Brickend

Woah! Massive. That design kind of eats into where the load space should be. A 'blunt force' approach to giving it motive power. I stopped working on this when it wouldn't work at 62.4 tyre scale because I realised it would require a stupid amount of motive power to move and steer. My preference is also for the Lego official sets scale; as things get bigger, they can get cruder and the strength of the Lego itself doesn't proportionally increase, the structures become larger to even support themselves.

My understanding of the literature is that they can't do a 90 degree crab, but they can crab at angles less than that - they don't have the burden of mechanics going through the turntables.

Other issues I forgot to mention, is that if the axle assembly is too wide, or too deep, it may foul the tyres of the nearest bogie in the turns - assuming that the outer bogie turns at different angle to it's neighbour when in conventional steering mode. You can space the assemblies out to eradicate this, but in doing so may ruin the overall appearance of the vehicle. The above images do look interesting - I never went above the aforementioned 62.4 tyres, with a 3 stud wide sub axle (no diff) because the vehicle was already massive. With 24x43 or larger you may get it to work, but again, if the tyres are too wide (i.e balloon), I fear the fouling issue may still arise. You will also need to work out, when switching between crab and conventional steering, if you have to reverse the drive to the rear of the vehicle depending on the drive layout. An additional method that I tried, was to suspend the turntable on a parallel link - it made the drive situation a lot easier, but complicated the steering, the advantage is that the drive needs to be a lot stronger than the steering.

I've tried to make the mining truck previously - ended up buying 8 turntables but failed due the implementation of a purely mechanical solution to the drive train. The problem was that I wanted drive, steering and suspension. The sub axle must be central to the turntable, or it will not turn without massive resistance. Adding differentials was also out due to the scale of the wheels (62.4x20). When the sub axle is central, suspension with drive is very difficult without some sort of splined shaft. Unimog sized wheels would offer the chance to add a motor to each sub axle and maintain scale,thus making everything much simpler, but I find that idea quite boring, even if it is closer in principle to the transmission of the real machine.

I'm afraid it is not mine, I have edited my post as I did not intend to in any way misrepresent vincez01's work.

Your gear system is overly complex for what it needs to do to create a 1:1 ratio between the motors and the sprockets - see this for a simple version of the same result: vincez01 - http://www.brickshelf.com/cgi-bin/gallery.cgi?f=476366 As for speed, it sounds like you needed the torque from the lower gear ratio, compared to your previously higher ratio. I think your undercarriage might be generating a lot of friction as well, but I'm not sure as it is unconventional (but I like it in terms of realism). You could add another battery pack (one for each motor) or you could add selectable gear ratios. Fast for flat, straight-line speed, slow for hills and turns - but both solutions require more space and add more weight. You may have to accept that you have reached the limits of the PF setup.

Yes. Furthermore, giving each XL it's own receiver and battery pack would improve performance even more.

Parallelogram is good, only the perpendicular connectors anchor to a part that starts three studs wide and decreases in the turn. The distance between the perpendicular connectors is fixed, hence the self destruction. It's harder to describe than to make work.

How is the track tension? Is there a lot of friction? May be worth replacing the rear idler with a sprocket just to ensure that the track returns to the drive sprocket as in line as possible, if friction is an issue.

I can't see it too clearly, but your suspension system looks like it is quite neat - good work not using the bespoke parts to achieve it.

Really like this. It feels like the culmination of a lot of different sets; some focus on drive trains (admittedly often non powered), some focus on a central gearbox, others on pneumatics - at most containing 2 of these 3 items. This model integrates these concepts into the most realistic set yet.

Power functions in not an fair analogy as it has a degree of flexibility that is not served by the traditional RC markets. It does not directly try to compete; it almost universally under performs in relation to specialised motor/drive train combinations designed for specific tasks because it is designed for universal functions and to provide safe and lasting durability. Even when employed wrongly, it protects the Lego from the user. Look at how the actual radio control cars produced by Lego did - wonder why they weren't on sale for too long? You mention the bespoke cockpit canopy - in a the town sets there may be 3 or 4 vehicles that can make use of that every year (shuttles, jets, boats) and then within that; police/fire/airport versions of similar vehicles. When you upscale to Technic size, the flaws in this approach become more obvious as the market desires more detail and don't need to collect a working town system. A lot of the parts you want for the helicopter already exist, just not as you would like them. If Lego built them smaller and/or lighter they would become incompatible with systems that have built up over 30+ years. If they were dimensionally compatible, then they could inadvertently be built into drive trains where their poor durability would make them self destruct. So a kit of parts that can only be reused in a helicopter or light applications and would have to be stored away from the more durable Lego. Even if the flying mechanisms were sold as self contained units likes the drive parts of Lego RC cars, unlike the cars, you couldn't customise them with Lego parts because they'd then be too heavy to fly. And like the RC cars, you'd be paying a premium over the cheaper to produce, better integrated and performing, specialized products already in the market. Only the point of paying a premium for Lego is completely wiped out by the fact that you can't in fact use it with existing Lego at all - I can't see any reason why this venture would even have to be considered by Lego - it may as well be a standalone enterprise aimed at a narrow market, rather than something that confuses the existing Lego brand.

I read up until you started describing your own thing, my thoughts are that you want Lego to make something that isn't Lego. If you want a helicopter kit, the market is already satisfied. If you want a lot of parts with general uses ("Jack of all trades, master of none"), that are durable enough to survive being trodden on and dismantled countless times, you'd buy Lego.

It looks central to me. The rendered image is a partial build up which is then cut through. The actual diff seems to sit central on top of the 9 stud liftarm. What lurks behind the red bushing is what gets me. There is a circle of red behind it and unless a 3L Universal joint connects direct to the 16 tooth cog (which I don't think they'd do) it doesn't add up. The most amazing thing about this model, is that in spite all of these images, many of the functions hidden within are still technically undisclosed.

Hmm, not sure about some of those proportions, the middle one seems to me to be more accurate. Not keen on the new tyres, the tread is over large for this scale of vehicle. But very good to see an axle system that can take the weight of a MOC this size on only 4 wheels.

The real U400 has VarioPilot, which allows the ability to slide the steering console from the left to right hand side. This feature will be a nice challenge to build.

You managed to resist reading the earlier discussion in this thread about the springs though.

I'm not sure I understand why TLG's crane is seen as a joke. It is a simple crane, it doesn't pretend to be anything else. It is small enough as give some idea of the attachments a Unimog can take without being beyond the capacity of the compressor or the spending power of the the market it is aimed at, whilst bearing in mind the B model.

Largest, non balloon, non motorcycle, would be the 24x43, which were 86mm high tyres. I would like to see those tyres on the Unimog as I feel their narrower profile may actually look better. I still think the Unimog could do with the ride height being lowered by a stud or two and having the wheel arches protruding slightly more, but the joy of lego is that this can easily happen.

Wrong Moggy, you want this one: http://www.unimog-international.com/content/unimog_int/mpc/mpc_unimog_website/en/home_mpc/unimogs/home/system_unimog/showroom_by_model/u300_u400_u500/technical_data.0002.html Short wheel base version - so it'll be a nice project to build the longer version.

Good effort, but far from a clone in the true sense of the word.

Would be fun to rebuild one of these with new power functions.

One thing about this MOC that intrigued me is the gearing in the rear axle. My interpretation was that the 2 pairs of 24 teeth gears were used to reverse the drive, but this seems redundant when the yellow knob wheel could just be swapped to the other side. Is there a reason for this method in truck trial?

The real thing is brutal looking, the MOC takes that even further. It's interesting in that I wonder how such design decisions were reached.

The above design won't be able to steer due to the position of the UJ relative to the turning point of the Upright. Nor would the suspension function as you would need two UJs in the space where you only have one.