Didumos69

No, it's shorter.

A closed loop system is a system with a feedback mechanism that regulates the primary system. That should be doable with LEGOs. Self-sustainable is not possible. I think this classifies as a closed loop system:

59:10 30:6 22:4 48:3 40:2 4:1 This was a great contest with so many entries. One of the main criteria for me was whether a model succeeded in what it aims to be. Bit vague, but works for me.

Aha, then having a yellow bent liftarm makes sense. As for the removable roof. I think it would make the roof too high. Without the removable roof the proportions are spot on for the wrangle. With the removable roof on top, it looks more like a camel trophy defender. I know I was in the camp of adding a removable roof, but when I look at this image, I'd say don't change a thing. There already is a roof. It has 2 gaps, but it is a roof.

It's awesome already, but one thing: Can you make the top of the front screen half a stud lower? If you use two 3L axles and center 3 yellow half bushes on them, you still have 0.75 stud at each end to insert in the yellow connectors. EDIT: You already did this. I didn't see the posts on this page when I wrote the above. I'd say if you make everything in the roof black, including the bent lift arms, but keep the wind screen and doors yellow, you don't need an additional roof. Also keep that black side window.

Valid point. I was not being accurate enough. With 4 XL-motors the whole model should be able to go faster than with 4 L-motors, so these bevel gears will suffer more too. If I don't want more torque on the bevel gears than in greyhound I should indeed use L-motors. With L-motors I could actually use a 12:20 mesh in the 90 degree transitions, because they spin faster. I think I'll need to test drive with a few layouts to find out what the best option is.

Who knows, but they are massively big. I have a few of them laying around though. I'm that old My experience is they are especially inefficient under high torque, so for instance when used directly on the output of the motor. But I use a 24t gear to drive the 8t gear. I do need to gear up towards the differentials. I could use a 36t-12mesh, but things would grow very big. Too bad.

At least that won't slip. I will keep it in the back of my mind. Thanks!

⬆️ The mirrors match this photo.

You are right that the bevel gears are the bottle neck in the gearing. If I can find a simple way to gear up more and gear down in the wheel hubs, I will do so. But the 41099 planetary hubs have a lot of friction, so I fear I will never get any speed comparable to greyhound with them. If my setup is optimal for forward drive, I am not going to bother too much about the swift back/forwards moves. Moreover, the whole gearing as designed now, is based on what I know the bevel gears can handle in greyhound. In this case I use XL-motors, but I also use a 15:7 ratio, which I reckon should give me more or less the same torque as with L-motors at the same vehicle speed. It's all theoretical of course. I will have to see in real life.

Those swift back/forwards moves are indeed too much for LEGO material, whatever you try. For those bevel gears this would mean less speed and more torque at the same vehicle speed.

I hope so. I can even imagine the same piece being used in front and the rear wheel archs.

Okay, time for an update. I'v build the front axles and made some test drives with it using a single rear wheel. Conclusion: The hubs with caster are too sloppy, having no Ackermann geometry causes too much tire scrub in turns and the performance is disappointing. So I decided to go all the way and use 2 Buwizz and 4 Xl motors: I changed the wheel hubs so nothing relies on pinhole-axle connections, which should reduce slack substantially. I still have a caster angle, but slightly more modest than the setup I started with. The setup also has Ackermann geometry and steering rods that are heavily secured. And last but not least, I decided that this will the model to incorporate the dual diagonal drive idea that I had waiting. (The dual diagonal drive idea originates from this project, which combines dual diagonal drive with a 4-speed sequential gearbox. At the end of that project, I decided to no longer combine the two ideas, but to split them over future models, which is happening now.) Background I have been playing with this idea for a while already, especially after seeing @KevinMoo's dual drive models (Mitsubishi Pajero and Dual-Driveshaft Pickup). @KevinMoo rightfully addressed the vulnerability of LEGO parts in RC models and the fact that using independent drive trains for the left and right sides, loses the benefit of differentials while cornering. This got me thinking. Using independent drive trains for left and right in a 4WD model does indeed drop the benefit of differentials while cornering, but what if we would pair the wheels diagonally, so pair the left front (LF) wheel with the right rear (RR) wheel, and pair the right front (RF) wheel with the left rear (LR) wheel? The resulting 'dual diagonal drive' (I borrowed the term from the electric skateboard scene) would serve two major benefits: While cornering, the LF and RR wheels will average to a speed that is very close to the average speed of the RF and LR wheels. So not having an open distribution by means of a differential between the two drive trains is much less of a problem as with separate drive trains for the left and right side wheels. On a very uneven surface, where one or two wheels may lose contact with the ground, the wheels that do have contact are typically lined up diagonally, see image. With dual diagonal drive, the vehicle would still have traction, even without locking any differentials. Only on slippery surfaces, there are chances of spinning wheels. So this model will have two separate drive trains, one for the LF (left front) and RR (right rear) wheels and one for the RF (right front) and LR (left rear) wheels. The drive trains cross using 16t gears and and two auxiliary 24t gears. So no clutch gears are involved in this crossing. Each drive train has 2 XL-motors. The outputs are geared-up 3:1 and then down 5:7 to engage with a new differential, one for each drivetrain. The overall wheel-motor ratio is 15:7. Currently I'm in the process of wrapping it all in a firm structure. I intend to incorporate a V8 mid-engine driven by a M-motor.

The V-engine piece uses the same angle as the bent liftarms. To rotate any piece to this angle: place an axle on the ground. Place a bent liftarms next to it along with the piece you want to rotate. Now select the bent liftarm and the piece you want to rotate and connect the angled axle hole of the liftarm to the axle. Now you rotated the liftarm and your piece. Finally delete the auxiliary parts. Btw, the bent liftarms and the V-engine piece are all strongly related to the Pythagorean triple (3,4,5). See also this thread for more info:

Very nice and original model!

Can you make a removable roof?

The 4x2 lift arm in the roof is not available in medium blue, but maybe you could do the roof dark azure. And the perpendicular connector with 1 axle hole and 2 pin holes is not available in white. Also the red T-bone is not available in white. You could use light bluish gray for those pieces though.

So if you build it, you will truly build it. That shines a whole new light on building. You can build and you can truly build, like you can drink a hasty coffee and you can sit down and truly drink coffee. EDIT: Awesome model btw. I would also truly build it .

As a side note: There is something weird going on with wheel weight. In a car, having heavy wheels has all kinds of negative effects. For an offroad car for instance, there would be lots of unsuspended weight bumping up and down if the wheels would be heavy. However, when you ride a bike up a hill on tarmac, you obviously want the bike to be as light as possible. But if you have a minimum weight requirement, like for instance for road races, you better put most of the weight in the wheels. For riding uphill that is. The reason is that you can put more kinetic energy in your bike with less speed. And more kinetic energy means your legs can put in more pulse like power shots instead of putting in an almost constant power level. More pulse like power curves are more natural. We all know how it feels to ride up a steep hill, when you stop pedalling, you lose your speed immediately. If your wheels would carry lots of kinetic energy, just like a flywheel, you could stop pedalling without slowing down that quickly. But that's of course all not important to this thread.

I will most likely try with both options and test whether there is a difference. I will have to find out how fast it goes. Weight is a factor too of course, hence the preference for using less parts. Although you need some weight to get some inertia, I mean to get a tendency to respond slow to changing forces. So it won't respond to every single bump and will tilt in turns. To an acceptable extend of course. With too little weight you get what we see so often with LEGO, a silly bouncing vehicle.

@amorti, turning the CV-joints around will make the wide cup of the CV-joint collide with the axle holes of the turntable. However, by squeezing a 8t gear (without doing damage) over the axle side of the CV-joint inside the wheel side of the turntable, the CV-joint gets a firm grip on that side of the turntable.

I have that as a backup and it indeed gives half a stud extra offset. To tie the turntables to the Defender rims was a challenge though and required quite a few parts. I'm willing to accept the slack in the wheel hubs against the extra parts for the turntables. That chassis is a marvel btw. Using a different pivot point horizontally and vertically won't work with the CV joints, which have one pivot point for vertical and horizontal rotation.

I tested it manually, not with motors yet. All pivots are in one plane and the pivot point of the CV-joint inserted in the wheel hub lies exactly in the middle of the pivots for the suspension arms. So it's all symmetrical. The only concern I have is that the CV-joints can insert slightly too deep into the hubs (0.2 studs), causing them to de-center slightly and maybe pull the other CV-joint out of the differential.

I'm working on a 4WD chassis that uses the new power-up motors and battery unit, the new CV-joints from 41099, the new differential from 42109 and the new rims from 42110. I found a way to use the new CV-joints with the old wheel hubs, at the cost of one stud offset. The setup also incorporates a substantial caster angle. I will be using the new defender rims form the 42110 Defender to compensate for the bad offset. I intend to use this chassis for a RC rally car. The model will have 2 stud suspension travel all around. I will use this topic to show progress.