XPost: alt.autos.4x4.chevy-trucks
The Nolalu Barn Owl <gordie@nolalu.on.ca> writes:
On Wed, 14 Dec 2005 11:40:14 GMT, "Steve Mackie" <stevemackie@ns.sympatico.ca> wrote:
Fishmouths & shear ties are a way to blend stiffness between a box
section
and a channel... which minimizes stress concentrations... Metal
You just seem to be stating the same thing over and over. I have never used >>anything but plain rectangular plates and they have always met stress >>requirements. I want to read into the theory to see if changing the way I do >>it is worth it.
Steve
I have looked and looked for information on the NET about fish mouthed re-inforcing plates and there isn't much to be had.
Basically you can use a plate cut to form what looks like an open fish
mouth on each end.
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You can also use a diamond shaped plate to give the same effect.
To weld the frame directly from the top to the bottom makes it likely
to crack again for reasons which I am not qualified to try and
explain. After over 30 years of working as a Millwright, I can say
that once a crack has been welded it quite often cracks there again so
a plate is used to bridge the repaired area and this plate is welded
with stitch-welding so as not to make a continuous weld. This way, if
one stitch was to crack it won't carry over to the next weld. The
fish mouth (or diamond) allows you to place welds that are not in a
direct line from top to bottom.
Since my explanation is wanting, and I am just a DIY repairman, I have
cross posted this message to a welding NG to draw in some expert
opinions for you - and for me :)
--
Gordie
There are tongues speakers who speak in an unknown language that actually
exists among the peoples of the earth. I recall one such incident in which a
tongues speaker got up and spoken in some unknown language. As it
happened, there was a priest in the audience who just happened to speak the
language this women was speaking as an unknown tongue. The priest asked
her if she knew what she was saying. The women had no idea so the priest
told her: "You were speaking my native language and what you were saying
was cursing God." http://www.saint-mike.org/Apologetics/QA/Answers/Faith_Spirituality/f0404120221.html
This looks to be a fatigue cracking matter...
Geordie seems to know from practical experience what does and doesn't
work to avoid fatigue cracks or how to repair them when it happens.
Steve - you've read and all seems fine and from that basis you
disbelieve and experienced practitioner.
Steve - you could do Finite Element Analysis modelling to see the
stress concentrations. FEA for the general region of the structure.
Here's a somewhat comparable example of me probing a feature I met
while actually out there as a welder
http://weldsmith.co.uk/tech/finiteelement/1609_beam_tjn_sim/160927_beam_w_column_w-wo_stiffplts.html
What I would bet is that you will see theory concurring with what
Geordie is telling you already. Steve - you'd benefit from "treading
the path" and seeing how where you come from can plug you into the
deep knowledge out there.
I take it you are proposing some feature with an abrupt "right-angled
in every way" change in thickness and possibly direction.
That will be highly fatigue-prone.
Steve I think you are being given a chance to learn and you are not
seeing it.
As best I can tell from message trail so far...
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