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[MOC] Audi RS6 Avant

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This small-scale model was meant to pack as much functionality as possible into a small-scale model.

It came about when a friend and I decided to each build a model of the same vehicle at the same scale. Quite naturally, this grew into a technical arms race!



-Independent double-wishbone suspension front and rear

-All-wheel-drive using a buggy motor, with three differentials and a micro V8 piston engine

-8-speed sequential gearbox, shifted via Servo

-Basic brake with M-motor

-Pneumatic compressor with L-motor

-RC LED lights

-Suspension height adjustment (independent left/right, controlled by two Servo motors)

-Four-wheel steering with M-motor and pneumatics

-Pneumatic opening front doors

-Manual opening rear doors

-Pneumatic opening hatchback


Here are some more details and images of the car's features:


I was pleased with the appearance, but it was undoubtedly boxy, and the exterior was greatly constrained by the space the mechanics took up.










The suspension is of a double-wishbone independent design, as far as the wheels are concerned, but the drive is more complicated. The differentials are inside ball joint frames, which attach them to the chassis. Directly out of this frame come the CV joints that drive each wheel. Because my width only allowed for these two CV joints, the driven part of the axle resembles a solid axle, but each end of the axle hooks up to a double-wishbone system which attaches to the wheel. The system would have worked fine, but in practice the model was fresh out of ground clearance once all the cables were routed underneath, so it was more a novelty than anything else.






Drive was done with a buggy motor, in a bid to get tolerable performance in a package smaller than a pair of L-motors would have been. After drive went through the gearbox, it drove a 16/24T differential, which then went to the two axles, where new HD differentials took the drive to the four wheels. There was also a micro V8 piston engine in the front. Performance was shockingly good when tested partway through the build, but in the end, the addition of bodywork and cables that scraped the ground severely degraded performance until it would only drive, grudgingly, in the lower gears.



Here is the drive motor


Here you can see the engine.



The gearbox for this model was lifted straight out of my Ram Rebel TRX model, and was as such seriously overbuilt for such a small model. (Not that an underbuilt one would be much smaller). Rather than controlling it with PU, as in the Ram, it was controlled using a PF Servo motor with a ratcheting mechanism. As with drive, early tests were promising, but the cramming in of hoses and wires ended up causing the motor to jam all too often, though it did work fairly well.





Here are a couple images of a very similar gearbox, taken partway through the build process of my Ram






Believe it or not, I had originally hoped to include disc brakes on this model. I was early convinced of the folly of such a notion, though, so I settled for a simple design in which an M-motor, using a worm gear, presses a rubber axle joiner against the 24T gear of the central differential to slow down the model. Crude as it may be, it is more effective than most of my disc brake designs!






The compressor was a simple affair with an L-motor geared up a little before running a single pump.




Ride height adjustment:

The ride height could be adjusted with two Servo motors, one for each side of the car. The outputs of the motor would rotate 2L beams to push the shocks down to lift the car. Unfortunately, the fully lifted mode still scraped the ground, making the lowered mode useless.







The steering began simply enough, with the front wheels being steered with a small linear actuator driven from an M-motor. On top of this, however, a worm gear was added to the motor's output, which drove an 8T gear, which drove an eccentric mechanism, which cycled a pneumatic valve through left, center, and right positions. This valve operated a small pneumatic cylinder which steered the rear wheels, though only if the compressor was constantly ran.  Additionally, the system was set up such that a slight steering angle of the front wheels activated crab steering at the rear, while a more extreme steering angle of the front wheels activated normal four-wheel steering at the rear. This system was not practical, naturally, and the rear wheels would hardly move noticeably unless the rear of the car was lifted up.



The M-motor visible is for steering. The worm gear is ahead of it, and the cam part operates the eccentric mechanism for the valve at the bottom.




Opening stuff:

The front doors were opened simply with small pneumatic cylinders, the rear ones were opened manually, and the hatchback was opened with a long, thin pneumatic cylinder. The cylinder was not actually attached to the hatchback, but rather just pressed against a slope attached to the hatchback. They all worked fairly well (Not exactly a theme for this model, I suppose!)







I was quite happy with this model. It compromised a lot in its pursuit of absolute functionality, but in terms of building enjoyment, they were worth it.

More images can be seen at:

Sheesh! What did I do to make the image so small! I'll have to figure that out the next time I edit a video!


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That's a lot of functionality in a small car! I see you even put a driven shaft through the base of a pneumatic cylinder to mount it. Now I wonder what your friend build so we can choose who wins!

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The ammount of technic functions inside is as impressive as the bodywork is terrible :grin:

I think you should stick to boxy cars, that Pickup truck you made looked quite good despite your dislike of doing bodywork. This one on the other hand... I am sorry.

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9 hours ago, Gray Gear said:

The ammount of technic functions inside is as impressive as the bodywork is terrible :grin:

I think you should stick to boxy cars, that Pickup truck you made looked quite good despite your dislike of doing bodywork. This one on the other hand... I am sorry.

Yeah, I agree about sticking to the boxy. It lets me put in less effort, while still having a better-looking result!

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