Giant Bow

[Badger]

Check me out building a giant bow for the discovery channel   https://www.youtube.com/watch?v=7qUivOCfGZ0

[dylanholderman]

thats cool

[GB]

That was really fun to watch.  Nice piece of engineering on that gigantic board bow, Steve.  It sure did its job.

[Del the cat]

Excellent .
I'll bet if they left you to develop it a bit more you'd have had it throwing about 3 times as far, prob' by adding a sling and letting the arm come further?
Your bit with the bow was best by far
Great the way they appreciated your expertise and feel and you ignored the CAD guy
They always cut these programs too short... I'd have liked to see heavier projectiles. The tuning of the device would have been a whole extra program for us bow nuts.
Del

[Marc St Louis]

I remember that Steve.  I'm going to save a copy of that vid

[Badger]

  I have had a few people ask me about it and I noticed the video was back up there.

[mullet]

Excellent, Steve! They were lucky to have your expertise, they would have probably hurt themselves with the bow. I'm going to have to watch this again.

[bubbles]

Sweet. 

[Badger]

  The most challenging part was not what you might expect. The actual build was just like any other lamination just bigger. The hard part was trying to figure out how to hit draw weight. I had zero help or advice from the engineer, he said just build it like the picture. I decided the only thing I could really go by was the crank they used to wind it up. I figured I would make it so one man pushing about 150# on the crank could just get it to full draw. I did some small scale models to test that theory out and just prayed it would scale up accurately which it did thank god, I got it just right on the first shot.

[bubbles]

I was wondering about draw weight actually and how you would try and predict or hit the goal weight.

[Badger]

   On the very tip of the 16 ft throwing arm it only built draw weight at about the same rate a regular bow does, about 3# per inch, but over about a 16 ft power stroke it added up to a few thousand pounds of stored energy with a peek draw force of about 500# or so. If you were to cut the throwing arm shorter to about 8 feet, the peek force was much higher and it would have been a lot more efficient. On the models I built I converted them to trebuchets and they worked outstanding.

[Del the cat]

Thanks for filling in some of your planning/figuring process.
Many years ago I made a model siege engine from illustrations in the Ralph Payne Gallwey book.
I spent ages making a nice throwing arm with a carved out spoon end... out of Pear wood.
First shot it snapped clean in half where it hit the horse hair stuffed leather buffer ....
I made a replacement from Elm that was fine and one with a sling too.
Got some nice pics of it lobbing a marble... down the bottom of the page here:-
https://sites.google.com/site/delsbows/home/other-stuff
It was back in the analogue camera days... I got the pics by working in a darkened room with a flash triggered by som contacts on the throwing arm
Del

[DC]

Are these people actually a$$holes or is it scripted that way? Nice job on the bow and you came across great

[Badger]

      Del, when I made the throwing arm I had to learn some new math. I figured out the approx speed and g forces that would be on it with a 5# weight and built the arm to just slightly flex on release. I was actually kind of proud of myself being a high school drop out and all.

    DC, yes they were a little bit of a holes but not too bad. The producers went out of there way to stir up trouble it seemed like.

[GB]

I thought the big gear, worm gear, and crank and the rope setup were cool, but the force the bow put out was beyond cool.  It's a shame that they didn't have the time to refine the throwing arm and get it to load and stop to its peak performance.  The guy's laptop would probably still be airborne.