Ok. I have thought about this for years but have never had the courage to ask because I have never seen the topic come up in ANY discussion. Leading me to believe I am overlooking something that, to everyone else, is sore-thumb obvious. Which is going to make ME look like an idiot for asking. But here goes. Why do Xbow manufacturers NOT follow in the footsteps of their compound bow maker brethren and make Xbows with let-off? I mean they make compounds now with up to 90% let-off! Can you imagine the stress that would save on limbs and strings/cables?! Especially on those all day hunts?
I don't know. My guess would be that it's because there's not some dude (or lady) trying desperately to keep the bow drawn while game gives them a shot? I'm sure there's members here who know the physics behind the real answer.
Not a bad idea actually. It would make the bow easier to cock and take a lot of pressure off the serving. Production wise its doesn't take a whole lot more when cutting the cams either. Let off may be the next "bell" or "whistle" to be offered on the next $2,000 crossbow!
Well, letoff does have some advantages. The frankenbow that Burky built for me has maybe 50% letoff (not sure), and 140# draw weight, so there's only around 70# on the trigger claws when cocked. Despite the sharp string angle, the center serving lasts a very long time. That said, you can't get the speed/power out of the arrow without flexing the limbs, which store the energy for the shot. Just because there is letoff doesn't mean the limbs are not stressed pretty hard to have stored enough energy to produce the speed of the arrow as it's fired. I believe the Mission Sub 1 series has 80% letoff. I had a Killer Instinct Furious bow, and those cams had letoff too. Not sure how many other brands do, but some compound crossbows definitely have letoff.
My guess that cam reduction would reduce the force of the power stroke for a portion of the stroke. This could only be recovered by lengthing the powerstroke or heavier limbs. The reduced portion of the stroke is small but I believe it makes a difference. This could be why mission crossbows have been slower even with heavier limbs.
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