18 Cylinders Isotta Fraschini (straight six-cylinder x3 )

[Foketry]

The crankshaft is identical to the crankshaft of a straight 6-cylinder

 

[Foketry]

The project is taking shape, the main components are designed

 

[ajoeiam]

The project is taking shape, the main components are designed

snip

Hmmmmmmmm - - - what program are you doing your modelling in please?

 

[Foketry]

Hmmmmmmmm - - - what program are you doing your modelling in please?

Fusion, but I think all 3D programs can do these simple designs..

 

[ajoeiam]

Fusion, but I think all 3D programs can do these simple designs..

Thanks - - - - I'll pass on that option - - - - for a number of reasons.
I 'gave up' (passed) on Microsoft's continuing and ongoing 'security opportunities'.
Autodesk has a history of pulling out the rug from under its low cost (and especially free) offerings.

AIUI windows is now even setup so that Win11 really doesn't work on even an air gapped machine which is the only way that I would run such.

Hmmmmmmmmm - - - if you call what you have presented 'simple designs' - - - - dunno what you might call complicated - - - grin.
You will have at least 40 if not 75 different pieces you'll need to model - - - hmmmmmm likely fall into my definition of 'not simple'.

Continuing to follow your intriguing thread.

 

[metalmangler]

Thanks - - - - I'll pass on that option - - - - for a number of reasons.
I 'gave up' (passed) on Microsoft's continuing and ongoing 'security opportunities'.
Autodesk has a history of pulling out the rug from under its low cost (and especially free) offerings.

Have a look at a Linux operating system (I use Mint), and Blender for the modelling. Both free.

 

[kvom]

Yellow is a great color for that swiss cheese header.

 

[Foketry]

Thanks - - - - I'll pass on that option - - - - for a number of reasons.
I 'gave up' (passed) on Microsoft's continuing and ongoing 'security opportunities'.
Autodesk has a history of pulling out the rug from under its low cost (and especially free) offerings.

AIUI windows is now even setup so that Win11 really doesn't work on even an air gapped machine which is the only way that I would run such.

Hmmmmmmmmm - - - if you call what you have presented 'simple designs' - - - - dunno what you might call complicated - - - grin.
You will have at least 40 if not 75 different pieces you'll need to model - - - hmmmmmm likely fall into my definition of 'not simple'.

Continuing to follow your intriguing thread.

so far I have 149 drawings and I have not finished.....
many are duplicated with minor modifications to optimize the design

 

[ajoeiam]

Have a look at a Linux operating system (I use Mint), and Blender for the modelling. Both free.

Thank you!
Have been running Debian testing for about the last 14 or 15 years. (Started w Linux somewhat over 20 years ago but as a user so now I get to the point where I need to 'dive under the hood').
In process of setting up a new machine (waiting for a replacement doa psu) that will be on Devuan 'testing' (daedalus (sp?)).

Blender warns of deprecation of gpus but the description and the linked lists don't really make any sense.

Perhaps spinning this off into its own topic might be best but I would like to know more.

TIA

 

[Foketry]

Cylinder and piston: in the original engine the spark plug is directly on the cylinder, the piston is concave and the petrol is ignited correctly. In my engine ,to have a correct compression ratio , I had to make a dome on the piston to leave the spark plug uncovered.
i think it is not a good solution but i have no alternative. I do not know if the ignition of the petrol will take place uniformly and immediately.
Your every suggestion will be appreciated

 

[Vietti]

Maybe the top/side of the piston doesn't have to be some exact geometric shape like a cone. Maybe a wedge shape like some V8s used or just a pocket for the plug etc.

Look forward to your build!!

John

 

[Peter Twissell]

Remember the spark will occur at some advance, before the piston is at the top of its travel.
If the cylinder head is flat, the piston shape will create a reverse squish band.
I can't guess what effect that might have on the flame front, but if it slows it down a lot, you will just need to use more advance on the ignition.
I am guessing you are not looking for maximum performance from this engine?

 

[Foketry]

Remember the spark will occur at some advance, before the piston is at the top of its travel.
If the cylinder head is flat, the piston shape will create a reverse squish band.
I can't guess what effect that might have on the flame front, but if it allows it down a lot, you will just need to use more advance on the ignition.
I am guessing you are not looking for maximum performance from this engine?

It would be a great success if all 18 cylinders worked, no performance is required, I don't have to fly, I just want to hear 18 pop in succession

 

[Steamchick]

Cylinder and piston: in the original engine the spark plug is directly on the cylinder, the piston is concave and the petrol is ignited correctly. In my engine ,to have a correct compression ratio , I had to make a dome on the piston to leave the spark plug uncovered.
i think it is not a good solution but i have no alternative. I do not know if the ignition of the petrol will take place uniformly and immediately.
Your every suggestion will be appreciated

View attachment 137158

As I worked with piston and combustion chamber designers on a couple of engines: "modern thinking" - as of the late 1980s~90s. was to simply flatten the piston and head as much as possible. On CAD: Draw a sphere at BOTTOM dead centre and it should touch the cylinder walls, head and piston with very little overlap. That minimises heat loss to the metal when a spherical flame develops as the piston travels down the bore. (This was developed in laboratories with single cylinder "see through" engines, lazers, etc.).
On Model (seriously small engines, sub-50cc per cylinder) the heat losses to adjacent metal are much worse than your small car engine, and low compression makes things worse.
I would therefore, remembering that the piston does not rotate, simply mill a small pocket for the spark-plug, and a curved bottom groove from there to the middle of the piston, with maybe a SLIGHT dishing of the piston crown). The flame generated by the spark ignition will then progress up the channel to the centre of the piston to meet the remainder of the charge and burn that as the piston travels down the bore.
I have done a quick sketch... - Hope it makes sense?

Ask more questions if you wish...
K2.

 

[Foketry]

As I worked with piston and combustion chamber designers on a couple of engines: "modern thinking" - as of the late 1980s~90s. was to simply flatten the piston and head as much as possible. On CAD: Draw a sphere at BOTTOM dead centre and it should touch the cylinder walls, head and piston with very little overlap. That minimises heat loss to the metal when a spherical flame develops as the piston travels down the bore. (This was developed in laboratories with single cylinder "see through" engines, lazers, etc.).
On Model (seriously small engines, sub-50cc per cylinder) the heat losses to adjacent metal are much worse than your small car engine, and low compression makes things worse.
I would therefore, remembering that the piston does not rotate, simply mill a small pocket for the spark-plug, and a curved bottom groove from there to the middle of the piston, with maybe a SLIGHT dishing of the piston crown). The flame generated by the spark ignition will then progress up the channel to the centre of the piston to meet the remainder of the charge and burn that as the piston travels down the bore.
I have done a quick sketch... - Hope it makes sense?
View attachment 137194
Ask more questions if you wish...
K2.

I really appreciated your suggestion, even a friend of mine who builds engine models suggested a similar thing to me. “The flame triggered by the spark plug must reach the center of the piston.“
In the next few days I will draw the piston by copying your drawing. It will be a bit complicated to mill 18+2 pistons on the head but I think it is the best solution. Thank you

 

[Steamchick]

Hi Foketry, I guess a simple jig will hold the piston while machining - repeatable multiple times. - For 26 cylinders, I would make it all on jigs, etc. (But I am not clever enough to design the jigs!).
K2

 

[ddmckee54]

26 pistons? You making 8 extras, or did I miss something?

 

[Foketry]

26 pistons? You making 8 extras, or did I miss something?

sorry for my mistake 18 pistons + 2 extras = 20 not 26

 

[leerkracht]

Hallo Foketry
The engine must work with your piston design as on -30- flame travel is short , first runs on glow fuel wiht glow plugs
the v 10 engine is the project i am working on (bore and stroke 26mm )my own design and make
gr

 

[Steamchick]

Leerkracht: That looks superb!
K2