Thursday, 25 January 2018
Mk2 Shooting Machine
The shooting machine is finished now.
I haven't done any test shots yet but I have mounted a relatively heavy bow and pulled it back testing the sliding latch and pulley system. I also tied the rope round the bow mounting clamp threaded it through the pulley and heaved as hard as I could with both hands, which must have loaded it up to a couple of hundred pounds.
One clever feature I've added is a magnet incorporated into the end stop at the top end of the track, this holds the sliding carriage at the top end ready for cocking the bow.
I've made the little wooden block that lifts the trigger as it reaches full draw and I've drilled holes so that can be set for 24",26", 28", 31" or 32" draw.
Looking forward to testing it at the weekend weather permitting. (Pic with Emily cat shows how it breaks down to two parts).
There has been some comment on a flight archery group where most people have approved of the machine but one bloke maintains that shooting machines are useless except for comparing bows at 3 foot range. Dunno if that even makes any sense. Sure it won't accurately replicate a human loose but at least it should provide a consistent platform to allow comparisons. Anyhow only time will tell, and I'm sure some work could produce a trigger mechanism that reasonably replicated a human loose by adding some friction into the pivot and some flexibility and length to the ends of the fingers of the latch.
I've learnt to rely on my own findings rather than the opinions of others, anyhow I don't s'pose he was testing heavy English longbows.
Meanwhile the Hazel primitive is progressing and needs me to check it out at full brace height and full draw then I can make a string and shoot it for about 50 arrows to let it settle in before any final tweaking and doing the grip.
Ah! Just checked it and it's only 35# @28" . The cleaning it up and taking out the tool marks has lost a couple of pounds. (bugger)
I could try re-doing the heat treating long and slow, or it might still be an acceptable weight. Failing that, there's a lady archer who is a coach and shoots all styles who hasn't got a primitive. I'm sure she'd like it.
I do have the sister stave to that one so I could make another (with a little more patience in the roughing out). This illustrates nicely that you can make a bow quickly, but not necessarilly to a precise draw weight. Those who suggest you can make 'em by numbers and make 'em like shelling peas don't know what the draw weight is until it's finished.
It's easy to take off weight, it's very hard to add it on.
Using a string from my other Hazel bow I had 3 test shots at a slightly tentative 27" draw, I then tweaked the arrow pass a bit and had a fully committed shot at 28", the arrow flew lovely and true.