Didumos69

My ratios are something like 0.16, 0.26, 0.33, 0.45, 0.6, 0.8, 1.0. Of course there is some symmetry involved. And no idler gears transmitting torque.

Funny, because I'm working on the same concept, but with a 2-phase shifter. Pulling or pushing the shift lever will first shift the unengaged gearbox to a higher or lower gear and recentering the shift lever will toggle from engaged gearbox to unengaged gearbox. I have a 0.8 ratio between the odd and even gearbox.

So you have an OR gate, which will induce a lot of friction by itself, as the torque will translate itself to a moment of force to the pivot point, which is the drive axle. Also, it requires the drive axle to reverse to select the other gear. If this is intended as high-low selector, you need another selector to reverse the input or not. How on earth is this going to help in making the above gearbox, which as depicted only works when a single clutch is engaged, an 8 speed gearbox? Can you make a sketch with black boxes for the main components and short descriptions of what they should do?

For those not familiar with the mods and improvements thread, here are 2 renders showing how @jb70 and I could simplify the stock drivetrain while adding a 8->1 gear block and a center differential which is used for both Drive and Reverse. If you run into problems with the stock drivetrain, now you know it can be fixed (and it could have been right in the first place).

Very nice! Thanks for putting this together! Here's a 2 renders showing the before (back) and after (front). Note that the center differential is used in both Drive and Reverse. EDIT: @jb70, I think the lime green (ox)-piece used to switch the high-low selector still needs to be reverted to its stock position in your files.

I don't know, but what you're showing here, is a 4-speed gearbox with 2 driving rings and 2 rotary catches (similar to this one). If you would engage more than one clutch gear, it will jam. Also, this gearbox relies on transmitting torque via idler gears that are not placed in one line, which is a recipe for severe friction in at least one direction. Still, and maybe that is what you're looking for, you could make two equal 4-speed gearboxes, with slightly different input ratios such that one can be used for gears 1, 3, 5, 7 and the other for 2, 4, 6, 8, and combine that with a selector (OR gate) that toggles between the 2 gearboxes. @Jeroen Ottens did something like that in his Audi R8. If you would go one step further and make a shift a 2-phase shift with phase 1 putting the not-engaged gearbox in the right gear and phase 2 selecting the not-engaged gearbox, you would have a real dual clutch gearbox. Or you could use 2 gearboxes and combine the 2 outputs with a differential.

When the suspension arms and steering links are not the same length, you get toe-in or toe-out when the suspension arms and steering links are not flat. In this case the model will suffer from toe-out when the suspension is not compressed. EDIT: When the suspension arms are angled (when the suspension is expanded), they will move the wheel slightly inwards. The longer steering links will be less angled and pull the wheel less inward.

Here's an attempt to add Ackermann geometry (and to get rid of the 9L steering links). Stud.io file here (based on @jb70's 3D file).

Bricklink.

It's hard to tell, but I suppose this is a real life example of what @allanp pointed out. Perhaps the upcoming pimped Sian by @jb70 will bring salvation. I also noticed that many axles are slightly bent out of the box. This is killing for drivetrain that need to run smoothly. I also always check my axles before I use them in a gearbox. I use the bent ones for construction only.

Normally you should be able to click them together again with some force.

Sure.

This is about the Bugatti. I need more context. Where did I post this exactly? EDIT: It was here. I guess what they did wrong is putting it in second gear before adding the tow ball assembly. You should stick to the instructions, just make sure it remains in 1st gear until you add the tow ball.

One that I'm pretty sure about is this 4-speed (without idlers transmitting torque). Instructions are in the link: And the one discussed in this topic should also work properly.

I don't think such a thing has been documented. You could make it an exercise trying to get the basics of the pimped Bugatti gearbox, without the center differential, using the stock parts. EDIT: Or use the images in this post as a source of inspiration: I wanted to add a touch of drama to the whole flawed gearbox thing.

@BaaaaL, read this. And then move on to https://rebrickable.com/mocs/MOC-16181/jb70/42083-pimp-up-my-bugatti/. The stock Bugatti gearbox was a total flaw and has been improved by MOC-ers dramastically. Courtesy of @jb70.

@Filthy Fox, @allanp, the stock Lamborghini gearbox has 4 idlers transmitting torque, of which one is very suspicious. I really don't understand why they made it so complex, because the same ratios can be obtained with much less gear meshes.

Very nice!

Thanks @allanp for this elaborate explanation. It makes total sense to me and confirms my own line of reasoning. This is why I always avoid idler gears transmitting torque. In my designs (except for some mods for Bugatti and Lamborghini) clutch gears are either engaged with a driving ring or they are just making dummy rotations and not transmitting torque. For instance in this 8-speed transmission tunnel. The gearboxes of the Bugatti and the Lamborghini have the high-low gearbox and the 4-speed gearbox layed out next to each other, with several idler gears transmitting torque from one gearbox to the other. In this 8-speed tunnel I layed out the same gearboxes longitudinally which allows them to be connected without using torque transmitting idler gears.

Yes, reasoning from engine to wheels. For that I would reason from wheels to engine, because this is a manual build, so the wheels effectively drive the engine. I would opt for the gearbox with the least amount of gearing up, so the least increase of rpm as the one that should be closest to the wheels. In the above case the high-low gearbox either has a 1:1 ratio or it gears down with 12:20 x 12:20 = 9:25 (reasoning from wheels to engine). The 4-speed gearbox actually gears up by 20:16 in 1st gear (again reasoning from wheels to engine), so I would connect that one to the engine and the high-low gearbox to the wheels, which is the case in the above example.

That's a valid question. Under high torque, like in RC builds with some gearing down, having a 8t-8t mesh is indeed not a good idea. Building gearboxes for RC puts completely different demands on the drivetrain. However, in a manual build, with a supposedly smooth running drivetrain, but even with some friction, this should not be an issue. This kind of setups have also proven itself in many manual builds, for instance the pimped up Bugatti. All of-the-shelf LEGO 8-speed gearboxes (42083, 42115) are in fact a combination of a high-low gearbox (bottom of the above image) and a 4-speed gearbox (top of above image). To make this work, without too much friction, the overall ratio variation should not be too extensive. In the stock Bugatti and Stock Lamborghini, the high-low gearbox has 2 ratios, 1:1 and 20:12 x 20:12 = 25:9, so the variation is 1:1 -> 25:9. The 4-speed gearbox ratios should be within this range; it should have a smaller variation to make sure the combination of low gear and 4th gear does not exceed nor level with the combination high gear and 1st gear. Another aspect to this is that the 4-speed gearbox itself (as do all sequential gearboxes of this type, see here), is required to have the ratio between it's inputs (in the above case (1:1):(16:20) = 20:16) smaller than the ratio between the front and rear ends of the driving rings (in the above case (20:12):(1:1)=20:12), otherwise you would never get the sequence right. And together they should not exceed the 25:9 of the high-low gearbox: 20:16 x 20:12 = 25:12 > 25:9. When we would replace the 20:16 with your 24:8 x 12:20 = 9:5, the 4-speed gearbox ratios (9:5 x 20:12 = 3:1) would exceed the high-low ratios (25:9).

It relies on my setup with the different reverter, the one with the 2 8t gears, where the DNR has different outputs ratios for Drive and Reverse to compensate for different input ratios for Drive and Reverse of the gearbox. It also restores the stock gear sequence. This one: @jb70, here is the file with this drivetrain.

I think the gearbox with center differential, separate inputs for Reverse and Drive and an 8->1 gear block should fit inside the 11x15 frame...

This observation remains valid. But the good thing is that things can be modded to make it work.

I enjoy all this suffering so intensely .