isotropic finishing

[Dave Koehler]

Newold.
Don't forget it all depends on torque anyway.
Any machined surface will have peaks and valleys.
When torqued we are crushing the machine mark mountain peaks which add up to less actual surface area.
Smoothed out would not more surface area be available for superior torque holding power?

[grandsport51]

I read some papers on it interesting in the sense
That it seems to increase fatigue strength
Noticeably!!

https://www.cryosciencetechnologies.com ... ec2003.pdf
Dave B

[Newold1]

DAVE, yes the machined surface on the rod and rod cap parting SURFACES help keep the body and the cap from moving across one another and in the newer cracked cap rods do an even better job of keeping those two pieces exactly mated and aligned. Two smoother surfaces would actually promote the opportunity for movement. These are two parts you do not want to move when properly joined and torqued.

[Dave Koehler]

I understand what you are saying.
However I don't believe they just slide around to be mean.
They are force moved by the up and down pressures as the big end breathes in and out.
Hence the parting line dilemma that comes when resizing.
Now that may be more a structure issue than anything else.
Might not make a darn bit of difference.
Sadly I have nothing to test it on.
All my AL rods have rough surfaces called serrations.
Oh, and they do move.
But hey, we are quibbling over micro inches are we not?

[Roundybout]

I thought serrated or those cracked cap/rods were to register the two pieces together correctly, not for preventing movement? The clamping load is supposed to prevent any movement. Although I wouldn't want mirror smooth, I wouldn't want coarse either. Or would I? Why aren't main caps serrated?

[Dave Koehler]

Because most have recessed registers. Guess which way they pull when things go south?
The only rods I have seen with registers are diesels like John Deere. Does that make them impervious to movement? No.

[Newold1]

I don't want us to get all wrapped up in rod cap movement as I was just trying to answer the OP's original thought about using this isotropic process to treat rod cap and body finishes. Don't think this is a needed or good place to use a process like this.

[Dave Koehler]

It obviously would be a good thing for gears and such.
Crank counterweights I am not so sure about but shiny sells.

It may or may not make a difference with mating surfaces.
I tend to think that with all the flex and movement of the rod structure it likely might do nothing.
I also lean toward that it won't make things worse.

Thought this 2 surfaces thing a bit further last night.
History teaches us that:
It used to be thought that a rough surface helped hold the head gasket.
Once it was understood that things move with expansion, contraction and pressure, smoother surfaces became the norm.
In the simplest terms, let it go where it wants to go within reason and design the gasket to move with it.

Once it was thought that the crosshatch on a rod big end helped keep the rod bearing in place.
This was likely championed by Joe Sunnen when he introduced the rod hone in the 1920s.
Bearing crush actually does the work so that idea kind of faded away.

One example that may or may not play into the rod/cap mating surface idea.
Have you ever wrung together two finely ground block spacers or 1-2-3 blocks?
Stick together pretty well don't they?
I wonder if that crosses over to the rod deal. Would any movement involved wring them together?

Since we are talking about micro-inches I have no idea how one could prove this out one way or the other.
That's all I got on the mating surfaces subject. Just thought it was interesting.

[Dave Koehler]

I got curious and nosed around Charlies site.
Geez, the guy has a lot going on as far as surface treatments go.
http://advancedtecneeks.com/

[stealth]

Valve springs?