I guess if you mess around with something long enough you either break it or get it right. I think this collection of odds and ends has finally decided what it wants to be when it grows up:
So I started having problems with dry firing and automatically assumed it was the delrin trigger mech that was failing. After quite a bit of tweaking and headscratching, I figured out it was actually the small blade spring that advanced the toggle into the lock position- I hadn't treated the steel right and it lost it's springiness, causing the mech not to engage fully into the locked position.
I knew when I decided to rebuild it one more time I was going to do four major changes: add a safety, provision for a cocking rope, a folding foot stirrup, and convert it to a completely standard string geometry. The first three are all about safety. My bruised fingertips were bad enough, but think about this for a second- this think is a muzzle loader, and some of the bolts are just long enough that just the very points stick out the end, in fact I have to push them completely home with a fingertip on the point. Just thinking about trying to explain a 5/16" hole in the end of my finger to my wife is scary business! Oh yeah, and I'm also going to make all my bolts for it an inch or so longer.
Here are the components of the safety, inspired by bits of a broken staple gun I took apart looking for treasure. When the string pushes the claw out of the way and the sear end of the toggle snaps up, the white UMHW plastic bit just slides under it, so it can't slip into the release position no matter what. Hard to see but there's a tiny hole in the end of the spring guide to hold everything in place, I was using that tiny screw but ditched it for a tiny pin that works much better.
Ready to arm:
pull and twist and it's ready to fire:
The new folding stirrup:
Before I just had a rotating hook that I snagged on a loop of cord I'd cleverly tied around my foot beforehand. That worked about as well as you can imagine, hence back to basics. I wanted to keep the weight down up front, so it's all aluminum.
The cocking rope:
This is an adaption of a previous device I made for a previous overpowered pistol crossbow. A single shared handle is much less fiddly to manage, and a further enhancement is to permanently attach it through a hole in the butt block, so I don't suffer any flare-ups of my chronic case of "where'd I leave that #%&@! cocking rope" syndrome.
And lastly I made a string and a couple of small plastic wheels to go on the nock axles and strung it up, no pulleys, no turnbuckles, no nonsense. I did that mainly because having the string attached to the block at the back meant totally unstringing it if I wanted to work on the mech. Brace height is 3", power stroke 7.5. That's a lot of bend for these little 80# fiberglass prods, I know. Of course I was also curious, and a little trepidatious, to see how my bench jalopy would handle full power.
I got my answer: Like a champ!
These are bolts I made for the last iteration:
Top is the lightweight commercial aluminum bolt I shortened and modified the fletches on to fit in the slurbow track. Flew OK, but bent just about every time. 19 grams.
Center is a quarter inch oak dowel with a 5/16" 125 grain field point epoxied on front and just enough aluminum of the same diameter on back to give the string a solid face to push, keep it aligned down the track, and hopefully add a bit of turbulence to help keep the point-heavy projectile pointed in the right direction. Only 14 to 15 grams.
Bottom is the heavy hitter, solid fiberglass with the same 125 grain field point. I carved grooves in back to move the center of gravity forward and, again, hopefully add some air resistance to the tail end. 30 grams.
I wanted to explain the "ammo" I was using to illustrate the Chrony results I got just now. That 30 gram bruiser averaged 232 fps muzzle speed, and the lightweight above it rang in at 305! That's the first time I've broken 300 fps with one of my homebuilts, I certainly never expected to do it with a pistol. So, in a roundabout way, I can finally say MISSION ACCOMPLISHED. I managed to cram full size crossbow power into a one-hand-wielded package.
I was snooping around on Geezer's New World Arbalest site the other day, and right on the homepage are these sage words of wisdom:"A note of caution: Bows in excess of @150 lb. of draw will be hard to pull, have more recoil and destroy more bolts than the lighter bows. They will not be as much fun to play with, and are more likely to seriously injure or kill your neighbors if you should have a shooting mishap in your back yard. All bows are dangerous if used unsafely, but the STRONG bows are REALLY DANGEROUS! We do not recommend you buy a bow in excess of 150 lb. unless you have some particular purpose for a very strong bow."
I agree with this sentiment entirely. Unfortunately, I just can't help myself, and this build is the most useless and dangerous thing I've put together yet. I should probably change my signature line to "Kids! Don't try this at home!"