Saturday, May 11, 2013

Zach's trebuchet

 The end of 8th grade at Bret Harte means the Builder's Olympics.  They can choose one of three projects to do.  A boat made solely out of cardboard and duct tape that they have to ride across a pool, a pasta car made only of pasta and glue that has to roll some distance, and finally a trebuchet that has to fling a tennis ball.  A what???  A trebuchet.  Sort of like a catapult, but gets it power from a counter weight only, no springs.  The most difficult project to me sounded like the trebuchet, which of course means that is what Zach chose.  Sigh.

 I tried talking him into the boat, but he held firm at the trebuchet.  So a trebuchet it was.

 I hunted around a little online and found instructions for one here.  The trebuchet could not be more than a meter when in the loaded position and the one on that site looked perfect.  It also had the word "easy" in the title so I was sold!

It was pretty easy and Zach did it himself with help from us.  As we were building I realized he would be graded on how far it went compared to others in his class.  No biggie I thought, we had 20 pounds of counter weight.  That is a lot!  Right?

 Actually it was not.  It would only fling about 15-20 feet, and I was hearing people on Facebook talk about theirs flinging 60 or more feet.  Ugh!! 
 Brian Tuck (a friend whose son did the project last year) to the rescue!!  He brought more weight and we raised it to 60 pounds!!  He also helped tweak a few things, changing the pouch to a 4 string instead of 2 (more consistent results) and moving the release nail.  We were consistently getting to about 60 feet at home.  Sounded good to us!

I loved it-- Zach and Pete strapped it to a wagon so Zach could walk it to school. (he was purposefully being a dork in this picture)

I couldn't be at the school for the launch so a friend took pictures for me.  He did great!!   65 feet!!  Not the best in the class, but very respectable and earned him an A.

That was his last project for the year (woo hoo!!).  Now to get through Joey's damn state report...

1 comment:

Suzanne said...

Great job! You should google Pumpkin Chunking. There is a whole series about the festivities and they make amazing trebuchets. That way, if you need to do it again for Joey, you will have arsenal. :-)