Didumos69

I never knew about this. Actually, I have never built the Bugatti . However, I do know that even though this construction is a theoretical fit, there is enough play to allow for the gear (old and new) rubbing the beam.

I have only broken 2 universal joints over time, but maybe you guys are pushing it to the limit more, which is understandable of course. Isn't the best option to use the new CV-joints like @amorti did?

Make sure your arm is rigid and mount it properly at both ends, preferably with a single axle running through the arm. When it's pushrod style, center the spring nicely (left to right) to balance forces. When the spring is more straight up, bring it closer to the wheel.

What about Reverse as the default? Should be as smooth as second gear with the rpm of 1st gear.

If this section is so vulnerable to bending, then that axle probably also suffers from friction.

This is great news! @stevenhalim, what @Filthy Fox is saying makes sense. You should also check for bent axles: Source.

Thanks @stevenhalim! Did you test these changes with the gearbox only or installed in the complete model / chassis? I suspect there is friction somewhere down the line towards the engine. 1st and 5th gear would be the most sensitive to such friction.

Yes, this is correct. That is much appreciated! There will always be friction in these kind of gearboxes, because some patterns will go through many gears. If changing the 24-8 before the engine to 20:12 would make things acceptable, that would be ideal I think, changing the ratios close to the diffs will have more effect, because it gears down the whole gearbox. I will see if I can do something with the gearbox such that it uses more simpler patterns in 1st and 5th gears, but I think I explored most possibilities already. I have to say though, that the pimped-up Sian is not my project, but it's @jb70's. I just provide input. It's up to him to decide what should go in. And that's also how I like it to be.

I'm sorry, but now I remember! I was having a short break from LEGOs back then, so I haven't registered your messages about those BIs very well.

You are right. Reversing this will be hard to combine with having the gearbox inside the frame and having Reverse use the center differential. The overall setup has a very high RPM of the engine in 1st gear. Slightly higher than the pimped up Bugatti. The idea is that it should be comparable to the Bugatti. However, the Sian has a higher input RPM in the gearbox than the pimped Bugatti, so more friction. My suggestion would be to gear down the drivetrain a little, preferably by replacing the 20:12 gears close to the diffs with 16:16. If that doesn't help, then it could be an option to revert to the previous gearbox setup @jb70 had, the one with some gears outside the frame, but with Reverse using the center diff, with a different reverter in the DNR. That gearbox will follow the most simple path through the gearbox in 1st gear. But I'll leave that up to @jb70.

Sure. Here's the Stud.io file. You can easily make it a single phase, but adding a rear output will require some work. I do have this one with rear output (also on Rebrickable):

Can be made even shorter

For a dual-clutch gearbox with separate gearboxes for 1,3,5,7 and 2,4,6,8, I need a shifter that has two phases: phase 1 should change gears in the unengaged gearbox and phase 2 should toggle between the gearboxes. Here's a working concept for the shifter.