Primitive Archer
Main Discussion Area => Arrows => Topic started by: agd68 on February 25, 2010, 10:01:59 am
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I seen a tool while cruising 3Rivers . It was a arrow shaft compresser. Apparently you run an 11/32 shaft in one end and it comes out a 5/16 on the other. What does this do for a shaft besides making it thinner ?
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it stiffens the arrow increasing spine. if i remember correctly
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Yes, what Ken said. I would think it might be a reasonable investment. In my opinion, smaller diameter, shafts are better if you can maintain the same weight. This is why carbon shafts are so thin. To let the arrowhead be wide if you want, but to keep the shafts thin and still have some weight to them.
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Reducing diameter reduces spine. ART
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Reducing diameter reduces spine. ART
I may be wrong...but I disagree...if you are taking the larger Diameter Shaft...and compressing the Fibers down to a smaller Diameter...hense tightening the Grain...this should increase the Arrows Spine,,,,not decrease it.... like sanding or trimming it to reduce Diameter....JMO
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El Destructo ,
The bending or buckling of a column is described mathematically as shown in
http://en.wikipedia.org/wiki/Buckling
Dy compressing the column you would make the moment of inertia smaller, see
http://en.wikipedia.org/wiki/Area_moment_of_inertia
Therefore you would reduce the spine.
Craig.
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I know that when you compress a Copper Wire for a Flaking Tool....It makes the Wire Stiffer...so I would figure that it would have the same effect on Wood....But If Science and Mathematics are against Me.... I stand Corrected......... :-X
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WOW,I should have listened more in school, ,I would compress one and see for my self.
I would have thought it would have stiffened it. Not by reducing it,we all know that would make it lighter but compressing it I would think it would make it stiffer. ??? i will have to do my own
scientific study on that. ??? ;) ;D
Pappy
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I do it all the time with a screw driver. I haven't noticed much difference in spine. I do believe it strengthens the shaft. Jawge
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you'll lose 5lbs of spine. if you use 45-50's , compress a 50-55 and you'll have what you need. buddy used one a while back. not worth the effort in my opinion. if you are doing this for better penetration use a tapered shaft. they are easy to make . same rule applies to tapered shafts. go 5lbs heavier and after a 12" taper you'll get back down to your desired spine.
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El Destructo
I know that when you compress a Copper Wire for a Flaking Tool....It makes the Wire Stiffer...
Absolutely correct but you are nor so much compressing the copper, that is changing its sectional area, as you are work hardening it. It is this work hardening that gives you a stiffer piece of metal. You are increasing the modulus of elasticity E in the equation when you work harden the wire.
Craig.
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Here's a though experiment. Take a pice of 30" copper pipe, 1/2" diameter, like those used in plumbing and bend it in your hands. Now keep the same length, but increase the diamter to 6". The larger diameter would be thinner, but would be harder to deflect. It would also be more prone to breakage.
I learned this lesson back in the 80's when I worked at a bicycle shop. That's back when the manufacturers started experimenting with over-sized tubing. Today, all bikes use the larger diameter for greater stiffness at the same, or less weight.
Goog
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Hey triple G,
I'm kinda like Pappy, but I shoot hardwood arrow shafts and usually like the big ole fat kind....but I can make small diameter stiff spined as well.....just change the wood. I really like black ash for my personal arrows (these weigh about the same as spruce but they are a lot tougher)....if I want to go small, but still want spine and weight I use maple or white oak.
Know that isn't really what you asked but like pappy, I should've paid more attention in school too. Changing wood was my solution, and I seem to do everything the hard way :D
half eye
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i guess common sense isnt all that common, i was wrong
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I learned this lesson back in the 80's when I worked at a bicycle shop. That's back when the manufacturers started experimenting with over-sized tubing.
Goog
I remember those beer can bikes!
I was just looking at that shaft compressor in their catalog yesterday. I bought two dozen 23/64th tapered cedar shafts last summer for $5 and I cannot get them to shoot straight. I left them full length (32"), put 160 grain field points on them and they still come off the bow hardnock right. The bow is pulling 50# at my normal 26" draw, but I can adjust my stance and pull 27 just as easy for a little more draw weight. I just kinda hoped with 4 inches over the standard 28, heavy points, tapered shafts, and overdrawing slightly I could make use of them. I suppose I will have to buy the tool and post my "product review".
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I think I have to both agree and disagree....and I want to be clear that I am not trying to act like an expert.....I am certainly not when it comes to archery, but I really like topics such as this as they provide insights into the "why" something is the way it is....
For wood, the modulus of elasticity (bending, not rupture) is really the measure of stiffness within the elastic zone. (i.e. how well does the wood react to loads applied perpendicular to the grain, loads small enough to not permanently cause set)...and could even be considered the resistance to shearing along the parallel grain orientation.
If I am not mistaken:
I agree that deflection caused by bending (classic beam theory) is highly dependant on the moment of inertia "I" (related to the relative geometric dimensions) and thus when the diameter is changed, so does the moment of inertia decease, and the deflection increases. (--sand away the shaft and the arrow spine gets lower)
However, when wood is compressed (ie. burnished) the density of the affected zone increases. Density of wood and strand/grain orientation is closely linked to strength and stiffness and increasing the wood density does increase the modulus of elasiticity. (---increase the density of the wood and the arrow spine gets higher)
Further, an arrow shaft without a burnished layer will be generally the same density of material (aside from ring density differences). But a burnished arrow is really a composite member, albeit with a very thin layer of more dense material. (think, a hollow cylinder of compressed wood filled with un-compressed wood)
I have to wonder if this denser layer, with a higher modulus (E) will decrease the deflection of an arrow shaft (during spine testing), more than the diameter change will increase the deflection of the shaft (during spine testing). Then again, maybe neither of these are as important as proper grain orientation when measuring arrow spine...?
It might be that the change in modulus resulting from the density increase is so small that it cannot counter the spine effects caused from decreased moment of inertia as a result of changing the diameter.
If changing the density of a wood had no effect on modulus, then heat treating the belly of a bow would have no noticeable affect either.
what do you think? Have I got it all mixed up?
Cheers,
J
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Hell I don't know ???
however it does say in the 3riversarchery catalog that the compression block reduces the spine of your shafting
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I'm grabbing a box of popcorn and pulling up a chair. ;)
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Diligence
E = modulus of Elasticity = Young's modulus = tensile modulus = the ratio of tensile stress to tensile strain. Now why would a fibrous material like wood have an increase in E just because it is compressed laterally. The same fibres are there to resist the tensile strain. If any change were to happen because of compression beyond the elastic limit, which must have happened for the wood to remain compressed, it would be because the wood fibres were damaged and the modulus would reduce.
I suggest that increase in weight due to heat treating is because of changes to the wood's cells not the change in density. Also as heat treating actually drives moisture out of the bow the structure becomes less dense not more dense.
Have you weighed a bow or arrow before and after burnishing? I would suggest that all burnishing does is compress the surface layer to a much smoother one than it had originally and thus make it less likely that a splinter will lift, it does nothing to the strength of a bow or the arrow.
Craig.
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modulus..... what did you call me ?? ;) ;)
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i love that there are people smarter than me , but ya'll make my head hurt , im gonna just watch not smat enough for this one !!
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Art already said that where us slow folks could understand it. I get some pretty arrows from Mr. Butner, I believe. ;)
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I thought the point was to harden the outside a little to prevent dings and dents in the wood. I have to agree with Art.
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Craig,
Excellent information....and I hope Mullet is enjoying his popcorn while chasing snakes in Brazil.
The basis of my thought regarding the increase in E as a result of compression is related to research (which I have only read about) that is aimed at utilizing second rate softwoods which are rapidly grown with weak internal structure. The idea is to harvest that material, compress it thru various means and end up with a product which can be used commercially for structures. Essentially increase the Modulus of Elasticity and of Rupture (MOE and MOR) thru physically changing (compressing) the internal structure. This is done thru heat and pressure at a fixed humidity.....I cannot for the life of me find the paper that I read, but it was a chinese study.
I believe that it is generally accepted that mechanical properties of wood are positively correlated with density and that mechanical properties of wood are highly dependent on moisture content and temperature. I am aware that there has been research that indicates a linear relationship (within a single species) between E and density.....I've attached a graph that I was able to locate on the web. This is not the one that I have seen previously (and which I could not find in my files), but it is representative of that relationship and was the basis for my assessment that the burnishing may increase spine for a fixed diameter.
If we can assume that the moisture content and temperature remains fixed, then I think where my logic has failed me is in the mechanism for that increased density of the outer layer of the shaft.
Where I made my mistake (as you pointed out) is in overlooking that when a tool is used to "burnish" a shaft it does that thru fiber damage. I agree, if the wood is simply crushed (ie. loaded beyond the compressive limit to cause plastic failure - and fiber and cellular damage) that the MOE and MOR will decrease.
Now, if we all had hi-tech equipment to heat and radially compress those shafts at the same time, I'll bet the spine would go up for a fixed diameter.
"Also as heat treating actually drives moisture out of the bow the structure becomes less dense not more dense."....I'm not sure I fully disagree with you, but as density is determined at a fixed moisture content I think we are both somewhat incorrect. That is, heat treat the belly at 7%MC...which will reduce the MC...then let it equalize back to 7%MC and the resistance to compression will increase for that MC. If the heat decreases the volume of the cell structure, then for a fixed MC (ie. no mass change) the density will increase.
"Have you weighed a bow or arrow before and after burnishing?".....nope, and I'm not likely to either....lol
For some light reading on a very good doctoral thesis which I found while looking for my graph, here is a link (9.5MB). Mechanical and Physical Properties of Semi-Isostatically Densified Wood. The fellow has applied pressures up to 140 MPa to samples, then measured their mechanical properties...some increased and some decreased....check out page 34 for some good photos of failed samples (pre and post densification)
http://epubl.ltu.se/1402-1544/2006/28/LTU-DT-0628-SE.pdf
This was fun....thanks for making me try to noodle my way through this, but my brain is now full.
Jaye
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That does it. My brain hurts too much now. I'm going to the SKS forum to decompress :)
Goog
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That does it. My brain hurts too much now. I'm going to the SKS forum to decompress :)
Goog
Yes, but will that decompression increase or decrease your spine? ;D
Swamp
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I have used a modulus regulator, on my framinizer, to which the zorchloct was attached, thus reducing the size of compressionable fibers, so that the inertia kniblingwat on the knob bobbin, will decrease the spine weight to some degree, but if I cantagalate it to the power of 3 squared, and use the tubular rimlac, similar to the one used on the Aston Martin Db5, it will remonitize the cellinodal compunctuator, and the formulinear reduction of the stimulus package! ::)
I am with ken, and Goog, talk abut something else, my head hurts, when I look at mathematical equations. :P
Buy one of those compressors, use it, tell us how it affected the shaft spine weight, before, and after, and then put it on E-Bay.
Craig will you do my Taxes? ;D
Wayne
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way too funny!
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Hi Diligence,
Interesting!!!!!
Unfortunately could not open the link you provided. Will try again later as it sounds interesting.
Have come across various forms of so called engineered wood, some where resins were injected prior to heating and compressing, others that relied on heat and pressure alone, the high heat used plasticised the wood prior to and during the compression process so as not to damage the fibres in the same manner ac cold compression would.
I believe that it is generally accepted that mechanical properties of wood are positively correlated with density and that mechanical properties of wood are highly dependent on moisture content and temperature. I am aware that there has been research that indicates a linear relationship (within a single species) between E and density.....I've attached a graph that I was able to locate on the web.
Absolutely correct as far as I am aware, the correlation of mechanical properties with density is the basis of badger's mass theory and for years the correlation in single species has been recognised by bowyers etc, they may not have realised what property they were finding better in more dense woods but they saw how the wood behaved.
Craig.
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Man......I can't take it any more..I got to go and Dumb Down.....this Thread Hurt my Head too much....going to the Ooga Booga Thread for some R and R....... :P
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Yeah, El D, I think I will heat up the left over field peas, and maybe even make some corn bread to go with them, and have a beer, to kill off the damaged brain cells, that were actually trying to follow that stuff. I didn't know "Werner (Verner) Von Braun" was into primitive archery...... ;D See ya in the Ooga Booga section El D. 8)
Wayne
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I'm buying some tapered carbons from Chad at the Classic.
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Boy, I'm sure glad I'm soooooooo simple minded ;D. ART
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The compression block from 3rivers needs to be heated with a torch before used. Oogabooga mike =)
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Well I have been spouting all this theory, what about someone with the block actually telling us what happens, there must be someone out there with one.
To those I have given headaches I apologise most profusely, I would recommend a few decent beers, (not of course that you yanks have any decent beers ;D.)
Craig
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This Ole Yank......drinks W.L.Weller....107 proof Suthin Mash Whiskey...
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Art, You know what I mean ;D
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I would really like to hear from anyone who has actually done this. I wont say you science guys are wrong but I just cant wrap my caveman brain around the theory that if you take X amount of material and compress it to a smaller diameter ,without removing any material ,that it can get weaker. ???
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been done. you lose 5lbs of spine. block needs to be heated with a torch and then the shaft is pressed through with a drill.
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Learn it first hand from burnishing shafts and checking on my tester...........ART
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Tested the idea on several types of wood. I was trying to understand the dynamics of bending wood, not building arrows.
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I wonder if an 11/32 shaft which has been reduced with the burnishing tool to 5/16 has a larger spine than a 5/16, non-burnished shaft? (ie. measure of spine differences as a result of burnishing and compressing, rather than spine losses from the smaller diameter).
I would guess that the spine is higher for the burnished 5/16 shaft, as compared to the non-burnished 5/16 shaft. (of the same shaft material)
anybody?
J
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Diligence,
I wonder if an 11/32 shaft which has been reduced with the burnishing tool to 5/16 has a larger spine than a 5/16, non-burnished shaft? (ie. measure of spine differences as a result of burnishing and compressing, rather than spine losses from the smaller diameter).
Given the differences in spine between different pieces of wood I doubt that you could get a definitive answer to the question unless a large number of tests were done and you would have to start with pairs of 11/32 shafts of equal spine, reduce one by use of the swage, the other by say a plane. You would also have to prove that mereley reducing the diameter of a pair of shafts that began at the same spine produces smaller diameter shafts of the same spine.
Craig
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To keep it simple, thin bends easier than thick, Nootons Law of Compression.
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I like fig Newtons.
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Ok, lets see if I got it all. Given you compensate for the loss of spine at the new diametre, a compressed shaft should be tougher and heavier than a noncompressed shaft of same wood. Right ? :-\
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That's what I was thinking.
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Ok, lets see if I got it all. Given you compensate for the loss of spine at the new diametre, a compressed shaft should be tougher and heavier than a noncompressed shaft of same wood
Correct, so I understand else why bother.
Mind you we are still waiting to hear more about it than Jamie's:
you lose 5lbs of spine
Craig.