18 Cylinders Isotta Fraschini (straight six-cylinder x3 )

[ajoeiam]

One of the reasons I know about flywheel spokes is that if they are not thin and curved, when the cast iron cools it generates tensions that causing breakage or detachment.
In my case the brass didn't have this problem, I made the fins inclined so as to create a small movement of air for the cylinders.

That (!!!!) is quite what I was looking for!!!!

Thank you!!!!! (for your sharing and your beautiful model!!!!!!!!)

 

[Foketry]

Timing gear case
This is the most complicated, demanding and challenging part to accomplish. The rotation of the crankshaft must reach, with a reduction ratio of 1:2, the 3 camshafts of the 3 heads, the distributor and the oil pump. The 2 right and left heads are inclined 40 degrees with respect to the central head, and here I found the greatest difficulty .
I thought of different solutions to transmit the rotation of the crankshaft to the camshafts, transmission chains, spur gear sets, then finally I found some 40 degree bevel gears and I chose this solution which is the same used by Isotta Fraschini .
I positioned the 1:2 ratio bevel gears directly at the output of the crankshaft so I simplified the construction by reducing the number of gears compared to the original solution by Isotta Fraschini

The gear diagram from service manual

 

[Foketry]

 

[ajoeiam]

View attachment 144431

Hmmm - - - - stupid question warning!!!
Wonder why they didn't use your solution on the original?

Any ideas?

(One very nice model is being built - - - literally before us! - - - kudos!!!!!!!!!)

 

[Foketry]

Hmmm - - - - stupid question warning!!!
Wonder why they didn't use your solution on the original?

Any ideas?

(One very nice model is being built - - - literally before us! - - - kudos!!!!!!!!!)

I preferred to do the 1:2 reduction directly after the crankshaft to halve the number of revolutions of the transmission shafts arriving at the camshafts and therefore less noise.
My gears are low quality, not ground on the teeth and alignment is critical.
In the original engine the 1:2 reduction is on the camshafts (bevel gears Z14/Z28) , the gears were of good quality (I think) and turning faster the torque is halved and therefore smaller shafts and lighter gears.
I too would have chosen their solution, but my shop is not equipped to obtain high quality hardened gears....
The original engine has 2 distributors and a double ignition system, like all aeronautical engines, 6 camshafts, mine has only one distributor, 3 camshafts.
My engine doesn't fly, the original does

 

[Foketry]

I drew the timing gear box 5 times before getting a definitive solution , every time I printed it with a 3D printer, I mounted bearings and gears, made functional and assembly tests, up to the final solution.

the 5 versions , PLA

the final version

 

[Foketry]

Aluminum casting instead of PLA

 

[Mechanicboy]

In the distributor cap, it seems until the contacts are close together that the spark from the rotor can jump over the other contact to one of the cylinders that should not have ignition while under compression. Shouldn't there be a greater distance between the contacts so that the spark does not jump to the others from the rotor? 2 or 3 distributor caps can be a solution if it is not good that the spark jumps to the other contacts.

 

[Peter Twissell]

Provided the gap between the rotor conductor and the active plug lead conductor is smaller than the gap between the rotor conductor and the adjacent plug lead conductors, by a factor greater than the difference between the gaps required to permit sparking in compressed Vs uncompressed cylinders, then it will work.

 

[Foketry]

Distributor cap for 18 cylinders, (6+6+6 on 3 levels)

I was inspired by the distributor of an old Ferrari 12 cylinder, 6+6 on 2 different heights , i added a level , so 6+6+6 on 3 different heights to avoid the spark jump in the wrong contact , the distance between one contact and another is at least 10 mm.

Ferrari Distributor cap, even Lamborghini 12 cylinders is the same (Ferrari and Lamborghini factories are a few tens of kilometers from my house)

My distributor cap not yet complete, all the brass contacts are still missing

 

[Foketry]

Provided the gap between the rotor conductor and the active plug lead conductor is smaller than the gap between the rotor conductor and the adjacent plug lead conductors, by a factor greater than the difference between the gaps required to permit sparking in compressed Vs uncompressed cylinders, then it will work.

Hi Peter , what do you think of my blue distributor ? Will it work???

 

[Foketry]

In the distributor cap, it seems until the contacts are close together that the spark from the rotor can jump over the other contact to one of the cylinders that should not have ignition while under compression. Shouldn't there be a greater distance between the contacts so that the spark does not jump to the others from the rotor? 2 or 3 distributor caps can be a solution if it is not good that the spark jumps to the other contacts.

Hi Jens , same question , what do you think of my blue distributor ? Will it work???

 

[Mechanicboy]

Hi Jens , same question , what do you think of my blue distributor ? Will it work???

Seeing that there is a greater distance that there is zero chance of the spark jumping to the nearest contact and setting the spark in the wrong plug during compression. This is how Ferrari had already thought when they use one and the same distributor cap for several cylinders that are distributed 6 + 6 instead of 12. That is the best solution.

 

[Mechanicboy]

What is most important is the charging time of the magnetism in the low-voltage coil in milliseconds before the magnetism collapses and induces the high-voltage coil and gives enough strong spark when the engine uses one and the same coil instead of 3 coils if you run the engine at high rpm since there is a short time to charge up enough magnetism in the low voltage coil between each ignition in an 18 cylinder engine.

 

[Peter Twissell]

Hi Peter , what do you think of my blue distributor ? Will it work???

Yes, 10mm gap should be plenty.
I assume the radial gap between the rotor contact and each plug lead contact will be less than 1mm.
Regarding the coil charge time, you'll need a low resistance coil so that the current can build quickly.

 

[G54AUST]

I wonder what the dielectric strength of the 3D printed plastic is ?????


Regards,

Trevor.

 

[raveney]

I made the project in 3D, printed the PLA mold and made the brass casting.

Amazing work Foketry,
How was the mold for the flywheel removed from the sand?

 

[Mechanicboy]

Amazing work Foketry,
How was the mold for the flywheel removed from the sand?

See here..Viola

 

[Peter Twissell]

I wonder what the dielectric strength of the 3D printed plastic is ?????


Regards,

Trevor.

Not brilliant. The plastics used for extrusion are typically quite hygroscopic, which doesn't help.
I made the "test" distributor cap for my radial from 'water clear' acrylic resin, poured into a mould. It works ok so far, but it's only been used for bench testing with no compression on the plugs.
The ideal material is phenolic resin.

 

[Mechanicboy]

The ideal material is phenolic resin.

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