tips on a 2 piece?

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cool hand luke
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tips on a 2 piece?

Post by cool hand luke » August 29th, 2017, 11:51 am

Last year was my first year helping to coach a middle school sci oly team (and our teams first year to ever compete) I mainly helped on all the builds. I'm a civil engineer, so towers is near and dear to my heart. I read most of the posts here last year, and we did decently in towers.

Our backup tower placed 5th at state, (somehow between the hotel room and the event we broke our primary tower! thank goodness for backups!)

Our much better towers we had been doing before state would have been in the 2-3 range.

So, all that being said, what do I need to do for a two piece?

Do you build 1 jig for the bottom, a separate for a top, and potentially a 3rd to connect them?

What works for the joint connecting the two pieces?

anything else I should know going into a 2 piece tower?

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Re: tips on a 2 piece?

Post by Balsa Man » August 31st, 2017, 11:38 am

I'll be getting more detailed thoughts posted, but here are a few initial ones:

Back in 2011/12, last time tower rules demanded a "2-piece" tower configuration, we used two jigs- one for the wider, lower base section and one for the narrow upper, 'chimney' section. We worked hard for the top dimension (i.e., the leg positions of the tops of the base section leg) to be the same as the bottom dimension (i.e., the leg positions of the bottoms of the chimney section). Then we sanded the top of the base flat/parallel with testing base, and bottom of the chimney flat (so it was perpendicular to the testing base), and then glued the chimney on top of the base- drops of glue on bottom ends of the chimney legs, carefully lowering onto the base so lower and upper legs were aligned. With very careful jig building, and connection of chimney to base, it worked .... pretty well. But, unless you get a really good alignment of upper and lower legs, it won't, and loading onto base legs will not be symmetrical. That experience is saying to me the way to go is a 'one piece' jig, that allows you to put both lower and upper legs on the same jig.

Doing this with an Xs only bracing configuration (with the Xs glued onto the outer leg faces) will work well, be easy to work with. Using a ladders and Xs configuration (with ladders butt jointed between adjacent leg faces), there was a major issue in the upper/chimney section jig (where the legs slope in very little); the ladders having clearance issues with the jig- meaning you couldn't lift it off the jig. The slant on the base section was enough to not have interference issues). We ended up with a.... complicated, pain in the tail solution where we could collapse/pull the jig panels inward after the bracing was installed, and were able to lift the chimney off. I don't recommend such an approach.... both because of the hassle, and because results from last year say an all Xs bracing approach yields better performance (higher scores) than a ladders and Xs approach.

That's my two cents worth....
Len Joeris
Fort Collins, CO

cool hand luke
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Re: tips on a 2 piece?

Post by cool hand luke » September 1st, 2017, 12:57 pm

Awesome, thanks so much! as soon as the rules drop on tuesday we are figuring our jig out!

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