GTA
General Discussion To Gateway To Airguns => The Shop => : RedFeather March 25, 2009, 04:57:14 AM
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If you could, say, find a spring with about 80 - 100 pounds cocking effort, what modifications would be required in order to prevent the gun from demolishing the piston/seal/transfer port? (Don't go asking "Where is it? How much???", because it's only supposing.) And is there a maximum amount of air by caliber that a spring piston gun can transfer before encountering too much back pressure/severe diminishing returns?
Yeah, I am thinking about something a bit unconventional.
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I would think it is possible in a larger cal. but not 177 more like 45 cal or higher. howie
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One thing more. Is the effort required to cock a springer one - for - one (i.e. - 30 pounds to cock = 30 pound spring) or is there a mechanical advantage (30 pounds to cock = 60 pound spring)?
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I dont know what you are up to my Friend??? I have known you long enough to know you have a small "Evil" in Ya,,,,,,,I admire that!!!! LMAO!! Tim.
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Just looking at the set up of my Gamo Maxima. I'd say that you would have a 6:1 to 7:1 Advantage. Ie Barrel pivot to pivot on the spring lever of about 6cm over the ballel length of 40 (to the center of hand position when cocking) 40:6 is 6.6:1 of Mechanical advantage. so 30 pounds to cock would be about 198 pounds to compress the spring fully without having any MA. I think my figures are correct!!
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If that is so then what I was thinking about might not work. I think you have to measure the compressed distance of the spring and the length the barrel swings. Maybe once you work out the ratio then times the cocking effort. I was initially thinking the spring's load was the same as the cocking effort but it has to be much more. My idea was to find a heavier spring (not coiled) but it would have to be much higher than I imagined.
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WOW...That would be a spring rate of 135lbs....most air guns have a 35 to 45 lbs spring rate.
So..thats a 135lbs of force for every 1" the spring is compressed...so a gun that that compresses the
spring 3" would have a total spring force of 410lbs..... 130/150 is the avarage...think yer would need
a REAL strong barrel so it don't bend while cocking..then a pnumatic brake at the end of the stroke
"same as a cushion stop air ram" other than those two factors it possable....
LETS BUILD ONE.....Then Gene can tune it. "and we want it silky smooth gene"
Heres another Theoretical one.....
how about useing a .22 blank to power a pellet...
Have thought about it....Have 3 full boxes of Ramset
nail gun blanks.".Yellow Low power ones"
l
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Kiwi, there already exists two different blank guns, one by Mendoza and the other by a different Mexican company. What I was thinking about was a spring gun that operates in the fps range of some of the bigger (DAQ) PCP's. I just didn't realize how heavy the existing springs are. If you up the bore to something like .36, you could shoot things like lead conicals.
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the idea has been tried, rifle was basicly unshootable, check the back blogs at PA, Tom had one a long time agoo about a really big bore springer
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You know that has actually been done. It was a Mexican made gun. Wish I could remember the name. But it used a blank cartridge to propel the pellet down the barrel. Cool!
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Dam.....And I wanted to be the first.
O well back to the drawing board "CAD"
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My idea was not to use a coil spring but a hybridized stone or "bullet" bow. These were crossbows that shot a small missile instead of a quarrel. Used from the Middle Ages up until the late 19th century for taking birds and small game. Actually had competition shoots in Europe. They are much less powerful than conventional crossbows. The bullet bow seemed to have died out around the time that modern spring guns were just coming into existence due to better metallurgy. I was wondering if a springer and bullet bow might be merged. The front half would be conventional springer with breech, barrel and compression chamber. The spring would be replaced by the crossbow arms (prod) and string to drive the piston. (Like that gimmicky adapter for compound bows sold recently, but much more highly refined.) Since you can buy prods of up to 200 lb draw weights, it seemed that a fairly powerful "spring" could be incorporated, but it turns out that wound springs operate within the same force range. Now, if you are industrious, you could probably come up with a much more powerful prod of seven or eight hundred pounds pull, similar to some of the heavier war crossbows or hunting rigs. Of course, you would need a windlass or ratchet mechanism to cock it (ala Whiscombe). A larger caliber would probably work at these levels, same as a .25 Patriot. Well, back to the drawing board. (Still might work up a bullet bow, though, just for S&G's.)
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I just finished reading "Airgun from Trigger to Target" by the Cardews. If you are seriously going to try and build any airgun I think this would be GREAT reading.
Martin D. White
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Naw. For the price of that book I could buy another gun to play with, LOL. Half the fun is dreaming this stuff up. Not so much when you find your idea's been done some time before. I posted a similar thread on the Yellow and someone said the Whiscombes can run over 400 pounds. Well, would have been nice. Now, a 500 pound bullet bow could be something. I have a reprint of an old book on crossbows in which the author rebuilt a Medieval military crossbow using the original steel bow and furniture. When they cocked it in the shop by adding weights to the string it finally drew at 1200 pounds.
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I bought the book from amazon.co.uk for $30
http://www.amazon.co.uk/Airgun-Trigger-Target-G-V-Cardew/dp/0950510823/ref=sr_1_3?ie=UTF8&s=books&qid=1238243726&sr=8-3