GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: FuzzyGrub on January 15, 2022, 01:26:39 PM
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I needed another Mrod valve to finish a project. Having seen some pictures of the SAM valve along with some measurements that were shared, thought that this would work well for one of my aftermarket reg'ed Mrods. I had roughly calculated about an 8cc gain over a "standard" Mrod valve. The part # is SAM-100 and cost $25.55 which about the same as the "standard" valve.
It uses a "C" clip style retaining the valve spring, poppet and spring guide, like many aftermarket valves. It has "reliefs" for trigger assy screw, for use in Gen 2 and Gen 1 Mrods. The breech screws, valve exhaust, and valve screws, all line up, too. There is a ledge on the back of the valve. On the SAM an O-ring goes there, and believe that it helps with an air cushion, to assist with the hammer bounce, re-cocking method used on it. It is not needed for what I plan.
It uses the "standard" delrin crosman poppet. Porting is equal to standard valves, with the exception of the internal body. On Mrod valves, I would use a 0.495" reamer to give a little more plenum volume. This valve is already there. The exhaust is 0.145" with the pocket below the poppet at 0.200", and inlet cap ID is 0.275".
The valve spring is shorter and stiffer than the standard valve. While the poppet stem extends out the same at 0.25", it goes to coil bind before the poppet end reaches the back of the valve. This is most likely because of the SAM cocking method and much heavier hammer than a standard Mrod. I'm planning to use a lighter spring and may bore the cap/spring retainer for a little longer one. Valve spring is made from 0.055" wire, with 0.360" OD by 0.740" length.
The SAM valve is 0.700" shorter than a "standard" valve, and doesn't have the threading and screw in cap, which save precious volume. I don't have a stock valve out of a gun to do that comare and more refined calculation. But will provide in the future.
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Looks like it would work as long as Breech screws line up should be fine may want to do your spring mod you were talking about
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It would take some measurements to know for sure, but it looks touch and go on that working in a Gen I tube - the forward trigger screw looks like it will be very close to the o-ring . . .
Of course I know John has the parts to measure and say for sure!
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The part # is SAM-100 and cost $25.55 which about the same as the "standard" valve.
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Where did you get the valve? OK to PM if you don't want to advertise source. Thanks :-)
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The part # is SAM-100 and cost $25.55 which about the same as the "standard" valve.
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Where did you get the valve? OK to PM if you don't want to advertise source. Thanks :-)
Can't you just order from crosman like all the other parts?
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Wow that valve is much shorter, definitely looks like it saves some volume, but for me wouldn't work unfortunately due to me using p-rod trigger assembly on my m-rod.
Seems like there is some potential here for those running regulated mrods that want more volume, look forward to more analysis.
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The part # is SAM-100 and cost $25.55 which about the same as the "standard" valve.
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Where did you get the valve? OK to PM if you don't want to advertise source. Thanks :-)
Ordered from crosman customer service. Use part number above. 1.800.724.7486
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It would take some measurements to know for sure, but it looks touch and go on that working in a Gen I tube - the forward trigger screw looks like it will be very close to the o-ring . . .
Of course I know John has the parts to measure and say for sure!
Yea, I didn't check it for distance. I don't have a gen 1 tube here. Not sure what the 2nd relief would be for, though. I will give you some measurements. ;)
PS: The SAM uses a different trigger assy then G2 or G1. It might have a different screw location then G2. I'll check that, too.
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The part # is SAM-100 and cost $25.55 which about the same as the "standard" valve.
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Where did you get the valve? OK to PM if you don't want to advertise source. Thanks :-)
Ordered from crosman customer service. Use part number above. 1.800.724.7486
Thanks. Was briefly confused. The EVP I was looking at was not the right one and it said "Parts not available from Crosman".
Am familiar with phone ordering parts from Crosman and will put that PN on my next shopping list.
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Wow that valve is much shorter, definitely looks like it saves some volume, but for me wouldn't work unfortunately due to me using p-rod trigger assembly on my m-rod.
Seems like there is some potential here for those running regulated mrods that want more volume, look forward to more analysis.
The project I needed another valve for is using a Prod trigger assy w/Lloyd's sear. It was not planned for that though, and have to play musical valves with another gun. It will be going in a 25 cal that is regulated. It would not work given where I drilled and mounted the Prod trigger on the G2 tube.
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Thanks. Was briefly confused. The EVP I was looking at was not the right one and it said "Parts not available from Crosman".
I have seen that in a few EVPs, but as of yet, haven't found that to be true. ;)
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Wow that valve is much shorter, definitely looks like it saves some volume, but for me wouldn't work unfortunately due to me using p-rod trigger assembly on my m-rod.
Seems like there is some potential here for those running regulated mrods that want more volume, look forward to more analysis.
The project I needed another valve for is using a Prod trigger assy w/Lloyd's sear. It was not planned for that though, and have to play musical valves with another gun. It will be going in a 25 cal that is regulated. It would not work given where I drilled and mounted the Prod trigger on the G2 tube.
Ah so we share the same pain to a degree, cause ya my aluminum tube is drilled/tapped for the prod.
Wonder if there is more meat between valve seat and tp on this valve?
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The standard valve has a 1/4" ID inlet, and calculated 0.56 cc's.
Using the ID of the tube of 1.050", calculated 9.9 cc's.
A 1" aluminum spacer calculated to 2 cc's.
So the gain is 7.34 cc's.
The two relief's are for the two G2 trigger assy screws.
No extra room for bigger exhaust ports. Measures same as standard valve. I was hoping for that too. ;)
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Doing the porting is easier when you can see a little better. :) I went to 0.187" porting.
Now I did find something that is unique to the SAM valve. The poppet stem hole is slightly larger than the standard valve. A number drill that I measured as 0.126" will slide easily into the SAM valve, but is very tight to even start in the standard valve. I checked three standard valve bodies and they were all the same. This leads me to believe that crosman is using some of the air leakage to help cock the hammer, not just hammer bounce.
Now I have to decide on:
- Sleeving the poppet hole with brass tubing
- Saving it for the SAM future mods
Leaning toward the 1st, because porting is more than I planned for the SAM.
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What do you suspect the od of the stem hole is? Would have to be a decent gap to have any significance in helping re-cock the hammer, and the area to which it leaks would have to be air tight to hold that pressure, and ideally be of very little volume, all that said, curious what the OD is.
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There is an O-ring that goes on the back of the valve and from what I understand, the air tube has reduced length slots. I thought that they were just using an "air-cushion" to assist. But this leads me to some air assist.
The valve is in a short rai tube for leak check, ie make sure I didn't nick the seat. Outside of the number drills, don't have a better measuring tool for small holes. What I first noticed was the wiggle in the poppet. My estimate is that it is about 0.002" larger diameter, than standard valve.
The brass tubing I have is not much tighter in fit, so will hold off on that. I do see some that should be better fit. I just might end up trying it to see how much blow-by there is, before sleeving.
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.002 is negligible for blow by, during the valve operation of 1-2 ms that has a chance to flow a really low amount.
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I hope so, but if not, have a path to make it less.
I went forward and made the spacer. The tube is installed and pressurized and will sit overnight for a leak check.
I did find a lighter valve spring. I forgot to write down the specifics, though. ::)
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Wouldn't this mess with the position of the gauge block? I mean it's not super hard to work around that but just something to consider, you may need to make a spacer or just delete the gauge.
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Yes, I made a spacer from 1” aluminum tubing, 0.7” long.
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I'd hog out the gauge block or get a hill are you going to regulate it ?
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I'd hog out the gauge block or get a hill are you going to regulate it ?
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Yes, this is going in a Mrod that had the 25 cal Huma w/gauge port. There is some meat there that could net a few more cc’s.
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If you get the Huma external regulator tester and their quickfill gauge you could just extend the spacer tube and delete the stock gauge entirely. If you're chasing max plenum volume that would be the best route.
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If you get the Huma external regulator tester and their quickfill gauge you could just extend the spacer tube and delete the stock gauge entirely. If you're chasing max plenum volume that would be the best route.
Chasing max would be going this route
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Id go with hill Guage fitting they are opened up a lot and could add a spacer in front of it to gain more plenum will be able to see your set pressure then bypassing gauge wouldn't really gain a lot more over the hill gauge block they are hogged out pretty good already just a suggestion
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I agree with pike if you want to push it add the external plenum
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Yeah I mean an external plenum works but that kind of defeats the purpose of the SAM valve mod too... like if you're strapping a bottle to the outside of the gun anyway then 8cc from a shorter valve isn't that big a deal. I'm just talking about max plenum volume in a stock package.
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I understand that the gauge block is shorter as well. Would you lease post If you have the part number for the gauge block?
I put a huma into my Field and Target, but it required a 30 mm plenum. If this valve and gauge block are available, then the standard 40 mm plenum might just fit.
Hunter
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I understand that the gauge block is shorter as well. Would you lease post If you have the part number for the gauge block?
The gauge block part number is # SAM-103
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I wanted to tune this one for 50-55FPE w/34g JSB, so needed a little bigger plenum, without eating into the air res. Aluminum tubed that will go in a Turkish Walnut stock.
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I wanted to tune this one for 50-55FPE w/34g JSB, so needed a little bigger plenum, without eating into the air res. Aluminum tubed that will go in a Turkish Walnut stock.
Yeah I mean an external plenum works but that kind of defeats the purpose of the SAM valve mod too... like if you're strapping a bottle to the outside of the gun anyway then 8cc from a shorter valve isn't that big a deal. I'm just talking about max plenum volume in a stock package.
The sam valve inside a non-sam is not a 'stock package' technically. 8 cc from a shorter valve for me would be a lot even with my already present 53 cc's of volume, I'd take another 15% increase, sadly I cannot as this won't work in my 'stock package', without additional parts...
I see no point removing the gauge on a gun, how many cc's would that even provide? I was just poking fun in how backwards your thinking was anyhow...I am not familiar with people removing pressure gauges to gain 1-2 cc.
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The field target air tube is 2 inches longer than standard mrod, I'm pretty sure that the SAM is also.
This tube should fit the Turkish Walnut stock, right?
Hunter
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The field target air tube is 2 inches longer than standard mrod, I'm pretty sure that the SAM is also.
This tube should fit the Turkish Walnut stock, right?
Hunter
There is a specific Turkish walnut stock for the F&T / SAM, because the gauge is in a different location. Call crosman and talk to Cs.
What I'm working with, is an aluminum tube that is the same as the standard tube.
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I wanted to tune this one for 50-55FPE w/34g JSB, so needed a little bigger plenum, without eating into the air res. Aluminum tubed that will go in a Turkish Walnut stock.
Yeah I mean an external plenum works but that kind of defeats the purpose of the SAM valve mod too... like if you're strapping a bottle to the outside of the gun anyway then 8cc from a shorter valve isn't that big a deal. I'm just talking about max plenum volume in a stock package.
The sam valve inside a non-sam is not a 'stock package' technically. 8 cc from a shorter valve for me would be a lot even with my already present 53 cc's of volume, I'd take another 15% increase, sadly I cannot as this won't work in my 'stock package', without additional parts...
I see no point removing the gauge on a gun, how many cc's would that even provide? I was just poking fun in how backwards your thinking was anyhow...I am not familiar with people removing pressure gauges to gain 1-2 cc.
Look I'm not going to get into an argument with you about this. By stock package I just meant the form factor, not completely stock, otherwise you couldn't use the HUMA reg. I guess I should have said form factor so I'm sorry that I confused you.
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So I dug out a Gen I tube to get a measurement to see if this valve would work in that generation . . .
The distance from the centerline of the valve mounting hole and the forward most edge of the forward most trigger group hole (closest to the muzzle) is right on 50 mm (1.97 inches), give or take a few tenths of a millimeter as I was eyeballing the center of the mounting hole.
From looking at the pictures, I doubt that will work - it looks like the valve to tube o-ring is inside of that, or very close. That would put a hole into the air reservoir. That said, it might work in a regulated way if one were to have a plenum that covered that space . . . .
Hopefully John can report the measurement on the valve and we can know for certain.
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Alan,
I'll check the next time it is out of the gun, but believe you are correct, it will NOT work in Gen 1 Mrods. It looks like the two reliefs in the valve are in leu of the slot (slight machining savings?). Both are for Gen 2 trigger assy screws.
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I had installed this back in the 25 cal gun. Porting, springs, hammer, etc the same as before. I seem to be getting hammer bounce at spring tensions I didn't before. I validated with crosman that the poppet stem leakage was by design for the SAM. I took it back out.
While contemplated sleaving or adding an O-ring, remembered getting a spare poppet for the Akela. These poppets are HUGE compared to the Mrod. They incorporate an O-ring on the stem, and have a tapered sealing surface. This then jogged my memory of some Mrod valves I was trying to modify for large 0.200" - 0.220" ports. These were valve bodies that had gotten ruined in early modification "learning" experiences. ;) I had bored them deeper and was going to make a plug/higher seat. But this would need a new poppet, so I had stopped at that point.
Taking some measurements, the Akela poppet looks like it will work for that. It has a longer stem than the Mrod. Anyway, I'm midway through modding a standard Mrod valve for this. As always, a challenge for caveman tools. If it seals and holds up, I'll do the same for the SAM valve.
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All - The SAM pressure tube moves the regulator and gauge port farther away from the valve for more plenum. It also has a short gauge port for the same reason.
The SAM valve stem hole is around .132" I cannot remember off the top of the head. The increased size helps to blow the hammer back.
John
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It sounds like the stem hole is larger than I thought. ::)
Finished up the test valve today. Aired up and no noticeable leaks. A big plus. Tomorrow, should be able to take some test shots. If it fails, it will be an underwear changing moment. ;)
The plug that was epoxied in yesterday.
The poppet OD taken down from 0.452" to 0.370" with slight taper toward spring end.
Exhaust port opened to 0.200" and counter sunk.
Made Delrin tubing transfer port with ID of 0.200".
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If the stem is a tighter fit I'd ditch the oring it can mess with extreme spread just my opinion
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interesting , thats one classy looking valve in the sam
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If the stem is a tighter fit I'd ditch the oring it can mess with extreme spread just my opinion
+1
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If the stem is a tighter fit I'd ditch the oring it can mess with extreme spread just my opinion
+1
If high Es is my only issue today, it will be a good day. ;)
The “donut” was under vice pressure while the epoxy set and cured, but whole different thing when it is 2-3k psi and the dynamics from shot to shot. I did use the "steel reinforced" epoxy which has the higher rating of 5000psi.
I will say, the stock poppet when in Akela, produces some of the lowest non-regulated Es I’ve seen. Very different dynamics though.
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If the stem is a tighter fit I'd ditch the oring it can mess with extreme spread just my opinion
+1
If high Es is my only issue today, it will be a good day. ;)
The “donut” was under vice pressure while the epoxy set and cured, but whole different thing when it is 2-3k psi and the dynamics from shot to shot. I did use the "steel reinforced" epoxy which has the higher rating of 5000psi.
I will say, the stock poppet when in Akela, produces some of the lowest non-regulated Es I’ve seen. Very different dynamics though.
The reason your Akela or any gun with a thicker than 1/8 valve stem can achieve a very low ES relative to a 1/8" stem is because the added closing force that occurs over the duration of the valves dwell...it absorbs minor fluctuation of hammer energy better than a stem with less force acting on it over that time period (think of a pellet in the wind and time as a factor just as much as your stem and pressure acting upon it with dwell).
Makes me wonder how a balanced valve with a 9/64" valve stem would perform, and if that would potentially reduce the variation caused be 'break-out friction'. Then again, thats off subject, but just food for thought for any who reads.
Thicker valve stems (ideally not in the throat, only in their bore) also respond to hammer strike changes much less than thinner valve stems, meaning it takes more preload to go up or down 100 fps on a thicker valve stem then a thinner one. These two MAJOR 'effects' are due to the 'cause' of the valve stem.
Assuming the stem + oring are the od of the bore as mentioned earlier, .132" has around 10% more force acting upon it than a .125" stem.
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I shot three mags and no big surprises, with the test valve. :) I'll keep shooting it, to get a few hundred cycles on it, before starting work on the SAM valve. There are a couple of things I will do differently, process wise, and it will also be a little easier given the shorter depth.
Yes, it will need more hammer energy, but thought most of that would be because of the larger diameter sealing surface. I wasn't aware that stem diameter also plays a role. The Akela poppet stem is 0.195" at the large diameter, and a smaller diameter of 0.155" at the flow path. I opened the poppet hole for the larger diameter stem. From my test shots, I'll be going up on hammer weight.
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I shot three mags and no big surprises, with the test valve. :) I'll keep shooting it, to get a few hundred cycles on it, before starting work on the SAM valve. There are a couple of things I will do differently, process wise, and it will also be a little easier given the shorter depth.
Yes, it will need more hammer energy, but thought most of that would be because of the larger diameter sealing surface. I wasn't aware that stem diameter also plays a role. The Akela poppet stem is 0.195" at the large diameter, and a smaller diameter of 0.155" at the flow path. I opened the poppet hole for the larger diameter stem. From my test shots, I'll be going up on hammer weight.
From my experience with the akela the hammer is already too heavy. The Kral hammer is 45gr and will do 60 shots in 22 at 30+fpe the akela hammer from my gun iirc was like 60gr. Both using the same valve, poppet and stem.
Edit: I thought you were comparing missed the part where you installed the akela stem in an m-rod valve.
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Edit: I thought you were comparing missed the part where you installed the akela stem in an m-rod valve.
No problem. :)
I would like your opinion on why you think they went with such a large poppet on these guns given the small caliber. Faster closing time? or just over-built to prevent breakage?
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.195 stem in the bore is massive, holy. that explains a really nice ES ;)
A bit excessive but really drives my point home on how much stem diameter plays in taming ES (talking to you balanced valve guys)
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I hadn’t been following this thread but will now. The stem diameter’s influence on closing force and ES has come up from time to time but so
infrequently that it seems to be largely overlooked as a tool when modding and tuning. Especially when the goal is to squeeze out those last few FPE, it’s tempting to go ever smaller with the stem.
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The kral valve is an Evanix Rainstorm clone so I doubt much thought was given other than the material. They did reduce the throat from .300 to about .275 on the newer guns as well but haven't done a direct comparison on what that means. It definitely cracks easier but I don't see a huge difference in ES between the two styles.
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.195 is bigger than alot of transfer ports are I'd sleeve it to .125 and not look back
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For now, I'm stuck with this poppet. I would have to make a custom poppet to replace it. So, for supporting a 0.200" dia exhaust port, what should the pocket dia should be? Ie should the cross-sectional area be 10-20% more than the exhaust?
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For now, I'm stuck with this poppet. I would have to make a custom poppet to replace it. So, for supporting a 0.200" dia exhaust port, what should the pocket dia should be? Ie should the cross-sectional area be 10-20% more than the exhaust?
Sleeve it and make a custom poppet, imo they are quite easy to make, and white delrin is stronger than black by about 20% fwiw, its what I use if going delrin, and can be had cheaply at grainger for 1-2$ per foot.
Black delrin yield: 9k psi
White delrin yield: 11k
Peek yield: 16k
For a .2" port, the throat should be .26" if your stem OD in the throat is .155" as you stated earlier.
Pretty nuts.
I would sleeve the poppet bore to .125", make a custom poppet, have it be around .11" at most in the throat...then your throat would only need to be .234", which will be a lot easier to crack than the above version. I got an extra long 1/8" drill bit from Harbor freight for around 5$ that can make about 8-10 poppets (12 inch drill bit lol)
So the above can be done really inexpensively, just a bit of time.
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I've used a chunk of cold rolled 1/8 in steel round bar from hardware store for poppet stems working good
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For a .2" port, the throat should be .26" if your stem OD in the throat is .155" as you stated earlier.
I'm at 0.263", which is about 12% larger cross-section. When I saw Troy's comment about the valves having 0.300" and 0.275", got me wondering.
I have some peek and black delrin, but would need to get poppet stems. This poppet has a taper on the sealing surface for an edge seal. Not sure I could do a good job of the taper with caveman tools.
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No need to get fancy mine are just press fit into peek a couple thousandths and clean them up with some sand paper and drill then polish .002 .003 under 1/8 inch isn't going to cause a big enough leak to worry about for short time it is open
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Derlin is pretty forgiving when it comes to sealing up but I understand your worry
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The other things I've done is turned down the old poppet stem using a drill press and a file takes a bit to get it right though
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That was before I got a lathe though
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If throats already .263" then its pretty settled to handle that thick stem in the valve throat.
That said, with a .125" stem, the .263" throat could handle porting up to .225" which is where I have my valve, but I use .234" throat and a .055" stem lol with peek on the poppet. Super easy to crack for the power it pushes out on traditional valve. Of course that kind of porting takes oblong work and about 10 degree offset angled to the back of the valve, and a bit of breech widening for a custom tp, but theres enough room to have healthy walls on a tp that fit snug in the valve/barrel inserts which Iirc are around .28", leaving .02"-.025"~ for your tp walls.
Its a limit pusher but mines held up great for the last 2 years.
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I've went down to .080 on my Marauder 25 and had no problem with it at one time I remember reading some one running a stem down to .040 on a marauder and was having good luck with it
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If throats already .263" then its pretty settled to handle that thick stem in the valve throat.
That said, with a .125" stem, the .263" throat could handle porting up to .225" which is where I have my valve, but I use .234" throat and a .055" stem lol with peek on the poppet. Super easy to crack for the power it pushes out on traditional valve. Of course that kind of porting takes oblong work and about 10 degree offset angled to the back of the valve, and a bit of breech widening for a custom tp, but theres enough room to have healthy walls on a tp that fit snug in the valve/barrel inserts which Iirc are around .28", leaving .02"-.025"~ for your tp walls.
Its a limit pusher but mines held up great for the last 2 years.
Sent you a PM
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I've went down to .080 on my Marauder 25 and had no problem with it at one time I remember reading some one running a stem down to .040 on a marauder and was having good luck with it
Ya thats me, I try to keep the minimum od to .05" now, the .04" I had in my Marauder was fine but I changed to .05" when changing to a .225 ported valve over a .212 valve. Old poppet was .25" OD and didn't work out on a .234" throat/seat, so redid poppet at .275" with a .05" stem. I like to push limits though, and that is extreme. Although now that I've had it running for a few years without fault, I would recommend anyone take all stems down to in the throat for airflow and to allow larger porting on smaller throat od's, but one must consider your intended hammer energy levels / force holding the valve shut ect, but nominally I can see .045"-.075" working fine for most applications till you approach really high power levels, at which point you should balance the valve, which would bring you back within aforementioned usable stem od margins.
Anyone that has gone down that road tends to not go back as its value has plenty merit in our application. I consider it a part of the process in making a poppet just as much as any other step.
A large valve stem in the throat has unnecessary volume which not only requires larger seat diameters that increase hammer energy requirement, it also deflects more of the air path than the smaller counterpart, think of the stem as having a thin layer of skin that no air can travel over, the thicker the stem the more surface area the skin has. As marginal as the difference is, most of us will take an fps or two when we can even by finely tuning our air paths to the best of our ability where we can. It creates a slightly more efficient air pathway.
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I did find a couple of pieces of steel rod that someone gave to me for poppets. It is only 0.076" dia, and don't have brass tubing that small.
The test valve is set, but the mods to the SAM valve are not final.
Matt, I'm curious to the power level that your 25 valve achieves.
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My raw valve is .260 ish throat and .325 peek poppet about 55 cc with power plenum running a .123 ish stem in the throat cobra chamber mod also at 150 bar it was over 950 fps with Huma reg at 125 bar I'm running 905 fps with barrel being choked point at .200 port so 60 ftlbs at 62 shots with 34 gr jsb mk2 pellets it isn't the greatest efficiency but it does ok I also lightened the hammer to 60 grams from the original hammer if I pushed it I bet I could get to just over 1000 fps about at 150 bar but I don't need it so I don't
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Pike what kind of power and efficiency out of yours being more well versed in this are you getting I'd be interested too seems like you know your numbers really well which has me intrigued
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I did find a couple of pieces of steel rod that someone gave to me for poppets. It is only 0.076" dia, and don't have brass tubing that small.
The test valve is set, but the mods to the SAM valve are not final.
Matt, I'm curious to the power level that your 25 valve achieves.
For the stem bore I wouldn't go under 7/64 myself, going down from .195" to .125" will take a huge load off (half the force acting upon the stem during valve open), but on an unregulated gun will reduce the bell curve / psi range.... and only reduce the stem to .076" inside the throat where its exposed to port pathing. Really depends what you want out of the gun. If going regulated you can go further.
Pike what kind of power and efficiency out of yours being more well versed in this are you getting I'd be interested too seems like you know your numbers really well which has me intrigued
This was the last string I ran, all my guns data is on here. I am running 140 bar now though with a bit more power (66 fpe peak) where as this one was 135 bar~ or so with 63~ fpe peak.
(https://i.ibb.co/q5L6Xmh/26230748-10159792475860057-5167189840025115594-n.png) (https://ibb.co/YZ4gYfJ)
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THX Matt, That is quite the spreadsheet. Nice! 8)
I'm targeting low 50's
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THX Matt, That is quite the spreadsheet. Nice! 8)
I'm targeting low 50's
Thanks.
I'm doing that 60 fpe on a 7.7 lb spring with .6~ preload and a 49 gr hammer. 4.6 lbs cocking force to start, 11.165 lb finish. Very reasonable for a traditional valve making that kind of power.
If I were to target low 50's I'd run the same exact setup as I have now at 125 bar, valve would open a bit easier and probably get nearly 32 shots on a fill from 3250~ (about where I fill my mrod). Its attainable.
One of the key features I like about large ports, is you can really extend your usable psi range with those valves by running lower regulated pressures than a smaller ported counterpart, which frees up usable psi. Without a retracting probe, the largest I could go was .225" on an mrod with gen 1 style bolt modified.
Our air path flow rate variables are effected primarily in the following order
1) Port pathings (diameter)
2) Pressure
3) Bends (not relevant to as we don't add or remove bends but their presence greatly effects flow rates)
4) Obstruction efficiency in airway (valve stem and bolt probe)
Any drop in diameter from bore causes flow loss, the further from bore diameter you get, the more you have to raise pressure to start making back the power you had before, and vice versa, if one were to reduce pressure in a valve, you'd want to increase the port size to regain the flow rate, or vice versa (a pressure increase requires reduced pathway to retain same power).
So at least in regulated applications, it really is only beneficial IMO to have your ports as large as reasonably possible, regardless of desired power.
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Yes, I am currently gated at the bore with the standard G2 25 cal bolt which has a 0.160" probe. I was going to sleave a 22 cal bolt which has a 0.125" probe. I do have a G1 25 cal flow through bolt, but it would seem to need some considerable grinding to get to the equivalent cross-section area. This will be just a pellet shooter, JSB 34g.
Any retracting bolt would need some machine work to the breech, which would be a "big" challenge given my tools.
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While the "plugged" test valve hasn't failed yet, decided to take advice and not do that to the SAM valve.
I sleaved the poppet stem hole with some brass tubing. Reduced the oem poppet stem to 0.100" below the poppet seat, for the 0.225" pocket. Oblonged the exhaust from the pocket to a 0.200" TP. Kinda like a three sided funnel to stay away from the oem seat. Valve countersunk to 0.26", like the test valve.
I did order some 1/8" steel rod to try a peek poppet in the future.
PS: I put the info in the spreadsheet and will take the poppet stem to 0.080", as Mark did, to get 10% greater than the TP cross-section.