Measuring Draw weight?

[ishoot4thrills]

I have a hand held Bear Archery bow scale(the same kind found in the archery supply catalogs). I've had it since the '90s and when I check the weight on bows, it has never read the same as what the bow shows on the lower limb. I use an arrow that is marked every half inch measured from the valley of the nock and draw the bow until I get to the mark on the arrow(at the point it reaches the back of the bow) that is the same as what is written on the lower limb as it relates to the draw length specified. I always get a reading that is lighter in weight than what the bow says it is. I figure it's because I draw the string back with 3 fingers versus the hand held scales' very tiny thing it holds the string with. Is this a logical assumption, that, since I have more surface area pulling the string back with 3 fingers, I am bending the limbs more and actually pulling more pounds than I am with the bow scale?

I'm just wondering, what do bow makers use to measure draw weight? Do they use some sort of device to mimic pulling the string with 3 fingers?

[lpcjon2]

Does your scale allow for calibration,is there a small screw on the bottom?

[ishoot4thrills]

There is no screw or any type of calibration adjustment. Thanks for your reply though, Timothy.

So, once again, what do bow makers use to measure draw weight? Do they use some sort of device to mimic pulling the string with 3 fingers?

[Whip]

I can't speak for all bowyers, but I think they use a variety of different types of scales.  I have seen some that are simple all the way up to a really expensive air operated press with digital readout.

I use a couple of different spring scales myself, and have been eyeing up a little nicer one.

One thing I can tell you for sure, not all bowyers scales are the same.  It is not unusual at all to have a variation of 1-4 pounds from one bowyer to another.  I can't say who's scale is the most accurate, I just know that two bows marked a given weight at a given draw length don't always measure the same on my scales.

[vtmtnman]

Doug,I have that same green bear scale.I have to add 5 pounds to any reading I get and it is spot on.

Perhaphs yours is the same?

[ishoot4thrills]

Perhaps, Rich.

Does anyone use something else on the string besides the small diameter thing that is on most scales? It just seems to me that a person's three fingers pulling the string would have a higher weight reading than the tiny string grabber that's found on most scales.

Am I way off on this theory?

[Richie Nell]

Another way to measure your bow weight is to get a good size straight stick like a broom handle, cut a groove for the string on one end, measure down 28", 29", etc.  Put the other end of the stick on good bathroom scales and push bow down.  I have found that to be very accurate.  It showed that my Black Widow is exactly what it is supposed to be.

Just an idea.

[luvnlongbow]

I'm no expert by any means but here are my thoughts. Assuming that the weight of the bow is marked 50#@28" I would take it to mean that the bowyers scale read that poundage at that draw. That will be the weight at that draw length no matter what you use to pull the bow with. The weight however will  be distributed over the surface area of whatever is used to pull the string back. Try drawing the bow with one finger then draw the bow with three and you will feel a differance. However the draw weight is the same. One other thing to consider is that production bows are often labeled as one poundadge and will actually be a couple pounds high or low. Like I said,just my thoughts.

[Earthdog]

I uise the same method as Richie Nell,with the same results.
As to Bowyers,,,the only one I know of (Samick) uses the lunar month,multipled by the time of day last tuesday,or some version of that,,anyway,it's very similar to the method Hoyt uses for it's Dorado an game master.
Maybe neither of them can afford a good set of bathroom scales.

[rickshot]

There are going to be accuracy issues from one scale to another and I’d usually consider it an accident for a low end scale to be spot on. Best you can do with any scale is test it against a known weight…and with something like the bow scale mentioned I’d suggest that known weight to be in roughly the same neighborhood as the bow you are checking.

On the other issue, I would think for practical purposes drawing an arrow to 28” is going to be 28,” regardless. If fingers factored in then using a release would factor them out so it would almost be pointless, from a manufacturers standpoint, to fine-line every condition over which the archer has final say.  

Good luck with it. Rick.

[Apex Predator]

AMO standards state that draw length is measured from the throat of the grip.  For a 28" draw measurement, it's measured from the string to the throat of the grip 26 1/4" away (I'm pretty sure).  If your riser is deeper than 1 3/4" then your weight will be light when measuring to the front of the riser.

[Paul Mattson]

Here is the AMO Standard.


AMO BOW WEIGHT STANDARD
For Conventional Bows
Bow weight is the force required to draw the nocking point of the bow string a
given distance from the pivot point of the bow grip (or the theoretical vertical
projection of a tangency line to the pivot point parallel to the string). Draw length
from pivot point shall be designated as DLPP and shall be referred to as TRUE
DRAW LENGTH.
For the purpose of uniform bow weight previously on the more massive wooden handle bows. designation, bow weight is the force
required to draw the bow string 26 1/4” from the pivot point. This weight will be
marked on bow as being taken at 28” draw (26 1/4” plus 1 3/4” = 28”) See
DRAW LENGTH STANDARD.
EXAMPLE: Weight Adjustment Range: 45/55 lbs.
Weight Set At: 50 lbs.; Hold 32 lbs.
Draw Length Range: 29” - 30”
EXPLANATION: The pivot point is a more realistic measuring point (when
compared to the variations of profile of the back of bows at the handle section)
for establishing bow weight since the pivot point is a constant in all bows as well as the contact point of the bow hand from which the true draw length is generated.
The 26 1/4” DLPP is the approximate equivalent of the 28” draw used

[wingnut]

Yep we had the same frustration when our spring scale started going gunnysack on us.  We bit the bullet and bought a highend digital that measures to .1 pounds.

No more problems.

In your case I'd say your scale is off a few pounds.

Mike

[cacciatore]

I experienced the same problem with the same scale you are talking about.More,in our club we had quite a few of those scales and all of them had a lower poundage reading of what marked on the bows.I had much better results with a Viking scale from Hanson,very accurate,but it takes 2 guys for best performances.