Blodg

I have read that the Mathews LX was one of the most efficient bows ever produced. I have no idea if that is true or not but since my buddy has an LX in the exact same draw length as my Allegiance I thought it would be interesting to compare them. With both bows set at 70 lbs. following are the force draw curves:



Interesting notes:

The above draw cycles reveal how the "front loaded" draw cycle of the Allegiance compares to a typical one-cam. In fact, the LX reaches peak draw weight 3 inches farther into the draw cycle and drops off peak weight a full 4 inches farther. This is why many people feel they can draw more weight easier with the binary cam because your elbow and shoulder are at more efficient angles early in the draw cycle. The feel of the two draw cycles is, of course, subjective but the above curves are not.

The LX has been touted as a very smooth drawing bow and from the shape of the draw curve I can see why. It has a very smooth entry and exit from peak weight with no peaks or humps at all. The LX does not, however, store near as much energy as the Allegiance even with a 5/16" shorter brace height.

Draw length - both bows are draw length specific 27 1/2" models and both measured exactly 27 3/4" AMO draw length. On the Allegiance I had moved the draw stop to the 80% position which increased the draw length an extra 1/4". On the LX I can only speculate that the string has stretched some as this test bow was about 1 1/2 years old.

The speed of the LX is quite a bit slower than the Allegiance, but remember it is also storing less energy. The Allegiance does have a higher dynamic efficiency, which means it is converting slightly more of its stored energy into kinetic energy. Both of these are great bows but my testing here indicates that the Allegiance with the binary cam may be one of the most efficient bows every produced, especially at shorter draw lengths.

Sylvan

A couple of questions. You said that the draw length of both bows was 27 3/4" but your graph clearly indicates they are both over 29". I'm a bit confused. Also, the efficiency of 84% is a correct calculation if the bow you measured shot 304 ft/sec but you indicate that the 304 is an IBO speed which is the speed the bow shoots if the draw lenght is 30 inches which of course it isn't. If I take the IBO speed and convert it to a 27 3/4" draw length I get an efficiency of 76.5% and a virtual mass of 116 grains which is more in line with other bows on the market.

buckeye

Slyvan I am sure he means 304 as he tested the bow shooting 5gpp at his DL. The bows IBO specs are 322-328fps.

Sylvan

buckeyebuckhntr,

Could be, but on another recent thread he posted similar data and did not measure the speed himself so that and the fact that the efficiency ratings are unusually high as well as the draw curve data not matching the stated draw length makes me question the data. I'm still not ready to accept that these bows are shooting efficiencies levels that are being claimed. Jerry NJ posted data that he measured with a chrony that were more in line with what would be considered more typical of the current state of the art.

Don't misunderstand, I'm not questioning blodg's veracity I'm just trying to understand the data in proper context.

Blodg

You are correct Sylvan, or "were" correct. I did have an error on the draw length scale and have now corrected it, thanks for pointing it out.

As far as the 304 IBO that is referring to the IBO standard of 70 lbs. and 350 grains arrow weight but at the measured draw length of 27 3/4". Like Buckeye said the true IBO at 30" is 322 - 328 fps and that is with string and cable silencers installed. It would have made no sense to try to calculate a dynamic effeciency using speed different from the draw length that I used to measure stored energy. I understand my scale error had you confused but your interpolation of 76.5% is not even close. The 84.1% calculation is correct.

I am not sure what speed Jerry posted but I have collected various posted speeds from a few different forums since the binary cam came out (one of these may have been from Jerry). All of these from several different people are all inline with my data:

Listed on Birth Certificate:
D.L.---Lbs.---Wgt---FPS
27"----70.7---350---295
27"----70.7---350---295
27.5"---70.5---350---299
28"----60.8---301---306
29"----70.8---350---320
29"----60.7---300---317

User measured speeds:
D.L.--Lbs.--Ar Wgt--FPS
28"---60---400---265 loaded string
28"---61---398---271 loaded string
29"---65---360---302 loaded string
29"---65---335---311 loaded string

Remember, effeciency testing is not normally done with a loaded string. I assure you my measurements and calculations are fairly accurate. You need to find a shop with one and shoot it for yourself if you have trouble believing some of the forums.

PABowhntr

Two thoughts.....

One, and building on Sylvan's comments....how are you measuring draw length? AMO or "true draw"? If it were a "true draw" of 27.5 then that would put it at a 29.25 AMO...though the chart does not necessarily reflect that either. It would be interesting to hear the explanation. However, the overall shape of the draw force curve and the comparison between the two is definitely food for thought...which brings me to number two....

I wonder if a comparison could be made in terms of the area between the 11 inch and 18 inch mark where the Allegiance draws more weight and from 17 inches to 24 inches where it appears the LX has the proverbial "upper hand". There is a term for the entire area under the draw force curve and I guess I am looking to compare the two being illustrated.

walks with a gimp

,, Good stuff Blodg!!! The force draw curve of the Allegiance does feel like the graph looks You sure you don't work for NASA in Ohio?????

walks with a gimp

Blodg,, I've got a test for you to do!! Turn the weight down on your Allegiance to the point that it shoots the same speed as the LX with the same arrow,,, PLEASE

Blodg

PABowhntr, the DL is AMO, see my correction post above. The area under the curve is the "stored energy" in ft.-lbs. This stored energy is from brace height to the full draw length. Are you asking for the area under the curve just in the locations you mentioned? If so then:
- from 11 - 18 inches on the Allegiance the stored energy is 37.0 ft-lbs.
- from 17 to 24 inches on the LX the stored energy is 39.4 ft-lbs.

Sylvan

Thanks blodg! Now just to continue to be a pain in the a__. From your answer I take it that you did not measure the speed yourself but if I understand correctly, you take an IBO condition speed provided by Bowtech and then calculate a theoretical speed at 27 3/4" You then use that velocity to calculate dynamic efficiency using the stored energy you did measure?

The reason I tend to be skeptical is that manufacturers are notorious for exagerated claims. I've been measureing bows for many years and I've simply been around too long to accept what they claim without verification.