Tuesday, March 1, 2011

Serious fun ...?

Serious fun. Can there be such a thing? I always told my students that Woods Technology classes were about having "serious fun". No surprise the majority heard and locked onto the last word in my statement! The saying goes, "Everyone like to learn but, nobody likes to be taught."

Keeping that in mind, I dare to try this.

The following list contains the Tech Vocab words that have been used or covered in the Bridge building process to date. In "school" this would result more often than not in a test (punishment in my day, now they call them assessments) of some sort. Take a look at the list. Imagine you were on a game show or over coffee, struck up a "bridge building" conversation.  How would it go?

Technical Words Used in a Bridge Building Context...
26-29 words - 90% - Advanced -- Ahead of Time - In Front - Very Progressive
28-23 words - 80% - Proficient -- Highly Competent - Skilled
22-20 words - 70% - Basic -- Fundamental - Essential
19-17 words - 60% - Minimal -- Smallest Amount - Least possible
Less than 17 words - You cross the bridge first.

Air Dried
Alphabet of Lines
Annual Rings
Board Feet
Doyle Scale
False Work
International Scale
Isometric Projection
Kerf to a Line
Kiln Dried
Orthographic Projection
Parallel Clamp
Scribner Scale
Tree Nails
View Projection

The best part of building things I find is the instant feedback. Although responses will vary here is what I would say in a "Bridge Building" conversation applying the Tech Vocab covered to date...

When logs are sawed the resulting Cants may have some Wane (bark on the edge) on them because the sawyer is trying to get wider boards out of the log thereby increasing the efficiency of yield. The Board Footage for the sawn boards can be calculated (T" x W" x L' / 12) longhand or there are several "yard sticks" (Doyle Scale, International Scale, Scribner Scale) that have scales on them that give you the Board Footage results directly. Wane will not be a problem for some things like False Work the bridge is layed out on or Stickers used to separate layers when stacking the boards for drying. The rough sawn boards contain a lot of moisture (green state). The Chords and Web pieces that make up the Lattice truss must be Kiln Dried down to 17% moisture content so that when they dry out naturally and shrink the wood around the Trunnels (Pegs) does not crack. The rest of the bridge parts can dry out naturally (Air Dried) and will shrink harmlessly over time.

Good blueprint drawings are critical in making any project. Isometric Projection sketches will help to visualize the finished part. More detailed three view Orthographic Projection drawings using the Alphabet of Lines and following the rules for view projection come into play when parts are to be layed out. Like a Button to hold floor joists tight to the Truss Chords for example. A 3 inch rise or Camber will be built into the Chords of each Lattice Truss. In the assembly of the Chord it is important to observe and orientate the Annual Rings of each piece used correctly. Another detail will be the process of sawing the Kerf To A Line at each joint in the Chords to insure a tight fit up. Many, many Parallel Clamps will be used to hold the Chord/Truss assemblies in place until the Trunnel holes are drilled.

It would be advised to build Jigs and Fixtures so that the Trunnels (Pegs) can be made consistently to size. Turning a slight Chamfer on the ends of the Trunnels using a Lathe will make driving them into the holes easier.

Puzzler - What's next? Hint, It will be pretty sweet...
Tech Vocab - Each month I will continue to add to the list.

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