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

["Jon Lockwood" <jn_lockwood@xxxxxxxxx>]

So we some metallurgy people on this site?  COOL!


----- Original Message ----- 
From: "Martin Gutkowski" <martin@xxxxxxxxxxxxxx>
To: <dmcnews@xxxxxxxxxxxxxxx>
Sent: Wednesday, February 08, 2012 1:53 AM
Subject: 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.
>
> Martin
> Sent from my BlackBerry®
>
> -----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
> #5508
> Lic  9D NY
>
>
>
> On Feb 7, 2012, at 1:53 PM, Matthew wrote:
>
>> http://www.industrialchassisinc.com/Web-blog/?p=622
>>
>> --- 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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> 



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