[WIP] Audi R8

[Jeroen Ottens]

Hi,

Here is my latest MOC, a 1:8 scale replica of the Audi R8. I got inspired to start working on this when T_LEGO showed his Lamborghini Centario. From the get-go I wanted to incorporate as many functions as I could imagine in this model. Furthermore I wanted it to be largely motorized, modular and designed in an efficient way with a stiff and light chassis inside.

The chassis

To start with that, the chassis of this model is extremely stiff and light. This is due to the extensive use of the new 7x11 frames. No less than eleven frames where used. Instead of the classic central column I made a chassis that gets a lot of it's stiffness from the sides as well. Here you can see how the frame sits in the model:

The model is modular as well. It splits in three parts, the front axle, the midsection and the rearaxle. Each section is connected to the next one with two 3L pins-with-bush. To strengthen the connection further also a connection over the wheels is made with beams. In the picture above these beams can be seen quite clearly over the right front wheel.

The motorized functions

Now to the functions. First of all I wanted to use a small gearbox centered around a waveform selector to be able to select four different functions all driven by one motor. I placed two of these units in the car, one behind each seat. This then gives eight functions in total:

– Move the seats forward/backward (2x)
– Recline the seatrests (2x)
– Open the doors (2x)
– Select sportmode or comfortmode
– Raise/lower the rear spoiler

The doors are scissor doors. This is not a standard feature on an Audi, but I first developed the chassis before I decided on the make of the car. And apparently there are aftermarket door kits to upgrade your Audi to scissordoors, so it is not completely unheard from.

The gearbox

The next feature to mention is the gearbox. I wanted to build something different than the regular 8D+N+R gearbox that I used in the DB11 already back in 2016. So this time I made a transversal mounted, motorized, double clutch, sequential 7+R gearbox. Instead of using a 4-speed combined with a high-low gearbox this gearbox consists of two gearboxes that each have half of the gears. The gearbox on the right of the car has the R-2-4-6 gears and the gearbox on the left has 1-3-5-7. The gearratio range is bit limited, the highest gear is 2.1x the lowest gear (The full range of ratios is: -9.6 / 12.8 / 15 / 16 / 20 / 21.3 / 25 / 26.67).

The sequential selector

The sequencer mechanism is a bit more convoluted, because it should alternatingly switch the left and the right gearbox and furthermore it should also switch between the two inputs of the gearboxes. When the 1^st gear is selected the left gearbox should get the power from the engine and when the 2^nd gear is selected the enginepower must go to the right gearbox.

The sequential selector starts with the lime coloured knob gear. This one is driven by a Control+ L-motor, used as a servomotor. The lime coloured knobgear drives the yellow knobgear, which, through a 12:24 gearreduction, drives the yellow axle with a 2L beam-with-crossaxle. Every quarter rotation of the motor will result in a 45 degree rotation of this 2L beam. That gives eight positions between the two end points (0-45-90-135-180-225-270 degrees). The motor can be calibrated with the endstops.
The next red knobwheels are used to drive the two gearboxes (orange) and the input-switch (blue). As uou can see in each hole of the knobgears a 2L bar-with-towball is put. These towballs drive the orange knobgears and the blue knobgear. The orange knobgears are only switched every half turn (and out of phase of each other).
The orange axle has a 90 degree locking mechanism, which is basically a 5L beam that is springloaded against the #2 connector. This way the waveselector is always at 90 degrees increments, even though it is not constrained fully at the input.
The blue knobgear is switched back and forth with every 90 degrees of the red axle. Also this move is springloaded to ensure that the blue gearselector is always either left or right.

The rest of the designprocess

When I completed the chassis, the motorized functions and the gearbox it was time to decide which car I was actually going to build. It had to be a two seater, with a mid-engine, preferably all-wheel drive, a relatively long area behind the seats and not too much inward-taper on the sides towards the rear wheels. Especially that last requirement did throw out most of the modern hypercars. In the end it was a choice between a Pagani (Zonda or Huayra) or the Audi R8. Since I already had made a Pagani before I decided to choose the Audi.The bodywork of an Audi gives quite some interior space. Especially next to the V10 engine where some gaping holes that could easily fit a Control+ XL-motor on either side. That gave me the idea to also motorize the drive & steering. So I added that too.

The suspension setup

Until this point in the design I had a pushrod suspension setup in the front with ride height adjustment. For an Audi that actually didn't make much sense, but I had that designed as the first thing when I started. But when I wanted to motorize the drive and steering I needed place for an extra Control+ hub. And the only feasible place was right above the front differential. So I ditched the pushrod suspension and replaced it with a more standard suspension, but still with rideheight adjustment. When I started to play with it I noticed a difference in stiffness between the two rideheights, so I did the maths to see what was going on.

I attached the top mounting point of the suspension springs to a small lever than can rotate 90 degrees. When the lever is vertical the springs are angled more inwards and the wheels are lower then when the lever is horizontal. In that case the springs are oriented more vertical and the wheels sit a bit higher. As a consquence of these changes in geometry the suspension is about 20% stiffer in the sportsmode than in the comfortmode. The car is quite heavy, but with two springs per wheel the car sits about in the middle of the springtravel in comfortmode. In the following picture the change in geometry is shown:

As you can see the car sits about one stud lower in Sportsmode, but the suspensiontravel is also 0.5 studs less. Since the springs have the same stiffness in both setups this means that the effective stiffness of the sportsmode setup is 20% higher. I calculated about ten different geometries, but it turned out I had accidently chosen a geometry that was the best compromise between difference in stiffness between the two modes and difference in rideheight between the two modes.

Since I already had a Control+ hub over the rearaxle it was then a small step to use the same suspension setup in the back and change the ride-height-adjustment feature to a sportsmode feature.

The steering geometry

Also in the steeringgeometry I wanted to do that little bit more than the usual LEGO supercars. Of course it is an all wheel driven car. But next to that the frontwheel setup has a small casterangle and Ackermann geometry.

Final thoughts

Cramming this many functions in a car will lead to some compromises. In this case the interior space is quite small. Ideally the chairs could move another 4-5 studs backward, but that space is now occupied with all the gearing for the motorized functions. Also the building process has some pretty tricky steps where large modules have to come together while aligning a couple of axles at the same time. Also the drive mode selection probably requires manual help. The car is likely to be too heavy for the motor to lift it a stud.

A big letdown from the Control+ architecture is the lack of programming capability. These hubs are essentially useless unless you make something that uses the exact same setup as either offroader, small racecar or the excavator. I personally feel that LEGO dropped the ball on this one. I hope they soon release some form of a programming environment to really use these hubs. Until than, or until Sbrick pro is launched with Control+ support this model will stay WIP.

Comments, suggestions and questions are as always appreciated

Leg godt,

Jeroen
 

 

[Gray Gear]

It looks like an intresting model, do you have a video showing off the functions?

 

Your approach to building on this model is very weird...

1.Designs chassis with tons of functions, motorizing everything (exept driving+steering?!)

2. Decides what car could be built on the completed chassis (more or less, features dont really fit)

3. Realizes there is space to fit drive+steering, so time to add it.

What the hell dude?  

 

Also adding some more pictures would be cool, right now the front grill looks like a black hole, and I'd like to see the rear as well.

[Gimmick]

32 minutes ago, Jeroen Ottens said:

Hi,

 

The motorized functions

Now to the functions. First of all I wanted to use a small gearbox centered around a waveform selector to be able to select four different functions all driven by one motor. I placed two of these units in the car, one behind each seat. This then gives eight functions in total:

– Move the seats forward/backward (2x)
– Recline the seatrests (2x)
– Open the doors (2x)
– Select sportmode or comfortmode
– Raise/lower the rear spoiler

 

The sequential selector starts with the lime coloured knob gear. This one is driven by a Control+ L-motor, used as a servomotor. 

[...]

That gave me the idea to also motorize the drive & steering. So I added that too.

[...]

Final thoughts

A big letdown from the Control+ architecture is the lack of programming capability. These hubs are essentially useless unless you make something that uses the exact same setup as either offroader, small racecar or the excavator. I personally feel that LEGO dropped the ball on this one. I hope they soon release some form of a programming environment to really use these hubs. Until than, or until Sbrick pro is launched with Control+ support this model will stay WIP.

Comments, suggestions and questions are as always appreciated

Leg godt,

Jeroen

 

The amount of functions is realy impressive, I will have to read a few things again to understand what exactly is going on. Maybe, as Gray Gear already said, you can add some more pictures or a video that shows the functions.

Did I understand correctly, that you have:

2 motors to select the function for each seat individually

2 motors to drive the selected function for both seats

1 motor for the sequential gear

1 motor for driving

1 motor for steering

?

If you do not want to open the doors while driving, this may be possible to configure in the poweredup app.

[Didumos69]

Very nice and interesting! I love the gearbox setup. And building the chassis first is what I always do. Would also like to see a video of the functions. Those new 7x11 frames are indeed a game changer when it comes to building a stiff chassis.

[Jeroen Ottens]

36 minutes ago, Gray Gear said:

It looks like an intresting model, do you have a video showing off the functions?

 

Your approach to building on this model is very weird...

1.Designs chassis with tons of functions, motorizing everything (exept driving+steering?!)

2. Decides what car could be built on the completed chassis (more or less, features dont really fit)

3. Realizes there is space to fit drive+steering, so time to add it.

What the hell dude?  

 

Also adding some more pictures would be cool, right now the front grill looks like a black hole, and I'd like to see the rear as well.

No video, because all the functions depend on the servo ability of the Control+ motors. And since there is no proper SW platform to do these kind of advanced programs I can's show anything... I don't even know myself whether the functions work... More photos will come.
The design process was not really my standard process , but it was a fun exercise.

11 minutes ago, Gimmick said:

The amount of functions is realy impressive, I will have to read a few things again to understand what exactly is going on. Maybe, as Gray Gear already said, you can add some more pictures or a video that shows the functions.

Did I understand correctly, that you have:

2 motors to select the function for each seat individually

2 motors to drive the selected function for both seats

1 motor for the sequential gear

1 motor for driving

1 motor for steering

?

If you do not want to open the doors while driving, this may be possible to configure in the poweredup app.

The motors are divided as follows:
1 L motor to select the functions such as the chairs, the ridemode, the spoiler and the doors.
2 L-motors to drive these functions (one for each side)
1 L-motor for the sequential gearbox
2 XL-motors for drive
1 L motor for steering

It is a good suggestion to have some logic to check for the doors vs drive. Of course that does require some init-sequence when you start the car to ensure that the SW knows the state of the doors.

10 minutes ago, Didumos69 said:

Very nice and interesting! I love the gearbox setup. And building the chassis first is what I always do. Would also like to see a video of the functions. Those new 7x11 frames are indeed a game changer when it comes to building a stiff chassis.

Thanks. These frames are really amazing. This model has ~3100 parts, so 500 parts less than the Sián and a lot more functions (and lot easier bodywork). Most of this economy of parts is due to the use of these frames (I used 11 of them in the chassis).

[jorgeopesi]

Damn, at last a big R8 before mine, it just taking me 8 years not to finish it  . I think it is a bit low, at first sight it remembered to me the audi le mans.

Edited June 6, 2020 by jorgeopesi

[Gimmick]

1 hour ago, Jeroen Ottens said:

No video, because all the functions depend on the servo ability of the Control+ motors. And since there is no proper SW platform to do these kind of advanced programs I can's show anything... I don't even know myself whether the functions work... More photos will come.
The design process was not really my standard process , but it was a fun exercise.

The motors are divided as follows:
1 L motor to select the functions such as the chairs, the ridemode, the spoiler and the doors.
2 L-motors to drive these functions (one for each side)
1 L-motor for the sequential gearbox
2 XL-motors for drive
1 L motor for steering

It is a good suggestion to have some logic to check for the doors vs drive. Of course that does require some init-sequence when you start the car to ensure that the SW knows the state of the doors.

Thanks. These frames are really amazing. This model has ~3100 parts, so 500 parts less than the Sián and a lot more functions (and lot easier bodywork). Most of this economy of parts is due to the use of these frames (I used 11 of them in the chassis).

Disclaimer: PoweredUp app does currently not save the state when the app is closed, so I assume that the model is always shut down in an initial state (first gear, first mode, steering at center,...) or has to be calibrated every time.

I would count 5 modes: chairs, ridemode, spoiler, doors, drive

Mode selection with 1 button: 1,2,3,4,5,1,2... the numbers can be displayed, the function behind cannot be described

Mode 1-4: The sliders control both L motors or one slider for both motors (spoiler needs only one motor?)

Mode 5: The slider control 2XL for driving and L for steering + optional: switch first L motor to spoiler mode and lower/rise spoiler depending on motor speed

Mode 1-5: two buttons for gear up/down. Gear can be displayed as number

Work: A lot! I'm sure @kbalage would be happy to help xD :p I would recommend to use his basic driving interface as basis. :)

Edited June 6, 2020 by Gimmick
Great image added ;)

[All_About_Lego]

It looks great! - and wow that's a lot of functions - I also especially like the headlights you've created too! Great job!

[kbalage]

Amazing job as always, tons of features and some really fresh ideas in this one!

3 hours ago, Jeroen Ottens said:

A big letdown from the Control+ architecture is the lack of programming capability. These hubs are essentially useless unless you make something that uses the exact same setup as either offroader, small racecar or the excavator. I personally feel that LEGO dropped the ball on this one. I hope they soon release some form of a programming environment to really use these hubs. Until than, or until Sbrick pro is launched with Control+ support this model will stay WIP.

Actually at the moment they only have a programming capability for Powered Up (Control+ for me stays only the Technic set-specific app, the product family is PF 2.0 or Powered Up) and barely anything else. The non-Technic sets have the set-specific profiles in the Powered Up app, the Technic sets have the same in the Control+ app, and you have the advanced visual coding environment in the "free play" area of the Powered Up app. What we don't have at the moment that'd make it actually useful:

• official documentation
• customizable interface

I made a code block guide to help a bit with the first problem, but that's not a full documentation rather a description of each available block. You mentioned in another topic that you don't want to spend time with coding, actually to test the functions you don't need much. There are only a couple of code blocks that you need to use to control the motors (e.g. rotate 90 degrees), it shouldn't be difficult to set up the code for testing. If you need some help with this just PM me, if you tell me which hub and which motor on which port shall do what then it shouldn't be difficult.

About the interface - well that's a tough one, there're two interfaces with fixed elements at the moment, and even the better one is far from being good for anything else than a tracked vehicle. The next release should be around the corner with an important update for servo steering control, I'm not sure we'll also get any interface changes this time but I'd wait to see before starting to build the proper control interface.

[1963maniac]

This is a great bit of design and creativity. The transmission and suspension are new ideas.