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allu's projects


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Old 12-13-2015, 10:05 PM   #11
RalphG
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Nice results allu! I see the 2nd prod idea clearly worked. So now you have more power, the next you will want more accuracy, then a better stock and trigger mechanism.... and before you realize it you will have rebuilt he thing completely
You seem to be hooked and cannot stop to tinker? Well,definitely a sign of a beginning addiction
If you are worried the string may break, now that you can spend some money, get yourself a spool of dracon, sold in archery supply stores either as brownells b50 or BCYs B55. a 1/4lbs spool costs about 10-12€ and has 4300ft/lbs of thread - thats enough for many strings and will save you some money in the long term. String making is not overly difficult, there are many tuts on youtube and its also a valuable skill for other projects. Just dont forget to measure the intact string before it eventually breaks.


As for shortening the 2nd prod, I already said it, make sure the ends are properly rounded off, maybe even tapering in thickness a bit. A fellow from another forum stacked 2 150lbs prods, it worked for a while but eventually broke exactly at where the shorter one ended. He deduced this was from the too sharp edge of the inner, shorter prod.

allu's projects - Slingshot Crossbows
allu's projects - Slingshot Crossbows


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Old 12-14-2015, 03:54 AM   #12
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That's a serious change. Nice pictures.


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Old 12-15-2015, 09:17 AM   #13
allu
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Quote:
Originally Posted by RalphG View Post
Nice results allu! I see the 2nd prod idea clearly worked. So now you have more power, the next you will want more accuracy, then a better stock and trigger mechanism.... and before you realize it you will have rebuilt he thing completely
You seem to be hooked and cannot stop to tinker? Well,definitely a sign of a beginning addiction
If you are worried the string may break, now that you can spend some money, get yourself a spool of dracon, sold in archery supply stores either as brownells b50 or BCYs B55. a 1/4lbs spool costs about 10-12 and has 4300ft/lbs of thread - thats enough for many strings and will save you some money in the long term. String making is not overly difficult, there are many tuts on youtube and its also a valuable skill for other projects. Just dont forget to measure the intact string before it eventually breaks.


As for shortening the 2nd prod, I already said it, make sure the ends are properly rounded off, maybe even tapering in thickness a bit. A fellow from another forum stacked 2 150lbs prods, it worked for a while but eventually broke exactly at where the shorter one ended. He deduced this was from the too sharp edge of the inner, shorter prod.

allu's projects - Slingshot Crossbows
allu's projects - Slingshot Crossbows
Yeah the whole thing could be rebuild for something better. Especially the trigger is a bit primeval for 21st century and could do with an upgrade. But gotta live with it now, no way to change it. Thanks for the tip, I'll definitely start making my own strings if needed!

That's what I was thinking as well, it can't be good for the main prod if half of it is way stiffer and the tips flex normally. This just results to uneven flex/bend and most likely breaks the prod in the long run. Shouldn't be a problem if the second prod is nearly as long as the main one and the draw weight is spread evenly. But on the other hand it eats strings more often, so it's kind of lose-win situation at the same time. Can't have it all, it's either extra power over durability or vice versa. As long as the cocking mechanism doesn't break I'm fine with shorter string life.

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That's a serious change. Nice pictures.
Thanks!

-allu
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Old 12-16-2015, 08:57 PM   #14
allu
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Painted the stock today:

allu's projects - Slingshot Crossbows

Also made two new arrows and tried out new fletching method. Just simply glued on the vanes from those broken cheap aluminium bolts. Tried to make them slightly bend to make the arrow spin in flight, but we'll see how that worked out tomorrow

Also there's a small problem with the string wanting to slip over the second prod on one end of the string. To describe it better here's a pic of how it's close to slipping off already:

allu's projects - Slingshot Crossbows

Fortunately I found a way to replace the string. Super easy and quick to do, but without the stock it's quite painful for your hands:

allu's projects - Slingshot Crossbows

If the slipping keeps happening I may try filing the tips of the second prod to V-shape so the string would automatically keep itself in place. But hopefully that won't be necessary, but we'll see tomorrow.

-allu
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Old 01-03-2016, 06:15 PM   #15
allu
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Pardon my inactivity, work and life issues haven't spared me a moment for my projects but it's getting better now.

Still having issues with the string slipping off the second prod and there doesn't seem to be a simple way to fix it. Even with a groove on the second prod the string starts slowly sliding upwards after every shot until it slips off. Gotta figure out something else for that matter.

I'm planning on building a simple survival crossbow flipper thing, something dead simple and quick to build but also effective. Planning on making it out of 10 x 20 mm metal square pipe, 4 mm flat steel and an aluminium u-rail as, well, the rail. We'll see how quickly I can get the supplies for it, though first gotta design it

I was having hard time deciding between my flipper or an improved version of the cobra as my next project, but turned out the flipper is far more powerful. And it's completely home made, using a commercially made prod feels like cheating What helped me decide was simply shooting the same projectiles out of both weapons and comparing the damage done. Some pics:

7 mm and 9 mm plywood completely penetrated, cobra could penetrate only the first one completely.

allu's projects - Slingshot Crossbows

2 cm thick wooden plank and 9 mm pierced. This was a real surprise for me since nothing I have shot with the flipper has ever come close to splittering to wood, but aluminium pole with dart head tip did it

allu's projects - Slingshot Crossbows

allu's projects - Slingshot Crossbows

Hopefully more updates soon!

-allu
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Old 01-11-2016, 09:44 PM   #16
allu
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Finally three days off and got my some supplies, going to start building tomorrow. Hope my workshop heats up a little bit, it's been over -30C here and it's lacking a proper heating equipment so I'm hoping not needing to work at +10C. But if that's all I can have then I just gotta suck it up and craft

Made a quick sketch with paint (of course, the best program for this kind of stuff!!! lol). Didn't bother marking different layers and parts with different colors nor naming them, because I remember them myself Here's the sketch anyway.

-allu
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Old 01-14-2016, 07:11 PM   #17
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So after two days the stock looks like this:

allu's projects - Slingshot Crossbows

allu's projects - Slingshot Crossbows

Made out of plywood and pine board mostly used for indoor applications. Not the best type of wood for the job but dirt cheap and easy to obtain. Hopefully the plywood and aluminum rails are enough to keep it from bending or twisting, but time will tell. Got it in a pretty good shape today, hopefully tomorrow I can finish the trigger and glue the parts together. More about that next time whenever I have time from work and personal life.

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Old 01-19-2016, 08:19 PM   #18
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Still -30C here but that doesn't slow me down anymore, so used to this crappy cold weather that can't even care anymore Got a lot done and it's pretty much in a shooting condition at the moment but still requires plenty of fine tuning.

allu's projects - Slingshot Crossbows

allu's projects - Slingshot Crossbows

The trigger works very well, way better than I expected! Had to make three different trigger nuts because of my own stupidity, eyeballing the measurements never work Rather heavy to pull (not much leverage due to its short length) but very consistent and secure, medieval engineers knew what they were doing

The only thing preventing me from shooting it is the fact that while the frame holding the arms is at the right angle, somehow I managed to fail secure it in place and now it twists slightly and lifts the bow string off the rails. Gotta figure out a better way to attach it tomorrow, hopefully I can get the first shots off after!

-allu
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Old 01-20-2016, 12:54 PM   #19
allu
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First shots fired and results are quite disappointing to be honest :/ It hasn't got a great deal of power to begin with which would be alright if it was accurate. That's not the case, I guess the pulleys just multiply the problem of the arms not being 100% identical (I haven't got high tech enough tools for that). So each arrow got a small nudge on the left, enough to throw them off balance and make them fly anywhere but straight. The only arrow that could resist this was a new one that I made. Very front heavy and best fletching I've ever made and it flew relatively straight. Until it decided not to and missed the target and back stop and zipped into the snow never to be seen again Waste of 30 minutes but at least I learned more about fletching.

So I started looking for ways to get around the problem and turned out with a few modifications I can get rid of the pulleys and make this like a... erm, pulley-less flipper But more about that in the next update!

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Old 01-26-2016, 07:41 PM   #20
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Yesterday while shopping for new gym shoes ended up visiting a local hardware store and couldn't resist buying some crossbow stuff. Found some dirt cheap wooden poles to use as arrow shafts, 1,90€ a pack of 5 (8 mm diameter) and 10 mm poles came in pack of 3. 50 cm long each, made out of beech and surprisingly sturdy! Magically also 2 commercially made 20" arrows and a rope cocking device found their way into my shopping cart, no idea how that happened That 5€ for a rope cocking device was just too affordable to miss out.

Finally the crossbow saw some real improvement as well. Totally changed the arms from pulleys to non-pulley ones and also added an attachment point that allows two springs each side instead of just one. Some other minor changes were an improved arrow rest that totally removed the problem with misfires, and making the connection between the frame holding the arms and the stock more rigid, with a nail, so high tech Some pics:

allu's projects - Slingshot Crossbows

allu's projects - Slingshot Crossbows

allu's projects - Slingshot Crossbows

allu's projects - Slingshot Crossbows

Shoots fairly well already, 20 inch arrows nearly go through 9 and 7 mm plywood stacked together. The performance can definitely be improved by tightening the string and more significantly by adding another pair of springs However I may have to redo the stirrup, because I'm afraid it might snap under such heavy load. But we'll see if that's necessary.

-allu



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