Didumos69

Instructions are on Rebrickable. Please let me know if anything is not okay.

Thanks @Jim! Here is a video showing how the front and rear axles communicate and how the center module averages between them.

Cool!

Here's a first impression of the instructions. This is in fact the first and most delicate stage. It uses auxiliary parts just to get the gear alignment right: https://photos.app.goo.gl/nApcjaJFDebufCrx8

Sorry to bother you again guys, but this model is just so much fun. Also the low center of gravity pays off...

Here is the final video (turn on your speakers ):

I won't share the digital files. I will share instructions later this month. Thanks! To give an impression of the size; it's wheelbase is one stud longer than the Greyhound. Track width is 2 studs narrower.

Nice to see it together with the Greyhound. I also noticed 42099 is bigger then one would expect.

They are really fun. From couch to outdoor.. Take 1: Take 2:

Kids like to challenge it

Thanks! Luckily this model works with the control interface of the A-model, even without flipping the device upside down. I now even fall in love with the tilt-indicator, as it really follows the angle of the body, which is the interesting aspect of this B-model.

Thanks! I don't spend as much time as I did before, but I still enjoy building. Yeah, that's new for me too. And I even covered some empty holes with redundant connectors Yes, I will be making instructions. Won't share the digital file, because some building steps can not be deduced from the digital file alone. Thanks!

Rocky - 4WD Rock crawler buggy I would like to present to you 'Rocky', a rock crawler buggy with a body tilting angle that averages the angles made by the front and rear axles. My shot at a 42099 B-model. When I saw the first images of 42099, I noticed that the amount the body tilts sideways, is mostly defined by the rear axles angle, because that axle's suspension is the hardest - it carries the battery/control unit - and it's not pendular. That got me thinking; wouldn't it be nice to make a setup in which the body tilting angle averages the angles made by the front and rear axles? Just like how a Mars Rover averages it's body angle between it's rocker bogies - with a differential - but now sideways, not lengthwise. That way it should be possible to mimic the character of 4-link suspension, which is often seen in rock crawlers. So that was my objective with this B-model and the nice thing is that this model contains exactly the parts needed to build something like that. Axle articulation Here is the setup that interconnects front and rear axles. Like in rocker bogie suspension, you should regard the body as the differential house. The body tilting angle is defined by the two axles that point sideways. I used 4 gears in the differential itself to minimize slack in the system. There is some rotational slack of course, but this is even further reduced by 1:3 given the 20:60 gear ratio with the turntables. Center of gravity Besides the differential, the center module also houses the battery/control unit, because that unit includes the tilting sensor and I wanted the tilting sensor to show the tilting angle of the body. I also wanted to keep the center of gravity low and centered. However, putting the unit in this central spot did cause issues later on... The battery/control unit - not depicted here - plays an essential role in form-locking the whole center module. The battery/control unit can be slided out sideways after removing a few pins and parts. Spring suspension Besides axle articulation, I of course also wanted to include actual spring suspension, so I attached two main suspension arms to the turntables, one for the front axles and one for the rear axles. I suspended the main suspension arms with springs placed between the turntables and suspension arms. The springs are mounted differently to the front and rear suspension arms, giving the car a little more lift in the back, which adds to a nice inclination, or rake angle, of the whole model. The whole model nicely sinks into the spring suspension under its own weight up to about 40% percent of the overall spring travel. Drivetrain I wanted to have the most simple drive train possible, so the motors are directly attached to the frames holding the differentials. This is a crawler and with the new portal hubs, there is no need for any up or down gearing. The motors add to the stiffness of the main suspension arms. I also wanted to have a track width that is two studs wider than the stock 42099 build. After some playing around I found out I could use the new CV-joints the other way around to make that possible. Steering For steering I wanted minimal slack and double sided steering rods like in the stock 42099. I limited the steering angle to make sure the maximum angle the CV-joints make, does not cause any damage. I noticed the CV-joints start wobbling when the angle they make is too big. The steering rack assembly - as well as its back side counterpart - use a trick to minimize unintended movement (slack): The assemblies are 3 studs deep and incorporate 3L axles with end-stop. The end-stops are sticking out of the assemblies and make them slightly deeper than 3 studs. For this to work the end-stops need to slide along a smooth surface. This trick makes for a very nice fit with little play and still allows the assemblies to move very smoothly. Ground clearance To increase ground clearance I used a double wishbone setup, not suspended, to take advantage of the extra lift provided by the inclined wishbones. The rear wishbones are inclined more than the front wishbones, because there the CV-joints don't need to deal with the steering angle. At this stage I also added a set of minimalistic fenders ;-). Bodywork Finally, bodywork. This was the most challenging part for me. It needed to be removable, to provide access to the battery/control unit and I wanted it to live up to my foolproof standards. The whole model can be lifted by the roof or by the A(?)-pillars. At this stage I practically used all the pins that came with the set, so I had to do a lot of backtracking to get some pins available. I ended up using all pins, including the ones that came as spare parts. Interior RC don't have interior . When I wanted to test drive with a first bodywork attempt, I found out the hard way that I could not reach the on/off button of the battery/control unit. I had not taken that into account. Eventually I found a solution in making the roof openable, as if it were a hood, just by releasing two pins. The red 10L axle in the back can then be used to turn the controller on. After opening the roof, it can be removed easily, after which the sides of the body can be removed separately to access the battery/control unit. All together this has been a great experience. Especially the limited and pre-defined set of parts made it a real challenge. It forced me to revisit all constructions over and over again, and leave in only what is essential, without making concessions to my self-imposed building standards. I ended up using 828 of the 958 parts.

I can confirm. Where one suspension arm compresses, another can relax / expand. When taking a bump, the expanding one is typically the one opposite (diagonally) the compressing one. This is also more realistic. You are right of course and I admire the fact that you incorporate this approach in your models. It's very realistic. I grew up with my father's Meccano chassis and got stuck in center column chassis. Indeed very insightful. They also reflect what I tried to say in my response to @suffocation.

I can think of 2 things. 1.) Use transversal beams that lock together the frames you have running along the outside of your main structure. By locking these frames transversally, there will be less room for play / slack in the transversal pins tying your frames to your main structure. That way the frames also add to torsional rigidity. 2.) Suppose you have a center column with a lot of torsional twist, but with properly squared side walls (with frames) like in your carrier. When you look from above or from below while you twist it, you will see that the upper and bottom sides of the side walls will slide / rotate a little past each other, longitudinally. To fix this you can add frames or other connections that prevent the side walls of your column from sliding past each other, both in the top side and the bottom side of your column. In my rugged supercar this is exactly what I did (also after being disappointed about too much twist) and it made a lot of difference (see image below). I see you already have this kind of frames underneath the front and rear axles, but I don't know about the mid-section or the top-side of your center column.