So... What the %$^! IS Virtual Mass???
01-09-2004, 09:12 AM
#21
Fork Horn
Join Date: Feb 2003
Location: Kenosha, Wi USA
Posts: 499
RE: So... What the %$^! IS Virtual Mass???
Virtual Mass:
A factor that expresses the dynamic efficiency of the bow and arrow combination. It is the weight in grains of an imaginary mass shot from the bow bow at the indentical instant and with the identical velocity as the arrow.
The virtual mass represents all of the inefficiencies that are inherent in the shooting of the bow and arrow combination. The sum of the kinetic energy of the arrow and the imaginary kinetic energy of the virtual mass equals the total stored energy the bow.
The lower the value of the VM, the higher the dynamic efficiency of the bow and arrow combination. The VM concept is not totally correct whan applied to the dynamics of the bow and arrow combination, since it is not a constant for every given bow. It is close to constant for many recurves and longbows, but varies with arrow weight for most compounds. It is extremely useful for interpolating and extrapolating performace (primarily arrow velocity) for any given bow when dealing with arrow weights that have not been specifically tested. It is general practice to list a value for average VM in lieu of providing a full spectrum of this factor for the wide range of arrow weights tested.
That's from Norb himself. So the short version is that VM is the imaginary mass to account for the difference between the theoretical total energy in the bow/arrow combination, and the real world results that show the inefficiencies of that bow/arrow combo in dynamic action.
A factor that expresses the dynamic efficiency of the bow and arrow combination. It is the weight in grains of an imaginary mass shot from the bow bow at the indentical instant and with the identical velocity as the arrow.
The virtual mass represents all of the inefficiencies that are inherent in the shooting of the bow and arrow combination. The sum of the kinetic energy of the arrow and the imaginary kinetic energy of the virtual mass equals the total stored energy the bow.
The lower the value of the VM, the higher the dynamic efficiency of the bow and arrow combination. The VM concept is not totally correct whan applied to the dynamics of the bow and arrow combination, since it is not a constant for every given bow. It is close to constant for many recurves and longbows, but varies with arrow weight for most compounds. It is extremely useful for interpolating and extrapolating performace (primarily arrow velocity) for any given bow when dealing with arrow weights that have not been specifically tested. It is general practice to list a value for average VM in lieu of providing a full spectrum of this factor for the wide range of arrow weights tested.
That's from Norb himself. So the short version is that VM is the imaginary mass to account for the difference between the theoretical total energy in the bow/arrow combination, and the real world results that show the inefficiencies of that bow/arrow combo in dynamic action.
01-09-2004, 09:47 AM
#22
Nontypical Buck
Join Date: Dec 2003
Location: Idaho
Posts: 2,072
RE: So... What the %$^! IS Virtual Mass???
It is the co-efficient of the blast measured by the anal spectrometer. It is used by the underware industry. Actually I dont know and my arrows are flying just fine without it. Have a great day, shoot a bow.
01-09-2004, 09:59 AM
#23
Nontypical Buck
Join Date: Feb 2003
Location:
Posts: 2,994
RE: So... What the %$^! IS Virtual Mass???
A factor that expresses the dynamic efficiency of the bow and arrow combination. It is the weight in grains of an imaginary mass shot from the bow bow at the indentical instant and with the identical velocity as the arrow.
So I WAS right!
Wasn't I?
I guess they needed all that gobbly gook to justify all the money they spent on their education, when "It tells you how efficient your bow passes it's stored energy to an arrow, and the more efficient your bow is, the more energy it will pass".
01-09-2004, 11:56 AM
#24
Nontypical Buck
Join Date: Feb 2003
Location: Brampton Ontario Canada
Posts: 1,038
RE: So... What the %$^! IS Virtual Mass???
Summary:- The HIGHER the number of the 'virtual mass' the smaller the number of the 'arrow mass'--energy used to acelerate the arrow.
Now it's time for my first TWO TYLENOLS for today!!!
Now it's time for my first TWO TYLENOLS for today!!!
01-09-2004, 12:23 PM
#25
Giant Nontypical
Thread Starter
Join Date: Feb 2003
Posts: 9,175
RE: So... What the %$^! IS Virtual Mass???
Well, I know a little more now than I did when the thread started.... but I don't understand a whole heckuvalot more than I did.
If the bow shoots a quick arrow and feels pretty soft in the hand, then it's obviously got a low virtual mass. If it shoots a slow arrow and causes a couple of teeth to swap holes from the recoil, then it's got high virtual mass. That about sum it up from a practical, non-engineering standpoint?
If the bow shoots a quick arrow and feels pretty soft in the hand, then it's obviously got a low virtual mass. If it shoots a slow arrow and causes a couple of teeth to swap holes from the recoil, then it's got high virtual mass. That about sum it up from a practical, non-engineering standpoint?
01-09-2004, 12:43 PM
#26
Fork Horn
Join Date: Feb 2003
Location: Kenosha, Wi USA
Posts: 499
RE: So... What the %$^! IS Virtual Mass???
Arthur-
I wouldn't say that hand-felt recoil is a very good indication of VM values.
You take a fairly harsh recoil bow, take all the measurements of arrow weight, launch speed, bow poundage, stored energy curve, etc, and determine your VM amount. Now slap on a pair of Limb Savers on the limbs and a Doinker for the stabilizer and it will feel much differently as far as hand recoil, but all the measurable paramters that gave us the VM value haven't changed. I think hand-recoil is more a factor of design geometry, vibration absorption, and such.
You could have a smooth shooting bow, but have lots of friction in the axles, cams, etc- which will give a higher VM amount. Or you could have a more harsh bow that may be from a nasty draw curve of the cam design, but it has bearings in the cams and very low friction amounts with better overall efficiency and will have a lower VM.
My Darton Mav felt a LOT better after adding my Limb Savers, front stab, and a set of NV donuts. But the VM of the bow/arrow combo never changed.
I wouldn't say that hand-felt recoil is a very good indication of VM values.
You take a fairly harsh recoil bow, take all the measurements of arrow weight, launch speed, bow poundage, stored energy curve, etc, and determine your VM amount. Now slap on a pair of Limb Savers on the limbs and a Doinker for the stabilizer and it will feel much differently as far as hand recoil, but all the measurable paramters that gave us the VM value haven't changed. I think hand-recoil is more a factor of design geometry, vibration absorption, and such.
You could have a smooth shooting bow, but have lots of friction in the axles, cams, etc- which will give a higher VM amount. Or you could have a more harsh bow that may be from a nasty draw curve of the cam design, but it has bearings in the cams and very low friction amounts with better overall efficiency and will have a lower VM.
My Darton Mav felt a LOT better after adding my Limb Savers, front stab, and a set of NV donuts. But the VM of the bow/arrow combo never changed.
01-09-2004, 12:56 PM
#27
Fork Horn
Join Date: Feb 2003
Location: Kenosha, Wi USA
Posts: 499
RE: So... What the %$^! IS Virtual Mass???
bowhack,
You're right, you don't NEED to know anything about VM or lots of other very technical aspects of archery to shoot some deer. But some tech-heads of archery DO like to delve into these topics. Knowledge is power.
Without people wanting to know more, experimenting with new ideas, or getting into the nit-picky details of archery, you wouldn't have the "hybrid cams" of today, fancy riser designs, carbon arrows, aluminum arrows, or even a compound bow to begin with. Heck, if it wasn't for some creative caveman that thought of launching a smaller version of a spear by pulling back on a branch with some string tied to both ends, we might be still throwing rocks at deer....
You're right, you don't NEED to know anything about VM or lots of other very technical aspects of archery to shoot some deer. But some tech-heads of archery DO like to delve into these topics. Knowledge is power.
Without people wanting to know more, experimenting with new ideas, or getting into the nit-picky details of archery, you wouldn't have the "hybrid cams" of today, fancy riser designs, carbon arrows, aluminum arrows, or even a compound bow to begin with. Heck, if it wasn't for some creative caveman that thought of launching a smaller version of a spear by pulling back on a branch with some string tied to both ends, we might be still throwing rocks at deer....
01-09-2004, 01:19 PM
#29
Join Date: Jul 2003
Posts: 24
RE: So... What the %$^! IS Virtual Mass???
Oh I know....I didn't mean to sound like I was bashing somebody for being intelligent......I think some things are better not known......i guess maybe i'm a little envious when it comes to things like that because half the time i'm clueless.
But I do know that bowhunting is Kool stuff and i'm just getting started......yeehaa.......
But I do know that bowhunting is Kool stuff and i'm just getting started......yeehaa.......
01-09-2004, 01:33 PM
#30
Nontypical Buck
Join Date: Feb 2003
Location:
Posts: 2,994
RE: So... What the %$^! IS Virtual Mass???
bowhack, I myself was pretty much clueless when I found this forum. Hang around long enough and your bound to soak something up like I did as these guys know their chit and are very happy to scatter it freely...
That's a compliment, by the way...
A bit of technical knowledge allows you to make the right choices for what you are looking for. Until I started posting and reading here, I didn't even know what I was looking for...
That's a compliment, by the way...
A bit of technical knowledge allows you to make the right choices for what you are looking for. Until I started posting and reading here, I didn't even know what I was looking for...