vehicle’s sides. Therefore sides of the model had unequal weights, which I have almost fully compensated with nearly 200 grams of additional ballast on the model’s right side, next to the slidedoor.

As for the slidedoor, it was moved by a simple rack & pinion mechanism driven by a 71427 motor. Thanks to the use of safety clutch, it could be also moved manually at any time. The inertia that appears while this type of motor is stopping had added an unintentional effect that made the door appear heavy. The door’s construction turned out to be much more tricky than I have expected, as I was determined to build the door from plates, and therefore it lacked some stiffness. I have solved this problem by using a long horizontal rail attached to the bottom of the door, and additional short upper rail, that kept top of the door pressed against the hull. It required a small horizontal opening in the hull’s lower side, but worked very smoothly.

The rear turret was a tought matter, as it can be slided back to the APC’s rear wall in the movie. I have considered a number of ways to recreate such a movement, taking into account mainly the use of a chain & tread links. The limited size of the model, plus the amount of space occupied by its suspension made me drop that idea completely – such a chain would require at least 16-teeth gears to put it on, and the space behind the rear suspension barely sufficed for the steering system. Moreover, even with the space issue solved, it would be very difficult to make the turred slide steadily while mounted on such a loose structure as the chain. It would be very likely hung at angle while slided back, due to the backlash in the chain. To deal with it, a complex system of rails would have to be employed, resulting in an even greater need for internal hull space. Having considered that, I have used a turret able to rotate, but not slide, and made the rails on the back of the hull appear acid-soaked. Thus the immobility of the turret, which was inconsistent with the movie, could at least be explained in a movie-related way.

Both front & rear turret were rotated by separate motors through a safety clutches. I have used two various motors because of the very limited internal space in the hull’s front part, but both motors ran at similar speeds and rotated the turrets through exactly the same gear ratio. It resulted in very similar speeds of the turrets’ roration, and their independent movement if one of them became locked (which was inevitable in case of the front turret, whose range of rotation was limited by the hull).

The hull was built in a very non-Technic way. I wanted it to appear reasonably smooth – which meant for me using smooth surfaces where possible, but not trying to cover every single stud. This is well seen in the case of the top armour, which was fully covered with tiles in Havoc’s version while I attempted to use large tiles with studs on sides to render the pattern of riveted armour plates.

I have used a large number of stickers to decorate the hull, larger than the original vehicle had, on assumption that a military combat vehicle must bear a number of markings. Stickers in the front part of the APC were consistent with the original ones, and I have found and used military badges designed for the movie in some of the other stickers.

The model was warmly received, and many viewers considered it better-looking than the earlier Havoc’s version. The colour issue was brought up, and I agreed that the model would look better in dark grey, but it would be much more expensive and difficult to build, and still remain somewhat inconsistent with the movie where the original APC’s colour was a very dark green. I have, however, made the model unicoloured, just like the original one was. As for the performance, the model went through a lot of test-driving and performed very well, although its off-road capabilities were greatly limited by the very small ground clearance. Still, it was easy to drive and manoeuvre, and had plenty of torque. I’ve kept its speed low because it runs at such speed through the most of the movie, and I was afraid that it would be very difficult to access the drivetrain, should it malfunction while starting or stopping such a heavy model at a high speed.

Photos:

Video:

Media reference:

Klocki, JoeMonster