The Ballista

Here is a snapshot of Firefly’s new limbs at half draw.

The bowstring needs to be shortened by a couple on inches, but for now it will work as I get the bundles slowly torqued up.  I’ve decided to leave it cocked like this overnight to see if its measly 2000 lb draw weight slackens off a bit as the springs get tired.  It is clear that to achieve full draw I will have to remove the dynanometer as the current winch set up does not have enough draw length to accommodate it.  That may be a problem because I will need to get some draw weight readings when we start hitting the 5000 lb level.

This is how it looked at 5.00 pm Saturday evening.

In the photo below:  the strap that stops the bowstring flying off the limb has been modified with the addition of a 3/8″ hardwood dowel to lock the strap and it’s binding firmly together.

Addendum:   After two hours the reading on the dynanometer had dropped from 2000 lbs.  down to 1800 lbs.   Leaving it overnight the draw weight dropped down to 1750 and held steady until I released it from bondage around noon.  At that point the bowstring seemed unusually loose;  it may well be that it was the string that  found some slack spots rather than the springs.

These limbs weighs in at 8 1/4 lbs. each.  More of this mass is set back closer to the fulcrum in the center of the bundle than any previous set  we have tried.  A good thing for speed, it would seem.

I was lucky to find a tight grained piece of ash (The Rebecca stifles a comment) to make them out of.    With their increased cross section their weight would have soared to over 10 lbs. apiece if I’d used hickory.  I’ll fit them into Firefly tomorrow.   Fingers, thumbs, toes, and all other binary appendages, are firmly crossed.

This may not seem like much of a development over where I was a couple of months ago, but at least the wheels seem to be turning again.  Several readers of this blog have contacted me to express their concern for my health and welfare after so long an absence.   Thank you,  I just needed to hide under the covers for a bit.  These madcap projects can take a toll if you let them.