Tale of THREE BRods - .25, .30 and .357 Completed, Page 19 !

[rsterne]

I know it has been a while since I posted in this thread, but summer is an impossible time for me to work on airguns because the Motel is too busy.... During the winter, I worked with Travis and Jim designing an adjustalbe regulator to go inside their drop down tank block.... I just received one in the mail today, and it is gorgeous....



I got both tank adapters, one for 5/8"-18 UN threads, and one for 18 mm x 1.5 mm threads, so I can use any tank.... The burst disc is on the output side, and is a 3K, as I won't be using more than about 2200 psi.... However, I understand the output can be adjusted higher than that, depending on the Bellevilles installed....



It has room for two gauges, the upper one reads output pressure, and the lower one tank pressure.... The adjusting screw is an allen set-screw on the bottom of the block.... It moves the HP seat towards the piston (CW) to reduce the output pressure and away from the piston (CCW) to increase it.... I can't wait to try it out on the tube I have the Cothran valve installed in.... It will be the perfect arrangement for that, because you must adjust the pressure to adjust the velocity....

Bob

[Dairyboy]

Those look awesome! Very excited to see the results!

[Sfttailrdr46]

  Looking good Bob Can't wait to see some results . How can it be busy I thought you only had three guests a year in the busy season way up there in the middle of nowhere   

[YEMX]

 

[rsterne]

That would be three rooms full, almost every day, right now.... all my wife and I can do to keep up....

Bob

[grand-galop]

I know it has been a while since I posted in this thread, but summer is an impossible time for me to work on airguns because the Motel is too busy.... During the winter, I worked with Travis and Jim designing an adjustalbe regulator to go inside their drop down tank block.... I just received one in the mail today, and it is gorgeous....



I got both tank adapters, one for 5/8"-18 UN threads, and one for 18 mm x 1.5 mm threads, so I can use any tank.... The burst disc is on the output side, and is a 3K, as I won't be using more than about 2200 psi.... However, I understand the output can be adjusted higher than that, depending on the Bellevilles installed....



It has room for two gauges, the upper one reads output pressure, and the lower one tank pressure.... The adjusting screw is an allen set-screw on the bottom of the block.... It moves the HP seat towards the piston (CW) to reduce the output pressure and away from the piston (CCW) to increase it.... I can't wait to try it out on the tube I have the Cothran valve installed in.... It will be the perfect arrangement for that, because you must adjust the pressure to adjust the velocity....

Bob

This will have many love from people out there..   I`m one of them..

[rsterne]

This project has been on the shelf over the summer, both for lack of shop time and because I have been waiting to received one of the new ART/SS valves to try.... The hope is that it will match the Cothran, both in performance and ease of opening.... with the added benefit of being able to adjust the velocity with hammer strike, something you can't do with the Powerhouse valve.... you have to change the pressure to change the velocity.... Anyways, the wait is over and my valve arrived today, many thanks, Travis.... 

The valve is a stock JSA "SS Balanced Valve" as they supply for the MRods.... It comes with a 3/16" exhaust port and the stock recess for the transfer port, which would not work in my BRods, as they are set up for a 3/8" OD transfer port with a 1/4" exhaust port.... Travis assured me that there was plenty of meat to enlarge the ports, and there certainly was.... I usually angle my exhaust ports about 20 deg. but with that big a port and no experience with this valve, I choose 15 deg. instead, and I'm glad I did.... At 20 deg. with a 1/4" port, I think I would have broken into the back of the valve and ruined the seat.... The valve throat is 0.281", which works out to the same area, once you subtract the 1/8" stem, as the 1/4" exhaust ports.... This is the same size throat as what I had on my modded MRod valve with the PEEK poppet, but the area is smaller than the Cothran valve.... I didn't want to drill out the throat at this time, but I did blend the new 1/4" exhaust port into the throat with a spherical Dremel burr.... There is certainly lots of port area for lots of flow....

I got the valve installed in the tube for one of my BRods and it seems to be holding pressure.... I will leave it overnight and plan on doing extensive testing tomorrow, tethering the gun at 1900 and 2900 psi in both .25 and .30 cal to get the baseline preload curves and assess what the opening forces are like compared to the Cothran valve and my modded MRod valve.... This should be FUN !!!

Bob

[shorty]

Super interested in the results.....

Most importantly the hammer weight,spring rate or force, and efficiency. Definitely would like to know how much you shoot below reg pressure before the valve/hammer bounce) runs away "if it does" and pulls a pressure dump.

Almost forgot to ask what port/jet size is being used in the valve.

[rsterne]

Here is the first set of results for my BRod .30 cal with the ART/SS valve installed.... I tethered it at 3000 psi (a more accurate, digital gauge says my regulator was not set for 2900 as I previously thought), and tried the 50 gr. JSB/Daystates and also the 67 gr. NOE BBTs.... I tried all the SSG settings from maximum preload (way too much), through zero gap, to 10 turns of gap (over 1/2").... I then repeated the procedure with the 45 gr. JSBs and 50 gr. JSB/Daystates tethered at 1900 psi.... Lastly, I connected up my 500 cc bottle which has a regulated 1900 psi output and shot one 7-shot magazine of the 50 gr. pellets at several gap settings to find the pressure drop and calculate the efficiency.... Here are the results....



First some comments about this valve.... IT OPENS EASILY.... nowhere near the hammer strike required of my modded MRod valve.... I will be doing the same testing procedure with my Cothran valve to get an idea of the relative hammer strike required, but don't have that data yet.... It is much more responsive to changes in hammer strike than the Cothran, although still exhibits a VERY sharp velocity drop if you try and tune it for tiny sips of air (ie low velocity).... This sudden drop could well be due to the jet size installed in the inlet of the valve, I only got one with the valve, presumably a "stock" one, whatever that is.... and I can tell you it's pretty tiny.... With that tiny jet, and the huge drilled out exhaust port, I may be operating the valve outside its normal parameters.... in fact you can almost bet on it.... I hope Travis has some ideas to try and will send me some other jets to play with.... not that it really matters, I never tune my guns on the downslope anyways.... If I wanted a lower velocity, I would reduce the regulator setpoint and move back up onto the knee of the curve....

I am using an MDS hammer with a 3/4" steel core that weighs 51 grams.... The hammer spring is 0.48" OD x 3.00" long, and is made of only 0.051" wire, so has a spring rate of just 8 lb/in.... It is currently set up on the SSG with 0.60" of preload (4.8 lbs.).... and when set to zero gap, with the hammer stroke I have of 0.79" takes a maximum force of only 11 lbs. to cock the gun.... If you notice from the data in the graph, I can run the SSG gap at about 6 turns out (0.33") at 1900 psi (cocking force 8.5 lbs) and about 3 turns out (0.165") at 3000 psi (cocking force under 10 lbs) with hardly any velocity loss.... Those settings are basically at the top of the "knee".... With the 50 gr. pellet at 1900 psi, at 6 turns out, the velocity is 922 fps (94 FPE) and the efficiency is 1.04 FPE/CI.... The knee is quite long and gentle, making velocity adjustment quite insensitive, until you approach the "cliff".... Just before you get there, the velocity seems to get unstable, and the ES increases.... and then suddenly you are teetering on the edge of the cliff, where just a quarter turn more gap and the velocity tanks to under 400 fps....

The maximum performance (plateau velocity) with this valve is a few fps better than my modded MRod valve or the Cothran valve at 1900 psi.... and virtually the same with the 67 gr. BBT at 3000 psi.... but with the 50 gr. pellet at 3000 psi it was about 30 fps faster (1100 fps).... However, it also had virtually no velocity drop as you increased the SSG gap until it suddenly fell off the cliff.... almost acting like a Cothran valve.... However, this is so far out a normal condition (50 gr. pellet at 1100 fps) it doesn't really matter.... it's more an anecdote.... One other thing of note.... If I reduced the SSG gap to negative (ie introduced preload) the air consumption, report, and recoil all went "stupid".... I can only assume that the closing forces on the balanced poppet are so small that they are overwhelmed by the 5 lbs. preload on the SSG, and it increases dwell to the point the valve is still wide open when the pellet leaves the muzzle.... and YES, it's THAT dramatic.... When I was testing the pressure drop with 2 turns of preload, I actually got 640 psi of drop in my 500 cc bottle in just 3 shots.... compared to 370 psi drop in 7 shots with zero SSG gap.... Pretty much BOOM when you pull the trigger, complete with 6" or more of muzzle jump.... 

The 8 lb/in. spring is OK for use at 3000 psi, but realistically I need to either reduce the preload on the SSG, or fit an even weaker spring for use at 1900 psi.... The SSG gap is too large at that pressure, and I might find a velocity difference shooting up or downhill from gravity slowing the hammer.... This change would make the gun even easier to cock, which seems silly, as it's sooooooooo easy now.... I can tell you, I'm SURE impressed at the reduction in cocking force with the ART/SS valve.... Travis and Lloyd sure came up with a winner here.... I can see that I will end up converting all my Big Bores and bullet shooters over, to get rid of the massive, long stroke, hard to cock hammers.... Incidently, I resized a 109 gr. Lee HP in .308 cal down to 0.300", and although it was still hard to chamber, I got 811 fps with 2 turns of preload (159 FPE) at 3000 psi.... accompanied by a huge roar and muzzle jump.... Yes, this valve can move a LOT of air....

Bob

[rsterne]

Here is the data for the .25 cal BRod using the ART/SS valve.... The methodology was the same as for the .30 cal.... except the pellets used were the 25.4 gr. Kings and 34.1 gr. King Heavies at 1900 psi and a 52.7 gr. RN .25 ACP bullet at 3000 psi.... Here are the results....



The SSG gap where the gun fell off the cliff was virtually the same at the same pressure, about 7 turns at 3000 psi and 9 turns at 1900 psi.... I was using the same hammer and spring, all that changed was the upper (receiver and barrel).... This gun drives the Kings way too fast, nearly Supersonic at 1900 psi, but the King Heavies look to be a great choice at this pressure.... At 7 turns of gap (just over 3/8") the velocity is 966 fps (70.7 FPE) but the efficiency is a bit low, at only 1.01 FPE/CI.... Still, this is pretty impressive performance at only 1900 psi, and should yield about 32 shots at 70 FPE from the 500 cc bottle.... nothing to sneeze at....

As a bullet shooter at 3000 psi, the gun is solidly over 100 FPE, peaking at 115 FPE.... This is the highest FPE (by a whisker) I have seen with the .25 cal BRod at this bullet weight, and with a 60 gr. bullet would be even higher I am sure.... I didn't do any efficiency testing at that pressure, as I am short of cast bullets at the moment, and don't want to stop testing to make more.... Once again, if you crank in actual preload on the SSG, the gun roars and kicks as it blows air out the muzzle after the bullet is long gone.... It appears obvious that this valve (at least with the big ports) needs either an SSG or SSS to have any chance of behaving in a civilized manner.... It does offer some range of velocity adjustment, and the efficiency, like the Cothran valve, is best when operating just above the cliff.... However, with the ART/SS valve, that range is a lot broader and easier to tune to....

With the ART/SS valve using a 1/4" exhaust port, my BRods will be great with pellets when regulated at 1900 psi.... and are capable of shooting with bullets in both calibers at 3000 psi.... I'm pretty pleased with the results for initial testing.... I do need to try less preload on the spring to try and reduce the gap on the SSG, particularly when regulated.... I hope to get to that soon....

Bob

[PeterL]

That's some great power Bob. I know you'll wring out even more out of it.

I know you're using a longer barrels but assuming you were running this on 20" barrel with just a hair over 7/32 barrel port and valve at .250 TP, .300 throat and .047 jet on a stock Synrod tube with no depinger; how close to a 100fpe would one come after having the chance to play with the new ART valve? Curious as to what I'm seeing happening in my quest to relearning this valves behavior. Thanks.

Peter

[shorty]

Same question here.

Great info.

[grand-galop]

At 1.40 efficiency and the FPE you are at, this is now one of the best hunter I have seen... Those cast bullet are a major candidate for long shot and the energy they are at right at the top of the food chain....  BRAVO for the update and results..

[rsterne]

I reassembled a BRod with the Cothran valve this afternoon just to assess the comparison between the required hammer strike with it and the ART/SS valve.... To my surprise, the new ART/SS valve was easier to open than the Cothran....  .... Even with the preload reduced to only 0.40" (3 lbs.), the Cothran valve fell over the cliff at a 3 turn smaller gap than the ART/SS valve, with the same pellet at the same pressure.... Now BOTH these valves are a LOT easier to open than a conventional PCP valve of the same dimensions.... That is the big advantage to balanced valves, you can use huge ports, throat and poppet, and not have to end up with a gun that is impossible to cock....

I rechecked the Cothran valve, and it remains stubbornly "ON" or "OFF".... You really have no control over the velocity with the hammer strike, you need to change the setpoint pressure to do that.... Yes, the Cothran valve uses less air when tuned just above the cliff, but it cant be turned down a bit before it ceases to cycle properly and the velocity drops to near nothing.... It is when operating just above the cliff that the ART/SS valve can be tuned for good efficiency while remaining stable (unless you get too close to the cliff, as mentioned earlier).... That region with the Cothran valve is very narrow, and when you get close to the cliff the velocity becomes unstable, although if you get it just right, it also exhibits improved efficiency.... It is just way fussier to adjust than the ART/SS valve....

To make large adjustments to the velocity with the ART/SS valve (at least in my large ported version) you still need to alter the setpoint pressure.... However, having a 100-200 fps range of adjustment without changing the pressure sure makes it easier to find a suitable tune.... It seems that the heavier the bullet, the wider the velocity adjustment range.... I suspect that with a stock ported ART/SS valve the adjustment range might be even wider.... It looks like I may have to find a weaker spring to reduce the SSG gap down to the desired level when running regulated at 1900 psi.... but before I make that change, I think I will completely remove the front jet and see what happens....

Bob

[rsterne]

Peter, I don't know how the jets affect this valve, nor do I have any to play with.... You gun will be limited by the 7/32" barrel port (I am using an oblong port).... I'm surprised that you can run that big a port on a .25 cal without loading problems.... Also, you will be needing to run a bolt probe of 3/32" just to keep the chamber open enough to match that barrel port.... My .25 cal barrel is a LW 23.8" Polygonal, and I got 115 FPE with a 53 gr. bullet at 3000 psi.... You should be tickling 100 FPE with a stock 20" barrel at the same pressure.... but we're not talking a bell-curve starting at 3000 psi and ending at 2500.... but a single maximum power shot at 3000, and then descending velocity as the pressure drops....

Yes, Alain, nothing much wrong with 890 fps with the 34.1 gr. Heavy (60 FPE) at 1.42 FPE/CI on only 1900 psi.... That should be 50-55 shots on 500 cc from 3000 down to 1900....

Bob

[PeterL]

Peter, I don't know how the jets affect this valve, nor do I have any to play with.... You gun will be limited by the 7/32" barrel port (I am using an oblong port).... I'm surprised that you can run that big a port on a .25 cal without loading problems.... Also, you will be needing to run a bolt probe of 3/32" just to keep the chamber open enough to match that barrel port.... My .25 cal barrel is a LW 23.8" Polygonal, and I got 115 FPE with a 53 gr. bullet at 3000 psi.... You should be tickling 100 FPE with a stock 20" barrel at the same pressure.... but we're not talking a bell-curve starting at 3000 psi and ending at 2500.... but a single maximum power shot at 3000, and then descending velocity as the pressure drops....

Yes, Alain, nothing much wrong with 890 fps with the 34 gr. Heavy (60 FPE) at 1.42 FPE/CI on only 1900 psi.... That should be 50-55 shots on 500 cc from 3000 down to 1900....

Bob

Ok. The 7/32 barrel port doesn't interfere with loading my 55gr slugs but I can't speak for pellets as I don't shoot them in this particular setup. Also, I'm running a Gen 1 modded bolt for flow so it shouldn't be too restrictive I don't think. I ordered a few jets to play with as the one I received just was not cutting it at all. Currently I'm running a 0.0417 size jet and I can barely hit 89fpe without dumping 200psi per shot. Alternating between a stock spring and a ten pound spring with different weight MDS hammers and fill pressure. My previous ART valve was able to get me 97fpe Max but with a heavy spring(17lb). I do understand barrel length plays a part but I seem to be going backwards. Hopefully, you can get a few more jets to play with to compare all the variables.

Peter

[rsterne]

The 55 gr. slugs are probably long enough to easily bridge the barrel port, so they can't fall in while sliding past....

My jet is a # 87.5.... It is a loose fit on a 1/32" (0.03125") drill.... so I will take a guess that the numbers are 1/100ths of a mm.... because 0.875 mm = 0.0344".... I just pulled it out, leaving about a 1/8" hole, and will test that in the morning....

From my limited experience, running any preload against the hammer when uncocked may lead to excessive air use.... It certainly does with my SSG, even with only 3 lbs. of preload, once I run negative gap (ie preload) the gun gets LOUD and kicks like a mule.... I have seen it use over 200 psi per shot from a 500 cc bottle once there is preload.... It has blown the diffusers right off my Chrony, I mean I'm talking BIG TIME DWELL....

Bob

[PeterL]

Yes. No problem loading them at all. Smooth as butter.

That's the size ports mine came with. 87.5=0.0370inches. I'm currently running the 100=0.0417inches. I worked my way up to that size and was just having issues with the dwell/stability with zero pressure on the valve stem. I was thinking my issue was jet sizes being parallel to hammer weight and strike but it was just all over the place and unstable on various strings with same psi refill and same settings. However, after reading this(reply#19),    https://www.gatewaytoairguns.org/GTA/index.php?topic=137844.msg1382081#msg1382081
It summed everything up.

Peter

[rsterne]

Today I tested the ART/SS valve without any jet on the inlet side.... just about a 1/8" hole there.... I still had the preload on the 8 lbs. hammer spring on the SSG set to 0.40" (about 3.2 lbs).... I tested the .30 cal version with the 50 gr. pellets at 1900 psi (only), and realistically there was no significant difference with the jet removed.... The valve still took very little hammer strike to open it.... So, I then swapped out the MDS hammer with the steel core (51 grams) for one with an aluminum core that only weighed 27 grams.... For some unexplained reason I lost about 10 fps from the maximum velocity (which I would not tune for, it would be too inefficient).... but as expected I now needed less SSG gap to get to the cliff.... Here are the results, compared to where I started with this valve (black line)....



Changing to the 0.40" preload from 0.60" is what moved the top of the cliff from 9 turns of gap to 8 turns.... I didn't plot that curve because it essentially tracked the black line except for the earlier cliff.... You can see that with no jet installed (purple line) there was less of a "knee" to the curve.... still some, but there was less velocity adjustment before you got to the cliff.... The same setup but with the 27 gram hammer (the orange line) shifts the cliff to only 5 turns of gap, but I can still reach the plateau with 1 turn of gap.... This gives me an adjustment range of 4 turns, and makes the amount of gap where I would adjust the gun just about where I like to see it.... around 1/8"-3/16".... The only way to reduce it further would be a lighter hammer spring, or reducing the hammer stroke.... I can actually DO that with the aluminum cored hammer, as it has a steel setscrew insert for the striker (currently set flush).... One other thing I noted with the very light hammer.... The range of velocity adjustment between plateau and cliff increases significantly.... leading me to believe that light hammers and this valve would be a great combination....

I did one "efficiency run" by shooting one 7-shot magazine with the velocity set to just over 900 fps with both setups.... Small changes in the exact velocity make big changes in the efficiency at around that velocity with these big ports.... but essentially I believe there is little difference in the efficiency if the velocity is the same with the jet removed.... HOWEVER, it does give you less velocity adjustment just above the cliff, and if you are tuning for efficiency I think you would struggle to get the best combination of power and air usage without the jet.... If all you are interested in is pure power with a light hammer strike, however.... this valve is a BEAST.... It requires MUCH less hammer strike than even the Cothran Powerhouse valve in the testing I have done so far.... I'm impressed.... 

Bob

[shorty]

Super interested in the results and the data collection.

 Say, I would really like to put your SSG settings and valve jet size into minitab for a 2 level factorial design to see if it can predict what would be the best setting (jet size and ssg setting) for a desired power level and efficiency.

I think you have enough data collected for me to run predictions. I would be looking for a fixed caliber with a High/low SSG setting and High/Low jet size. Looks like you have the jet size High/low and the SSG setting High/low.

If you can or would, is there a chance you can hook me up with a table so I can run the numbers. If so, and if the program works, I may be able to map the valve at any SSG setting,jet size, for any power level and or efficiency.

If not, that's ok too. Thanks in advance

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