The way I test my bows is as follows.
First I look at the "standard" self-bow setup:
Pyramid style flat bow with 6" unbending portion of handle
True set @ 1-1/2" or less.
No reflex
No Recurve
6" of unbending tips
67" bow length and 66" Nock to Nock
50# draw weight
28" draw
500 grain arrow
Bowstring weight is about 3 times the draw weight and (in grains)
Hemp or flax bow string
Brace height = (length of bow x .086) or about 5-3/4", in this case, measured from the neutral plane
Hold at full draw for 2 seconds before release
With the above parameters, the average arrow speed will be 150 fps. If you keep all the proportions the same, you should get 150 fps even from "miniature" bow & arrow sets.
Variation of any of the the above will change the arrow speed. All other variables unchanged, altering the the bow length up or down from 66" decreases arrow speed, low set increases speed, reflex resulting in higher draw weight at brace height increases speed, shorter unbending tips decreases arrow speed, longer unbending tips increases speed up to a point, higher draw weight increases speed, longer draw increases speed, lighter arrows increase speed, heavier bowstrings decrease speed, lower brace height increases speed up to a point, and holding time at full draw will decrease speed the longer you hold and increase speed the shorter you hold. Also, drawing the bow slowly at first then quickly toward the end, with no hold time, increases speed.
All the bows I make these days (except for warbows) are shorter, with shorter draw lengths, and with less power than the example above. I just tested a 51" bow last week. It pulls 43 lbs and shoots 430 grain arrows with a 24" draw and 4-3/4" brace. I'm getting 140 fps on average and I'm satisfied. I could get 150 fps easy by using some of the "tricks" above but I don't.
