Primitive Archer
Main Discussion Area => Around the Campfire => Topic started by: Badger on August 29, 2015, 12:13:46 am
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Check me out building a giant bow for the discovery channel https://www.youtube.com/watch?v=7qUivOCfGZ0
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thats cool ;D
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That was really fun to watch. Nice piece of engineering on that gigantic board bow, Steve. It sure did its job.
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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
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I remember that Steve. I'm going to save a copy of that vid
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I have had a few people ask me about it and I noticed the video was back up there.
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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.
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Sweet. :)
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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.
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I was wondering about draw weight actually and how you would try and predict or hit the goal weight.
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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.
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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 (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
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Are these people actually a$$holes or is it scripted that way? Nice job on the bow and you came across great ;D ;D
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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.
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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. ;D
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Very cool. My favorite part: "I lied to ya just a little bit."
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If they'd made the arm out of Osage it would've worked, right
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If they'd made the arm out of Osage it would've worked, right
YEW!
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... The producers went out of there way to stir up trouble it seemed like.
Yeah, I hate that sort of thing >:(.
I call it engineered (or manufactured or manipulated) conflict. They think it makes it more "interesting"... no it just makes it irritating at the expense of the real interesting stuff.
Wish they'd save that stuff for the soap operas.
Del
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A friend of mine worked on the reality series "Hoarders" for a short time. He witnessed staff members working a woman over with questions like, "Do you think your kids hate you behind your back because of this? Do you think they will ever bring their children to see you when you live like this" and so on. When she had a breakdown they motioned for the cameras to hustle in and revel in the terror they had whipped up in this poor woman's life.
He refuses any work involving that production company, even if it means going hungry. But hey, whatever it takes to entertain the masses, right?
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So ...... when is the build at Pappy's going to be? You could build it, and build it the right way, with a shorter, arm, and have it go more forward, and then notify the local news, people, to come watch, and make the Davinci production people look like the idiots they are by showing it can be done, and without any artificial drama, or arguments. And that the machine works! ;) Cool machine. Davinci was definitely a genius!
Wayne
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Wayne, I would rather build the giant 80 foot bow Da Vinci designed, Hickory would be perfect, make it from hickory boards, pine core. The limbs would be about 12" thick and 2 1/2 feet wide. Not sure Pappy would like something like that jamming up his property. LOL.
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What would you shoot out of it? Telephone poles maybe?
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30 foot telephone poles, ( skinny ones)
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Haha "If at first you don't succeed you're running about average." I like that crazy guy.
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That was a fun watch, although I agree with everyone that the manufactured drama was not only unnecessary but took away from the episode. It would have been far more interesting if they had shown some of the process you had to go through to figure out what the draw weight and such was.
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A funny side note. One of the guys from my club is a giant. Ge must be seven foot two. You can imagine the draw length on a guy like that. Its a darn good thing he is as good a bowier as he is if u know what i mean xD
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Steve that is awesome that they picked you to help with the build. I'm really glad they had enough brains to find someone in the primitive archery realm to help with the build.
I would have liked to see more of your design work as well. I also was trying to figure out why they had the arm stopping so short and not using all of the stored energy that was left in the limbs. Patrick
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Very cool Steve,enjoyed it. :)
Pappy
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I would have liked to see more of your design work as well. I also was trying to figure out why they had the arm stopping so short and not using all of the stored energy that was left in the limbs. Patrick
I was also wondering why they didn't go with something that had a bit more "give" to it, like a spring or another flexed piece of wood if that would be more in style with the device and have that span of rope as the emergency back-up.
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Actually the amount of " give " in the bow was just about right. If it had more give it would have been too weak. The drum in the middle only needed to make 1/2 revolution with about 1/4 revolution preload. As the project progressed we actually imagined several configurations on the same principle that could have been really effective. I think back in Da Vincis day they would have done it the same way, start off with one project in mind and then modify it accordingly. We were not allowed to modify, it had to look just like DaVinci drew it on his plans.
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I think these things were just Leonardo's doodling. Keeping his mind busy. He's my hero, has been since I was a kid. :) I was so exited when that show first came on(it was a series) and those boneheads screwed it up with their bickering. There was another show the BBC did called "Rough Science" that had 4 or 5 people working on a project. They got along great and the show flowed smoothly. But producers seem to think they need drama.
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Sorry, I didn't mean give in the bow, that part looked perfect, what I meant was give in the arm stop. First there was no stop at all so the arm smashed, then they use a rope that yanks the arm abruptly at the end and it winds up cracking just above where it's tied on. Maybe that was just bad luck or a hidden flaw in the wood...
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I agree with you on that sudden stop, I had calculated the g forces of acceleration with a 5# weight on the end of the rod and built it to just flex with that much force on it. Comming to a sudden stop had far too many g's for it to survive. I warned them about it.
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So that's why you brought in the shorter, more sturdy arm. It's funny how people that think they are smart don't know very much.
I think it would be cool to build that thing on its side and see how far the bow it's self would fling a projectial! Patrick
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The original compound bow.... it has all the elements, just in the wrong order. Kinda like a Picasso.
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The thing that bugged me the most about the build was the lack of communication with the engineer. If I asked him a question I never got anything in the way of an answer, I had to go over to the machine and try to figure out what they were doing in the way of gears and such. I did make them rebuild the big steel gear so it would detach from the drum after winding up the bow. Getting that big flywheel spinning would have robbed all the power. That arguement got a little heated, I guess the language involved wouldn't work for TV.
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I think it would be cool to build that thing on its side and see how far the bow it's self would fling a projectial! Patrick
On PBS they showed a special called "Leonardo's Dream Machines" that had two different teams, one building a ballista and another an airglider based off of sketches Leonardo did. Trailer can be viewed here: https://www.youtube.com/watch?v=6y4bgibiRdg
Badger, I would have loved to see THAT debate (argument) rather than the silly post-it note nonsense. Also think it would have been awesome if you could have gotten in on the ballista building. The Dream Machines makers seemed to be a lot more concerned with authentic period technology with no spot welding or modern glues used.
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The thing that bugged me the most about the build was the lack of communication with the engineer. If I asked him a question I never got anything in the way of an answer, I had to go over to the machine and try to figure out what they were doing in the way of gears and such. I did make them rebuild the big steel gear so it would detach from the drum after winding up the bow. Getting that big flywheel spinning would have robbed all the power. That arguement got a little heated, I guess the language involved wouldn't work for TV.
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Good for you bud! It almost sounds like all they wanted was a machine that looks like it would work. Then if it didn't they would of came up with something like, " DaVinci new it wouldn't work, that's why he never built one". Patrick