Bugatti straight 8 cylinder with blower, design, 3D printed molds, castings , machining, assembly

[Foketry]

The brass cast manifolds

manifolds in drilling phase

 

[Foketry]

exhaust pipes after brass welding and after painting with high temperature paint

 

[Foketry]

assembled to the engine

 

[delalio]

That is some awesome work. Great demonstration of several skills there. I tip my hat to you Sir!

 

[Foketry]

The blower, I built and milled all the aluminum castings but for now I install it without the rotor bilobe , first I have to start the engine only with the carburetor, without unnecessary complications

The original blower






My drawings



Cover


2 Bi-lobe rotor


My aluminum casting obtained through the lost PLA / plaster method







After milling and sandblasting



partially assembled

 

[Foketry]

The blower assembled to the engine

 

[Peter Twissell]

Superchargers are pure engineering porn!
Wonderful.

 

[gbritnell]

Fabulous work! The detail is first rate!

 

[michelko]

Wow that blower came out reale nice

 

[ajoeiam]

The blower, I built and milled all the aluminum castings but for now I install it without the rotor bilobe , first I have to start the engine only with the carburetor, without unnecessary complications

The original blower


Cover
View attachment 121958

2 Bi-lobe rotor
View attachment 121959

I'd be curious as to how you fabricated and machined the bi-lobe rotor - - - please?

(That is if you are going to create it or have created it! Merci beaucoup!)

 

[Foketry]

I'd be curious as to how you fabricated and machined the bi-lobe rotor - - - please?

(That is if you are going to create it or have created it! Merci beaucoup!)

Maybe in future, if the engine works well, I will complete the blower with 2 rotors
The rotors will be printed with 3D printer, aluminum poured and milled only on the small rectangular protrusions you see in the model photo. Of course I will also make the 2 central holes to lighten the rotors
Extreme precision is not necessary because it is only a fan, +/- 0.1 mm is enough, in my opinion , i hope

 

[Peter Twissell]

Hi Foketry,
In my experience of this type of supercharger, i.e. positive displacement, as opposed to a turbine type, it is important that the rotors have very small clearances.
When the rotors become worn, the efficiency of the blower degrades quickly to the point where it takes more power to drive it than is gained from the boost.
If I were making a blower with long rotors like the Bugatti design, I would probably make them in short, manageable sections, keyed to a shaft.

Pete.

 

[stevehuckss396]

It doesn't take much to spin the blower unless it's making boost. If clearances are real loose it will not make boost and wont steal much power. Of course it would make more sense to leave the case empty if you don't plan to make it fully functional and at least make enough boost to replace the power lost to the blower load.

 

[Foketry]

Hi Foketry,
In my experience of this type of supercharger, i.e. positive displacement, as opposed to a turbine type, it is important that the rotors have very small clearances.
When the rotors become worn, the efficiency of the blower degrades quickly to the point where it takes more power to drive it than is gained from the boost.
If I were making a blower with long rotors like the Bugatti design, I would probably make them in short, manageable sections, keyed to a shaft.

Pete.

Hi Pete
I have no experience with blowers, I got information in a workshop near me that restores vintage Bugatti, he told me that there was clearence between rotor-rotor and rotor-casing, over 0,1-0.2mm (0,010 inch)
I saw the disassembled rotors and the finish was not particularly sophisticated
You must consider that we were in 1923-1930 , at that time in the United States the Ford T was built
I found on internet ,months ago, an analysis of clearance and leakage, about bi-lobe blower, analysis speaks of clearance 0.011-0.014 inch
In any case it would be my great happiness if my engine ran ,even without blower

The analysis , a page of 11

 

[Foketry]

It doesn't take much to spin the blower unless it's making boost. If clearances are real loose it will not make boost and wont steal much power. Of course it would make more sense to leave the case empty if you don't plan to make it fully functional and at least make enough boost to replace the power lost to the blower load.

Hi Steve
Yes correct , at the moment I leave the case empty, I don't know if the engine will work well without blower, I'm not looking for complications.....

 

[Foketry]

The head cover, underneath, flows the cooling water which, through 4 flanged pipes, collected in a conical tube, goes to the radiator

after chrome plating










after brazing

 

[ajoeiam]

Hi Pete
I have no experience with blowers, I got information in a workshop near me that restores vintage Bugatti, he told me that there was clearence between rotor-rotor and rotor-casing, over 0,1-0.2mm (0,010 inch)
I saw the disassembled rotors and the finish was not particularly sophisticated
You must consider that we were in 1923-1930 , at that time in the United States the Ford T was built
I found on internet ,months ago, an analysis of clearance and leakage, about bi-lobe blower, analysis speaks of clearance 0.011-0.014 inch
In any case it would be my great happiness if my engine ran ,even without blower

The analysis , a page of 11

View attachment 122017

Please - - - would like the reference to the article (if possible)?

 

[Peter Twissell]

Re. Supercharger clearances:
The clearance will need to be smaller in a small blower, both in proportion with the rotor diameter and because the smaller blower has a cube law capacity relationship to a larger one and a square law leakage relationship.
So if the blower is simply scaled down 1:2, it will have 1/8 capacity but 1/4 leakage.
A leaky blower will consume almost as much power as a good one. The rotors displace exactly the same volume, but much of the flow is wasted as it leaks back from the hp side to lp.

 

[Foketry]

Please - - - would like the reference to the article (if possible)?

here is the link:
https://downloads.hindawi.com/journals/ijrm/2006/079084.pdf

 

[Foketry]

Re. Supercharger clearances:
The clearance will need to be smaller in a small blower, both in proportion with the rotor diameter and because the smaller blower has a cube law capacity relationship to a larger one and a square law leakage relationship.
So if the blower is simply scaled down 1:2, it will have 1/8 capacity but 1/4 leakage.
A leaky blower will consume almost as much power as a good one. The rotors displace exactly the same volume, but much of the flow is wasted as it leaks back from the hp side to lp.

yes i agree, i had not considered the size, my blower is 3.3 times smaller than the original, it means the max lobe / lobe clearance should be 0.03 mm (0.001 inch)
I can not maintain these tolerances with my self built CNC milling machine, on such a complicated profile
I will leave the blower empty