Hysterisis and performance

[Badger]

  Pat, when I comes to flight shooting their really are prizes for the freshest bow of the day. The old bows you mentioned that must be loaded with hysterisis. Not so! That is the biggest place they had us beat! They definitely had it under control. You cannot get high dry fire speeds from bow with high hysterisis no matter how far you draw them.

   

[PatM]

I disagree. You can see the pictures of the bows being drawn. They have to be in that zone.
 One of the bows that set a record was crafted from a shortened broken York longbow. Hard to break a bow without  stressing it to that point.
 Some of the bows also shot record type distances for years or set records after being shot in damper conditions and then shot again in dry conditions.
 These guys probably never heard the word.

[scp]

First thing first. We need a graph of whatever that is being measured. Is it two-dimensional, three-dimensional, or even four-dimensinal?

[Badger]

  SCP, laying it out is where I feel like I failed. I was trying to condense it the best I could because it was too lengthy as it is. Each componet being measured requires almost a page of explanation.

  Example. The first step is measuring the force draw curve of the bow. We all do this the same way. The fact is that if a bow with no hysterisis or very low hysterisis is measured it is pretty accurate, but if a bow has hysterisis it is a false measurement because we can't measure a force draw fast enough to keep up with the hysterisis factor. So all we get is a measure of how much work we are doing, it has very little relation to how much potential energy we actually have. This is the starting point for all the testing so if we don't find a more accurate method here everything downhill from this measurement is junk. Not having gone to school for any of this stuff I don't have the right terms to use. But starting at this point in the begaining if we don't identify the actual force going back into the arrow it will get lumped in with the virtual mass and thow everything else off.

    Pat, the bows you are talking about doing so well are indeed low in hysterisis. The builder has no need to know anything about hysterisis if he knows what a good bow feels like. Successful flight shooters in the past were very aware of avoiding breaking down their bows. What I am talking about here in my thread is only useful for developing strategies to build bows, it just offers a way to prove certain theories that have been floating around for the past few hundred years.

  The current record holding bows in the 50# class were all shooting in the high 220's maybe low 230's. We have bows now that are shooting in the high 250's and low 260's. Only because more attention was paid to hysterisis. Once I get the proper arrows to match thse bows I can back that claim up. The 50# records should all be over 400 yards , at present none of them are.

[PatM]

 I really doubt they coddled them like that. They shot them until they broke down to the point of not being competitive.
 The goal was maximal distance, nothing else.
 I think you mentioned the bow that you gave the girl which set a record was well shot in.
 

[Badger]

  Pat, actually I would like to see the term shot in become a thing of the past. If we get lucky and build one well inside its stress limits we can shoot it all we want and it never changes. My broadhead record holder I have been shooting for 5 or 6 years now, every year I have to scrape a pound or two off of it as it seasons and it keeps gaining speed. I don't likee the term a fast bow is 90% broke, I use to believe that. Now I figure a good bow is no where close to broke. My crude backyard testing shows that the 80% strain recomended by quite a few physics guys is actually overstrained because the set starts happening before that.

   I see bows right here at PA all the time that would do very well in flight shooting.

[stickbender]

     I was enjoying this till you started using math.   

                                    Wayne

[PatM]

But they were shot in.
 The current record is still Harry Drake's by my reckoning and that bow dropped about 28 pounds while setting the record.
 I'm still wondering why people are defiantly avoiding making similar bows to the style that worked far better back then.

[Badger]

  Pat, is that a regular flight bow or is it the yew bow he used in the complex composite? I would like to know more about that bow if you have information

[PatM]

It was apparently just a medium length Yew recurve around 60 inches long. Very narrow and thick and pulling 87 pounds according to Dan Perry.
 Before unidirectional glass came into use Drake made bows with toxhorn bellies and woven glass  backings which showed set after use.

[Badger]

  That might not have qualified for the present primitive classes because of the arrow rests and overdraws. I wish I could find more info on that bow. I rememeber Dan saying that Harry felt that the Yew on that bow was the best he had ever seen. I would have been interesting to see how the arrows performed as the bow was being shot in. I think that bow shot 603 yards. Don Brown currently holds the unlimited complex composite record with 619 yards, not sure if Harry built that bow or Don built it. They never listed the bowyers only the shooters.

[PatM]

They were both built by Harry. The yew bow shot 544 according to most sources.
 However many of the old time bows were not shot with an overdraw. that seemed to be a later feature.
 The picture of Murray Yantis shooting well over 400 yards(I think 466) shows no evidence of an overdraw and he has the long arrow cranked past his jaw.
 PS  Are you including sinew backed and simple backed composites in this discussion?

[Badger]

  As long as they are natural materials. I know they had several guys shooting bows over 400 yards in the 60 and 70 pound range. I am not sure if they were all natural or not. I really don't think it would have made a lot of difference.

[avcase]

Steve,
Your opening post on this thread is excellent!  I always viewed hysteresis as a fixed loss that I had no control over, so I never bothered giving it much more thought. But you have put together a really novel idea, to use hysteresis and virtual mass as a tool to explain the health of the materials in the bow.  The challenge is being able to easily measure it. I wish I had a draw board that would measure the force draw curve of a bow in as little as a few seconds. Wouldn't that be nice to have?



Alan

[Badger]

  Allen, It would be nice. That was the reason I chose to use an extemely heavy arrow and just measure the speed instead of plotting the curve. Plotting the curve doesn't pick up on much of the hysterisis. The part I avoided going into here involves juggling a few percentage points at the start and finding where the virtual mass seems to either hold at the most stable point or change in a more linear fashion. Using the heavy arrow to figure stored energy I am forced to estimate somewhat the efficiency but because of the weight I am only working around a couple of percentage points.