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

[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. 

[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]

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!

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!! 
Watching,
Jesse

[Rob M]

more parts being made.. the steel tube that came in the mail was bought as .620 i.d , it came as .655 ish i.d .. so i had to wait again.. in the meantime tackling the linkages .,

20210803_123111 by murphyrobert9, on Flickr

20210803_123100 by murphyrobert9, on Flickr

20210803_123159 by murphyrobert9, on Flickr

should have the big arm connected to the coupler block tonight ..as for ther valve i finally decided that a longer stock valve was the way to go so i made one

20210803_123625 by murphyrobert9, on Flickr

i WONT be building additional pressure with the stock pistons , so i figured more volume would be beneficial.. Also because of that , i switched to 22 cal .. A 22 will benefit more than a 177 from gains in volume alone //

[Rob M]

heres the first part of the lever arm./..


20210803_124510 by murphyrobert9, on Flickr

needs deburr and sand . then mount to linkage coupler.

[Rob M]

i dont like those cap heads on the linkages , might need to to make 2 cover plates for those.

[Rob M]

takes some imagination but the thirds piece should be near the underside of the grip//


20210803_130711 by murphyrobert9, on Flickr

20210803_130715 by murphyrobert9, on Flickr

20210803_130718 by murphyrobert9, on Flickr

[dan_house]

sweet

[Rob M]

heres a mockup , nothing bolted up.. final length will be about 2 inches longer than a factory 1322.. third part of the pump lever coming tommorow.. should terminate about the base of the grip

20210803_154507 by murphyrobert9, on Flickr

20210803_154555 by murphyrobert9, on Flickr

the length will be good news , with the super long lever pumping should be fairly easy.. AND yes , ill be taking better quality photos as it gets near completeion.

[JuryRigger]

Lookin' good... 
Jesse

[rsterne]

I'd sooner go with a longer single pump, rather than doubling the effort required.... but it's a nice bit of work.... Good luck with it.... 

Bob

[BigBird]

I'd sooner go with a longer single pump, rather than doubling the effort required.... but it's a nice bit of work.... Good luck with it.... 

Bob

Put some more support on top (on either sides of the iron sights) and make it a foot pump on the handle 

Nice milling there.  I once dreamt about a double 1322 that had hammers connected with a threaded rod that connected to a sear.  Receiver and barrel on top in the middle.  Transfer ports going in at angles.  Then thought about how many things wouldn't work and came to my senses.  Yours looks like a much better idea.

[Rob M]

Yes Bob , i could have just made a 1377 main tube with a 1 inch piston ( or longer stroke) , that would have been easier , but i saw something similar to this built on the green forum about 10 yrs ago , it was stuck in my head since..
Bigbird , yes, the first iteration i saw of this on the forums actually had 2 seperate valves , tubes and hammers, but the breech was a manifold taking the air from both tubes,, triggers, hammers, and so on had be to linked. I dont think it will be hard to pump , ill know by tommorow .
i do likee the lidea of a massive SSP gunn though , where the gun lays on the ground and is cocked by standing on the sidelever (-'

[sb327]

I’m glad to see that mill in action! Somehow missed this thread till today.

Nice work going on there. Looks like you’re having fun with it and your machining looks great.

Not sure why anyone would bring up cocking force as a problem with this design….it offers higher volume per stroke and if effort is too great on the tail end, you can design in a pin that drops one side out and let you ‘shift’ into a lower gear…..

I like it.

Dave

[Rob M]

thanks Dave .. well , the basic math says it wont be bad - ill be gaining 50 % lever length from the pivot hole ( the lever arm has another section not posted yet )
MA diagram by murphyrobert9, on Flickr

So ill have 1.5 MA against 2.1 ish required force to move the pistons ( the .1 accounts for the additional friction caused by surface area and 2 linkages )
So it will be roughly 40 percent harder than stock , or thereabout. im also likely to add a foster on the main block to account for future laziness

[Rob M]

heres a more accurate depiction of the lever length .. and it still needs a wood handle below ( i might not keep the second arm as is , i dont like it cosmetically )

20210804_084840 by murphyrobert9, on Flickr

[Rob M]

caution , im not a woodworker.. SO i decided to recycle .. this knub is off an old wrecked benjamin 342.. I chopped a piece , cut a channel , mounted it then restained it with some rub ion walnut

20210804_121011 by murphyrobert9, on Flickr

20210804_121312 by murphyrobert9, on Flickr

if theres a clearance issue during real world pumping ill trim it .

[Rob M]

real world color

20210804_122619 by murphyrobert9, on Flickr