Lucullus

Hello, I would like to show you a prototype of a torque distribution system for AWD cars. I made this because I am currently waiting for parts for my WRC car and when I thought about my next MOC I decided, that it should not be a rally car again, but still a motorsport vehicle and still have AWD, so i came across AWD touring cars. Among others, that also made it on the future moc list, the Nissan Skyline GTR R32 Group A came to my mind. Even though this car and especially its successors are a little "overhyped", it features an interesting AWD system, called ATTESA ETS. Basically it is a RWD drivetrain with a PTO to the front axle, connected by a multiplate clutch. This clutch is controlled by an ECU and steering, yaw, throttle and wheelspeed sensors. As I do not have any Mindstorms parts, I decided to use pneumatics to mimic the original system. How it works: The L-motor represents the normal RWD drivetrain as powersource. Yellow +o+ part represents front axle driveshaft. The differential is used as a clutch, when the diff housing is braked, torque will be transmitted to front axle. Braking is done by an 1x4 L-Beam that is pressed on an axle with a pinion gear. This pinion gear meshes with diff housing. Whenever the motor/driveshaft rotates, the pneumatic pumps are working, but the resistance is low, as long as the pneumatic valves do not seal the pneumatic system (air/pressure can escape). The valves are meant to be mechanical connected to throttle pedal and steering. When they are closed by throttle or steering input (or lack of it), the pressure increases and the cylinders press against the L-Beam. When pressure decreases again, the springs retract the cylinders. The pinion gear with friction pin is there for demonstration purpose (resistance at front axle). Video for demonstration: https://www.youtube.com/watch?v=rctAZeHzsLs Maybe the new 2h2018 pneumatic valves will be useful in this case (better implementation, more precise). Of course the playability of this feature will be limited, especially as I am planning to make the vehicle non RC, but a normal AWD would be too boring. I hope you like it, its not very advanced but a little different to the usual AWD systems arround.

Absolutely impressive. Do you have considered to use a transverse gearbox layout during development? Those are quite rare in Lego Fwd cars, unfortunately.

It is nice to see a rollcage in the rally car but the (fictional) rally car driver will have a hard time entering or exiting the vehicle, as he has to climb over that unfavorably placed 16l link. I think two axles and a #4 connector on each side would work better.

When the high res picture of the mack was made, no one seemed to care about the gap at the upper part of the cabin and the loose sticker near the front outriggers lever.

You even added technical features, as the real vehicle has no central diff (there were prototypes for 2017 season, that had one, but as VW stopped rallying after 2016 they were never used). However, it will improve the models playability. Sorry for this criticism, but as I am currently building the exact same thing (in bigger scale), I had to mention it.

What is the purpose of those 9l links? As they are connected to 3l beams, which seem to be able to rotate, they won't affect the suspension. Are they used for the b model?

Nice truck, but I think the suspension has one (theoretical) limitation based on the fact that the upper spring mounts seem to provide just one axis of rotation. If the suspension is compressed on one side only, the corresponding lower spring mount follows a curve. The resulting lateral movement must be compensated by the flexibility of the spring.

Maybe it is possible to replace the small turntables by normal wheel hubs, so that there is less offset when using wheels. It would require some modification of the axle units to fit with the wider center-part of the wheel hubs compared to turntables.

If you want to keep your suspension geometry as it is now, you have to connect the spring to the upper wishbone. Sometimes, the force, that is required to disassemble a lego connection, is smaller than the force that occurs while operating a mechanism. In your case, the spring disassembles the ball joint. If both wishbones were parallel and in equal length, you could simply add a vertical link to brace the connection, as it is in most official lego suspensions.

Are you sure that the crankshaft layout is correct? As far as I know, inline-4 engines use 180 degree crankpin offset.

According to manufacturers of cars with unsymetrical torque distribution, its main purpose is increasing the vehicles balance while cornering/corner exit. Therefore I think its hardly possible to observe any difference in performance of a lego car equipped with it (even if someone would be able to create a flawless lego representaion of the real system). PF and even buggy motors seem to be not powerfull enough to use such a systems potential. But if someones goal is to create a detailed representation of a vehicles drivetrain it might be worth to think about it.

Ok, my bad, i did not note the changing in rotational directions, its not locked but its a senseless construction (more like a complicated rear wheel drive). Please ignore it.

I found a solution to avoid permanent internal diff movement while keeping the uneven torque distribution. As a classic diff is nothing else than a planetary gear made with bevel gears, it is possible to swich positions of output and input. Something like this: In this case engine input comes from the u joint, while rear axles output is on the right. As long as both axles rotate at the same speed, the bevel gears wont move, but there is still more torque sent to the rear output, so the rear wheels will start to slip earlier if both axles have the same amount of traction. I tested it and it works fine.

The interesting thing about torque vectoring is, that its a misleading term as long as we use it to describe the rear axle mechanical torque vectoring diffs which can be found in Evos or Audis Sport Diff. Basically, they do not have the ability to 'send' more torque to a specific wheel than a classic Lsd or torsen could do, instead, their real advantage is to force both wheels to turn at different rotational speeds, just like a tracked vehicle. As the gearset of a TV diff causes the outer wheel to rotate faster, the maximum torque is even smaller as it would be without this device (more speed means less torque). In terms of centre diff, torque distribution is a more precise term regarding the way it works and does not necessarily need any limited slip device to work. Adding such a devise would upgrade it to a variable torque distribution.

Real AWD cars with unsymetrical torque distribution usually have planetary gears as central diff (e.g. early BMW xDrive) because those can be combined with viscous couplings or clutch packs as central diff lock. Your lego version would work as long as you dont add a diif lock directly to the central diff housing, but you could use a clutch to lock the front and rear driveshafts after they were geared up/down.

There is no need to use a central diff, if you want to stay as authentic as possible. The real version of this car uses a haldex clutch in front of the rear axle to transmit torque. Later, they used rigid coupling to connect the rear wheels in the competition version because the haldex clutch causes bad handling characteristics (unpredictable oversteer).

You could also put the tail rotors bevelgear to the left side of the helicopter. It makes more sence if it counteracts the main rotors rotation.

Thank You, yes, this cone-shaped arrangement of gears will be a 5-speed sequential gearbox, operated by a gear rack that slides a clutch gear. Underneath, there is an axle with five 16t gears, visible in the second picture, one of those gears meshes with the differential. The goal behind this arrangement (and behind the whole moc) is to recreate the original shape and position of the drivetrain-components as good as possible. Therefore it won´t be very suitable for power functions. I even doubt that it will roll very well because WRCs were not allowed to have a central differential till 2017 but, on the other hand, this makes building a lot easier. The double set of 16t gears in front of the diff shall represent an adjustable differential lock. You can either use none, one, or two clutch gears for different lock up levels or lock the diff completely by using normal 16t gears. Don´t expect this thing to be finsihed soon, I am not building frequently and it´s not easy to find technical information about WRCs. This picture seems to be the best source so far, it shows the internals of an s2000 car, the drivetrain is basically the same as the WRCs one.

Hello, I recently made a quite robust McPherson suspension as a part of my VW Polo WRC moc. It is far from beeing finished, but I think it will work well. I am not sure if this is adaptable to the Porsche as it uses the deeper rims and the shock absorbers may be to long. By the way, the layout with the damper passing in front of the hub can be found on the real rally car as well. It is used to gain bigger suspension travel. Sorry for the bad quality pics.

Test. WRC Suspension