Date: Fri, 27 May 2011 15:56:30 -0500
Reply-To: John Rodgers <inua@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <inua@CHARTER.NET>
Subject: Re: Torque spec that requires calibrated fingers
In-Reply-To: <1306505587.30903.58.camel@TheJackUbuntuNetbook>
Content-Type: text/plain; charset=UTF-8; format=flowed
When machines are built - like cars, trains, planes, and other
mechanical things - they are engineered. Every piece has a specification
in terms of materials, strengths, etc, and the assembly of same also has
specifications as to torques, pressures, tensions, etc. There are
reasons. The minute any one of these is changed, the what-ever is on the
road to destruction. As designed - it will hold up - when changed - it
will not.
The greatest familiarity I have with this is in the aviation industry. I
do not want wing mount bolts on the airplane I'm riding in to have been
replaced with bolts that are not to spec - no way. And I do not want
those wing bolts tightened by some mechanics calibrated wrist. No way.
As the 'Lil Boy sez "When the wing falls off, the pilot ain't gonna park
that baby on no cloud!". Now on a car or Vanagon, it's not quite so
critical, but the parts in them are also spec'd and if you want it
right, and you want it to last, do it by the book. Be sure all fasteners
are installed to spec. Of course, by the time we get to work on our
20-something year old vans, many, many things have been changed - many
times by shade-tree mechanics - like us. But of course - again - if
something fails, there is always the side of the road to park on. So,
unlike airplanes (but it does happen) - low spec, poor quality materials
and fasteners find their way into the machines. If we are lucky, nothing
bad happens, nothing life threatening, even if a part does fail. All
that given - it is far better to use the proper quality materials
meeting the proper quality standards, and the properly specified forces
applied to hold it all together.
So, if a torque value is given, use it. And apply it with a good,
accurate torque wrench. Even screws will have a torque value. Use the
correct torque wrench. There are many different kinds, made for
different applications - but it is all about getting the right pressures
on materials so things hold together and don't fail.
One of the scariest things I ever saw what an aircraft engine on which
the cylinder hold down studs had not been torqued properly. Pilot came
in complaing about and oil leak on the upper part of a radial engine. On
inspection it was discovered that several of the cylinger flange stud
were broken off. That was really something! On that particular engine
thos studs were the size of my thumb. Investigation determined that
because of the awkwardness of getting at some of the studs to tighten
the nuts - the calibrated wrist had been used!! The result was near
failure of the cylinder - which would have cause massive engine failure
and possible loss of the airplane and all aboard. So if there is a
factory spec, or a standard spec for bolts, nuts, screws, etc. Use it.
Now all that said - if there is something that isn't going to be a
safety issue - shop practice was always tighten nuts and bolts finger
tight plus one quarter turn. Never saw that cause a failure. But if no
factory spec was present, and there was any question at all - then the
'ol pocket ref standards book was pulled out, and the specs on the
hardware looked up.
Just my $.02.
John
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com
On 5/27/2011 9:13 AM, Rocket J Squirrel wrote:
> tencentlife's adapter kit for connecting a adapter which allows a fellow
> to mount a oil pressure gauge sender alongside the stock oil pressure
> warning light sender has this to say about torquing:
>
> "Torque recommendations are meant as relative guides, it will not
> generally possible to actually use a torque wrench on the fittings in
> this installation."
>
> "...Tighten the fitting carefully, it has a taper thread so it will seal
> into the case hole with moderate torque, generally less than 8-10ft.lb."
>
> and
>
> "The compression fittings should attain a good seal with only
> 10-12ft.lb. of torque, so don't overdo it."
>
> I'm assuming that some of yinz have fingers calibrated after many years
> of experience. Is there any wisdom that can be shared here?
>
> -- RJS
>
>
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