Didumos69

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. Instructions are available on Rebrickable. 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.

So it has vertical cohesion, which is good, but when your model is going to weigh 2.5kg, you need some cohesion in other dimensions too. One thing I notice is that you are using quite a few lengthwise beams with their holes placed vertically. At this stage this will behave fine, but when your model gets heavier, the chassis will want to bend under its own weight. With the vertically oriented beams in your chassis, not bending will rely on friction-locking rather than form-locking. The bend-under-own-weight forces apply vertically and the pins holding the structure together are oriented vertically too. These forces only need to overcome the friction implied when pulling a pin straight out of a beam. When you use beams with their holes oriented horizontally, the bend-under-own-weight forces will apply orthogonal to the pins holding your structure together and we all know it is very hard to pull a pin out by pulling it sideways. This is what we refer to as form-locking. This is very recognizable! Even when you only add Ackermann geometry the handling gets so much more fun, even in very light-weight models (I know the model below has very poor geometry apart from Ackermann). You might consider assembling them yourself from the cheaper 2909c03 (Technic Shock Absorber 9.5L with Soft Springs) and non-LEGO springs. On doctor-brick.de the following springs have been suggested:

Interesting topic. In my believe, the two main aspects of building a good chassis are 1) coherence and 2) rigidity, in that order, because you first of all don't want your chassis to come apart too easily. Rigidity is sometimes not even a requirement, the UNIMOG chassis for instance has flex by design. Then again, when a model stores a complex drive train with gearbox etc. and you want it to run smoothly, rigidity becomes equally important. Personally, I tend to strive for both coherence and rigidity. Coherence - Coherence (the quality of not coming apart easily) of a model can be obtained by using form-locking. Form-locking, as opposed to friction-locking, means that the main forces your chassis gets to deal with, work orthogonal to the main pins and axles that hold together your construction. For example: When you have several connected beams spanning the length of your chassis, it is better to have them oriented with their pinholes horizontally than with their pinholes vertically. Otherwise your vehicle is likely to fall apart under its own weight. However, if the first line of pins or axles holding together your structure can easily work their way out over time, your chassis will still come apart. If this is a likely event, you need to form-lock these pins and axles too, which means adding form-locking in a 2nd degree / dimension. Likewise you can add a 3rd form-locking dimension. To understand how, I need to explain a little about 'assembly closure'. People that know my builds, will probably recognize that my constructs (read larger assemblies) are usually 'closed' or 'locked' with 'closure' pins or axles. The 'closed' construct is completely locked-up in all 3 dimensions and will only come apart by breaking pieces or after removing the 'closure' pins or axles again. This is also why I often have 3L pins with bush and axles sticking out of my main structures. Rigidity - To avoid bending in your chassis it is important to have some kind of bridge or console running through the middle of your chassis from the front all the way to the back. The higher, the better. I would say at least 5 studs high. To avoid torsional flex in such a bridge, you have to make sure the beams setting up your bridge remain squared. This is where triangles and squared elements such as frames and panels come into play. This allows for stiff but narrow bridge / console. So making use of frames and panels adds to overall rigidity, but even more so when used in all 3 dimensions and even more so when form-locked into your structure. To obtain a structure which incorporates frames in all dimensions, I usually work with base layers: lengthwise beams with horizontal frames in odd layers and widthwise beams with vertical frames in even layers.

That makes perfect sense. Probably, however, the distance between shock and rotation point is one thing, but the length of the suspension arm also plays a role. The distance between the shock and the rotation point defines the relation between weight and shock compression, but a longer suspension arm may feel softer simply because it has more travel. It will require less weight (= less shock compression) to make the same absolute travel. So a light buggy may sink into its suspension under its own weight just as much as a heavy car using the same shock placement, simply by applying longer suspension arms. Great car btw

I think the up gearing was done to protect the cv-joints and differentials. The one good thing about this model is that it follows the best practice on how to avoid slipping gears, broken joints and twisted axles in the drive train / differentials: it works with high rpm / low torque instead of low rpm / high torque. And the first thing you want to do is nullify this design pattern. Imo, the real problem behind the poor performance lies in the controllers cutting off power too soon.

If a MOC reviewer would emerge on this forum, someone who would be for MOCs what @Jim is for sets, there would be room for critisizm too. Such a reviewer would be able to relate to other MOCs and share info on building style (say something on illegal constructions if applicable), techniques and experience (say something about nearly impossible building steps if applicable) from a knowledgeable point of view and this info could be very useful for people looking for a MOC to build. I know from the MOCs I shared on rebrickable, there is quite a large group of AFOLs who like to build MOCs with the parts they own, or at most few parts to buy. In fact that is the whole essence of rebrickable.

Based on what? Do you actually build MOCs? Going by what is frontpaged on this site I believe you have a sense for what is awesome, but I don't believe you have thorough knowledge of, or interest in, out of the box building experiences or building techniques shared by MOCers on this forum. I fully agree with @nerdsforprez's line of arguing in this subject.

Even better?! I'm looking forward to seeing a video.

Very cool! With the new wheel design the tires seem to fit excellently

This is an awesome model! One question, can it shift gears while driving?

But then you also need something that keeps the body centered.

Yeah, with the new rotary catch a much more simple 4-speed should be possible. I hope it will be nothing like the 42056 gearbox because in that gearbox everything is wrong that you can possibly do wrong.

Live axle is better for crawling very uneven surfaces and independent suspension is better for offroad racing. Look at the buggy's race classes. In Ultra4 (4wd) live axles are most common and in class one (rwd) independent suspension is more common. Ifs, and also irs, are gaining terrain also in Ultra4 though. This has a lot to do with better parts, such as narrower differentials. And independent suspension gives better ground clearance. One more thing: Also a LEGO-built 4x4 with independent suspension can be quite capable on uneven surfaces, as long as all wheels can participate in traction, which means enough suspension travel and smooth articulation. In serious awd SUV land, the competition is more about keeping traction on a slippery surface, or while one wheel is off the ground, which means smart torque balancing etc. This is a great field of exploration too.

You are quite right. You would expect them to have used the small bright light orange panels, as they already exist. This makes me believe it's not bright light orange, even though I still hope it is.

I think the color is 'bright light orange', as in:

From the same site: The real model appears to have double wishbone suspension:

My eyes are constantly drawn towards the line of roofing tile along the flanks. It just feels so misplaced.

I agree the axle hole is the weak link during play, but when the model stands still for months it will slowly twist the torsion axle under its own weight. I know this from experience. Only when the torsion bar is auxiliary and carries only a fraction of the weight, causing only light torsional tension, it won't twist over time. The black axles from the 1970s had a different blend and did not twist over time, but these could break fairly easily under serious torsion.

It looks like something like this, but I very much doubt if LEGO would add such a feature. It will twist the torsion axle over time. I hope so too. If it uses the new CV-joints from 42099, I suppose at least the rotating part of the wheel hub will be new too. So why not also the new hub with Ackermann geometry we see in 42099, hopefully without the gear reduction.