Saturday 6 October 2018

Successful First Crossbow Shot

I made some new deflex wedges for the crossbow limbs with less deflex, I made a couple of stringer clamps too.
That all took longer than it should as I had one of those days where I couldn't pick anything up without dropping it and I couldn't put anything down without losing it! I wanted to take a tad off one of the wedges using the belt sander. The belt was drifting to on side and wouldn't adjust ??? Then the bracket that mounts the adjusting screw fell in half, damn... I set to and made another.
Finally I tried to sand the wedge but the belt sander wouldn't switch on!... It would run while I held the button, but the relay wouldn't latch on.
I opened it up, cleaned and tightened the connections, then finally it worked... but where had the wedges gone? Arrrrggghhh! I tided the bench, looked everywhere, even emptied the rubbish bin... nope.
There was only one possible place they could be, down the slot in the table of the table saw where the blade comes up (the table saw gets used as a secondary work bench). I shone a torch in there.. yes! I had to lie the table saw on it's side, take the bottom off and clean it out. Having recovered the wedges I stuck some duct tape over the slot in the table saw as I only use it about once every 10 years as I tend to use the bandsaw or my circular saw.
Anyhow, I eventually got the crossbow all back together and glued on the string catchers which I'd salvaged from the previous prod. Ready for testing, once I could brace it, and that took an age, the first stringer string just stretched too much, eventually I used an old crossbow string with the clamps I'd made and got it braced to a decent height and tried a first test shot. It seemed pretty good and didn't shake itself to bits. The string settled down a couple of mm above the track, so the prod mount will need a little adjustment, but that's no problem.
Video here:- https://www.youtube.com/watch?v=XcI_GfUmB1A&t=38s

Next step will be to inspect it all to check it's all secure, then make some improvement to the prod mount and to adjust it a bit.
I've already checked to see if the prod has taken any set, it has, but just 1/2mm over the straight central section of each limb, and I feel that's ok.
I'll shoot it some more and measure the speed through the chrono'.
Update:- I shot it through the chrono' 255fps I'm very pleased.
The limbs are tending to twist upwards slightly as the string line is above centre, the limbs being tapered up from the lower edge. Some tweaking to the prod mount should sort that out.

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