18 Cylinders Isotta Fraschini (straight six-cylinder x3 )

[ajoeiam]

1 -gasNitriding is done by a professionel firm
2 - bronze ( RG7 )bearing shells have a light press fitting and a silver steel pin of diameter 4mm prevents rotating (the hole is for the oil )
3- center hole 6mm in the cranckschaft for the oil > closed on the webs , feeding from an oil gallery in the lower crankcase
oil from the center hole trou the connecting rod journals by a 1.6mm hole , connecting rods are from 7075 riding direct on the Nitrided cranckshaft (this works just fine on my 2 12 cilinder engines )

pressurised filtered oil via oil gallery in the lower crankcase tho the bronze cranckshaft bearings then to the connecting rods lower end , just like the real ones

Thank you for the information!!!

Are the gas nitriding services very far away from you?

 

[Foketry]

cylinder machining :
material: G25 cast iron from centrifuged bar, piston diameter 24mm
the piston in the image has been modified to facilitate the ignition of petrol, see previous posts

first phase on the lathe

internal drilling and boring

21 cylinders, 3 more in case of rejects


cylinder lapping

zero setting ring 24mm for bore gauge

 

[Foketry]

drilling and threading 6 holes M3, long and tedious work

22 finished cylinders, centering, drilling, threading with 3 taps, total 660 phases

threaded and countersunk hole for spark plug

 

[Foketry]

Like many aircraft engines of those times, this 18-cylinder also has the cylinder liners covered with a thin water jacket which contains a small volume to reduce weight.

Initially I thought of using brass, starting from a thick tube, but I didn't find very thick brass but only solid bars with a prohibitive cost (+ 70% in 2 years). Brass is easily machinable and weldable, but I found only very thick aluminum tube.

 

[Foketry]

 

[Foketry]

Cylinder fixing flange to the block
Through this perforated flanges , a retaining ring and 6 M3 screws I fix the cylinders to the block, I could not make the flange integral with the cylinder because otherwise it is not possible to insert the water jacket.

 

[Foketry]

Retaining ring for cylinders : are commercial rings, generally used for bearings but my supplier had many sizes available, but not the one I need.
I would have had to buy a whole box, 1000 pieces from another supplier , I therefore decided to build, using a standard Seeger and grinding it on the external diameter via my tool post grinding.

 

[Foketry]

Cams and rocker arms
This engine has overhead camshaft, it is a DOHC engine.
For simplicity of construction, I have designed a single camshaft for each head with the exhaust and intake cams on the same axis, contiguous to each other, each cam has a rocker arm.

my design

 

[Foketry]

I also joined the two exhaust and intake cams in one single piece, the 2 cams are rotated 110 degrees to each other (red is exhaust, blue is intake) , each cam operates one rocker arm, one left and one right, each rocker arm has a valve clearance adjustment screw

for the milling I used a disc cutter, diameter 26 mm

after a simple turning I got the finished cams

the red dot is the exhaust cam

 

[Foketry]

The camshaft and rocker arms must have a support flange which also supports the bronze bushings.
These support flanges (blue color) are fixed in position with two M3 screws, I created a small enlargement at the base to have a better support ,
the biggest difficulty is that all the seats for the bushings must be perfectly aligned with each other otherwise the camshaft will not rotate freely

Initially I had thought of building them by casting aluminum or bronze but later I found two recovery aluminum plates in my small warehouse, so I milled a few days to scrape off the aluminum plates.


First step

Second step , a small fixing and reference jig, through 2 pins

third step

Last step, counterbore and sandblasting

 

[Foketry]

I turned the valve with 4 successive steps in order not to deform and bend the stem.
The valves have a 3 mm diameter stem and a 9.6 mm diameter poppet , the diameter of the raw bar is 10 mm
40 valves on my little CNC lathe , I bought this lathe from a school, price 200 euros.
Is very old but used very few hours. I redid the whole electrical panel, replaced the motors and encoders, the mechanical part is almost new and now it works well.

Second and third turning step

last step

The groove for seeger was later turned manually , the CNC lathe only made a small groove to indicate the correct position

 

[Steamchick]

Next you should try and find an old Delapena valve grinder. Then you can put a double angle face on the valve -44.5 degrees and 45 degrees - like the professionals. (I last used on in 1972! Good hunting!)
https://jalopyjournal.com/forum/threads/40s-b-d-valve-grinder-restored.1121749/https://www.ebay.co.uk/itm/25568721...464579&customid=SI_valve+grinder&toolid=10049https://www.luckyoldcar.com/uncategorized/lot-810-valve-grinder-no-reserve/

K2

 

[Foketry]

Next you should try and find an old Delapena valve grinder. Then you can put a double angle face on the valve -44.5 degrees and 45 degrees - like the professionals. (I last used on in 1972! Good hunting!)
https://jalopyjournal.com/forum/threads/40s-b-d-valve-grinder-restored.1121749/https://www.ebay.co.uk/itm/25568721...464579&customid=SI_valve+grinder&toolid=10049https://www.luckyoldcar.com/uncategorized/lot-810-valve-grinder-no-reserve/

K2

Hi Steamchick , thank you for your suggestion
I turn the valves 44 degrees and the bronze seat 45 degrees, then lapped with silicon carbide and WD40
In case of problems of leaks, I go to the house of a friend of mine who owns a Dekel like this one and I grind the 44 degrees surface.
It is very important that the contact circle between valve and seat is as small as possible, max 0.2-0.3 mm to obtain a good seal.
If this area widens I have to repair the valve with Deckel to remove the contact area and re-lapping

 

[Steamchick]

Good stuff. Glad you know all about this.
It makes a huge difference to success...
Your work looks great from the pictures.

Cheers.
K2

 

[ddmckee54]

Foketry:

Did I miss the memo, or will you be cutting the o-ring groove in the cylinders for the upper water jacket seal at a later time?

Don

 

[petertha]

Very nice work. Maybe I missed it but what material are the valves machined from? I was impressed with the movies showing a tiny amount of shavings coming off each pass. And I didn't see any lapping so the finish was good enough off the lathe to run in the valve guides?

 

[Mechanicboy]

It is very important that the contact circle between valve and seat is as small as possible, max 0.2-0.3 mm to obtain a good seal.
If this area widens I have to repair the valve with Deckel to remove the contact area and re-lapping

Not such a small width of valve/valve seat contact because cooling is needed via the cylinder head so that the valves do not get too hot. The exhaust valves have a wider contact area than the intake valves since the exhaust valves are more exposed to heat and must conduct the heat away from the valves to the cylinder head.

After running in, there is full contact between the valves and the valve seats so that it is no longer 44 degrees versus 45 degrees. Only at the start is there a difference between the two angles before the valves are ground and driven in until the valves are completely sealed.

 

[Foketry]

Foketry:

Did I miss the memo, or will you be cutting the o-ring groove in the cylinders for the upper water jacket seal at a later time?

Don

Yes, I will do the grooves for OR later, first I have to weld the water inlet and outlet pipes to the water jackets. They are brazing on aluminum, I have never done brazing on aluminum and I don't know if there will be deformations or defects. In this case I will have to put OR with a larger section or find another solution, silicone, Loctite etc.

 

[Foketry]

Very nice work. Maybe I missed it but what material are the valves machined from? I was impressed with the movies showing a tiny amount of shavings coming off each pass. And I didn't see any lapping so the finish was good enough off the lathe to run in the valve guides?

the material of the valves is 36SMnPb14, an easily machinable steel but which contains Carbon and Manganese which make it resistant and also hardenable in water or oil.
Each roughing stepover is 0.3mm and 0.15mm finishing passes with repeat at zero stock .
I didn't take a photo, but before taking the valve off the lathe I polished the 44 degree cone with 600 sandpaper.

 

[Foketry]

Not such a small width of valve/valve seat contact because cooling is needed via the cylinder head so that the valves do not get too hot. The exhaust valves have a wider contact area than the intake valves since the exhaust valves are more exposed to heat and must conduct the heat away from the valves to the cylinder head.

After running in, there is full contact between the valves and the valve seats so that it is no longer 44 degrees versus 45 degrees. Only at the start is there a difference between the two angles before the valves are ground and driven in until the valves are completely sealed.

yes correct, I don't know after how many hours the engine has be running the contact area will extend but it will happen