Primitive Archer
Main Discussion Area => Bows => Topic started by: Del the cat on April 21, 2015, 12:45:04 pm
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I've had various discussions about this so I thought I'd try and really see on my Hazel warbow.
I stuck two 6" long bits of bamboo kebab skewers to the back of the bow about 4 1/2 " apart, sticking out from the back.
They were fixed with some rapid epoxy (mounted in little blocks of wood about 1/4" square).
I did it with the bow braced. I videoed it as I winched it back to 28" and from the video I could work out the tips of the skewers spread apart about 6mm (by scaling it off a brick :laugh:)
The other interesting thing was, just unbracing it moved the tips inwards by another 2.5mm! (with all these figures I've been careful to not exaggerate at all).
Stills from the video have been put together, I've inverted the shot where they are spread and placed it so the spills are tip to tip for comparison.
Dunno if this is of any interest what so ever, but I felt the need to justify my assertion that my bow was flexing in my hand. It does show a usefull technique for showing small deflections... or maybe I'm I'm just a bit OCD ;D
Also a pic of them being glued on.
Del
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Leave it to an engineer! ;D
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Are you going to try it on any of your other bows as a control/comparison group?
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Leave it to an engineer! ;D
I think we need a mathematician to work out a bend radius or angle of deflection now ::)
To me the interesting thing is that it was much easier to feel than to see. In a previous thread on warbows there was an argument (no change there then ::) ) about the handle only starting to bend as in neared full draw. My assertion was that it was bending all the time, but only became obvious/visible as it approached full draw. After all there are no cams or levers to suddenly get the middle working.
I think this shows that even at brace there are small deflections not visible to the unaided eye, but detectable with the use of sophisticated kebab skewers ;)
Del
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Are you going to try it on any of your other bows as a control/comparison group?
It would be interesting if I didn't have other even more interesting stuff to do.
I s'pose it would be interesting to stick spills all along the limb and video it under strobe lighting, maybe with dancing girls? ::)
You are of course free to continue this ground breaking research... hmm I wonder if there is a research grant I could apply for ;)
Del
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Well there goes that idea Del. I can break ground and break wind, but my research and mechanical aptitude is poor! Thanks for sharing the research. I do like the idea of strobe lights and dancing girls though. ;)
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As long as a force is being applied it will always bend to some degree, no matter how ridged.
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Del, that was cool, now just develop a long tape strip with those little skewers sticking out. Yu could stick it on the back of a bow to look for stiffer spots.
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I think your data is skewed :P ;D
Brilliant experiment! Thanks for sharing :)
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Good for you, Del. I'm glad that what you felt was confirmed. Jawge
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That's nice!
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Very cool experiment and the resulting "proof's", however I'm most struck by your comment regarding the " feel" of the bend. I have always been impressed with just how sensitive the human hand is. You knew it was bending, and torquing and the feel of the draw curve. Pretty cool to demonstrate what your senses had already told you.
rich
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Very cool experiment and the resulting "proof's", however I'm most struck by your comment regarding the " feel" of the bend. I have always been impressed with just how sensitive the human hand is. You knew it was bending, and torquing and the feel of the draw curve. Pretty cool to demonstrate what your senses had already told you.
rich
Cheers Rich, I don't think you'll have any need for that sort of test, we all know those shortie bad boys of yours are really bending :laugh:
Del
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Del,
We would need a larger sample size to accommodate the request for analysis. If we consider your first test to be the beta, then we would build off of that. There would need to be an agreement as to the parameters of the test, including your willingness to push the boundaries of the bow ( in order to get the most outliers). Form there we can plug in a basic SD calculation to produce some statistical information. It would be a fun project to be on. We could also test other woods, configurations, and draw weights to see if there is a ratio of movement to material/ weight.
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Yo, thanks, but I'm not really serious about analysis as i think there are too many variables and mesurement areas to make it worthwhile. I think it's really an illustration of the value of hand and eye.
Mind it would be interesting to see that converted to an angle of bend or a bend radius... not sure which (if either) would really mean much to me tho'
I think it would be usefull on laminated designs and I expect such things have been used in the past, not to mention strain gauges and CAD.
I like watching the bark crack off, natures strain gauge :laugh:
Del
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If you want to get silly I can see distance sensors mounted to the end of each skewer, fed into a computer that compares the distance and lights an LED on the end of the skewers to designate the area that needs tillering. But then that would make it too easy ;D
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Agreed. It would be useful, I think, in a full production mode. However, with the basic layout not withstanding, making a bow out of a stick is very much done by feel, with lot's of mistake based learning along the way. It would be difficult, but not impossible to apply standard proccesses to. My input was more for levity than an actual project plan. Nice work on the bows though
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Agreed. It would be useful, I think, in a full production mode. However, with the basic layout not withstanding, making a bow out of a stick is very much done by feel, with lot's of mistake based learning along the way. It would be difficult, but not impossible to apply standard proccesses to. My input was more for levity than an actual project plan. Nice work on the bows though
Ah excellent.. you had me going there for a minute... (a ";)" would have helped me decipher the nuances!)
Del
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Are you going to try it on any of your other bows as a control/comparison group?
It would be interesting if I didn't have other even more interesting stuff to do.
I s'pose it would be interesting to stick spills all along the limb and video it under strobe lighting, maybe with dancing girls? ::)
You are of course free to continue this ground breaking research... hmm I wonder if there is a research grant I could apply for ;)
Del
The grant money would be there but it would all be I singles. ;)