Didumos69

Great stuff! It will be hard to make a B-model out of these sets, but at least you can make your own parts relatively easily. Appearantly they are not offering the truck yet: https://ugears.onlin...chanical_models Maybe they are going to present it later as their first Ultimate set .

And this is an image with a 24o steering angle. Taking slack into account this will probably not fit.

Here's an image of the new wheel hub (from the official video).

Okay, the rims make the offset better, of course. For a moment I was thinking/hoping the hubs would have improved after all...

What is more realistic about the wheel hubs? They can be extended more easily because of the axle holes, but does that make them more realistic? Agreed.

One more thing about the steering angles. When driving over 50km/h you must be a very experienced driver to make use of more steering angle than what seems to be offered by the Porsche right now. (For the ones who need a good reason to accept the limited angles )

I was kidding ofcourse..

I was even thinking that using a differential doesn't really make sense given these steering angles :wink: , but let's not forget that on other aspects - gearbox, bodywork- this remains to be a truely great model. To a certain extend it resembles the state of the art that has been established by MOC-builders. Enough to complain, but also something to be proud of.

Thanks for clarifying!

What is 'not boxer' about the engine?

I think you're right. The suspension arms seem to be inserted much deeper than in the 15038-rims (by one stud if I'm not mistaken):

I was thinking the same. The new hubs have axle holes instead of ball joints, but I don't think the geometry differs from the old hubs. I don't know about the rims though. It would be nice if the hubs are inserted deeper into the rim than with existing rims. Does anybody know?

I think you're right. These are the max steering angles shown in the official video:

I agree with krisandkris12 that the whole idea could best be seen as an auxiliary system you engage when the surface is slippery. In that case the clutch gears make no sense, as there will be no windup on a slippery surface. And if you would incorporate clutch gears, I also agree that their operation will be far from smooth.

As for the battery boxes; they keep the center of gravity low and that's a good thing. You can read the increased weight from the suspension. You might end up needing two shockabsorbers for each axle . Or you could consider using independent lengthwise torsion bars for the upper wishbones.

Very nice! Those yellow wheels being loaded must be from a giant little big dump truck

Do you mean that also the U-joint dislodges from the wheel hub axle? Did you try placing two half bushes on the 3L axle between the CV-joint and the U-joint? That will at least prevent the 3L axle from being eaten up by the CV-joint. I had something similar once. The shaft of the CV-joint allows the 3L axle to move in and out while steering, which is necessary given your steering setup. However, when torque is applied the shaft tends to pull the 3L axle in, bit by bit, turn by turn. In my case the result was that the CV-joint pulled itself out of the differential.

Something like this (with the top-right axle being the extra input axle):

I can't help thinking about how to make this suitable for normal surfaces as well. If you could somehow put a 24 tooth clutch between each of the diffs out axles and the extra input axle, then the left and right out axles would have a chance to escape windup. That way this might also work on a surface with friction.

You are right. This is a compact solution and very suitable for ice or other slippery surfaces. More advaced solutions that would also work on normal roads would grow much bigger.

Absolutely amazing!

If I understand correctly you are forcing a fixed speed ratio between the left and right rear wheel. This works very well on ice, but on a surface with sufficient friction (a road) bypassing the differential this way will cause tyre scrub and windup. The idea is nice, but it would be even better to make a system that controls torque ratios rather than speed ratios. You could do this by combining a limited slip differential with a 3-speed gearbox on one of the output axles. The gearbox ratios should be symmetrical, for instance 3:1, 1: 1 and 1: 3. Now if the limited slip differential confines left-right torque ratios to [2:1 - 1:2], then you can force this to change to [6:1 - 3:2] or to [2:3 - 1:6] using the gearbox.

I really like the Chieftain, especially the 4 wheel steering combined with the single left-right differntial. I also like the absence of flex axles in it's body work. This way it looks sturdy and the few rough edges suit the vehicle well.

I found this easy to understand article in this matter, which states that under static conditions, "the friction angle must be larger than the lead angle to prevent back-driving", with the lead angle being the opposite of the helix angle. EDIT: When traversing the internet, the helix angle and lead angle appear to get mixed up quite often, especially in the context of worm gears. I suppose DrJB was referring to the same condition with his statement: "helix angle must be larger than the friction angle for the gear set to be reversible". The article also states that "It is usually impractical to design irreversible worm gearing with any security". If the statically self-locked worm gear is subject to shock and vibration, the friction coefficient between worm and gear may suddenly drop, causing the friction angle to drop below the lead angle. During the short time the friction angle drops below the lead angle, the gears are no longer self-locking and back-driving can occur. Once started, back-driving usually continues because the friction coefficient decreases once the gears are in motion. This effect has actually caused accidents in cases where lift devices relied on self-locking worm gears to hold the cargo in a desired position. Now back to LEGO. It is clear that with the lack of lubrication and the amount of friction involved, a LEGO worm gear mesh can be regarded as irreversible. However, as the OP's video showed us, the amount of friction involved in a worm gear mesh is a practical problem. This brings me to the following question: How to build a heavy load lift from LEGO (as in the video) that does not suffer from this progressive friction, but does prevent back-drive? My idea would be to combine both gear arrangements from the video (both with the same ratio, one with worm gear one without) and use them in parallel. The normal gears will take over where the worm gear would suffer from too much friction and the worm gear will prevent back-drive. Would that work? EDIT: Propably not, the normal gears will drive the worm gear.

The charm of all this is that in the end we've all come to a thorough understanding of the operation of worm gears. I truly think that's a good thing. Cheers!