possible 1377 valve mod
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possible 1377 valve mod
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Topic: possible 1377 valve mod (Read 3518 times))
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
possible 1377 valve mod
«
on:
February 27, 2017, 03:04:57 PM »
I'm thinking about modifing my 1377 exhaust valve in the shown way (see the dotted lines and the result in the second picture).
expected advantages:
- yet more air storage volume
- better/shorter airflow geometrie
- smaller diameter valve seat > smaller area affected by the pressure > less force to open the valve
If I'm lucky I may be able to drill out the new valve seat by using a 11.5 mm drillbit and making a small 45° seat/seal area by using a 90° countersink.
Also the valve piston itselve must be fitted/turned to a 45° angle on its seat. The valve stem must be shortened.
What do you think ? Is all this possible without a lathe ? Would the valve be airtight again ?
Has someone possibly had the same idea allready and successfully implemented this ?
BTW - Further, on the right end, you can see a stem seal done with a small o-ring and a plastic cap, wich acts as a hammer stopper at the same time.
The screws holding it is not one below the valve stem, like in the drawing, but two to the left and the right of the valve stem.(thats just for easier drawing)
This I have implemented already.
Greetings Martin
«
Last Edit: February 28, 2017, 02:02:35 AM by ^^artin
»
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Hessen, Germany
Gippeto
Sharp Shooter
Posts: 863
Re: possible 1377 valve mod
«
Reply #1 on:
February 27, 2017, 03:40:01 PM »
Would be very difficult to keep things concentric without a lathe...odds favor a lot of grief getting it to seal...if ever.
Maybe you're extremely lucky?
With limited tooling (drill press and vice??) best chance of success (jmo) would be to flat face the valve, break the edge and use a perimeter sealing valve stem. Still going to have some grief getting it to seal, but with limited tools a flat face will have a better chance of success than a tapered seat.
Al
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Alberta, Canada
CraigH
GTA Senior Contributor
Posts: 3540
Real Name: Craig
Re: possible 1377 valve mod
«
Reply #2 on:
February 27, 2017, 04:25:15 PM »
Anything is possible - I would not try it without a lathe - just a little lathe will do it.
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Lone Tree, Colorado
With freedom comes a terrible responsibility
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26926
GTA Forums Person of the Year 2017
Real Name: Bob
Re: possible 1377 valve mod
«
Reply #3 on:
February 28, 2017, 01:48:14 AM »
Conical valves made of soft materials (ie plastic) tend to wedge into the valve seat, which actually makes them harder to knock open.... Whether or not the reduction in seat diameter you show would be enough to offset this, or would even occur once the poppet pounded into the seat, would be the question....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
Re: possible 1377 valve mod
«
Reply #4 on:
February 28, 2017, 03:43:06 AM »
In detail it should more look like this.
The wider this small ring seat is the less it may tend to cut into the plastic valve piston or get stuck.
But also the harder it might be to get it tight.
But I also thought about making the valve piston from brass then.
«
Last Edit: February 28, 2017, 03:49:23 AM by ^^artin
»
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Hessen, Germany
39M
GTA Senior Contributor
Posts: 2171
Re: possible 1377 valve mod
«
Reply #5 on:
February 28, 2017, 06:54:50 AM »
Well, it works on a car engine.
But... they have a much stronger spring holding them closed. And a mostly solid unstoppable force, to counteract that strong spring, pushing them open.
And even then, if the spring is too soft they will float.
Logged
Texas
"You'll shoot your eye out kid!"
POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
Re: possible 1377 valve mod
«
Reply #6 on:
February 28, 2017, 07:19:25 AM »
Usually the airpressure inside the valve holds it close by itself.
After a few pumps the force applied by the airpressure is much stronger then the forces applied by the valve spring.
With each pump it get's harder and harder to push the valve open by hand, for example.
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Hessen, Germany
39M
GTA Senior Contributor
Posts: 2171
Re: possible 1377 valve mod
«
Reply #7 on:
February 28, 2017, 07:23:58 AM »
It looks like it could work.
There are really no other forces against it. Not like it's a full auto.
Logged
Texas
"You'll shoot your eye out kid!"
POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
Re: possible 1377 valve mod
«
Reply #8 on:
February 28, 2017, 07:38:57 AM »
Yes, I guess I will give it a try by time.
Just want to order a replacement valve first to work on it.
And my pistol also is still on the road for warranty servicing...
«
Last Edit: February 28, 2017, 07:40:35 AM by ^^artin
»
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Hessen, Germany
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26926
GTA Forums Person of the Year 2017
Real Name: Bob
Re: possible 1377 valve mod
«
Reply #9 on:
February 28, 2017, 12:46:56 PM »
39M, car valves are not made of soft plastic, they don't extrude into the throat.... For a given diameter of throat, experiments on PCP valves have determined that the easiest to open is a flat seat with a slightly concave poppet sealing on a narrow margin around the outside edge.... Deep tapers are the worst.... Hard plastics are easier to open but harder to seal at a given pressure.... but they don't extrude into the throat as easily....
The only really successful tapered poppets I have seen are Motorhead's, where he uses PEEK (a very hard plastic) in regulated guns at relatively low pressures (though more than a pumper)....
Bob
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
39M
GTA Senior Contributor
Posts: 2171
Re: possible 1377 valve mod
«
Reply #10 on:
February 28, 2017, 03:07:50 PM »
Bob, I'm sure you are right.
Do you suppose that eliminating the convex, thereby spreading the load over a larger area and in turn creating a larger seating surface might be advantageous in this situation?
Logged
Texas
"You'll shoot your eye out kid!"
POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177
Gippeto
Sharp Shooter
Posts: 863
Re: possible 1377 valve mod
«
Reply #11 on:
February 28, 2017, 11:41:54 PM »
Forgetting the Hatsans Bob.
39M...increasing surface area at which the seal takes place doesn't always work. Need a certain amount of seat pressure/stress (force on the poppet/area where the actual sealing takes place) to get enough distortion to affect a seal. Not enough seat pressure and it won't seal...
Conversely, if that seat pressure/stress gets too high, you get a lot of distortion on the plastic parts resulting in damage....something of a balancing act.
Al
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Alberta, Canada
39M
GTA Senior Contributor
Posts: 2171
Re: possible 1377 valve mod
«
Reply #12 on:
March 01, 2017, 12:49:51 AM »
Yes, apparently why there is usually a narrow rim that the softer surface can form a seal around.
Logged
Texas
"You'll shoot your eye out kid!"
POWERLINE 35
Blue Streak. 1377. 880
Blackhawk Elite. Daisy 131.
Remington Vantage 1200.
CRUSHER NP.
Torpedo 100x .177
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26926
GTA Forums Person of the Year 2017
Real Name: Bob
Re: possible 1377 valve mod
«
Reply #13 on:
March 01, 2017, 01:02:22 AM »
Good catch, Al.... *oops*.... I guess the seat width is enough to resist deformation on those.... Some guys are making PEEK seats for them now, to allow larger throats without issue....
Bob
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
Re: possible 1377 valve mod
«
Reply #14 on:
April 15, 2017, 04:24:33 AM »
Considering your concerns I thinked over and have redesigned the valve seat and poppet again and now have modified it.
The new design was relatively easy to make without a lathe. Of course it took some time and I needed to make some special hand tools to get it done.
For the 11,6 mm boring I did crank the drill bit gently by hand -before, I did break the spiral cutting edge with a grinding stone though, that the bit could only cut at the front cutting edge.
To flatten the end of the boring I builded two tools from a tight fitting wooden dowel. One with a flat cutting edge on the end, crafted from a bit of a hacksaw blade
and the other just a flat dowel with a small round piece of sandpaper glued to the end.
The valve is pretty tight again and I got no residue air left in the valve up to 20 pumps (just not tested for more pumps by now).
Unfortunately I yet can't test the shooting performance because the new barrel is still not on my gun.
BTW I also needed to shorten the valve stem and I needed a slightly longer valve spring.
«
Last Edit: April 15, 2017, 04:42:45 AM by ^^artin
»
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Hessen, Germany
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26926
GTA Forums Person of the Year 2017
Real Name: Bob
Re: possible 1377 valve mod
«
Reply #15 on:
April 15, 2017, 12:58:05 PM »
Increasing the valve volume will not likely increase the power in .177 cal, although it can help in .22 cal.... When you increase the volume it takes more pumps to reach the same pressure, so of course you can pump more before the valve retains air.... The longer the barrel, and therefore the greater the barrel volume, the more chance you have of increasing velocity by increasing the valve volume....
Bob
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
Re: possible 1377 valve mod
«
Reply #16 on:
April 15, 2017, 01:38:56 PM »
I'm about to build in a 15 inch long cal .22 barrel.
I guess more valve volume would help increasing the power then.
Of course I know it will also takes more pumps then to get the same pressure.
But also the pressure would'nt drop as much as with less valve volume, when it expands and accelerates the pellet.
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Hessen, Germany
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26926
GTA Forums Person of the Year 2017
Real Name: Bob
Re: possible 1377 valve mod
«
Reply #17 on:
April 15, 2017, 02:00:28 PM »
The pressure in the valve always goes to zero when you dump all the air, but you are correct, for equal valve (starting) pressure, you will have greater residual pressure at the muzzle with a larger valve.... which means you are wasting more air, because that does nothing once Elvis has left the building.... It just makes the gun louder.... You may notice a very slight improvement in velocity with a 15" barrel in .22 cal, IF you pump enough to get the pressure back up to what you had with the smaller valve volume.... You WILL notice less velocity as low pump numbers, because the initial pressure will be less, of course.... There will be some point (number of pumps) where the velocity will be the same with the larger valve, because the extra volume of air will make up for the lower pressure.... The initial air pressure has the most effect on the velocity.... The longer the barrel, the more effect you get from a larger valve volume, because it is the ratio of the two that governs power and efficiency....
Bob
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
^^artin
Shooter
Posts: 79
yes
Real Name: Martin
Re: possible 1377 valve mod
«
Reply #18 on:
April 15, 2017, 03:16:39 PM »
Sounds not very promissing.
I have no idea how big the benefit of this valve mod may be but I'm still very curious.
I did a quick calculation for the old and the new barrel volume:
old barrel volume, cal .177, 25cm long: 3.98cm³
new barrel volume, cal .22, 38cm long: 9.03cm³
Does'nt this ratio also give the factor I may extend the valve volume without getting uselessly large ?
Another benefit may be that the "transfer volume" (volume between valve seat and pellet bottom) is smaller now.
«
Last Edit: April 15, 2017, 03:21:29 PM by ^^artin
»
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Hessen, Germany
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26926
GTA Forums Person of the Year 2017
Real Name: Bob
Re: possible 1377 valve mod
«
Reply #19 on:
April 15, 2017, 08:40:03 PM »
Yep, you are correct, you can double (actually as you say 9/4 times) the valve volume going from a 10" in .177 to a 15" in .22 cal.... but you will also have to double (9/4) the number of pumps to get to the same pressure.... That is not at odds with what I stated, that at some given number of pumps, the velocity will end up the same (given gun, barrel, pellet) with both the stock and larger volume valve.... and below that the smaller valve will be better and above that the larger valve will give more power.... It will simply end up a matter of how many times you want to pump.... Does that help?....
The largest valve volume that makes any sense is 1/2 the barrel volume (and even that wastes a lot of air), but most pumpers use between 1/4 and 1/3, because the larger it is, relative to the barrel, the lower the efficiency (more air wasted after the pellet leaves the muzzle).... A stock 1377 valve is about 1.6 cc, or about 40% of the barrel volume, putting it on the larger side of the norm.... In a 1322 (.22 cal 10" barrel), that drops to 26% (in the sweet spot), and in a 2289 (14.5" barrel) it is on the small side, at 18%.... The new 2289s have a 12" barrel, so in those, the valve is 22% of the barrel volume....
I have used a bored out valve in a 2289, with a volume of about 2.2 cc, and that works really well with it's .22 cal, 14.5" barrel, if you are interested in power, and prepared to pump a bit.... I bored the valve to 0.500" ID for a depth of 0.400", which adds 0.44cc.... I also shortened the threads by 0.100" (2 threads) which adds another 0.11cc, for a total of 0.55cc (about a 1/3 increase in volume).... The bored valve is about 24% of the barrel volume.... Unfortunately, I don't have recorded the crossover point where the larger valve increased the power.... but it would have been done with a Flat-Topped Piston anyways, which drastically reduces the number of pumps required for higher pressures.... If I recall, there was basically no power increase until after the original valve started retaining air with the stock hammer spring, and after that the additional pumps gave a bit more velocity.... The 1/3 larger valve would have taken about 1/3 more pumps before retaining air.... Sorry I no longer have the data, it was several years ago....
HTHs....
Bob
Logged
Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
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possible 1377 valve mod