So as I am want to do, I was playing with some handle/limb combinations this morning and can't get the math to match my actual results. Here's the story.
17" handle, limbs marked 50#@27". pull just over 52#@28". Put them on a 19" handle and they are pulling 53.4#@28". Was expecting the extra 2" of handle length to reduce the poundage by 2-3# so it would pull around 50#@28". Not a big deal, but was surprised by the outcome. Thoughts?
The longer riser is forward of the axis between the fade outs on the 17", THEREFORE, the limbs will bend less, you are right to expect less draw weight at the same draw length. The reason might be, your pulling it further, because of the shape of the handle. Measure the distance to your 27" mark for the 19" riser. You might be weighing it at 28"+.
Definitely difference in handle profiles. Handle on left is highly deflected so will be less draw weight with same limbs. Handle on right is more straight up/down so even with it being longer in effect you are drawing the limbs farther because of handle straightness.
Well Chuck, to answer your question... I guess I was out to lunch. Didn't see this thread. That said, it looks like y'all got it figured out just fine without me.
westrayer, and Chuck, too, has it. There's a difference in limb pad angles. Without measuring, I'd bet it's shallower on the longer riser, which puts more initial stress/weight on the limbs.
A couple of degrees of limb pad angle will also change the weight. I know that Morrison Phoenix risers all have a different limb pad angle. Coupled with their Max 6 limbs, you don't see much difference swaping risers.
Draw a line ( mentally) from center of bolts, top to bottom, for each rig shown. Does that line bisect the arrow rest at the same place, and with respect to the grip cut out ? They seem, from what i see, to have differing profiles regarding forward handles. If different, that difference in pre load to make similar brace height might make the difference. Pictures sometimes lie ( distort), and i can't tell from your pic.
Steve...where are you ? As a dummy, i can make some guesses. First, did you change strings ( use a longer string on the now longer bow) ? Is brace height identical ? Is the limb angle the same on both risers ? Seems to me if ALL else is identical, a longer bow means less actual movement of each limb with identical length of draw, hence, less draw weight. Not sure if 2" difference is discernible though.