On 5/23/2012 11:15 AM, Kirk Eppler wrote:
> All
>
> As I mentioned in passing a week or so ago, the younger daughter had to
> build a bridge as her final projects in physics.  She chose a classic
> trestle design (from a bridge in Baltimore I think).  We went to the
> hardware store, guesstimated our needs (typical galoot project, huh?), and
> bought some basswood and balsa wood.  Once we got home and started laying
> out the components, and figuring the cuts, we realized we needed more wood
> (again, typical).  So I started her cutting and gluing the pieces we had,
> and went back to the store.  Of course, they were out of stock on the sizes
> we needed, so had to buy bigger stock (again, typical).  Once we got the
> few main pieces cut glued and clamped up, using all my available
> lightweight clamps (again, typical), she got sidetracked (again, typical).
> She decided some embellishment on the base might be nice, maybe carving or
> stamping some words or dates into the standards.  So, I set her up with
> some basswood blocks and the carving chisels, and away she went (again,
> typical).  I took a nap (again, typical).  When I woke, she was still side
> tracked on carving, and not on the 2nd round of glue ups (again, typical).
> Got her back on track, and a bridge got built.  There were a few course
> corrections and design changes along the way (again, typical), and
> execution not being able to meet design standards (again, typical).  We
> spent most of Sunday and a little time Monday on it.  Finished it well
> ahead of schedule (not typical), but we thought we had a much shorter
> timeline to due date.
>
> The weigh off was today, the criteria to win, most weight held / bridge
> weight, while spanning 2 benches.  She tied on the most weight held, but
> the other girl's bridge was smaller and lighter.
>
> Then, being the daredevil that she is, she asked me "Do you think the
> bridge is strong enough to let a small person stand on it."  I assumed she
> meant in spanning mode, so said no, only about 20#.  But, once she had her
> grade, she was free to experiment.  With the bridge on the floor, it
> finally failed at, 243 pounds.  One of the cross pieces let go, not quite
> enough glue, the balsa fractured.  I was AMAZED it held that much.
>
> My contribution to the project: Loaning tools and explaining how to best
> use them, holding pieces while clamping, little bit of engineering and
> geometry review, and financial backing
>
> Tools used: mini miter box and razor saw, all my little clamps and some
> clothes pins, small squares, Incra marking tool, dividers, drafting
> triangle, sandpaper, Titebond
> Diversion tools used but not part of project, carving gouges, mallets,
> safety glove.
>
> A few pics here
>
http://kirkhmb.smugmug.com/Woodworking/Carly-Bridge-Project/23135936_Krh7zW#!i=1863802019&k=kgGBJx7
>
>
>
You both earned some pride there!
Don

-- 
I have tried too in my time, to be a philosopher; but I don't know how, 
cheerfulness was always breaking in. - Oliver Edwards
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