Main Discussion Area > Flight Bows
Hysterisis and performance
PatM:
I'm still skeptical about this line of reasoning.
I think records are still set with bows that are "shot-in" but not "shot out".
Badger:
The biggest thing here I was kind of excited about was that I feel like for the first time I am able to actually evaluate a process with some accuracy simply by comparing measurements we have been using for years. We have never been able to identify with any accuracy real efficiencies of bows because we couldn't quantify the hysterisis factor. On bows with very low hysterisis all the measurements worked out pretty good, but great designs that were suffering from hysterisis in the wood gave faulty results if evaluating the designs, mass, efficiency etc as individual componets. I plan to play with this a little more.
It is hard trying to explain the concept of the process just because so few people use those concepts when measuring things, a lot of the process explanation gets watered down and drug out because it is neccessary to explain all the steps in order for it to make any sense.
scp:
Badger, I'm not even sure whether you are talking about hysteresis or limb vibration. Is there any way you could post some diagrams or pictures?
Badger:
I don't think anyone knows what I am talking about. The vibration would go more with the virtual mass, the hysterisis is more just internal losses within the wood. I don't know how you could illustrate it. For the most part it is useless information to about 99.99999% of the population. I find it cool only because I have been chasing it for so long.
KS51:
Badger, I've been mulling over what you're talking about and I think there may be 2 effects that you'd be actually measuring. The first is the reaction speed of the wood. Basically, the energy stored can only flow through the limb to the string and then into the arrow. There is a minmum amount of time for the energy to flow through the path. As you lighten the arrow, you eventually reach the minimum reaction time for the 3 materials ( bow, string, arrow) and by default the max affective arrow speed. The other internal energy loss due to the internal "friction" of the materials is also measured. I think this internal energy loss is the true hysteresis.
I do think there are some interesting variations of your experiment with different types of arrow material, string material, and species of wood that could lead to an extrapolation for your mass principle, to give a starting point for the limb width. But it would require that the reaction speed of the wood (by species or SG) be known. It would be nice if it could be SG related, but I suspect it is a combination of SG and basic wood structure ( ring porous, diffuse porous, etc).
Enigineering hat on - a taguchi analysis structured experiment could shed some light on this if the under-lying variables are understood.
Ken
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