Tech Directions - April 2008 - (Page 14)

at 80 pounds. The total finished weight of the bridge would be 19 tons! To get some first-hand experience with the materials, we obtained samples from the sawmill to handle and practice with. Nailing five 2" × 12"s together to make a 44' long beam (five beams were required) and cutting through a 6" thick timber would require some tooling. Our customer bought and donated to our program a cordless Paslode framing nailer and a Beam saw, which is like a giant portable circular saw but has a 16" dia. blade and can cut through 6-1/4" thick wood! We found the Beam saw by researching timber frame construction on the Internet. ing a wrong cut would scrap out a costly piece of timber and replacement would take weeks. Cost estimates for materials ran $12,000 to $14,000. From our experience with the sample timber materials, we decided two things: First, we would construct a 1/4" = 1" scale model to “proof out” the final CAD drawings. Second, we would design and build miter boxes with guides and stops so that anyone taught to use them could cut the individual timbers accurately and repeatedly. We would work smarter not harder, just like real craftsmen in the skilled trades. The 1/4" = 1" scale allowed us to use standard 2 × 2s for the 6" × 6" timbers and 1/2"-thick plywood ripped to 1-1/2" widths for 2" × 6" truss material. This also proved one of many “teachable moments” in reviewing the nominal size vs. the actual sizes of materials. We even made 1/4-scalemodel fixtures, which provided valuable experience in designing and using each of them. The real-world prob- Scale model, above Success at bridge building called for teamwork. We even found specialized timber frame bolts, which we ordered from a company in Oregon. The students got quotes and compared prices and shipping costs. This was additional real-world learning, and it was exciting. We were spending the customer’s money in a responsible way, saving some of it where we could. As the plans developed, the intricate angles became critical. Making a mistake would be a disaster. Mak- lems of cutting, handling, and assembling the full-sized timbers were greatly reduced through careful attention to detail as we practiced during construction of the 1/4-scale model. The students could break down the many large and complex problems safely. They could analyze each problem, discuss solutions, make judgments, and evaluate their decisions. Our decisions were objectively evaluated every day—it either fit or it didn’t. It either worked the way we planned it and went up in place or didn’t. Construction began in November 2006, and I estimated that we would need 130 class periods to complete the bridge. With only 90 class periods in a semester, it would require work outside of the regular day. It was an aggressive but realistic estimate—it was real world. Scheduling and organization would be critical to the timely success of this project. We designed and set up an ordering and accounting system. We decided on procedures for planning orders, placing, and receiving them. Being late took on new meaning to the students when they scheduled a group of helpers to unload a 2 P.M. delivery that didn’t arrive until 5 minutes before the class ended. Their help left and the materials got “dumped” in the wrong location. We kept a running total of expenditures, with the dollar amount of each purchase recorded. At a glance, everyone could see the value of the materials being put into the project. Just as in real-world work, we had made a commitment and we had to keep it. The students’ integrity depended upon it. They had to make the effort, not excuses. At the end of 75 class periods and about 100 hours of outside work, the students had the walls up and the trusses set in place. They had produced very impressive-looking work. What was just a pile of wood a few months ago was now a very impressive structure. I tell my students that if you go anywhere, you’ll cross a bridge sooner or later. These three students know what it is like to build a bridge, and “crossing” a similar one in their future will be no problem! Postscript This impressive project ended up drawing attention to Darlington’s CTE program locally—and from the other side of the world! Coverage of the project aired on our local TV station, Channel 3, featuring interviews with the three students and lots of footage of the bridge itself. And the story won the voting for the 14 techdirections ◆ APRIL 2008

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Tech Directions - April 2008 Technically Speaking Contents Direct from Washington The News Report Technology's Past Technology Today Mastering Computers A Bridge to the Future Aeronautics Study Takes Off! Glider Design for Beginners Project Engineer in the Heavy Construction Industry for Renewable Energy Annual Buyers' Guide More than Fun

Tech Directions - April 2008

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