back to the P Rod....

back to the P Rod....

Joined: March 1st, 2002, 12:22 am

June 22nd, 2012, 5:18 pm #1


<rnat>

Ive been working on some other stuff, and working the P Rod as I get a break from the other stuff.

Had a hugely crushing setback Wednesday night that totally negated a months worth of work, and I didnt do anything then or yesterday. Taking the break has helped clarify some thinking......

To Wit: I think (hehe I hope:) ) Buster and I are on the same page now as far as what is called what and what it changes. Phew. But now maybe that was the easy part.

the question still is, why is my Prod hotter than others? Buster thinks a weak spring is holding his back, and I'm sure that _does_ have a fair amount to do with it. If he were close enough, I'd have him bring his gun over, and we'd tear them down side by side and compare them and swap some parts around and see what happens. Its probably fairly obvious if both guns where side by side, but what the heck are we overlooking?

Is the HDD contributing to higher speeds? The bigger TP?  And one thought I dont really wnat to consider... maybe its the synergy (and oh good grief do I hate that word) of the HDD, the bigger TP, a decent spring, testing and shooting at 4500 ft etc etc etc that makes the gun what is seems to be. But that sucks long term, cuz you cant reproduce test setups and results, short of coming here and testing in my workshop with your gun.

And brings ux back to "Now What?" Test every mod/change at 200 psi intervals for 2400 to 3000 PSI fills? Take the gun bck to OOB condition and rerun all the tests? Tell Buster to come to Bozeman (got a bunk for ya itf ya do) and have a side by side teardown?

Dont get me wrong, I'm very pleased the gun performs as it does. But I wnat everyone's P rod to run strong, and its very annoying to not be able to explain why mine is and his isnt. errrrr

</rant> 


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: February 17th, 2010, 3:30 am

June 22nd, 2012, 5:33 pm #2

however, I must admit that I've had trouble following this thread.... I know just from the reading I've done that the transfer port on the PRod is very restricted, and opening it up increases the velocity significantly.... I have a 2260 based Carbine that delivers 16 shots at 20 FPE (700 fps with 18 gr. JSBs within 5% ES) from the same size reservoir as a PRod with only a 2000 psi fill.... Maybe that will put your results in context with what is possible with that volume of air.... I'm using a stock Disco valve with a smaller than stock transfer port (0.125" instead of 0.140").... I understand that the stock PRod transfer port is only about 0.081" because of the higher fill pressures, however....

Bob
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Joined: March 1st, 2002, 12:22 am

June 22nd, 2012, 6:10 pm #3


1) take the HDD out with the .101 TP left in, rerun all the tests

2) leave the HD in, and swap back in the Stock TP, rerun the tests

3) stock TP and remove the HDD

4) get a ~.95 TP and install it, with/without the HDD

3 things have chnaged on that gun: the TP, adding an HDD and the preload adjustments. the adjustments have had this gun., with .101 TP and the HDD installed, going from 398 to 806 with hust a twist or 6 of a couple hex keys. Having thought this through as I type, starting to think that a return to the factory TP is the starting point


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Southwest Montana's headquarters for Airgunning Supremacy
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Joined: June 15th, 2004, 11:49 pm

June 22nd, 2012, 6:17 pm #4

<rnat>

Ive been working on some other stuff, and working the P Rod as I get a break from the other stuff.

Had a hugely crushing setback Wednesday night that totally negated a months worth of work, and I didnt do anything then or yesterday. Taking the break has helped clarify some thinking......

To Wit: I think (hehe I hope:) ) Buster and I are on the same page now as far as what is called what and what it changes. Phew. But now maybe that was the easy part.

the question still is, why is my Prod hotter than others? Buster thinks a weak spring is holding his back, and I'm sure that _does_ have a fair amount to do with it. If he were close enough, I'd have him bring his gun over, and we'd tear them down side by side and compare them and swap some parts around and see what happens. Its probably fairly obvious if both guns where side by side, but what the heck are we overlooking?

Is the HDD contributing to higher speeds? The bigger TP?  And one thought I dont really wnat to consider... maybe its the synergy (and oh good grief do I hate that word) of the HDD, the bigger TP, a decent spring, testing and shooting at 4500 ft etc etc etc that makes the gun what is seems to be. But that sucks long term, cuz you cant reproduce test setups and results, short of coming here and testing in my workshop with your gun.

And brings ux back to "Now What?" Test every mod/change at 200 psi intervals for 2400 to 3000 PSI fills? Take the gun bck to OOB condition and rerun all the tests? Tell Buster to come to Bozeman (got a bunk for ya itf ya do) and have a side by side teardown?

Dont get me wrong, I'm very pleased the gun performs as it does. But I wnat everyone's P rod to run strong, and its very annoying to not be able to explain why mine is and his isnt. errrrr

</rant> 


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
every time I read someone discribing the PRod and reading what was written in the OM I get somewhat confused. At least you and I see eye to eye on the verbage.

I agree with you on the point of be able to be close enough so that both Prods could be dissected side by side to discover their difference, but that probably wouldnt prove anything that obvious.

My stock springs will be here in a few days, until then its only speculation on my part as to why my gun ( with either a .094 or .101 TP) doesnt shoot like yours. as posted before and in PM to you, even with a heavier spring ( cr2200 cut to 180mm , stock spring is 160mm) the numbers were not the same. along with the stock springs I also have a valve assembly and some valve springs and if need be, removing either the valve spring or replaceing the complete valve assembly. the valve is the only other variable that hasnt been discussed as a possible difference. having a weak hammer spring and a weak valve spring, might just be that difference's we have.

I appriciate the offer of the bunk bed Dan, but I dont think the wife would let me go on a long trip by myself ( TEXAS to Montana). I think she'd be afraid I liked it there way too much and not want to come back LOL ( being retired has some rewards ). The thought of popping GH is very enticing , I've already done in most if not all the tree rats around these parts LOL and need something else to sharpening my skills on. paper punching gets old .

We'll get this worked out eventually and will probably end up knocking our heads against the wall that the answer was something so simple and so over looked .







Buster
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one step closer to the ultimate goal
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Joined: August 16th, 2004, 7:32 am

June 22nd, 2012, 6:37 pm #5

<rnat>

Ive been working on some other stuff, and working the P Rod as I get a break from the other stuff.

Had a hugely crushing setback Wednesday night that totally negated a months worth of work, and I didnt do anything then or yesterday. Taking the break has helped clarify some thinking......

To Wit: I think (hehe I hope:) ) Buster and I are on the same page now as far as what is called what and what it changes. Phew. But now maybe that was the easy part.

the question still is, why is my Prod hotter than others? Buster thinks a weak spring is holding his back, and I'm sure that _does_ have a fair amount to do with it. If he were close enough, I'd have him bring his gun over, and we'd tear them down side by side and compare them and swap some parts around and see what happens. Its probably fairly obvious if both guns where side by side, but what the heck are we overlooking?

Is the HDD contributing to higher speeds? The bigger TP?  And one thought I dont really wnat to consider... maybe its the synergy (and oh good grief do I hate that word) of the HDD, the bigger TP, a decent spring, testing and shooting at 4500 ft etc etc etc that makes the gun what is seems to be. But that sucks long term, cuz you cant reproduce test setups and results, short of coming here and testing in my workshop with your gun.

And brings ux back to "Now What?" Test every mod/change at 200 psi intervals for 2400 to 3000 PSI fills? Take the gun bck to OOB condition and rerun all the tests? Tell Buster to come to Bozeman (got a bunk for ya itf ya do) and have a side by side teardown?

Dont get me wrong, I'm very pleased the gun performs as it does. But I wnat everyone's P rod to run strong, and its very annoying to not be able to explain why mine is and his isnt. errrrr

</rant> 


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
First, I noticed that the port on the valve itself is ~.105. That explained the transfer port porting increases to me. I want to try opening it a little to see if it increases performance but just haven't had the time. It' is about, air gun project # 3 on my list.

I also want to try a softer stem return spring to see what affect it has.

I have received identical 22XX valves from Crosman - same part # - that had different size stem return springs. My theory is they ran out of one and used a different one until they restocked the correct size. I would measure such things as springs and port on the next teardown, perhaps you may find something.

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Joined: February 9th, 2006, 10:35 pm

June 22nd, 2012, 7:50 pm #6

<rnat>

Ive been working on some other stuff, and working the P Rod as I get a break from the other stuff.

Had a hugely crushing setback Wednesday night that totally negated a months worth of work, and I didnt do anything then or yesterday. Taking the break has helped clarify some thinking......

To Wit: I think (hehe I hope:) ) Buster and I are on the same page now as far as what is called what and what it changes. Phew. But now maybe that was the easy part.

the question still is, why is my Prod hotter than others? Buster thinks a weak spring is holding his back, and I'm sure that _does_ have a fair amount to do with it. If he were close enough, I'd have him bring his gun over, and we'd tear them down side by side and compare them and swap some parts around and see what happens. Its probably fairly obvious if both guns where side by side, but what the heck are we overlooking?

Is the HDD contributing to higher speeds? The bigger TP?  And one thought I dont really wnat to consider... maybe its the synergy (and oh good grief do I hate that word) of the HDD, the bigger TP, a decent spring, testing and shooting at 4500 ft etc etc etc that makes the gun what is seems to be. But that sucks long term, cuz you cant reproduce test setups and results, short of coming here and testing in my workshop with your gun.

And brings ux back to "Now What?" Test every mod/change at 200 psi intervals for 2400 to 3000 PSI fills? Take the gun bck to OOB condition and rerun all the tests? Tell Buster to come to Bozeman (got a bunk for ya itf ya do) and have a side by side teardown?

Dont get me wrong, I'm very pleased the gun performs as it does. But I wnat everyone's P rod to run strong, and its very annoying to not be able to explain why mine is and his isnt. errrrr

</rant> 


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
I used my Secret Decoder Ring!

P Rod - Benjamin Marauder Pistol
HDD - Hammer Debounce Device
TP - Transfer Port
PSI - Pounds per square inch
FPE - Foot/Pounds of Energy
JSB - Josef Schulz Bohumin - Czech company know for their outstanding pellets
Disco - Benjamin Discovery
PIA - Pain in the A** (Note, * = s)
PM - Private Message
CR2200 - Crosman 2200 multi-pump air rifle
LOL - Laugh out loud
GH - Ground Hog
22XX - Refers to the Crosman line of CO2 airguns, the 2240, the 2250, the 2260 and similar guns. The 2200 is not part of the 22xx series.

I plink, therefore I am.
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Joined: February 17th, 2010, 3:30 am

June 22nd, 2012, 8:11 pm #7

for one post.... It was such a PITA I gave up.... LOL....

Bob
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Joined: March 1st, 2002, 12:22 am

June 22nd, 2012, 9:05 pm #8

I used my Secret Decoder Ring!

P Rod - Benjamin Marauder Pistol
HDD - Hammer Debounce Device
TP - Transfer Port
PSI - Pounds per square inch
FPE - Foot/Pounds of Energy
JSB - Josef Schulz Bohumin - Czech company know for their outstanding pellets
Disco - Benjamin Discovery
PIA - Pain in the A** (Note, * = s)
PM - Private Message
CR2200 - Crosman 2200 multi-pump air rifle
LOL - Laugh out loud
GH - Ground Hog
22XX - Refers to the Crosman line of CO2 airguns, the 2240, the 2250, the 2260 and similar guns. The 2200 is not part of the 22xx series.

I plink, therefore I am.
cool!

dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: April 28th, 2010, 12:23 am

June 22nd, 2012, 9:57 pm #9

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Joined: April 12th, 2002, 5:26 am

June 22nd, 2012, 9:59 pm #10

cool!

dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
tiny changes there make big differences in output, though in my opinion, it's the worst place to restrict the gun.... it's like putting a restrictor plate in a stock car intake.

I'd leave the large port in there, and find other ways to get the power, and gas consumption, down.If the factory adjustments wont do it, lighten the striker and/or its spring.
Last edited by classicalgas on June 22nd, 2012, 10:00 pm, edited 1 time in total.
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