18 Cylinders Isotta Fraschini (straight six-cylinder x3 )

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Hi
What material did you use for the valves?. Chips Looks like free turning steel.
What tolerance are you aiming between stem and guide?

Michael
Hi Michael, for the last engines I built (Porsche 917 and Bugatti T50) and also for this engine I used high speed steel turning , 36SMnPb14 , this steel, despite the lead, is hardenable with good hardness. This engine doesn't have to fly in an airplane, so no quenching is needed.
Valves have a 3mm stem, the bore is 3.00 mm, my stem is 2.98-2.96.
Some of my friends reduce the stem up to 2.95-2.93 and their motors work fine.
Their theory is that in case of small coaxiality errors between the head and the stem or errors between the cages hole and the 45 degree chamfer ,there are no leakage problems and everything is simpler and faster, maybe they are right.
 
Hmmmmmmmm - - - - given the level pictured here - - - - what might be your next challenge?
(LOL - - - maybe you'll have to design something new? - - - a turbine - - -for the engineering challenge - - - - this is an incredible build!!!)
My next project? A much simpler engine I'm thinking Fairbanks Morse 2-3 cylinder.
Does anyone have drawings or photos or dimensions of this 2-stroke engine?

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My next project? A much simpler engine I'm thinking Fairbanks Morse 2-3 cylinder.
Does anyone have drawings or photos or dimensions of this 2-stroke engine?

View attachment 145046
I am thinking you will find this also a fascinating project!!!

Spending a wee bit of time - - - - I'm not seeing too much information out there on this particular model.
Lots on the smaller engines and then on the the much bigger ones.

It will be interesting to follow your journey - - - even to where you can find information!

Wishing you well on your new journey!!!!
 
Valve lapping and control with vacuum pump, 36 valves, real boring work.
A first rough lapping was done with valves and cages not yet assembled on the heads, I pressed the cages into the holes of the heads with Loctite 620, I drilled the exhaust and inlet holes and then I did a finishing lapping ( grade 1000) and checking.
I closed the inlet and exhaust holes with conical silicone plugs, I sucked in with the vacuum pump through the hole for the valve stem .
The target to reach is from 25 to zero in one minute , otherwise repeat the lapping...

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Hi
the cams look a little rough. maybee they will eat away the brass (i gues) followers.
Will you leave them as they are or do they get some finetuning?

Rgards Michael
 
Hi Michael
the cams do not have a very high roughness , they are not ground and polished as in racing engines , but I believe that to work a few hours during the entire life of this engine , they can be acceptable.
I could also temper them to harden and polish them with sandpaper, but my experience tells me that is useless.
However, a little running-in with no load will make them smoother.
 
Hi Michael
the cams do not have a very high roughness , they are not ground and polished as in racing engines , but I believe that to work a few hours during the entire life of this engine , they can be acceptable.
I could also temper them to harden and polish them with sandpaper, but my experience tells me that is useless.
However, a little running-in with no load will make them smoother.
Yep.
Don't let perfection get in the way of good enough.
 
Hi Foketry !
I could also temper them to harden and polish them with sandpaper, but my experience tells me that is useless.
Can you explain ? Because I'm intending to...
Thanks !
 
What actually wears out cams and followers in full sized engines is usually fatigue stress at the surface, leading to 'spalling' of little flakes of metal from the contact surface. Hardening slows down or ideally eliminates that process by increasing the surface strength.

If you use soft material like brass for the followers I suspect they will wear out from abrasive wear long before a soft steel cam starts to show signs of surface fatigue. Also possibly the soft material will transfer to the cam and fill in the roughness somewhat.

I might also add that if your engine uses very light valve springs you can make the cam lobes from nylon, so long as the cam is not somewhere it will get too hot. It isn't subject to the surface fatigue wear mechanism, and will naturally conform to the followers so they can be left soft too. Many lawnmower engines are made this way.
 
What actually wears out cams and followers in full sized engines is usually fatigue stress at the surface, leading to 'spalling' of little flakes of metal from the contact surface. Hardening slows down or ideally eliminates that process by increasing the surface strength.

If you use soft material like brass for the followers I suspect they will wear out from abrasive wear long before a soft steel cam starts to show signs of surface fatigue. Also possibly the soft material will transfer to the cam and fill in the roughness somewhat.

I might also add that if your engine uses very light valve springs you can make the cam lobes from nylon, so long as the cam is not somewhere it will get too hot. It isn't subject to the surface fatigue wear mechanism, and will naturally conform to the followers so they can be left soft too. Many lawnmower engines are made this way.
My springs are not very strong, after an initial wear of the rocker arm and adaptation of the sliding surfaces, the lubrication will greatly reduce the wear.
It will be necessary to reduce the clearance using the screws I have provided .
This is what I predict, I hope I'm not too optimistic and have to redo everything......
 
But in reality, it is not like we run model engines all day every day, and generally we don't run them under load either, and so if an engine is run for short periods of time for demonstration purposes, it may last a long time without having to resort to exotic surfaces/materials.

.
 
My springs are not very strong, after an initial wear of the rocker arm and adaptation of the sliding surfaces, the lubrication will greatly reduce the wear.
It will be necessary to reduce the clearance using the screws I have provided .
This is what I predict, I hope I'm not too optimistic and have to redo everything......
On my Webster engine I used a mild steel lobe and an aluminium (6061) follower. After an hour or so of running there is a noticeable wear mark on the follower, but so far still usable. If I had my time over again I'd probably use something a bit harder for the follower. Brass like you've used would be a much better choice than aluminium I think.
 
I could harden the cams, they are built with C40 steel material which is hardenable in water or oil after heating to 850 degrees C
Thank you !
I'm learning about camshaft and crankshaft hardening...
I will and should start a new topic about it , as well as the question of whether it is necessary to hardening or not
 
I has used cam made of unhardened silver steel ( drill rod steel) and rocker arm of cast iron in my Webster engine. Last so well without problems. These is lubricated with motor oil.
 
Most modern auto engines will easily run for 200,000 miles without major problems, I got 250,00 out of my KIA Sorento and the engine was still running strong when I got rid of it. At 60MPH that works out to over 4,100 hours with the engine under load. Our engines will see maybe 100-200 hours of runtime in their entire life - max... And usually under no load conditions. That's only a few percent of the life of normal Big Boy engines.

Hardening parts and using similar materials to the Big Boy engines would be nice to do if you can, or want to - but it's not REALLY needed. Yes, our engines will probably wear more using softer materials but so what, we can always make replacement parts can't we? Getting your engine to run well enough that it runs long enough to wear something out under normal running conditions should be considered kind of a badge of honor.

Don
 
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