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All Springer/NP/PCP Air Gun Discussion General > Machine Shop Talk & AG Parts Machining

crosman 1377 double tube pumper ? about to find out ( pics

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Rob M:
theres a lot to discuss and explain , but hoping the inital pics do some of the work

20210728_092436 by murphyrobert9, on Flickr

had to get a basic shape , the drawing was kept simple to get from A to B fast

20210728_101935 by murphyrobert9, on Flickr

this is where the 2 pump tubes will go

20210728_104621 by murphyrobert9, on Flickr

threading done manually , had to be super square since in the future , the 2 linkages will be joined and move in unison
20210728_125242 by murphyrobert9, on Flickr
20210728_125604 by murphyrobert9, on Flickr

this part i did the material clearing on the cnc , then threaded manually with die holder. this is where the factory valve will connect

20210728_125608 by murphyrobert9, on Flickr

heres the porting front to back , VERY small , having them larger would result is too much pressure drop , i also dont want the compressed air stored torward the pump side of the block , i want the majority readily available at the back near the valve .. 3/32 connection holes

20210728_145900 by murphyrobert9, on Flickr

20210728_133245 by murphyrobert9, on Flickr

ill be using the factory parts, check valves , pistons , but making new copression tubes which im waiting on .. these are internally sprung and sealed to the block

i made this custom valve , angled port, .250 throat .200 TP , but i may still use the factory valve.. The challenge at the rear is poppet lift versus the ppoppet itself restricting flow by overtravel.. that will be sorted in the tuning and likely wont amount to much of an obstacle.. Making a longer valve would allow for more plenum IN the valve itself , and not stagnating in the block during the shot.. For now , im minimizing the internal volume on the far side of the block , as that will most likely be useless air .. Heres a mockup

20210728_135718 (1) by murphyrobert9, on Flickr

20210728_144441 by murphyrobert9, on Flickr
noww that i posted it i hope it all works out , gonna be a matter of tuning , a longer pump arm cut from steel plate or alum , and small tweaks..  I did the math a while ago , this will be equivelant to pumping a .882 diameter piston in a pistol.  ;D

Long_Gun_Dallas:
Ohhhh boy.  I can't help but think what a bear this is going to be to pump, lol.  You're going to want to mill some type of pump arm/link support.  Whatever grip you put on there will see a lot of force.

Looks good so far, though!

Rob M:

--- Quote from: Long_Gun_Dallas on July 28, 2021, 09:51:37 PM ---Ohhhh boy.  I can't help but think what a bear this is going to be to pump, lol.  You're going to want to mill some type of pump arm/link support.  Whatever grip you put on there will see a lot of force.

Looks good so far, though!

--- End quote ---

im thinking to use the stock 2 linkages , then put my long arm in between them , and have it extend down all the way under the grip , kinda like the 46 pistols
https://topairgun.com/product/177-air-venturi-av-46m-match-air-pistol/

avator:
Moving to Machine Shop gate.

JuryRigger:
Nice work!!  :D
Watching,
Jesse

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