42115 Lamborghini Sian MODs and Improvements

[Didumos69]

@I_Igor, @astyanax, guys, one small request. I would really like to see mods and improvements here and not all kinds of speculations on B-models with large images. This is not the mods and improvements and b-models speculations topic .

[Appie]

Great work on the gearbox @Didumos69! 

[1gor]

1 hour ago, Didumos69 said:

@I_Igor, @astyanax, guys, one small request. I would really like to see mods and improvements here and not all kinds of speculations on B-models with large images. This is not the mods and improvements and b-models speculations topic .

Perhaps you are right; it is complete turnover from some point of view...but if I could afford Lamborghini (Lego set of course) I would defensively try to make at least classic Miura

[astyanax]

3 hours ago, Didumos69 said:

@I_Igor, @astyanax, guys, one small request. I would really like to see mods and improvements here and not all kinds of speculations on B-models with large images. This is not the mods and improvements and b-models speculations topic .

But but... @Ngoc Nguyen started it! 

[Points finger and throws tantrum]

But seriously, seems like there's room for a whole "OMG can we recolor this and that MOC in lime now?!!1" thread... 

[Didumos69]

7 hours ago, astyanax said:

But but... @Ngoc Nguyen started it! 

[Points finger and throws tantrum]

But seriously, seems like there's room for a whole "OMG can we recolor this and that MOC in lime now?!!1" thread... 

Usually we have a thread for new parts if they feel like a game changer. I think the new curved wheel arches are a reason. They allow for many existing models to be redone.

EDIT: I made such a thread.

Edited June 17, 2020 by Didumos69

[Didumos69]

As a further development of the incorporation of a center differential for both Drive and Reverse, this is an option that does not need a 2nd new CV-joint because of it's longer axle (the model comes with only 1 such new CV-joint). In this case the DNR has a different ratio for Reverse (1:1) compared to Drive (20:16). The gearbox can easily be changed to compensate for this difference, giving 1st gear and Reverse again the exact same overall ratio. The dark azure pieces highlight the changes (the transparent piece could be removed). As a side effect, the gear sequence is back to the stock sequence again.

Edited June 17, 2020 by Didumos69

[astyanax]

I notice for the first time that the front and rear diffs both transfer drive through 2x 20z -> 12z gears. Why this redundancy? Does it avoid gear skipping?

[Magical Duck]

2 hours ago, astyanax said:

I notice for the first time that the front and rear diffs both transfer drive through 2x 20z -> 12z gears. Why this redundancy? Does it avoid gear skipping?

I expect so, as the model is easily as heavy as the 42110 Defender (which had gear skips), with an equally if not more complex gearbox and without a central differential to balance the speeds from each axle.

[JunkstyleGio]

Made an add-on for the Lambo. A stand for better display.

 

I will post Stud.io file with instructions if needed!

 

[Didumos69]

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...

 

Edited June 21, 2020 by Didumos69

[Filthy Fox]

Does anyone know why in some sets and mocs, the drivetrain has way more friction in one direction than the other?

This has been a long problem of mine and I haven't been able to solve it. (Land Rover, Porsche, the Lambo, mocs, etc.)

[DataNinja]

Hmmm, anyone notice there's a lot of room in the engine compartment just behind the suspension group when the fuel tank is removed?  I'm thinking that's an ideal possibility for 4 wheel steering.  This link indicates the real-world Sian has this feature, so would be accurate to the vehicle.  Rear wheels would turn much less than the front wheels (smaller rotation angle), so would need to be geared down significantly.  Maybe not even need a steering rack at all.  Could be tight, but I plan to connect up to the front steering group on the passenger side of the vehicle, above the transmission gears and probably weave through the headers.  Too much going on in the cockpit with the paddle shifters on the drivers side.  Just ideas at this point, but working on it...

 

[jb70]

 

In the last days I have build the Pimp up my Lamborghini Project in a real model. To be able to build it efficiently I created building instructions for myself and optimized them while building it so far.

I changed many small things on the way to go to make it work and satisfy myself (change sequence in the building instructions, modify some colors to get a clean build, optimizing some parts, etc.). Main technical change was in the Hand-Of-God shifting. I added two gear meshes to gear it down. Now the gear indicator only turns about 225 degrees between 1st and 8th gear. In my first solution with the knob gears it turned twice from 1st to 8th gear.

On page 95 the chassis with all the technical features for drive, gearbox and steering have been finished making it ready for a TEST DRIVE.

I am very satisfied with my TEST DRIVE. All modified features (Gearbox, HOG steering and shifting) work very smart and smooth. 

 

If you like, take a look at the digital model (MPD) and building instructions (PDF) so far. The project is still WORK-IN-PROGRESS, but I will upload regular updates on this page:

https://bricksafe.com/pages/jb70/42115-pimp-up-my-lamborghini

 

8 hours ago, Didumos69 said:

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...

@Didumos69 You really managed it to get all the gears inside the frame? - That's very cool!!!

I will have a look on this, test it in my real build and will give feedback to you!

Edited June 21, 2020 by jb70

[Didumos69]

1 hour ago, jb70 said:

@Didumos69 You really managed it to get all the gears inside the frame? - That's very cool!!!

I will have a look on this, test it in my real build and will give feedback to you!

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.

Edited June 21, 2020 by Didumos69

[SamuelYsc]

Sorry for step in the middle of the discussion, I have something of the gearbox design want to ask and learn:

Photo by Didumos69

On the right top corner of the photo above, we see there has 2 8T(new) gear1:1 used on the transition and follow by 20:16 gear.
I see a lot of gearbox design is using this kind of method in the transition, but I am worried about that 2 8T is not doing very good in high torque, although this is not a gearbox for RC car.
Is that could be replaced by 24:8 and follow by 12:20?

[Didumos69]

6 hours ago, SamuelYsc said:

On the right top corner of the photo above, we see there has 2 8T(new) gear1:1 used on the transition and follow by 20:16 gear.
I see a lot of gearbox design is using this kind of method in the transition, but I am worried about that 2 8T is not doing very good in high torque, although this is not a gearbox for RC car.
Is that could be replaced by 24:8 and follow by 12:20?

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).

Edited June 22, 2020 by Didumos69

[SamuelYsc]

 

 

 

 

 

 

 

 

 

 

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7 minutes ago, Didumos69 said:

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 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).

Thanks for the detailed explanation!
I am still new on gearbox designs and still so much to learn, thanks again!

After a few minutes of thinking I finally understand where is the problem. Damn, that was not a good idea.
Maybe the 8T-8T on that position will be the best solution.

And one last (stupid) question for the gearbox design, those number for example 20:16 are meaning [input]:[output] right?
Then on the case of high-low gear manual car design, would you prefer the gear-train run through the high-low gear selection than the 4speed OR the 4speed than high-low gear selection? or... it does not have much different?

[Didumos69]

4 hours ago, SamuelYsc said:

And one last (stupid) question for the gearbox design, those number for example 20:16 are meaning [input]:[output] right?

Yes, reasoning from engine to wheels.

4 hours ago, SamuelYsc said:

Then on the case of high-low gear manual car design, would you prefer the gear-train run through the high-low gear selection than the 4speed OR the 4speed than high-low gear selection? or... it does not have much different?

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.

Edited June 22, 2020 by Didumos69

[SamuelYsc]

11 minutes ago, Didumos69 said:

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.

Once again, thanks for the explanation!  

[astyanax]

Thanks @Didumos69, I'm reading along with great interest. (Also thanks @SamuelYsc for prompting him )

[Filthy Fox]

Here's a quick and crappy video of mine, demonstrating the friction in the Sian's gearbox. This only happens with 7th gear; it only works in one direction without grinding/stopping. (I've built it twice with no success).

 

Edited June 22, 2020 by Filthy Fox

[Didumos69]

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).

[astyanax]

2 hours ago, Didumos69 said:

and to get rid of the 9L steering links

Can you remind us what's bad about the 9L steering links?

(I've seen complaints about them in other threads, but never why...)

[Didumos69]

8 minutes ago, astyanax said:

Can you remind us what's bad about the 9L steering links?

(I've seen complaints about them in other threads, but never why...)

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.

Edited June 23, 2020 by Didumos69

[astyanax]

6 minutes ago, Didumos69 said:

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.

Ahhh that makes sense! I had been happily using the 9L steering links in my own builds, and was wondering if I had been doing something wrong all this time. But luckily I have a fetish for those wishbone suspension arms, which are also 9L... so all was right!