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PostPosted: Mon Dec 10, 2012 11:10 pm 
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I did some experimenting at 1550 psi (couldn't be bothered resetting the reg to 1600).... I had to swap out the QB hammer spring for a weaker one as I couldn't dial it to a light enough hit.... The new spring is 2.0" long made from 0.045" wire.... I tried three different stroke lengths, with the following results....

Image

What is interesting is that at maximum stroke, the velocity DROPS as you increase the preload to maximum.... The only thing I can think of is that the hammer is hitting the valve with enough force (less air pressure, remember) to rebound off it, shortening the dwell and reducing the velocity.... At one turn out from maximum stroke, the velocity has it's normal "plateau" or nearly so, and since I am going to be detuning the spring preload the hammer should never come in contact with the valve.... so that is the setting I used for the remainer of the testing....

I filled the gun to 1600 psi and bled and disconnected the fill whip so that the gun was operating on only the 28.5 cc of air inside the valve for the next tests.... The maximum velocity for a single shot at that pressure was 922 fps (48.0 FPE) with the 25.4 gr. JSB Kings.... That compares to 836 fps (39.4 FPE) at 1500 psi with the previous Carbine pumper I built recently.... so I've picked up over 20% in FPE with the longer barrel, bigger valve, larger ports, and a 100 psi increase in pressure.... I didn't spend much time trying for a two-shot setup, but I did manage 2 shots within 5% averaging 44 FPE at an efficiency of 1.0 FPE/CI.... I did play around until I got a good 3-shot tune at 38 FPE (808/834/813 fps) with an efficiency of 1.21 FPE/ CI.... That compares to the 3-shot tune at 31 FPE with the Carbine at 1400 psi with an efficiency of 1.10 FPE/CI....

I then filled the gun to 1800 psi and repeated the above procedure.... I never tried for maximum velocity, but I got 2 shots at 45 FPE with an efficiency of 1.00 FPE/CI.... and a 3-shot tune of just over 40 FPE (835/868/840) with an efficiency of 1.13 FPE/CI.... Those three shots used exactly half of the air in the valve, the ending pressure was 900 psi.... The setting required was about 4 turns out from coil bound with the 2.00 " x 0.045" wire spring, and the travel was 1 turn less than maximum....

Considering these are just preliminary results, I'm very pleased.... I have no idea yet how many pumps (or how hard) it will be to get to 1800 psi.... but based on the extra leverage the effort should actually be less than to reach 1500 with the Carbine.... I've won't be doing any pumping until the stock is finished and installed, which is 4 more days of oiling and sanding....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
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PostPosted: Tue Dec 11, 2012 12:03 am 
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How many pumps does it take to reach 2000 psi with the pump arm / piston (and not an external source like HPA fill unit or HPA hand pump)?

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PostPosted: Tue Dec 11, 2012 1:07 am 
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You didn't read the last line....

Quote:
I've won't be doing any pumping until the stock is finished and installed, which is 4 more days of oiling and sanding....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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 Post subject: Testing at 1800 psi
PostPosted: Tue Dec 11, 2012 10:46 pm 
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I measured the pump leverage on the extended Billet linkage compared to the stock linkage I used on the Carbine.... When you measure from the main pivot to the center of your hand, the new gun is 16.5" compared to 12.5" on the Carbine.... Since the pump stroke is the same (and the link pivot in the same place), that means this rifle should require the same effort at 2000 psi as the Carbine did at 1500.... The 3-shot tune I had on the Carbine started at 1400 psi, so I decided to tune this gun for a 3-shot string at 1800 psi.... Once I made that decision, and based on the previous testing, I went through a series of RVA settings at various hammer stroke lengths at 1800 psi to develop a baseline....

Image

I observed the same strange behaviour as previously at maximum hammer travel, so I took some measurements.... It turns out that when the hammer is adjusted for maximum stroke length, it can only open the valve 0.10" before it hits the back of the valve body.... Under normal operating conditions, this is not an issue, but a combination of maximum hammer stroke plus maximum hammer spring preload causes this collision to reduce the dwell, and hence the velocity.... However, since I would never run this gun at over about 950 fps (wasteful of air) I can run the maximum hammer stroke without a problem.... Each turn less on hammer stroke requires about a half turn more preload on the spring.... This increases the cocking effort and the load on the sear, and is likely to increase the possibility of hammer bounce.... so I maxed out the hammer stroke (to minimize the preload) and started looking for suitable tunes....

I wanted three tunes, one with a single shot at high power without wasting too much air.... a second one where you had two shots of equal velocity.... and the main one I was interested in, a 3-shot tune where the three shots were within a 4% maximum ES.... Here are the results, using 25.4 gr. JSB Kings....

Image

The graph shows the velocity of the following shots so you can see what is happening.... The single high power shot worked out to 951 fps (51 FPE) and used 500 psi of air (0.85 FPE/CI).... The 2-shot string was 898 fps (45+ FPE) and used 730 psi (1.04 FPE/CI).... The 3-shot string averaged 846 fps (40+ FPE) and used 900 psi (1.12 FPE/CI).... If you needed a 4th shot, it would be about 725 fps (30 FPE), plenty good enough for a close follow-up or Coup de Gras....

How does this compare with the Carbine I built previously?.... That gun maxed out at 837 fps (40 FPE) for a single shot, delivered two at 796 fps (36 FPE) , or three shots at 739 fps (31 FPE).... so I've picked up about 100 fps and 10 FPE across the board.... To say I'm pleased would be an understatement.... Another couple of days of oiling and sanding the stock and I'll be able to try pumping this beast....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Tue Dec 11, 2012 10:56 pm 
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Location: quebec
Another couple of days of oiling and sanding the stock and I'll be able to try pumping this beast....

and to show us ,, :lol: :lol:

How does this compare with the Carbine I built previously?.... That gun maxed out at 837 fps (40 FPE) for a single shot, delivered two at 796 fps (36 FPE) , or three shots at 739 fps (31 FPE).... so I've picked up about 100 fps and 10 FPE across the board....

noting to disapoint me hahahahah

target man

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PostPosted: Wed Dec 12, 2012 1:22 am 
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OK, OK, the lightbulb just went on.... The downturn of the maximum travel curves at maximum preload is the "bstaley" effect showing up.... I was just slow to recognize it.... I was thinking of it backwards.... Once you run enough preload it is possible to drive the hammer into the back of the valve IF the stroke adjuster is fully inside the hammer (maximum throw).... Here is the data replotted for the maximum preload with the 2.00" x 0.045" spring at coil bind....

Image

What is happening is that if the center of the hammer face (the striker part) is recessed as far as it can go, it is limiting the valve lift to 0.100".... That is what is happening at the "Maximum" setting in the above graph.... As you move the striker forward (towards the hammer face) it opens the valve further (eg. at 1 turn).... At 2 or more turns, the hammer is no longer hitting the valve body, so the velocity limits at it's usual "plateau" like I'm used to seeing.... If I continued reducing the recess in the front of the hammer (which also reduces hammer throw) I would again see a velocity loss....

I'm going to have to ponder this for a while....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Dec 15, 2012 12:27 am 
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Location: Coalmont BC
My version of the Millenium Pumper is finally finished.... It uses a .25 cal Lothar Walther barrel, a Disco main tube, and a Mac1 extended Billet linkage, and weighs 7.25 lbs. without the scope, which is a Leapers 4-16 x 40 AO MilDot.... Here's what it looks like....

Image

The Boyd's Blaster thumbhole stock has a swell in the forearm right where you grip it for pumping, and was a perfect choice.... The pump stroke is long, but significantly easier at 1800 psi than the Carbine was at 1500.... I have pumped the gun by hand to 2000 psi, and I would consider that a safe upper limit.... Over 60 FPE with EunJins should be pretty easy at that pressure....

Image

The pump actually works better than the one in the Carbine did, filling the 28.5 cc valve faster than the Carbine did its 27 cc valve.... It takes 80 pumps to fill to 1800 psi from empty.... The second graph shows the number of pumps to refill after each shot when the gun is set up for three shots of 40 FPE.... This gun actually takes fewer pumps while producing 40 FPE per shot than the Carbine did at 30 FPE per shot....

Image

Filling to 1800 psi gives a choice of three different tunes just by resetting the RVA.... I can get 1 shot at 950 fps (51 FPE), 2 shots at 898 fps (45.4 FPE), or 3 shots at an average of 846 fps (40.4 FPE) within 30 fps (less than a 4% ES).... While the gun can be pumped to 2000 psi, I feel that these three settings give the best balance between power and pumping....

Image

The graph above shows the velocity of the "next" shot in each string.... You can see that the 4th shot when the gun is set up for three shots of 40 FPE is still about 30 FPE.... plenty good enough for a close follow-up or a coup de gras.... I'm extremely pleased with the way this project turned out.... It surpassed all my expectations, and performs better than I could have ever dreamed or hoped for....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Dec 15, 2012 12:34 am 
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Location: Okanagan,BC
That is one beauty of a pumper!

Congrats on a great job.


:)


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PostPosted: Sat Dec 15, 2012 1:03 am 
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Joined: Thu Feb 02, 2006 11:35 pm
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Location: Alberta Canada
Well Bob you have out done yourself that is one very sweet looking rifle you have built there. Impressed.

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PostPosted: Sat Dec 15, 2012 3:59 pm 
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Posts: 1343
Location: quebec
i promise my self not to be jalous and stay sastisfied

t'l im, the even very happy owner
of your first version
tha small carbine disco pumper

Image
the first version was much more nice in real than the pics ,show us


i might say it very hard to not desired the new one :lol:
after i saw what you have done whit the new version 2.0 millenium pumper
all is ameliorate ,performence and operation ,etc,,,

i might say ,i was affraid the laminated stock came too pale whit oil ,,
but you have done something real great

its not only a nice .25 caliber pumper
its also a strong efficien multishot pumpers ,,
a real hunting rifle

i hope your wife understand you if you want to sleep close your new creation :lol: :lol:

no more words for now

target man

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PostPosted: Sun Dec 16, 2012 12:30 am 
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Somebody asked what the FPE was if I maxed out the settings at 2000 psi.... With 42.4 gr. EunJin Points, it hit 858 fps, which works out to 69.3 FPE.... Mind you, it took half the air in the valve to do that, and MAN was it LOUD !!!

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Dec 16, 2012 1:03 am 
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Good for you Bob! I will have to get back to making pumpers again since I got rid of my Hill hand pump. I am suprised you can reach such higher pressure with a simple pump piston!

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PostPosted: Sun Dec 16, 2012 2:14 am 
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Simply a gorgeous, functionally beautiful piece of work you have accomplished. 8) Surpassing your past efforts again, Mr. Sterne :prayer:

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PostPosted: Fri Jan 18, 2013 1:49 am 
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Bob.. Have you thought about making a dual tube pumper (one tube on top as the air reservoir, one at the bottom for pump piston)?? It would look something like your dual tube Disco PCP gun and probably weigh the same. You will have massive volume for valve and could put at least 10 inches of pump stroke at the bottom tube, the tube could be connected to the gauge port under the main tube.. Mind you might have to pump the gun up over 1000 times put you won't have to worry about bringing a bulky PCP hand pump when you go out to shoot the gun. Heck you could just build a mini 1 stage PCP pump and add a quick disconnect hose to it (poor mans PCP hand pump). Just a thought.

Here's the basic idea:

Image

You could even try building a 3-stage pump under there.

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PostPosted: Fri Jan 18, 2013 11:39 am 
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I've discussed it with Lloyd Sikes who does the Disco Double.... He's interested, but buried in projects at the moment (aren't we all).... Yes, we've already thought about the two-stage pump idea (should be plenty for the 2000 psi of the Disco).... This gun isn't that bad to pump with a 7.6" stroke and the long pump lever, I've taken it to 2000 psi with the pump.... If you got rid of the valve and added stroke the effort would go up, so either a lower pressure or a two-stage would be necessary....

The big problem is the huge number of pumps to fill a 135 cc Disco tube.... With this gun, it would take ~450 pumps, and even if you could get a 10" stroke single stage, it would take ~350.... A two stage pump would be easier to pump, but the number of pumps would increase (you don't get something for nothing).... The only way the gun really makes sense is to use it as a PCP with an onboard pump.... run it at the optimum pressure, and repump after every 2-3 shots.... That way your heartbeat can come back down between targets....

If you're going to do that, perhaps you don't really need a full Disco tube for the reservoir.... This gun can be refilled with just 11 pumps after 1 shot, 24 after 2, and 40 after 3 shots of 40 FPE.... How many times when hunting do you need more than 3 shots?....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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