This is just an update for those who may have wanted to see actual measured speeds. If you got your fill on the other thread just move along

OK, I spent a couple hours with a chronograph today with both the Allegiance and the LX. I shot several arrows at each weight to obtain an average speed. Here are some of the results with 27 3/4" DL at 63 lbs with a few different arrow weights:

-----------------------------------315 gr. 350 gr. 449 gr.
Alley 63 lbs, loop, peep, silencers -- 292 fps 279 fps 253 fps
LX at 63 lbs., loop, peep, silencers - 273 fps 260 fps 235 fps

I plan to shoot 3D this summer at 63 lbs. and am looking at 293 or 294 fps with no silencers on the string.

I set the Allegiance at 70 lbs. and shot with the peep and silencers still installed and got 294 fps. I then removed the string and cable silencers and got 295 fps. I was suprised to only gain 1 fps from removing the silencers. I next removed the peep to get a true bare string speed with only the loop and got 298 fps. This is one fps slower than the stated speed on the birth certificate. In my previous post I assumed another 5 fps for the removal of the silencers but actually gained only 1 fps.

Alley 70 lbs., 350 grains with only loop - 298 fps
LX at 70 lbs., 350 grains with only loop - 283 fps

Recalculating the dynamic effeciencies with the actual measured speeds puts the Allegiance at 80.7% and the LX at 78.6%. This puts the virtual mass for the Alley at 83.7 grains without a peep and 92.5 with a peep.

The Allegiance sustained more speed than the LX when dropping from 70 to 63 lbs. and shooting the same arrow. On a 350 grain arrow the Alley lost 17 fps over 7 lbs. where the LX lost 21 fps over 7 lbs. The Alley was also more efficient when shooting 5 grains per lb at 70 compared to 5 gpp at 63 lbs. The following were taken with a peep and loop but no silencers:

---------------------------------------70/350 gr. --63/315 gr.
Alley at IBO arrow weight of 5 grains/lb. - 295 fps ----293 fps
LX at IBO arrow weight of 5 grains/lb. ----280 fps ----274 fps

I have never seen a bow before that only loses a few fps when dropping weight and staying at 5 grains per lb?

One other interesting note: when switching back and forth between bows while shooting the arrows through the chrono it became very evident that the Allegiance had much less vibration and was quieter than the LX. Both bows had sights and stabilizers installed. I borrowed a chronograph from a friend and don't really know how accurate it is. But for an apples to apples comparison both bows were shot with same arrow back to back several times.

Below is new graph using the measured speeds listed above:

Pretty good stuff Blodg!! I wonder just how smooth and quiet the Allegiance would be compared to the LX if you turned the weight down on the Allegiance to make the two bows shoot the same speed with the same arrow

Oh shoot, I forgot you had asked me to do that. Since the Alley was losing 2.43 fps per lb. of draw weight turning it down 8 lbs. to 55 lbs. would put it very near the LX at 63 lbs. I am going to play with the chrono a little more today, I could verify that if you want.

By-the-way I got my bow press and am very impressed with the design and ease of use. Thanks a lot for such a great product!

Great data Blodg!

Just for fun I calculated the theoretical speeds for the Alley at 63 pounds by scaling your 70 pound measured values and using your 83.7 grains of virtual mass.

At 63 pounds.
Arrow---Measured--Theoretical
Weight--Speed-----Speed-------Difference
315------292------291.9------- -0.1
350------279------279.9------- +0.9
449------253------252.5------- -0.1

I love it when the theoretical matches the measured so well. Looks like you must have measured virtual mass pretty accurately. From here we should be able to predict speeds within a 1 or 2 feet/sec given any change in the peak weight or arrow weight or draw length.

For example 500 grains and 63 pounds yields 241.2
----------- 300 grains and 60 pounds yields 290.4
----------- 500 grains and 70 pounds yields 254.3
----------- 275 grains and 55 pounds yields 287.5


Looks like a great bow!

You're more than welcome!! Dosen't look like you can turn the Allegiance down to 55 pounds if your's is a 60 to 70 pound bow, maybe turn up the LX to match the Allegiance speed would be better
Thanks for doing all this informative work, I know it takes a lot of time to do this job as well as you have and it speaks volumes of your love of the sport

Figures!

I do not have a light source for the chrono so have to do it outside and the instructions said it's best to test on a cloudy day. Yesterday it was very sunny and it was getting near the end of the day when I did the testing for the above data. Today its overcast and I was curious if I would get the same results so I repeated some of the measurements. Today I got a full 3 fps faster at both 63 lbs./315 grains and at 70 lbs./350 grains. Also, more imprtantly, the repeat measurements were much closer today with less variation. Yesterday I took an average but some readings varied by several fps and I even had some fliers that were 10 fps lower and some around 10 fps higher than the average. This lead me to believe that maybe my lighting was not sufficient since the light source is critical for this type of chronograph. Today the numbers were very consistent from one shot to the next with no fliers at all:

Alley at 27 5/8" DL at 63 lbs/315 grains with peep and loop:
296.7
296.4
296.3
296.3
296.8
296.1
296.1
above average rounded off = 296 fps (yesterday I reported 293 above)

Alley at 27 5/8" DL at 70 lbs./350 grains with peep and loop:
298.4
298.3
298.3
298.0
298.1
above average rounded off = 298 (yesterday I reported 295 above)

If you take the 298 and remove the peep it would be right at 300 or 301 and the Birth Certificate said 299 so I still feel that the data from BowTech is fairly accurate. I am not going to recalculate the effeciency numbers but the above graph may actually be a few fps on the slow side. I will check the speed over the next few days to see what type of average I get over time. I would imagine that a chrono with a light source and shot indoors would at least provide a consistent number since outdoors is subject to changing light conditions.

I should add - I also angled the chrono slightly so that the arrow was passing above at the same angle. Yesterday I think my arrow was exiting the chrono an inch or two lower than when it was entering (not parallel). Don't know if this make a difference or not but that is another change I made since yesterday.

Blodg,
I believe temperature has more of an impact than a lot of people think as well. I use my chrony in doors with a light source and generally I get within 1 ft/sec on the same bow/arrow combo on different days. However, a friend brought a bow in one day for me to measure it (it had been overnight in his truck at 25 degrees) and after measuring a few times we noticed that the fisrt few were 2 to 3 feet/sec faster. This certainly wasn't a controlled test and I haven't tried to duplicate it but you might want to keep this in mind.

Yes temperature would definately be another variable to contend with when testing speed outdoors. Yesterday and today the temperature was fairly close, maybe a few degrees colder this morning.

Is there any way to calulate a theoretical speed if the peak on the FDC at 14" is maintained perfectly horizontal until the drop off at about 24"?

500 fps,
If I understand you correctly the answer is yes. I took Blodg's original force/draw data and arbitrarily changed the numbers to hold the 70#'s as you said. The total energy picked up was 2.875 ft/lbs. I then calculated what his 295ft/sec 350 grain arrow would do if we pumped in another 2.875 ft/lbs of stored energy. It came to 300.1 ft/sec.