"djenyc" wrote in message
ups.com...
On Sep 27, 11:39 am, "Ed Huntress" wrote:
"djenyc" wrote in message

ups.com...



Hi, I'm doing some hobby level wood and metal fabrication projects
around house - shelving, boat cradle/ boat lift / trailer implements/
carts / work tables/ bike racks etc. I'm mostly using scrap material
that I happened to come buy...

I'm not a mechanical engineer, and have no idea what load/deflection
ratings are for different materials. I've been using 2x4, steel
tubbing, angle iron ... just found 20 ft of 2" pipe another day ...
Currently, when I'm designing stuff, I just rely on limited prior
experience and eye measure. Some things turn out to be overbuilt and
sometimes things fail under load (hopefully it's not critical and I
get a chance at redesign ). For example, I built a manual forklift
last week and it crumbled while testing/lifting my dad - now I know
where to strengthen it , but is where a better way?

Would it be worthwhile to look up load ratings of common materials
like steel pipe and 2x4? Where would I find such information? Or are
this calculations so complicated, that I'd be better off continuing
with what I'm doing?

It would be worthwhile, but if you're not building anything that risks
life
or limb, learning by trial and error isn't bad, either.

For the examples you give there are two basic subjects you need to know:
strength of materials, and "statics." If you want to learn them, be sure
to
use texts written for technical schools and junior colleges, not for
four-year engineering-school students. The former explain it in terms of
high school algebra. The latter do it in terms of calculus. If you're
good
at calculus, use either one.

A basic study of these subjects will not make you a design engineer but
it
may prevent some of the grosser errors. And you may find it very
interesting. These subjects provide a lot of suprises and insights into
how
things work -- and how they don't.

I'd call a local community college and see if they have a program in
"engineering technology," or something like that, and ask what texts they
use.

--
Ed Huntress

Ed, thanks, I'll check on what books they use at community college. I
went to community college a while ago before transferring to
university, and found they courses to be more entry-level and
application oriented/ vs. more theoretical/fundamental stuff at 4 year
school. It is odd though that there are a lot of free books on line
(US Navy/Army, expired copyright, farming books, etc) about
metalworking, welding, drafting, quality control, fabrication, but
nothing on design... Even non-free selection seem to be more
production and college oriented...

Yeah, that is interesting. I never looked online. My own books on those
subjects are ones I bought decades ago, so I can't help you with titles.

I'll tell you what I do when I want technology books like that, though --
particularly for construction trades, welding, landscaping, etc. I find out
what the local community college is using and then I go look for them in
their library. Then I come home and order them on an interlibrary loan
through my local community library.

That is, for books I don't want to keep. I'm very cheap. d8-)

--
Ed Huntress