Requesting Information on the Bugatti EB110

[Matski]

@DataHunter I'm not really following any of that... but good work, genuinely impressive research and clearly a good amount of thought going in to this

Have you consulted any EB110 specific books during your research?

 

[DataHunter]

Thank you very much! I consulted the book Bugatti EB110 by Stefano Pasini, but a lot of my sources were images and video documentaries.

 

[Matski]

Thank you very much! I consulted the book Bugatti EB110 by Stefano Pasini, but a lot of my sources were images and video documentaries.

That's the first one I came across, seemed cheap enough to be worth a punt.

As another option, what about the EB110 Registry, they have an open Facebook page. Perhaps a well worded question there might yield an answer from a technically minded owner or fan... The Bugatti EB110 Registry Just a suggestion.

I'm surprised there aren't more official resources out there.

 

[DataHunter]

That's the first one I came across, seemed cheap enough to be worth a punt.

As another option, what about the EB110 Registry, they have an open Facebook page. Perhaps a well worded question there might yield an answer from a technically minded owner or fan... The Bugatti EB110 Registry Just a suggestion.

I'm surprised there aren't more official resources out there.

The EB110 Registry is absolutely awesome. I actually cited it at a certain point within this thread, but (amazingly) it had never actually crossed my mind to contact the owner of the site. Rest assured, I am composing an eMail as I type this.

As for the lack of resources... actually, yeah. I was pretty surprised to learn just how little online documentation there is for the technical aspects of this car. I mean... I could only find one patent for the entire EB110 era.

 

[whatever]

Luckily, I've been looking for the info myself.
After cracking my head, I've found out, there is nothing mysterious there.

This way the transmission looks a lot easier to understand.

Now here are the shafts and there your main point of interest.

So it's just a planetary gear, the shaft is hollow however. It's very fussy there.
The outer shaft is likely to be driven from the crank (via some gears). And the inner one is the one that goes to the front output. After there is a simple viscous coupling.

 

[DataHunter]

Wow! What an amazing find!!! Thank you so much!

 

[DataHunter]

Based on these new images, we can deduce a few things:

1) the front axle drive comes off the sun gear in the planetary center differential

2) The ring gear in the center planetary differential drives the rear axle pinion gear.

3) The center planetary differential appears to be a conventional epicyclic gearing system (not compounded), so the direction of rotation for the sun gear is reversed (so it is the same rotational direction as the ring and carrier). This is further supported by the fact that it drives through single gear reduction to the front axle drive shaft.

A while ago, I had a rough idea for the EB110's general layout. I drew up a sketch for visualization purposes.

 

[DataHunter]

Not to over-post, but here are some basic calculations I drew up.

Note that the negative sign for Mr and Ms is mostly meaningless; it only indicates that the direction of the torque is opposite to that of the carrier, which is expected of a reactionary torque.

Two reasonable solutions can be proposed for Nr and Ns (the number of teeth on the ring and sun gears, respectively):

1. Nr = 116, Ns = 44; torque split: 27.5% front, 72.5% rear*

2. Nr = 108, Ns = 40; torque split: 27.0% front, 73.0% rear (closest to the oft-quoted 27-73 split)

*likely the most reasonable, as the EB110 book by Stefano Pasini quotes the torque split as being 28-72 at one point - then 27-73 in the official specifications page

 

[whatever]

Yeah, engineer Nicola Materazzi wanted to set 27:73 ratio, but it was machined as 27:72.

So far, I have the only question, if the difference between this style (planetary gearset + viscous coupling) and a direct viscous coupling (the secondary shaft drives the output shaft, where the rear outputcan be narrowed

 

[whatever]

Damn, I don't why I can't edit a posted message, lol.


So far, I have the only question, if the difference between this style (planetary gearset + viscous coupling) and a direct viscous coupling (the secondary shaft drives the output shaft, where the rear output is fixed and front is driven through a viscous coupling). A viscous coupling can be filled with low viscosity oil, so the transmitted torque wouldn't be big.

I wonder what the driving difference is.

 

[whatever]

*the transmitted torque will not be big, i.e. it might be possible to achieve the same ratio.

 

[DataHunter]

To the best of my knowledge, the purpose of this planetary gear set is to ensure that a basic front:rear torque split is ensured at steady-state conditions. The viscous coupling only comes into play if the rear tires start to slip excessively. (as far as I'm aware) It will transfer additional torque to the front tires as necessary.

Would you happen to know the number of teeth on the planetary gears?

 

[DataHunter]

I didn't see the edit, either. How strange. I'm not 100% sure what the difference would be, but the Audi R8 uses a very similar VC unit, which can transfer up to 160 N·m to the front axle pinion. Of course, the front axle ratio is very different (42:16).

As far as that goes, I don't know if it would be possible to adjust the front:rear torque split ratio using a VC. After all, the speeds of the sun and ring gear are really close (within 3% of each other). I suspect the VC was used in the event that the rear axle experienced heavy slip. That said, it could be possible.

 

[whatever]

FYI, Murcielago's GKN viscous coupling is rated at 150 Nm at 100 RPM.
I'm 99.9% sure at Bugatti they used ZF/GKN stuff, just like everyone did in Europe.

General papers
http://www.easy2design.de/stuff/visco_sae.pdf
In particular
https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/14757/3/IJHVS_Paper.pdf

This one shows some interesting study of a low viscosity oil used in the VC unit, thus promoting a late reaction with slower torque increase and more neutral handling (which is better for a sports car, not an utility vehicle, obviously).

Actually, you're much better on gear counts, I can't help much. But I've tried various simulations of better ratios for a Diablo VT and gear ratio studies brought me here.

 

[DataHunter]

I want to buy you a beer. You are an absolute legend.

 

[Giannis]

https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/14757/3/IJHVS_Paper.pdf

FYI, Murcielago's GKN viscous coupling is rated at 150 Nm at 100 RPM.
I'm 99.9% sure at Bugatti they used ZF/GKN stuff, just like everyone did in Europe.

General papers
http://www.easy2design.de/stuff/visco_sae.pdf
In particular
https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/14757/3/IJHVS_Paper.pdf

This one shows some interesting study of a low viscosity oil used in the VC unit, thus promoting a late reaction with slower torque increase and more neutral handling (which is better for a sports car, not an utility vehicle, obviously).

Actually, you're much better on gear counts, I can't help much. But I've tried various simulations of better ratios for a Diablo VT and gear ratio studies brought me here.

A couple of note about your second paper. Loughborough university works closely with Ford and JLR. The head tribologist of JLR received his PhD from Loughboro.

The second name on the paper, Dr. G. Mavros has done quite extensive on automotive systems modeling. The third name, Prof. Rahnejat is considered amongst the best researchers in his field, worldwide!

 

[DataHunter]

Discussing the viscous coupling even further, it becomes clear that viscous coupling units can transmit more torque than advertised (under certain conditions): Comprehensive Theory of Viscous Coupling Operation . I (unfortunately) cannot access this paper at the moment, but it certainly seems interesting.

 

[tristatez28lt1]

Damn, this is some seriously awesome shit in this thread. Thanks guys!

 

[DataHunter]

You're welcome! It's always fun to try and reverse-engineer or analytically inspect such awesome machines.

Also, I have to say: the EB110 has really grown on me. It's now one of my favorite supercars, although I still don't like the styling.

 

[DataHunter]

Just a quick update: I recently downloaded diagramming software, so I can draw more coherent diagrams. Here is my most up-to-date model of the Bugatti EB110 Transmission system.

Note: blue lines represent a direct relationship with the front axle, red lines represent a direct connection with the rear axle, and the black lines represent a connection with the engine.