Re: [DML] Modified Trailing Arms For 1/2" Bolts
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Re: [DML] Modified Trailing Arms For 1/2" Bolts

Actually while hard materials tend to be brittle, it's not the same thing. Soft is not the same as ductile - eg carbon fibre composite has a very high tensile strength and low ductility but is nowhere near as hard as even aluminium. 

Hardness is a surface property, brittleness (resistance to crack propagation) and tensile strength, modulus of elasticity and ductility are all structural properties.

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-----Original Message-----
From: "K.L. (KAYO) Ong" <klo@xxxxxxxxx>
Sender: dmcnews@xxxxxxxxxxxxxxx
Date: Tue, 07 Feb 2012 16:15:08 
To: <dmcnews@xxxxxxxxxxxxxxx>
Reply-To: dmcnews@xxxxxxxxxxxxxxx
Subject: Re: [DML] Modified Trailing Arms For 1/2" Bolts

Too much hardness (brittle) is just as bad as too soft (ductile)...  
As for Toby's bolts.... So far, Toby's bolt has been serving my car  
very well on the roads and streets of NYC. since his introduction  
many years ago.   Before Toby's bolts, I had replace the trailing  
arms bolt twice!  First time, they were both bolts were bent upon  
inspection.  The right side bolt was more bent to the point a shim or  
two fell out.  The second time the right side bolt had actually  
snapped (sheared) off on a right turn!!!  I was luck to be one block  
from home...  Anyway, my DeLorean was then towed to Rob to have the  
replacement to have Toby's bolt installed...

For what it is worth about softness and hardness about metals from  
the aviation industry....

Some years ago a helicopter had crashed.  Upon inspection, the  
primary rotor blade's pivot securing bolt was at fault.  This bolt  
was made in mainland China, where quality control was not a critical  
issue.  To the manufacture, steel is steel... The problem was the  
bolt produced was way too soft and did not meet the required Rockwell  
hardness test as prescribed....  The bolt cost was $5.00 US.... It  
was five dollars versus the $20.00 US approved bolt by the  
F.A.A.!!!    From that failure there were major lawsuits and I  
believe the Chinese manufacture got away with it, for one, it was  
overseas and government affiliated and two, the company just closed  
shop and change it's name... So, that is about soft metal.

In the USA aviation industry/manufacturing, the rivets that are used  
are sent frozen from the manufactures until they are ready for usage  
upon assembly.  If the rivets are removed from the freezer and they  
are not used and or they have been sitting around beyond a designated  
time, they are automatically scrapped.  The reason is because the  
room temperature with bring up the molecules movements which raise  
their brittleness (work harden by temperature)... And also, the  
assembler who is pneumatically hammering the rivets must know that  
there are a prescribed amount of "hits" allow to the rivets.  This is  
to not to over "work harden" the rivets upon compression which may  
create a condition for premature failure!!!  Just several years ago,  
we have seen planes in the news with the fuselage parts ripped off or  
fallen off...  Rivet, rivet...  That is hardness in metals....

Kayo Ong
Lic  9D NY

On Feb 7, 2012, at 1:53 PM, Matthew wrote:

> --- In dmcnews@xxxxxxxxxxxxxxx, "Martin Gutkowski" <martin@...> wrote:
> >
> > Tensile strength is only part of the story, you have to be  
> careful with ductility, aka "brittleness" and in general with steel  
> the higher the tensile strength, the more brittle it becomes. A  
> suspension component should have a degree of ductility, but not to  
> the point of fatigue or elastic limit. The torque spec for the TABs  
> is far lower than would normally be applied to such a bolt.
> >
> > Martin
> >
> >

[Non-text portions of this message have been removed]


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