F1technical.net

Yes, standard bearing clearance is .0003 to .0005 in most machines, but I dont know much avout thermal expansion with aluminum and alusil/nicasil coatings. Steel will grow .002 per cubic inch every few hundred degrees so it can open up a decent amount but white metals I know little about right now.

Leominster12 wrote: ↑

25 Mar 2019, 20:00

Hey guys i was just curious if a 81.5mm piston can fit on a 81mm bore because in the past f1 cars this type of method (well not exactly) and makes alot of power because the gas is very compressed and tightly squeeze inside the engine and i know it is preheated before starting engine to expand the metal to let loose the piston, because of this it can create alot of power naturally aspirated like the mclaren mp4/4, if this is possible it can be used in drag racing and road racing.

Yes it can fit.
As to whether the engine will turn over or last more than few hundred meters is another matter.

No it won't fit. By the time you force it in, the piston will be permanently smaller, the bore will be permanently larger or both. (Unless you are considering a rubber piston?)

it can fit (depending on what is meant by fit) ....

if as we might guess 0.25mm from piston and to bore corresponds to only about 3000 ppm of strain in each component
any of the usual metals in a decently hard aka strong form can take this
(ie with little or no yield if that's what is desired ie to retain the benefits some might imagine to come from this fit)

and btw ....
yield in the strongest condition copper 2.5% beryllium (F1 legal 'alloy' used for valve seats) only starts near 10000 ppm strain
aluminium/titanium 'alloys' with comparably high yield might not be F1 legal ? (one man's alloy can be another man's MMC)

of course such a fit even at running temperatures prevents the engine running - the huge friction making that impossible

Good point TC.
Now consider the case where the cylinder wall is much thicker than the piston skirt (largest dia of the piston). This is always true at the deck on a closed-deck block. The strain in the piston skirt will be closer to 6000 ppm - beyond the yield point of most aluminium alloys (at room temperature).

I was kiding. I didnt actualky check if it will fit.
But here is a coolweb calculator for interference fits:

https://amesweb.info/press-fit/interfer ... lator.aspx

I tried with steel and alumnum. I got some crazy heating / cooling numbers! I think it is easier if i used aluminum and aluminum... Note the alloy of alumnum has to make sense of course since pistons are specifically designed for various thermal expansion rates and toughness etc.

It shooould.. Be possible.. To do without yielding? Didnt get to play around enough with it yet.

Put the piston in liquidnitrogen and the barrel in the oven to 350 centigrade. It will fit, movement?
Ponder this,,,

As always, foreplay is important.

If the extra 0.5mm is a sacrificial skirt/spray-on deformable/low-friction material, maybe?