over torqueing

[MAGN1T]

My posts go way over the top of most peoples heads. They just don't understand.

Did you actually understand that link about the weight saving??

To go slightly OT here, yet another example of how car "culture" becomes more of a religion than a science.... just because somebody wrote something that doesn't make sense but was written by someone who has some sort of authority... people are frightened to question it.... in case they are made to look silly.

Everyone makes mistakes... sometimes on purpose, to get a response.


Then of course somebody else will repeat what they read, again not understanding what they've read but it must be right because it was "on the net" and written by someone they have confidence in.

Steve

[pc]

As for the link.

I don't understand how putting a 10mm bolt into a 10 mm hole (in a block & head) is going to save any significant weight over a 12mm bolt in a 12mm hole.

Strange logic.... sure the bolts are lighter ...what about the holes?

Sure , steel bolts, aluminium head but?
Steve

I agree that the math appears is faulty... how does another 500g result from 10 slightly smaller diameter washers? And also the 600g saving in the example would also be incorrect because the smaller holes have not been taken into account.
The description on this web page sounds like a reasonable explanation why TTY bolts are used http://www.canadiandriver.com/articles/jk/040303.htm

P.S. providing info to help explain your viewpoint is more useful than having a rant.

[Dell'Orto]

My posts go way over the top of most peoples heads. They just don't understand.

Did you actually understand that link about the weight saving??

To go slightly OT here, yet another example of how car "culture" becomes more of a religion than a science.... just because somebody wrote something that doesn't make sense but was written by someone who has some sort of authority... people are frightened to question it.... in case they are made to look silly.

Everyone makes mistakes... sometimes on purpose, to get a response.


Then of course somebody else will repeat what they read, again not understanding what they've read but it must be right because it was "on the net" and written by someone they have confidence in.

Steve

I didnt actually read it tbh, but I know how much you like to go on about not believing everything you read on the net

[jondee86]

I don't understand how putting a 10mm bolt into a 10 mm hole (in a
block & head) is going to save any significant weight over a 12mm bolt
in a 12mm hole.

Strange logic.... sure the bolts are lighter ...what about the holes?

I think some people need to sharpen up on their comprehension !!!
This is what the article actually said....

"If the smaller bolt bosses in the cylinder head and block are
added, the total saving could be easily one kilogram.".

No mention of hole size... or hole weight

Cheers... jondee86

[MAGN1T]

Come on then ....explain.

Comprehension was never by best subject.

Steve

[jondee86]

The boss is essentially the tubular column of metal that surrounds
the bolt; both where it passes thru the head, and where it is threaded
into the block. This column of metal transfers the clamping force from
the head of the bolt to the gasket surface. In the the block, it transfers
the tensile forces into the surrounding metal to prevent breakout.

In the article, the suggestion is, that if a smaller diameter bolt is used,
then the bosses can also be reduced in size, saving weight.

Without getting into the engineering calculations involved, I can say that
if the bolt size went from 12mm to 10mm, and the boss size went from
24mm to 22mm, there would be an overall saving in boss weight.

I think this was the point of the article....

Cheers... jondee86

[JRS]

It's only an intermediate step, doesn't matter. The purpose of the intermediate steps is to ensure the bolts are done up evenly.

This isn't true for the angular torque method.

"Don't believe everything you read."

[fangsport]

It's only an intermediate step, doesn't matter. The purpose of the intermediate steps is to ensure the bolts are done up evenly.

This isn't true for the angular torque method.

so how critical is it

[jondee86]

You could estimate how critical the preload is, if you knew how many
degrees of rotation was required to raise the preload torque from 22 to
30 ft-lbs. If it was 5 degrees, then what you have effectively done is
torque the bolts 90 + 90 + 5 degrees.

Looking at the load vs elongation curve in the attached article, you can
see that the bolt stays in the plastic range for quite a while after it passes
the yield point, but before it reaches maximum load.

Assuming (and I think it is a realistic assumption) that the designers set
the tightening routine to make sure that the bolt reaches the yield point,
but doesn't go too far past. Then there will be a fair degree of overhead
to allow for such things as accidental over-tightening or re-use of the
bolts.

Re-use of the bolts is usually permitted if the bolt has not stretched
beyond a certain point, checked by measuring the length of the bolt.
Since you were using new bolts, the worst that will have happened is
that you have stretched the bolts a gnats more than expected. But
you will still be in the plastic range, and no harm done.

Cheers... jondee86

[MAGN1T]

So can you explain how the bolt is going to actually stretch at 30 ft lbs torque?

Steve

[Burning Angel]

So can you explain how the bolt is going to actually stretch at 30 ft lbs torque?

Steve

its not going to, but when you add the 90 + 90 to the extra say 5 thats was caused by over torquing the initial step the bolt will be stretched just a little more than intended