Porsche 911 (997) Turbo Cabriolet PDK

This car was previously called SuperCar 2011.

Note: PDK is the Porsche’s name to his dual clutch gearbox, and 997 is the generation (5th and actual).

Below you can find a more accurate description of the mechanisms

As fast details, the car weight 3.65kg, with around 3500 parts and more than 6 meters of wires

Final dimensions: 74 studs length, 31 width and 22 of height.

The car maintains all proportions of the real 911, either some of them hard to believe for example:

- the steering wheel axle is up to 22 degrees from the horizontal, as the real 911.
- the steering wheel turn exactly 2.6 laps, as the real 911.
- have a axle load weight, in 40% front and 60 rear(1460/2190gr), as the 911 Turbo Cabriolet version.

Electric system:

- 3 PF controllers
- 3 IR PF Receivers
- 2 RC motors
- 1 PF XL motor
- 5 PF M motors
- 3 PF lights
- 2 Lithium batteries
- 1 PF switch
- 3 PF wires 50cm
- 3 PF wires 20cm

The use of each element will be described in the next article.

Both lithium batteries are inside the front axle, there is the boot too, with 5x11x6 studs you can hold a PF controller.

For turning on or off the batteries is not necessary to open the hood, you only have to push a little lever located on the left side of the steering wheel.

Just in front of the co-pilot seat you can see a lever to open the hood.

The doors have a real lock, to open them just click the handle and will open smoothly. To close it, you only need push it and it will self-lock.

As outstanding remote controlled features:

- Front steering with working steering Wheel

- Front and rear lights

- Rear retractile and adjustable spoiler

- Folding top

- Handbrake

- Disc brakes with rear lights

- Dual clutch gearbox with 7+R speeds and auto-selection clutch

- Independent strenght clutch

- Remote progessive accelerator


The folding top and spoiler secuence.

Possibly, the most “wanted” photo for Lego Technic followers:

For finish a little video:





Complete Chassis

I have also copied (within the Lego limits) the structure of chassis and axle designs.

Unibody Chassis

Here you can see the car's unibody chassis, which is the most important and the more complicated part. It is very rigid and light.

Front axle

I have designed a McPherson as the 911 use. It has suspension, steering, disc brakes and drive.

Also this axle includes other mechanical features:

- Camber angle (~2 degrees)

- Ackerman steering

- Caster angle (~3.36 degrees)

Rear axle

This is a multilink axle type, as the 911 uses, which is much more realistic and also allows me to get away from the typical double-arm axles used in almost every Technic MOC. As extra feature this axle has camber angle(1 degree).

If you want more information about the chassis follow this link: SuperCar 2011 - Chassis

Gearbox and transmission

For describe more easily how the transmission works, I will go from drive motors to the wheels.

To start with, the transmission sequence has changed, from real:

- Engine -> clutch -> gearbox -> transmission -> wheels

to:

- Engine -> gearbox -> clutch -> transmission -> wheels

I’ve done it this way to keep the gearbox turning in every moment, so the transmission operates more smoothly.


Drive motors

For drive I have used two RC motors, because this combination is smaller than using 4 XL motors.

Each motor is connected to a battery (you can not connect 2 RC motors to one battery without electrical cut).

The motors send the transmission to the gearbox and to the fake engine, the classic Porsche Boxer-6.

Gearbox

As I previously said, I have used a dual clutch gearbox (Porsche’s PDK).

Really dual clutch gearboxes are two gearboxes, one with even speeds and reverse (R, 2nd, 4th and 6th) and other with odd speeds (1st, 3rd, 5th and 7th)

Here you can see gearbox structure:

Also I have copy the speeds ratio (or very close…).

A little graphical comparison between the real gearbox ratio and my MOC version (start with 1st=1):

The gearbox has a speed indicator over it. In any moment you can know the selected speed.

Clutches

I decided to do the never-done-before: radio-controlled friction clutches. Obviously the car has two of them, one behind each seat.

Probably, the mechanism for controlling them have been the most complicated challenge I’ve ever had.

Here you can see a little picture with clutches design:

The system push the last liftarm to the axle, and the round brick pushes the wheel to the first plate. By this system, torque passes over it and finishes in the transmission.


Clutches working

Clutch selection comes from gearbox through some mechanism and finished in the corresponding clutch.

And now, the best part of the car: the strength to push the clutches don’t comes from gearbox, comes of secondary motor, controlling this motor you can control the car movement, regardless of the accelerator, as a real clutch pedal!!!

While you keep the secondary motor working, the corresponding clutch will be connected, so when you let it go, the clutch will self-disconnect and the car stops.  

After the clutch, the force goes to central diff, and from there to the axles and wheels.

I know that is very strange, now I am filming a video with all features working.

Accelerator

To avoid having to keep two functions pushed at the same time, you can select a velocity for drive motors.

Both motors velocity are controlled by the integrated regulator in lithium batteries, this last one is controlled by an M motor from the remote control. Another way to make that is using a train controller, but that forces me to use a forth IR receiver.

In this picture you can see the regulator gears:

The front and rear lights works at the same time that motors.

The mechanism has a cap to prevent the motors turn in opposite direction. If you want to go back, you should select reverse in the gearbox.

Brakes

The car uses a disc brakes system in all wheels. The brakes are actuated by the same motor which actuated the clutches

You can see more pictures here:
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=471737

I hope you like it!!!