Primitive Archer
Main Discussion Area => Bows => Flight Bows => Topic started by: DC on March 24, 2019, 06:59:54 pm
-
I've been reading this old thread https://www.tapatalk.com/groups/paleoplanet69529/a-quick-study-of-the-stiff-limbed-hickman-thought--t16901.html that PatM gave me a link to. It talks a lot about high low gear bows. I understand the concept, I think, but can someone tell me about the hardware. What are the physical differences between the two?
-
I think maybe Alan is explaining at least some of it in this thread https://www.tapatalk.com/groups/paleoplanet69529/longbow-airbow-virtual-build-along-t16569.html
I'm still reading it. :D
-
I've finished reading. Interesting stuff. Now what is a high gear bow and what is a low gear bow?
-
You find lots of gearing info on other threads on that forum. There was some debate as to whether gearing truly exists.
-
I've bookmarked it and am slowly reading my way through it. It hasn't been very active in the last 2 years. As a ratio between tip movement and nock movement I would say it exists but whether it's of any use, I dunno.
-
Dan Perry is adamant that it does. Tim Baker does not believe it does. Dan has or had all the records though.
-
high gear bow bends more near the handle and less at the tips. Low gear is more "whip ended". Think about leverage. Tip bending is not maximising the length of a bow unless it's really short. More bending near the handle and less in the tips= more leverage and power delivered to the arrow.
-
Thanks Chuck, I've had a few thoughts about what might change the gearing but that wasn't one of them. It is now :D
-
And who used the analogy of high low gear. Kind of silly I think.. (lol)
-
Dc, gearing is why i was saying you want the fades to bend only in the last 3 inches of draw on your bow you just made. Last to bend is first to straighten on release. The inner part of the bow is all torque, and the outter limbs is all horsepower. It takes torque to get a car off the line, it takes HP to get it there quick. So ideally, on release, you want the limbs to lool like they are doing the wave, starting at the fades and moving toward the tips. The inner third gets the arrow moving, mid limb is mid range, and outter is top end red line.
-
And who used the analogy of high low gear. Kind of silly I think.. (lol)
Makes perfect sense to me... but, im a car guy.
-
Dc, gearing is why i was saying you want the fades to bend only in the last 3 inches of draw on your bow you just made. Last to bend is first to straighten on release. The inner part of the bow is all torque, and the outter limbs is all horsepower. It takes torque to get a car off the line, it takes HP to get it there quick. So ideally, on release, you want the limbs to lool like they are doing the wave, starting at the fades and moving toward the tips. The inner third gets the arrow moving, mid limb is mid range, and outter is top end red line.
I'm not sure about last to bend, first to straighten. When you pull a bow, even just an inch or so, the whole limb bends. The outers bend more, of course, but the inners bend too. Same on release, I think, the bow doesn't unwind, it all starts to move at the same time. I'm not so sure if it finishes at the same time :D
-
Dc, gearing is why i was saying you want the fades to bend only in the last 3 inches of draw on your bow you just made. Last to bend is first to straighten on release. The inner part of the bow is all torque, and the outter limbs is all horsepower. It takes torque to get a car off the line, it takes HP to get it there quick. So ideally, on release, you want the limbs to lool like they are doing the wave, starting at the fades and moving toward the tips. The inner third gets the arrow moving, mid limb is mid range, and outter is top end red line.
I'm not sure about last to bend, first to straighten. When you pull a bow, even just an inch or so, the whole limb bends. The outers bend more, of course, but the inners bend too. Same on release, I think, the bow doesn't unwind, it all starts to move at the same time. I'm not so sure if it finishes at the same time :D
The arrow keeps a load on the bow limbs, keeping them from sprining loos all at once. The heavier the arrow the more effecient and thays why.
-
And who used the analogy of high low gear. Kind of silly I think.. (lol)
-
And who used the analogy of high low gear. Kind of silly I think.. (lol)
This is all my take on this so far, opinions will vary.
If you accept that the nock can move differently than the bow tips. Say at the beginning of the draw the string moves 5" for every 1" that the tips move but at the end of the draw the string moves 2" for every 1" the tips move. (I picked the numbers out of the air) That's a 5:1 ratio and a 2:1 ratio. It's not a real stretch to compare that with changing gears in a car. Some bows will be closer to 5:1 through the whole draw-- a low gear bow, and some will be closer to 2:1 through the whole draw-- a high gear bow. I think I would have chosen "high ratio bow" rather than "high gear bow" but that's just semantics.
Oh, I don't know who chose to use that term to answer your question ;D
-
I think it was Dan Perry.
-
Dc, gearing is why i was saying you want the fades to bend only in the last 3 inches of draw on your bow you just made. Last to bend is first to straighten on release. The inner part of the bow is all torque, and the outter limbs is all horsepower. It takes torque to get a car off the line, it takes HP to get it there quick. So ideally, on release, you want the limbs to lool like they are doing the wave, starting at the fades and moving toward the tips. The inner third gets the arrow moving, mid limb is mid range, and outter is top end red line.
I think that is right, because I have videoed myself shooting my bows and played them back, paused them on release. I notice that the tips are vibrating slightly a few inches before returning to brace height. It does appear that the tips are the last to stop bending.
Nice to have a camera because I can rest it on the edge of a 2x4, cant do that with a smart phone. Good way to analyze your form and bow glitches.
-
tell me about the hardware.
string stretch seems to be a big part of the discussion at PP
-
It seemed like anytime Alan showed a graph with something cool on it he would then introduce string stretch and it would mess everything up. It seems to be the great leveller.
-
I never cared for the term gearing but I can see where it could apply some. For the most part efficiency is more important when shooting light arrows and high energy storage gets a slight nod when shooting heavier arrows. Practically speaking in most cases the fastest bow with any arrow will usually stay the fastest regardless of arrow weight. When you start getting extremely light or extremely heavy with the arrows this is where you really start to see a difference. Bows that bend more in the inner limbs near the fades will tend to store more energy but also tend to be less efficient because of increased opportunity for limb vibration. I am of the belief that if a bow is tillered so that the bend increases from the fades to the other it will mitigate most of the vibration. I also believe in as short of working limb as you can get away with and still not take set. When you measure the FDC and calculate stored energy and then find the efficiency based on arrow speed I think that cancels out the entire conversation on gearing. Bows with low string angles at brace will generaly store more energy than a bow with higher string angles and the same amount of reflex.
-
tell me about the hardware.
string stretch seems to be a big part of the discussion at PP
Your post quotes quote who is quote. What hardware.
-
woodlely,
"tell me about the hardware" was DC's request in the opening post. I was just dragging the string factor into the discussion. Some of us visit infrequently, so I apologize if the discussion seems disjointed.
Badger,
from the other discussion at PP, one of Dans goals was to put more energy (aka. acceleration) into the arrow earlier after the release, presumably so that it would not have to have so much delivered to the arrow at once at the end of the powerstroke. Wouldnt this make sense if one were trying to avoid undue flexing of the lighter flight arrows right at release? mabye even having an advantage that would outweigh having a setup that has the best efficiencys?
-
woodlely,
"tell me about the hardware" was DC's request in the opening post. I was just dragging the string factor into the discussion. Some of us visit infrequently, so I apologize if the discussion seems disjointed.
Badger,
from the other discussion at PP, one of Dans goals was to put more energy (aka. acceleration) into the arrow earlier after the release, presumably so that it would not have to have so much delivered to the arrow at once at the end of the powerstroke. Wouldnt this make sense if one were trying to avoid undue flexing of the lighter flight arrows right at release? mabye even having an advantage that would outweigh having a setup that has the best efficiencys?
Light tips and low string angles do exactly that. The arrow however light needs as much control over the tips as it can get. You can best accomplish this by having as much of the limb as possible already have completed its task, hence the elliptical tiller. I think most of the flex is right at the beginning anyway but don't hold me to that.
-
Steve
I have always been a bit unclear about the string angle terminology. To clarify, when one generally reads about 'string angle', are most talking about the angle between the string and the tip? and at full draw or at brace?
-
I've always thought(with nothing other than my gut and looking at FDC's) that a traditional bow gave the big push at the beginning of the power stroke and a compound sorta saved it for the middle/end. I thought this was why compounds were faster and it all made sense in my beady little brain. One of Alans graphs showed that it's the opposite. Trad bows save it for the end. So much for my brain. So, the idea is that we want a huge push at the beginning of the power stroke? Now does time enter into this at all? If we have a high gear bow the limbs are going to have to work a lot harder to get the arrow moving. This is going to slow the power stroke(like trying to start your car it 3rd gear) Does this matter? Do we care how long it takes for the arrow to clear the bow as long as it's going like a bat out of hades when it does?
-
I've always thought(with nothing other than my gut and looking at FDC's) that a traditional bow gave the big push at the beginning of the power stroke and a compound sorta saved it for the middle/end. I thought this was why compounds were faster and it all made sense in my beady little brain. One of Alans graphs showed that it's the opposite. Trad bows save it for the end. So much for my brain. So, the idea is that we want a huge push at the beginning of the power stroke? Now does time enter into this at all? If we have a high gear bow the limbs are going to have to work a lot harder to get the arrow moving. This is going to slow the power stroke(like trying to start your car it 3rd gear) Does this matter? Do we care how long it takes for the arrow to clear the bow as long as it's going like a bat out of hades when it does?
There js so much science into this that as soon as i try to place my point of view, i find myself with more questions than answers.
Im gonna say that when it comes to your 3rd gear scenario, the gearing isnt so important as tje power behind it, and the weight its pushing. The power to weigjt ratio. A motorcycle can start in 3rd gear and take off faster than a car in 1st. A bow that feels like its in 3rd gear would do better with a lighter arrow, and still empart as much energy into the arrow in form of a higher FPS than a 1st gear bow. Lets call 3rd gear biws flight bows that shoot ligjt arrows, and first gear bows, those are most effecient at 10gpp.
-
Tjings to consider are, where in the bow is what % of energy stored vs how effecient is its release from there.
How does an arrows level of kenetic energy affect the release of a bows potential energy based on tiller shape at diffent points on release.
Is a bows energy release best all at once, or gradual?
The handle has all the energy of a bow focused like a lense on it, and the tips have none. The flow of energy across the bow is like a wave, with the crest in the center, and trough at the nocks. The arrow needs to harness the energy flow best as it can, be it for penetration power with weight, or high speed with low weight. The gearing can be looked at as different parts of the wave and hiw they affect the arrow.
-
The arrow has 0 kenetic energy at full draw and the bow has 100% potential. As the arrows kenetic increases, the bows potential decreases, forcefully dropping the bows power to the arrows weight ratio. Using that logic, the first part of the bow that moves upon release should be built in a way that has high torque, is good to get weight moving, the last part of the bow to move should be built in such a way that low energy is most effecient at moving an arrow whose weight is being affected by its speed.
How does speed affect an arrpws weight? It makes the arrow feel heavier to the bow, as the bow struggles to keep up, its power no longer having the advantage over the arrows mass. Tjis part im still working in in my head because tje arrow mau actually be lighter to the bow as it is moving away and no longer resting its weight in the bow tips as hard. Still thinking.
-
It's interesting to talk about this stuff but I'm sure most of it is speculation(I know I'm speculating) and everyone has a different idea. Computer simulations seem to help although I'm with Del here, a little suspicious. Simulations are only as good as the input. A good example is when Alan ran simulations with a stiff string and then with a little stretch. A world of difference. One little input missing and the whole thing goes down the tube. Are we missing anything? This is why conversations like this are important. We may be having a nice little talk and something may come up with something that Alan missed. I'm picking on Alan because he's the only one I know of that's doing this stuff. Sorry Alan. Myself, I think it's all about acceleration and acceleration is all about weight. Even though I did some tip reduction tests that didn't show great gains, if any, I still think that the answer is in light arrow, light string and light limbs. I can't see that how or where the energy is stored has much to to with it. Just get that energy to the nocking point and physics will do the rest. Maybe getting it there is the key. Maybe that's what everyone else is talking about. I'm rambling.
-
Using that logic, the first part of the bow that moves upon release should be built in a way that has high torque, is good to get weight moving, the last part of the bow to move should be built in such a way that low energy is most effecient at moving an arrow whose weight is being affected by its speed.
We're going to have to disagree on that. I can't see how one part of the bow will start moving before another. That said, I can still see that the energy may be delivered to tha arrow at a varying rate depending on whether the leverage of the limbs(gearing) changes as the limb travels home.
-
Using that logic, the first part of the bow that moves upon release should be built in a way that has high torque, is good to get weight moving, the last part of the bow to move should be built in such a way that low energy is most effecient at moving an arrow whose weight is being affected by its speed.
We're going to have to disagree on that. I can't see how one part of the bow will start moving before another. That said, I can still see that the energy may be delivered to tha arrow at a varying rate depending on whether the leverage of the limbs(gearing) changes as the limb travels home.
I say that because if the resistance of the arrows weight against the tips.
-
So you think the weight of the arrow holds the tips back and so the inner limb moves first?
-
So you think the weight of the arrow holds the tips back and so the inner limb moves first?
I think it can, in conjunction with the mass of the limbs. But, the tips could be made to move first...
-
If the tips are held back how do the inner limbs know when to move? They can't move until the tips do because that's where the string is holding them from.
-
If the tips are held back how do the inner limbs know when to move? They can't move until the tips do because that's where the string is holding them from.
They move when the ristance to them is less than the force they are pushing with. Think of an arrow. On release, the entire thing doesn't move at once. The nock moves first, head last, causing the paradox we are so familiar with.
-
The resistance will never be less until the tips move. I think an arrow backward to this. The string is pulling on the tip of the bow but it's pushing on an arrow.
-
Think about the g forces everuthing is under when an arrow is pushed to over 100 mph in a fraction of a second. Weight matters. An arrows weight WILL slkw a bow limb down that isnt under much stress.
-
My coffee's in the garage and my tunes are turned on. I'll catch up with this later.
-
The resistance will never be less until the tips move. I think an arrow backward to this. The string is pulling on the tip of the bow but it's pushing on an arrow.
Ok, i see your point. The tips gadda move or the arrow wont. Im saying that the part if the bow under most tension must transfer and will transfere its energy to the tips before any part with less energy storage will. I was illustrating that poorly by referencing the part of bow that bends first releases last. Id better say the part of the bow that stores the most energy releases it first. Thinking of entropy here... The greater the potential difference in energry storage the harder it pushes, and will take precidence over lesser energy storage areas.
There is the possiblity that upon release, the bows energy storage equalizes instantly, all parts of the bow limb disperse energy equally ( taking into acount that a smaller area cant hold as much as a larger area) among the limbs mass.
-
All this is just thoughts in progress, i dont have it figured out yet. Im just happy to have a good enough underatanding that i can think of queations to ask, usually i dont even have the question, darn the answers.
-
all kinds of good video on Tuomo's channel.
https://www.youtube.com/watch?v=vj64_33-zJU
-
https://www.youtube.com/watch?v=QhVGsWEIVOE
-
Thought experiment: Applying arrow paradox to bow limbs on release. The most motivated part of a bows limb will move first and may move faster than the limbs tips. This loads the other parts of the limbs with energy until all energy is spread equally across the limb. Under slow motion, it probably looks like a wave. If the timing of this wave could be done correctly, the tips would be be at tje crest right when brace heightis hit, snapping the last of the energy into the arrow.
-
There is the possiblity that upon release, the bows energy storage equalizes instantly, all parts of the bow limb disperse energy equally ( taking into acount that a smaller area cant hold as much as a larger area) among the limbs mass.
I'm with this or at least something very similar to this :D
Thought experiment: Applying arrow paradox to bow limbs on release. The most motivated part of a bows limb will move first and may move faster than the limbs tips. This loads the other parts of the limbs with energy until all energy is spread equally across the limb. Under slow motion, it probably looks like a wave. If the timing of this wave could be done correctly, the tips would be be at tje crest right when brace heightis hit, snapping the last of the energy into the arrow.
I don't think that you can compare paradox with this. I think one is pushing and the other is pulling but I could be wrong. More thinking needed.
I don't think it moves first but it may move faster. I think the end result would be the same, your wave. But I can't agree to this and everything instantly evening out like you said above. Even more thinking. >:(
-
Thought experiment: Applying arrow paradox to bow limbs on release. The most motivated part of a bows limb will move first and may move faster than the limbs tips. This loads the other parts of the limbs with energy until all energy is spread equally across the limb. Under slow motion, it probably looks like a wave. If the timing of this wave could be done correctly, the tips would be be at tje crest right when brace heightis hit, snapping the last of the energy into the arrow.
Its all about the arc of the circle the tips are last to arrive home. Makes sense.
-
Thought experiment: Applying arrow paradox to bow limbs on release. The most motivated part of a bows limb will move first and may move faster than the limbs tips. This loads the other parts of the limbs with energy until all energy is spread equally across the limb. Under slow motion, it probably looks like a wave. If the timing of this wave could be done correctly, the tips would be be at tje crest right when brace heightis hit, snapping the last of the energy into the arrow.
I can see it looking like a wave if it is jim hamms turtle bow in TBB, but we always go with tips as light as practical in real life
-
good videos Pat.
going to .25 speed it looks like any part of the limb getting ahead of any other part only happens after the arrow is gone
-
Bow: 36#@27"
200 grain arrow: https ://www.youtube.com/watch?v=izv2y9qgJ8g
1100 grain arrow: https ://www.youtube.com/watch?v=Y4JCD2_O5uI
No difference in bending of the limb.
It is all about efficiency - string, arrow and limbs are moving as a one moving part. The bow is storing certain amount of potential energy, which depends on many things - and hysteresis is one of the most important factor in wooden bows. As Steve said earlier, a bow which is the most energy efficient, is the fastest bow: "the fastest bow with any arrow will usually stay the fastest regardless of arrow weight".
-
Bow: 36#@27"
200 grain arrow: https ://www.youtube.com/watch?v=izv2y9qgJ8g
1100 grain arrow: https ://www.youtube.com/watch?v=Y4JCD2_O5uI
No difference in bending of the limb.
It is all about efficiency - string, arrow and limbs are moving as a one moving part. The bow is storing certain amount of potential energy, which depends on many things - and hysteresis is one of the most important factor in wooden bows. As Steve said earlier, a bow which is the most energy efficient, is the fastest bow: "the fastest bow with any arrow will usually stay the fastest regardless of arrow weight".
No difference in limb bending but big difference in limb vibration
-
I always figured a low gear design is one that simply lacks “high gears”. It is one of those bows that is said to “like heavy arrows”.
A straight bow with zero brace height and long flexible limbs could be considered the ultimate low gear bow. The bow stores lots of energy in the draw, but the limbs won’t be able to get out of their own way fast enough when shot. The archer would almost be better off throwing the arrow!
For maximum efficiency, the ideal situation is where all parts of the bow return along the same path as when drawn. When a bow shoots a very heavy arrow, this is approximately what is happening and efficiency is relatively high. If the design can maintain this for very light arrows without additional waves of limb distortion or vibration, then the light arrow efficiency will also be very high. There would also be little visible difference in post-shot vibration on the high speed video between the heavy and light arrow.
Alan
-
No difference in limb bending but big difference in limb vibration
Marc, are you writing of limb vibration before or after the bow reaches brace upon release?
If the design can maintain this for very light arrows without additional waves of limb distortion or vibration, then the light arrow efficiency will also be very high. There would also be little visible difference in post-shot vibration on the high speed video between the heavy and light arrow.
Alan, you seem to be specific about limb distortion (from the path along which it is drawn) occurring between FD and brace on the powerstroke. Has this been observed photographically? Toumo sees no difference in his two videos, but of course, that is one specific bow used with two different arrows.
-
I don't know about gears in a bow! But if a bow has shock wethere from bow vibration or string related it ant good. That robs cast! We all ways won't to see full draw pics? To prove even limbs. Well if the bow goes back to brace even it won't have much shock! If the limb tips are narrow as possible the less the shock. Reflex adds shock is what I have noticed. But it transfers more energy to a point. To much reflex adds to much mass which will add shock. I pay more attention to the shock in the bow.
Set is the other enemy! I think it comes down to design where the bow is light on the ends has little shock , limbs come to rest evenly , and have a good force draw. Then you have to match a good arrow that flys straight and true. I guess I am in agreement with Alan . Lol
Arvin
-
Alan, you seem to be specific about limb distortion (from the path along which it is drawn) occurring between FD and brace on the powerstroke. Has this been observed photographically? Toumo sees no difference in his two videos, but of course, that is one specific bow used with two different arrows.
I have not accurately measured these limb vibrations photographically. I can pretty clearly see the symptoms post shot and measured the effect on efficiency. If I were to do it photographically, then I would mark the side of the bow with about 20 dots from the center of the riser to one of the limb tips. I’d start with the bow braced, then track the limb as it is drawn. Then I’d need to have pretty clear high speed video, around 5000-10000 frames per second, to track the return path of the limb during the shot. It would be an interesting exercise.
This is much easier to do with a computer model however. ;)
Alan
Alan
-
For maximum efficiency, the ideal situation is where all parts of the bow return along the same path as when drawn. When a bow shoots a very heavy arrow, this is approximately what is happening and efficiency is relatively high. If the design can maintain this for very light arrows without additional waves of limb distortion or vibration, then the light arrow efficiency will also be very high.
Solution: Rigid limbs. As Steve has said - minimize bending portion of the limb. Just like Turkish flight bows...
-
I made what I called a hinge bow several years ago with very extreme recurves and reflex, something like 12". The bow was about 4" wide in the bending area which I think was no more than about 8" long up close to the handle. It broke down quickly because of set and hysterisis but in the initial shots it was the fastest bow I had ever seen bar none with a 10 grain per pound arrow. I think it was like 212 fps on the first shot. And dropped with every shot until it stabilized after about a dozen shots. Once it stabilized it had no real performance left but it did confirm what is possible if the right materials were used. Short working areas solve a multitude of design problems with bows. The stored energy was over 125% of peak draw force.
-
What was it made of?
-
I made what I called a hinge bow several years ago with very extreme recurves and reflex, something like 12". The bow was about 4" wide in the bending area which I think was no more than about 8" long up close to the handle. It broke down quickly because of set and hysterisis but in the initial shots it was the fastest bow I had ever seen bar none with a 10 grain per pound arrow. I think it was like 212 fps on the first shot. And dropped with every shot until it stabilized after about a dozen shots. Once it stabilized it had no real performance left but it did confirm what is possible if the right materials were used. Short working areas solve a multitude of design problems with bows. The stored energy was over 125% of peak draw force.
I remember this bow. It was Osage. Steve, you are the only guy to break 200 fps at 10gpp, and hardly anybody even knows it. I think about that design often, trying to figure out how to stop the losses you encountered, then use that in my own short bow design. Probably won't ever hit 200 fps, but i want steady 180s, consistantly between bows. Im close. That bow was insane to see on your thread.
-
I think the limbs will move back exactly the same way as they are pulled back. You can do it slow, moving your hand back from full draw, or fast, relise. The speed depends just from arrow weight. My understanding of gearing is ratio between pulling the limbs back ( straight limb bow) and pushing them together vertically (5 curve bow). If to think, why braced bow have bigger string tension than full drawn bow....and why stringig a bow is easier with bending the limbs, than pressing the tips together (like kids bow), it could explane something.
Its hard to explain what i think in foreign language but i hope you get what i mean :).
-
This is much easier to do with a computer model however. ;)
Alan
Alan, Do you think that a FE type program, such as the bow-simulator that was discussed a while back, would have potential for these type of observations?
-
This is much easier to do with a computer model however. ;)
Alan
Alan, Do you think that a FE type program, such as the bow-simulator that was discussed a while back, would have potential for these type of observations?
Yes, I do believe so. I haven’t spent much time in that program yet, but I believe it has great potental.
Alan
-
Very interesting videos! I think the biggest reason for the limb vibration is mass inertia. The limbs move forward and when reaching the brace hight, they are suddenly stopped. The mid limbs still have some kinetic energy due to their mass. I think a bow with no mass wouldn´t vibrate at all!
-
Very interesting videos! I think the biggest reason for the limb vibration is mass inertia. The limbs move forward and when reaching the brace hight, they are suddenly stopped. The mid limbs still have some kinetic energy due to their mass. I think a bow with no mass wouldn´t vibrate at all!
The limbs reach their maximum speed around 2/3 the way through the shot and then the tips start decelerating even though the arrow is still accelerating all the way to the end. So it isn’t a sudden stop, but it is a rapid slowing. If the limb flexes between the handle and limb nock during this phase of the shot, then the center portion of the limb hangs on to a portion of that forward momentum rather than transfer it to the arrow.
One possible experiment is to clamp the handle and the limb tip down to something solid, then tap the mid-limb and listen to the frequency. A design that rings at a higher frequency between the nock and handle should be the better light arrow bow. A bow limb design with stiffer tips should have a higher natural frequency with with this vibration mode.
Alan
-
I made what I called a hinge bow several years ago with very extreme recurves and reflex, something like 12". The bow was about 4" wide in the bending area which I think was no more than about 8" long up close to the handle. It broke down quickly because of set and hysterisis but in the initial shots it was the fastest bow I had ever seen bar none with a 10 grain per pound arrow. I think it was like 212 fps on the first shot. And dropped with every shot until it stabilized after about a dozen shots. Once it stabilized it had no real performance left but it did confirm what is possible if the right materials were used. Short working areas solve a multitude of design problems with bows. The stored energy was over 125% of peak draw force.
Steve, i gotta ask if you built a follow up bow to that hinge bow, and where you took the idea?
-
If the limb flexes between the handle and limb nock during this phase of the shot,
This is confusing me a bit. What kind of flex are you talking about here. The bow is bending, that's flex, but I don't think that's what you're talking about.
-
I made what I called a hinge bow several years ago with very extreme recurves and reflex, something like 12". The bow was about 4" wide in the bending area which I think was no more than about 8" long up close to the handle. It broke down quickly because of set and hysterisis but in the initial shots it was the fastest bow I had ever seen bar none with a 10 grain per pound arrow. I think it was like 212 fps on the first shot. And dropped with every shot until it stabilized after about a dozen shots. Once it stabilized it had no real performance left but it did confirm what is possible if the right materials were used. Short working areas solve a multitude of design problems with bows. The stored energy was over 125% of peak draw force.
Steve, i gotta ask if you built a follow up bow to that hinge bow, and where you took the idea?
I never did, I was trying to find some fiberglass builders to build the bow but none that I know of took interest. the new border bows closley resemble the design. The main thing I was trying to estalish was the amount of design problems that can be solved by simply using shorter working limb areas. Stability at brace for highly reflexed bows has always been a major issue, as well as the distorsion in the limbs that Allen described above. It solves both of those issue. Bows built from wood just cannot tolerate that short of a working area unless they are drawn much shorter. This particular bow could have tolerated a 24" draw pretty well without breaking down.
-
Steve,
A Sinew-wood-Horn composite should be capable of handling the high bending strains of your design. If you recreated your bow and really thinned down the area of hinge-like bending, then used that as the core. The horn and Sinew would not have to extend all the way to the tips.
A Drake flight bow might be most similar to your design. The latest Border “Hex 8 super recurve” designs are a full working Recurve. A 35# bow stores almost as much energy as a 50# bow with a more conventional design. There is one major drawback as far a small flight shooting is concerned, the efficiency is relatively low and it starts to run into a wall below 8-9ggp. This is one design where the faster bow with heavy arrows is not the fastest with lighter arrows.
Alan
-
I don't like the full working recurves especially with light arrows.
-
There is one major drawback as far a small flight shooting is concerned, the efficiency is relatively low and it starts to run into a wall below 8-9ggp. This is one design where the faster bow with heavy arrows is not the fastest with lighter arrows. Alan
Why? What are the physical reasons of that?
-
I'm trying to wrap my head around that too. This bow will still shoot a lighter arrow faster than it will shoot a heavier arrow, right? But compared with other bows, not so good? Hard to get a piece of yew to bend like that though ;D ;D
-
I'm trying to wrap my head around that too. This bow will still shoot a lighter arrow faster than it will shoot a heavier arrow, right? But compared with other bows, not so good? Hard to get a piece of yew to bend like that though ;D ;D
The efficiency can drop while arrow speed increases. They are not the same. Just as an example:
A 10 gpp fires at 180 fps
9 gpp hits 190
8 gpp hits 195
7 gpp hits 199
6 gpp is 203
These are not real numbers but its showing how the energy ( velocity x mass ) of the arrow is decreasing as the arrow weight drops, making the bow less effecient in putting its energy into an arrow.
You can see that the lower weight arrow, though it is faster, its actually storing less energy because of its decrease in weight. An arrow at 10gpp may have X number of jules in kenetic energy, an arrow at 5 gpp would still have X Jules if the bow were 100 % effecient, but that would require the speed of the arrow to be MUCH higher for its weight, and the bow simply doesnt get more effecient as arrow weight drops, rather, less so. The difference in speed between arrows may be only 1 fps, if any difference, even if the 2nd arrow were only half the weight of the first, when the first weighs 2 grains, and the second weighs 1 grain.
-
But a bow that shoots a 2 grain arrow at 250 fps will always shoot a 1 grain arrow a little faster. Right?
-
But a bow that shoots a 2 grain arrow at 250 fps will always shoot a 1 grain arrow a little faster. Right?
I got pretty light (about 15 grains :o ) in this test (see link) and you can see the velocity goes up pretty damn quick as you get really light.
But there will come a point where it is too light to do much good (e.g very little kinetic energy or momentum.
https://bowyersdiary.blogspot.com/2011/11/mass-velocity-and-energy.html (https://bowyersdiary.blogspot.com/2011/11/mass-velocity-and-energy.html)
Del
-
I'm going off on a bit of a tangent but why do we care if the energy drops off as long as the speed is still increasing? It's the speed of the arrow once it leaves the string that's the bottom line isn't? Is there something we can do with the energy information?
-
I'm going off on a bit of a tangent but why do we care if the energy drops off as long as the speed is still increasing? It's the speed of the arrow once it leaves the string that's the bottom line isn't? Is there something we can do with the energy information?
Nope, if it is too light the drag will overpower it's momentum/kinetic energy.
I't the old ping pong ball vs golf ball thing.
Fastest tabletennis ball smash is about 70 mph, but it wouldn't go as far as a golf ball travelling at 70 mph.
Del
-
I'm going off on a bit of a tangent but why do we care if the energy drops off as long as the speed is still increasing? It's the speed of the arrow once it leaves the string that's the bottom line isn't? Is there something we can do with the energy information?
Nope, if it is too light the drag will overpower it's momentum/kinetic energy.
I't the old ping pong ball vs golf ball thing.
Fastest tabletennis ball smash is about 70 mph, but it wouldn't go as far as a golf ball travelling at 70 mph.
Del
That and the point is to get a bow to deliver the most energy into an arrow. Just because the arrow goes 300 fps it doesnt mean anything if the bow is only putting 50% its energy into it. Say, you hit 400 fps, big deal, it took a 400 pound bow to do it. Thats bad effeciency. Now 400 fps with a 40 pounder, now we are talking.
-
Just because the arrow goes 300 fps it doesnt mean anything if the bow is only putting 50% its energy into it.
It does mean something, it means the arrow is going 300 fps and it's going to go farther than a 200 fps arrow no matter how much energy was gained lost or wasted up to the time the arrow left the string.
-
Just because the arrow goes 300 fps it doesnt mean anything if the bow is only putting 50% its energy into it.
It does mean something, it means the arrow is going 300 fps and it's going to go farther than a 200 fps arrow no matter how much energy was gained lost or wasted up to the time the arrow left the string.
I guess if your only goal is speed no matter how it got there, then you have a solid point. But with how it relates to gearing, to hold a more solid comparrison, keeping draw weight and length the same, you need to work with effeciency.
-
Tru nuff ;D
-
But a bow that shoots a 2 grain arrow at 250 fps will always shoot a 1 grain arrow a little faster. Right?
Yes, speed will increase all the way to a dry-fire, similar to what Del’s graph shows, but not all designs do this at the same rate. This is why it is possible for a design that is good at flinging heavy arrows to be bypassed by a lower energy storage bow when shooting lighter arrows.
Del,
Is the graph an extrapolation based on virtual mass? Virtual mass is also not so constant either. If you do a lot of testing over a wide range of arrow weights, some designs will show a pretty consistent virtual mass regardless of arrow weight, others show decreasing virtual mass with progressively lighter arrows, and some designs will show the increasing virtual mass with lighter arrows.
-
Last mojam i upped my arrow weight and was shootung further with 13 grain vs 10gpp. It may have been the arrow, idk, but anobody else notice arrows gping further with heavier weight?
-
Nope, if it is too light the drag will overpower it's momentum/kinetic energy.
I't the old ping pong ball vs golf ball thing.
Fastest tabletennis ball smash is about 70 mph, but it wouldn't go as far as a golf ball travelling at 70 mph.
Del
[/quote]
50 ft-lb kinetic energy to a golf ball will send i the down range at 121.7 mph.
50 ft-lb kinetic energy in a ping pong ball is 502.3 mph. That will still hurt!
Now make the ping pong ball smaller in diameter so it has the same density as the golf ball, then the diameter of the 41.6 grain projectile is now just a bit over 5/16”, and that is going to punch a pretty nasty hole into just about anything it hits. ;)
Alan
-
Last mojam i upped my arrow weight and was shootung further with 13 grain vs 10gpp. It may have been the arrow, idk, but anobody else notice arrows gping further with heavier weight?
It really depends on the bow, arrow, and release method. When I last went to the desert to flight test my foot bow, the lighter and faster 115-125 grain arrows always out-distanced the heavier 145-165 grain arrows.
Over the last couple of years at the Bonneville Broadhead flight tournament, Jim Martin got much better distances shooting 650+ grain arrows than he did with the minimum 450 grain arrows.
Alan
-
@Alan:-
The graph on my post is just raw experimental data, no extrapolation, no fudge, no sprinkles ;D
I made the lightest projectile I could.
I s'pose could have tried a dry fire, but the non existent projectile wouldn't register through the chrono' ;)
Del
-
Either that or it would be going infinitely fast ::)
-
Alan, with all your shooting and testing do you ever think that you're getting a handle on this stuff or is the carrot still out of reach?
-
Virtual mass is also not so constant either. If you do a lot of testing over a wide range of arrow weights, some designs will show a pretty consistent virtual mass regardless of arrow weight, others show decreasing virtual mass with progressively lighter arrows, and some designs will show the increasing virtual mass with lighter arrows.
Could you please elaborate this? Surely there is some kind on trend? For example, it seems that high gear bows is the design, which shows decreasing virtual mass with progressively lighter arrows? What are the design features, as general?
Nope, if it is too light the drag will overpower it's momentum/kinetic energy.
I't the old ping pong ball vs golf ball thing.
That is true but what is the real effect with real arrows? For example, what would be theoretically difference in distance with two dimensional identical arrows - 150 grain and 200 grain - if the speed is for both 200 fps? Or other way around, how much faster 150 grain arrow should be that it would fly as far as 200 grain arrow?
I think that difference is insignificant and thus the fastest arrow arrow has the most potential in flight shooting.
-
Toumo i agree with Alan . That's what I have seen at the flats. Light is not always faster. The first five feet and where the arrow lands is two different critters. I've shot enough to witness this. And I have only been doing this a couple years. Maybe I did not understand your post either. It don't take much for you math guys to get over my head. O:). Arvin
-
Virtual mass is also not so constant either. If you do a lot of testing over a wide range of arrow weights, some designs will show a pretty consistent virtual mass regardless of arrow weight, others show decreasing virtual mass with progressively lighter arrows, and some designs will show the increasing virtual mass with lighter arrows.
Could you please elaborate this? Surely there is some kind on trend? For example, it seems that high gear bows is the design, which shows decreasing virtual mass with progressively lighter arrows? What are the design features, as general?
Nope, if it is too light the drag will overpower it's momentum/kinetic energy.
I't the old ping pong ball vs golf ball thing.
That is true but what is the real effect with real arrows? For example, what would be theoretically difference in distance with two dimensional identical arrows - 150 grain and 200 grain - if the speed is for both 200 fps? Or other way around, how much faster 150 grain arrow should be that it would fly as far as 200 grain arrow?
I think that difference is insignificant and thus the fastest arrow arrow has the most potential in flight shooting.
If the speed for both (dimensionally identical arrows) is the same, the heavier will fly further.... (but their speed won't be the same from the same bow).
Second question is possibly unanswerable! Prob' depends on the dimensions and properties of your "dimensionally identical arrows).
I don't think you can really separate the bow from the arrow except in thought experiments...
Del
-
Alan, with all your shooting and testing do you ever think that you're getting a handle on this stuff or is the carrot still out of reach?
Ha! Yes-Still out of reach, but if it was easy then it wouldn’t be nearly as fun. I feel the bows are fairly straightforward. Not necessarily easy, but the physics are straightforward using the same kinds of basic physics like those used to launch a car in space. Haha!
I don’t feel very confident that I have flight arrows figured out. I just don’t have enough data points. The only good news is that I have made a lot of progress with distances this last two years, after years of almost no improvement. But I can’t say for certain why the changes I have made seem to work. I just have a lot of semi-educated guesses.
Alan
-
There is one major drawback as far a small flight shooting is concerned, the efficiency is relatively low and it starts to run into a wall below 8-9ggp. This is one design where the faster bow with heavy arrows is not the fastest with lighter arrows. Alan
Why? What are the physical reasons of that?
I can send you a link to a video, and it will pretty clearly show a tremendous amount of energy left in the limbs when the arrow leaves the string. The physical reasons have to do with the distribution of mass and stiffness in the limb. It uses a long flexible limb with many high energy vibration modes, and this allows the limb to flex and buckle rather than force its own kinetic energy through the string and into the arrow. At slower speeds, this isn’t a problem. When I say slower speeds, I mean slow by flight shooting standards, but it is an incredible performer at typical hunting arrow speeds.
Alan
-
Ma. brain. hurt. I don't really understand the differences. can someone enlighten me?