Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on January 18, 2019, 05:15:07 pm
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Here's a couple of pictures of my shooting machine. The second pic is sighting to the target. The blue pointer is where the arrow is aimed, the red one is where it hits about 8" high. This would be 8" to the left if the bow was vertical. The target is 9' from the back of the bow. I have to use carbon arrows because my wood or bamboo ones break just about every time I shoot one through the machine. Can anyone see any glaring problems that might be causing this?
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My first thought would be too stiff of an arrow.
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The arrow is definitely too stiff and that was my first thought. I was using a new bow(the Doug maple) but it's 40# so I tried a 44# bamboo arrow. It shot about 3" lower but it broke >:(. If you look at the second picture you can see the ice cream buckets I use for light diffusers. The arrow actually brushes against them.
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too stiff, as in not hitting the backstop straight on? can you shorten the distance? or shoot into something softer? I have a cardboard box stuffed lightly with throw away plastic grocery store bags
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Here's a pic of how the arrow hits. The fletch is about 1/2" high and 1/2"to the right. The target is a plywood box filled with plastic bags and covered with heavy duty tarp material.
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but the stiff ones you are breaking might be hitting at a much more acute angle. some bare shaft tuning recommendations call for very short distances, like less than a meter, to prevent breakage before the arrow gets sideways
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What about the bow being clamped is not letting the arrow paradox...try shooting by hand at that distance
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I had the saddle for the bow lined with foam so the bow was free to rotate some. I just put that clamp on there today. It didn't seem to make any difference.
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The really stiff ones are carbon. They are 300's with lightish tips. The only reason they survive is because carbons are so strong. If the rain stops tomorrow I'll shoot a bunch of arrows until I find the one that flies the best. Then I'll sacrifice it. In the 5 or so years I've been doing this I've never broken an arrow other than hitting a rock dead on. Since I started using this machine I've broken close to a dozen. That's why I started using carbons. I'm thinking I'll buy a 600 or 700 carbon and see what it does.
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.try shooting by hand at that distance
It took a couple of hours for this to click in ::). I have shot many bamboo arrows by hand into this target. Worked fine. I was a few(maybe 4') further away. I'll try it from the same distance. I can't pull as far as the machine so the draw weight will be down but I can shorten the DL on the machine. Tomorrow. Thanks Brad that shpuld narrow it down.
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It looks to me as though you aren't actually lining up true.
The string seems to be coming up onto the latch mechanism, a bit like a crossbow with the bow mounted below the track.
If you run a straight edge along the track in line with where the .... hang on I'll draw a pic ... it's easier.
Don't run away!
I'm back....
My sketch shows how it should line up and you can see the arrow would be aiming up (if the bow isn't cut away to centre shot). On your one the latch is too high which makes it look like the arrow should go horizontal. But as soon as the string is off the latch it drops into line pulling the arrow into that point up, nock down alignment.
I made the same mistake on mine at first, I built it with the track lining up but forgot the height of the latch!
Del
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There are also some differences between a machine and a person too.
When you shoot, as the arrow getting forced left as it goes past the grip, the bow (and archers arm) is also pushed right (action and reaction). The effect is seen in the slo mo on my blog
https://bowyersdiary.blogspot.com/2014/06/slow-mo-hat-cam.html (https://bowyersdiary.blogspot.com/2014/06/slow-mo-hat-cam.html)
With a rigid machine you don't get that flexing of the archers arm this makes the arrow actually kick more than expected.
I notice your machine is mounted at the bow end which prevents any flex.
Mine is mounted nearer the back/middle and I've noticed a degree of flex in some of the slo mo.
If there are alignment probs, simply allowing the bow to twist in the "hand" clamp will help. As long as it shoots consistently it doesn't really matter that looks to be high.
Del
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Thanks Del. Fortunately I haven't glued the bow mount to the frame yet(I almost did yesterday) so I can raise or lower it. Your picture shows that I should raise it. Did you have to make spacers to compensate for different handle widths or is it not that critical? I originally had the bow mounted if foam(wet suit material)with a bungy to hold it down. The clamp was done yesterday as a test.
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Make spacers?
I have a box under the bandsaw with loads of custom made spacers in it ;)
Nah, I just have some bits of pipe insulating foam, rubber strapping and other such odds n ends. (this allows a bit of automatic alignment/twist etc)
Your set up is more of a precision job by the look of it. Mine was quick, dirty use it outdoors collapsible version just to get some slo mo vid of flight arrows. Not used it since, but it showed what I needed to know and it may get some use in the future.
I don't think the set up is hyper critical, it's just that you obviously aren't happy with how it's lining up at the moment. I expect you'll soon get a handle on cause and effect once you start playing with it.
Yes it looks like you should raise the bow. This will of course make it look like it will hit where you have seen the arrows are actually going.
You'll need to adjust the chrono position up a tad to match persumably.
Keep us posted :)
Del
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I guess I should have said "use spacers". ;D I don't even have a box under the bandsaw. It just builds up on the floor until it's nice day for burning.
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Del, did you ever use your machine at close range? Like ten feet or so?
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Del, did you ever use your machine at close range? Like ten feet or so?
Nope, think I used the mk1 at 10 yards.
You've found the prob already. I've heard of people using looser, softer targets to catch 'em gently.
That's why I use mine outdoors... it's very difficult to catch a flight arrow with out smashing it >:( :(
You may find the bungy hold down works better than the clamp... it's all trial and error.
BTW... your chrono is a full arrow length from the bow? (at risk of stating the obvious)
Del
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Yes my chrono is 36" away from the bow. I already made that mistake. Badger sorted me out. Anyway I raised the bow mount 3/4" so it looked just like your picture. The carbon arrow hit 4" higher and broke. It was spined way too heavy though. I think I'll go uptown and buy(grrrr) a 700 spined carbon. I'll have to try lowering the bow mount.
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Whoops, :-[ maybe there is just too much off-centre shot with that bow for that distance.
I assume you are lining up where it "should" hit, by lining up at full draw not brace? ( or lining up the latch in the full draw position but without the bow drawn) .
I think you are right...
Drop the bow to make it line up with where you want it to hit. BUT allow it to rotate in the clamp to align itself so you aren't twisting the limbs.
Just remember we do this stuff 'cos it's fun right ;D ::)
Del
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Just done another sketch to show what I mean about allowing the bow to twist when it is dropped to line up with your target/chrono...I expect you'd worked it out anyway.
It shows the aim line and centre-line being two different things.
It also shows the potential problem of the string hitting the track if the bow is too low.
With the your previous test when the bow was mounted high to give "correct" alignment... the whole machine then needed tilting down to get the aim line right to hit the target square on and not at an angle.....
I think you just gotta mess around until it does what you want >:D
I think I've been too clever for my own good... can't stop postint (hic)... too much red wine with my dinner! :-[ ::)
Del
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any chance you woud try a wood arrow,, when you go up town,, :) I think the carbon arrows are making it difficult to tune ,,but I am just spit balling cause I never shoot carbons,,
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I have the same chrono you do and I am happy with it. I must have about 8 in a box that quit working, different brands. I get less bad readings with this one than any of my others.
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I was just starting to think that way Del. I hadn't thought about the string hitting the rail if it's too low though. Good catch. When I was messing with it yesterday I put in a rail that the string could run along. It helped a bit but the wear on the string was awful.
Brad- I have a couple of wooden arrows but the wooden ones seemed to break the easiest. They were Hemlock though and it seems a little brittle. I bought a 600 spine carbon. Using the "proper" ;D spining method it is 50# spine which is about right depending on the tip weight. Unfortunately it is is only 315 grains which is 85 gr light for 10 gpp. It would also make the arrow speed over 200 fps which might aggravate the breaking problem.
I just tried shooting a bamboo arrow by hand from the same distance as the machine. It broke. I'm thinking the distance is the problem now.
The new carbon is a little limp at 15'.
I'm babbling
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I have the same chrono you do and I am happy with it. I must have about 8 in a box that quit working, different brands. I get less bad readings with this one than any of my others.
I have this one and a Chrony. They both work but the Caldwell seems to have a bigger sweet spot. Shooting by hand I have an awful time getting results with the Chrony. Err mesg etc.
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Some days I should stay in bed. ;D ;D ;D Took the new arrow out to test it. First shot was great, second shot for some reason I missed target and hit my chipper shredder.
Silver lining part. I could fix it and I found out the tip weighs 80 gr.
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Something that may be worth a try is to hang a softer lighter target from as couple of long a strings so that it swings back with the arrow to absorb the impact rather than stopping the arrow abruptly.
I used that trick when testing a paper crossbow bolt for a bet, had to stop the bolt without buckling it.
https://www.youtube.com/watch?v=zPzYazBqa9Q (https://www.youtube.com/watch?v=zPzYazBqa9Q)
Del
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That would sure help but I've got a roll up garage door there. Can't always get to the ceiling. I was thinking I could open the garage door and move the target further away but then if I missed the target I would punch a hole in the window of the camper/fifth wheel/caravan.
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That would sure help but I've got a roll up garage door there. Can't always get to the ceiling. I was thinking I could open the garage door and move the target further away but then if I missed the target I would punch a hole in the window of the camper/fifth wheel/caravan.
Magnets! You need magnets! ;D (-P
and string and stuff and duct tape!
Del
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Ok I get the feel of the sitution, if we were closer you would need to have a barbque and invite us over and we could fine tune your set up,,, (SH)
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I may break down and mount it permanently out in my range a suitable distance from the target but that would defeat the "indoor" part which is really nice. We do have a 50" hallway in the house but I think I might run into some resistance there. ;D ;D
Actually magnets and string might work except I think it would come down with every arrow. Maybe just screw eyes. Hmmm
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Who you callin' "screw eyes?" ;) ;D ::) >:D )-w(
Del
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I put a couple of screw eyes(snicker snicker) in the ceiling and put a loop of string through them. Filled a sack with old towels and blankets and made a couple of wire hooks for it. Now I can unhook it and open the garage door. The string loop just slides out of the way. I can't use the target when the door is open but that's not a problem for 3 months. Hung the target about a foot farther away. I could move the machine away but it would start to get in my way.
It seems to work. Catches the arrow without breaking it so far. Tried a few bamboo arrows no problem. Guess my old target was just too stiff.
This is just Mk1, I'll stuff the sack more and maybe put a stiffener across the top. Thanks for the suggestions.