the crank shaft its harmonic balance?

luigi90210 · 01-21-2013, 05:39 PM

Quote:

Originally Posted by XwChriswX

How do you know they've fused together though? They don't show anything removed...

Perhaps the installer just seriously over-torqued the pulley nut...

A better camera angle would be showing the gap between the pulley and the block to where you can see the fuse point.

Those video's clearly show something wrong, but like it was previously said, just using the pulley is a scapegoat is a premature diagnosis...

i dont know which is why i said i think

no need to attack me, i personally wouldnt install an underdrive pulley on my car but i wouldnt talk down someone who did

to each their own is how the saying goes

Trilitheum · 01-21-2013, 05:45 PM

I can explain why they get stuck together, they are not fusing. It is a galvanic cell which produces a layer of aluminum oxide on the inner diameter of the pulley.

The aluminum will corrode preferentially to the carbon steel shaft. The problem comes in the volume change when aluminum goes from Al to Al203 (aluminum oxide) the volume increase is about 2 fold.

So if the parts are in intimate contact when they were installed, the oxide layer when formed takes up additional volume and squeezes the inner shaft as it tries to expand with virtually no gap (except the machining tolerance) which is taken up quickly.

XwChriswX · 01-21-2013, 05:50 PM

Quote:

Originally Posted by luigi90210

i dont know which is why i said i think

no need to attack me, i personally wouldnt install an underdrive pulley on my car but i wouldnt talk down someone who did

to each their own is how the saying goes

I was not attacking you, good sir.

I just hope no one takes those videos as clear "evidence" against pulleys because they show nothing.

01-21-2013, 05:45 PM	#2 (permalink)
Trilitheum Base Member Join Date: Feb 2011 Location: Ontario Posts: 210 Drives: '11 370z 6M KAD Spt Rep Power: 16	I can explain why they get stuck together, they are not fusing. It is a galvanic cell which produces a layer of aluminum oxide on the inner diameter of the pulley. The aluminum will corrode preferentially to the carbon steel shaft. The problem comes in the volume change when aluminum goes from Al to Al203 (aluminum oxide) the volume increase is about 2 fold. So if the parts are in intimate contact when they were installed, the oxide layer when formed takes up additional volume and squeezes the inner shaft as it tries to expand with virtually no gap (except the machining tolerance) which is taken up quickly. __________________ 2011 Nissan 370Z Touring/Sport, 6MT, KAD

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