Update on AT44-10 Modifications
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Update on AT44-10 Modifications
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Topic: Update on AT44-10 Modifications (Read 12083 times))
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Update on AT44-10 Modifications
«
on:
February 13, 2017, 10:50:34 PM »
I have a new Hatsan .22 cal AT44-10 QE with standard barrel. These are the mods I just finished:
1) Disassembled barrel and gave it a good cleaning
2) Plugged 5 of the 6 holes in the valve with 6-32 x 1/8 setscrews & filled the groove with epoxy.
3) Enlarged the 6th hole to 0.177" (80% of .22). I went a little large in case my Transfer port was not in perfect alignment. (I measured it and it was 0.166" (75%+) so I left it alone.
4) I added a 0.0365 copper washer behind the valve needle to compress the spring a little.
5) I turned the hammer spring tension in to minimum, then backed it out (cc) about 2 turns until I got 870fps with the tank filled to 130 Bar, using JSB 18.13 pellets.
6) I also installed a groove in the valve threads and put a corresponding small notch in the tank, as a future vent for the regulator. With the 0-ring in place it still seals just fine.
I did all this in anticipation of installing a Lane Mk8 regulator which I got a good deal on. It is still in transit.
Before I made the mods, I shot 9 groups of 5 starting at 190 Bar (1750psi) and recorded the velocities as "String 1". [I stopped at 190 Bar because I knew this was well above my target velocity of 870fps] After the mods, I shot another 9 groups of 5 from 190 Bar with the JSB 18.13 pellets and recorded the results as "String 2". I then shot another 9 groups of 5 from 190 Bar using Crossman Premium Hollow Points 14.3 grain and recorded those results as "String 3". I had also shot 9 groups in stock configuration with the Cphp's but lost the data. I will attempt to attach the 3 graphs.
The stock configuration, string 1, had a bell curve, with the 1st 20 shots increasing steadily, then sort of leveling off for another 15, then falling off steeply for the remaining 10.
The two strings after modification started out almost flat for the 1st 20 then steadily fell off for the remaining 20. As reasonable, the lighter CPHP's started out significantly faster & fell off a little steeper. All in all, its a good start.
After installing the regulator, I do not have any further mods planned. The JSB's have significantly tighter groupings with about 1/3 being inside the 1" bulls eye at 50yds. I feel they should be better than that so maybe I will polish the barrel later. All the research I've done says my hammer weight is about 1/3 more than it needs to be. So maybe down the road I will play with that.
Any observations on the graphs results, and/or suggestions would appreciated.
Thanks. -Richard
PS: For you hand-pumpers out there, it is possible to fill the cylinder from empty. It was not easy, but it did finally seal and pump up using a little extra grease on the needle seat & tapping it to set the needle.
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Summerfield FL
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #1 on:
February 14, 2017, 12:01:37 AM »
It looks like you're on the right track. If you wanted to even out that curve without a regulator, you'd need to give it 1/2-1 turn back cw, and the shot curve would even out a little. Since you're adding a reg, I think any suggestions right now aren't going to do much good. You'll likely find that it shoots a little slower with the reg set at 130bar vs the tank pressure being at 130bar, because the regulator only has the air in the plenum to work with. The tank at 130 bar has the whole tanks worth of air to work with. Other than that, I'd just wait until the reg was installed, and go from there
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Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #2 on:
February 22, 2017, 12:35:16 AM »
OK, here's the latest good news/bad news update since installing the modulator. Attached is a file with 7 graphs: 1st is String 1 which is FPS vs Shots in stock configuration. 2nd & 3rd graph are the same results after the already listed modifications. The last 4 graphs are the new data since installing the Lane regulator: two are 'fps vs shot count' -one with CPHP 14.4gr & the other with JSB 18.13gr. The last two compare the 'FPS vs Turns of Preset' for the 14.3 and 18.13gr pellets.
I will start with the bad news. The last 2 graphs are nothing I expected or can explain. Instead of starting out with the lowest FPS at minimum preset (full CW), I get the highest velocities then a drop off. I am maxed out on power at only 2 turns (actually the 1st turn) & I really was hoping I could have the option to increase power. The 1st 2 turns out from 0 are very hard, by the 4th turn it is easy, & by the 6th turn there is no effort or friction at all. Do these preset graphs indicate something is wrong?
Now the good news. On this first try, the results of the regulated fps vs shot count exceeded what I was expecting. My goal was to get 25ft-lbs for 30 shots with the JSB 18.13's. I got the following:
Shots 1-20: Ave. fps =793, Ave ft-lbs = 25.3, ES =10 = 1.25% of Hi;
Shots1-25: Ave fps = 788, Ave ft-lbs = 25.0, ES = 20 = 2.5% of Hi;
(the 24th trigger pull shot 2 pellets so I wasted 1 of these & deleted its 666fps)
Shots 1-31: Ave fps =786, Ave ft-lbs = 24.9, ES = 32 = 4.00% of Hi;
The wind was blustery so I didn't bother at 50yds, going for 27yd instead. 3 of the 6 groups could be covered with a dime, all of them with a quarter & all of them in the 1" bulls eye. That could be way better, but that is another thread another day. [BTW, the CPHP 14.3 hit the 850fps range but had 2-3 times the scatter as the JSB's even though their ES values were only a little bit higher]
I was hoping to get closer to 850 fps, but I set the regulator to 120 Bar for max shot count and shimmed the valve spring 0.100" hoping that would drive the hammer preset down toward 0. I left the Transfer Port stock and cranked in 1turn of preset, so it was not set for power. I was hoping I would have adjustment with the hammer preload for optional power if wanted but this part did not come true. I wanted to be able to kill 30 squirrels at 50yds, and I achieved that goal.
I still would like to have the option for more power by just changing the preload setting. I could take some to the shims out of the spring (.35 + .35 + .30 = current .100") but that will probably hurt my shot count, as would upping the regulator. Would increasing the TP to match the .172 valve and not suffer much on shot count? But at only 120Bar, would that really show up as more ft-lbs? I would accept a 25 shot count if I could get the 850fps, but is that in reach?
Your suggestions are welcome -particularly on how I can access the hammer preset for optioal power! I am tempted to say I am lucky to get were I am on my 1st try, but that would not be giving the respect due to those on this list who have provided such a wealth of information! Thank you all.
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Summerfield FL
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #3 on:
February 22, 2017, 12:45:18 AM »
I forgot to add that I ran out of light for the chronograph, so tomorrow I will run another string of fps vs shot count but instead of at 1 turn, I will go the other extreme with 8 turns CCW from 0, and see if the velocities go way down as predicted by the last 2 graphs & also see how it affects the count. I will also run one more at 0 turns -according to the graph, the fps is identical, so maybe I'll get one more shot. Hoping for some answers.
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Summerfield FL
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #4 on:
February 22, 2017, 01:08:47 AM »
Go ahead and open the transfer port to .175. Open the barrel port as well to .175, but make sure there are no burrs when done. Opening those two will not hurt your efficiency. Making the gun flow better isn't only good for big power. It makes the regulator make better power at lower set points and helps with efficiency. The faster the air gets to that pellet, the faster that valve will close. I wouldn't bother messing with the valve spring anymore for now.
Also make darn sure that last hole in the valve is properly lined up, or you could end up chasing your tail if the velocity isn't where it should be. I feel like you should have a little more velocity than you do with your current configuration. Your un-regulated strings support my theory too. I don't see any real benefit in trying more hammer strike. It is also possible that the regulator setting isn't quite what it should be. Sometimes, they can be a little off from what they "say" they are set for, so I'd verify that by re-filling as soon as the gun comes off the reg.
If you don't want to open the other ports, you're going to have to raise that regulator setting a little. I think you can leave it where it is, and up the power a decent amount if you open everything else up.
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Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #5 on:
February 22, 2017, 06:33:23 PM »
Thanks Rallyshark, I haven't yet disassembled the gun far enough to check Transfer Port alignment but that will be my next step.
I organized some remaining data and added some associated tank pressures for the graphs of string 5 & 6, plus some ES & average velocities for various parts of the graphs.
I added a "ft-lbs vs shot" count graph for the 6th string.
And I added a graph that shows the power level for each 5 Bar interval from 90-160 Bar. I hand filled the tank to 90 Bar & fired 3 shots & graphed them. I refilled to 95 Bar & repeated incrementally to 40 Bars over regulator setting. The Lane Regulator video series says this will show if your gun's peak efficiency is within the regulated setting. If it is not, then there will be a spike before the regulated setting. The curve I plotted is the optimal result. So, though I am at a lower power setting, it seems my gun is well tuned? For those of you who have achieved a good tune, what kind of values of power/shot count do you have?
Hopefully I can get one or two additional ft-lbs by opening up the TP.
I still am flustered by my results with adding preset pressure to the hammer spring. I have seen other posts where it didn't go up because the airflow was blocked, but nowhere have I seen that the power went down as I am experiencing. Can anybody shed light on this?
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Summerfield FL
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #6 on:
February 22, 2017, 09:39:53 PM »
Don't forget the barrel port
You're just making all the power the gun can make, and more hammer spring is just wasting air with the current amount of air flow you have. This is what makes me think you may have an alignment issue.
«
Last Edit: February 22, 2017, 09:42:40 PM by Rallyshark
»
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Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #7 on:
February 26, 2017, 04:53:42 PM »
More good news/bad news. I disassembled the gun and found that the transfer port was aligned so I proceeded to drill out the port. I put the upper magazine with the barrel still installed under my mill and drilled it out to 0.173" (from 0.166). I didn't want to drill the transfer port bushing and its brass cylinder channel without removing it from the gun. Of course in order to remove it, the tp bushing has to first come out. Well the bushing was pressed in so tight that I damaged its o-ring surface attempting the removal. I ended up tapping the bushing with a 10-32 tap (the ID of the bushing is slightly greater than what is required for the 10-32 tap) and pulling it out with considerable force. In hind sight, I could have done this to begin with, and avoided damaging the bushing face. The threads from the tap would came out when I drilled it to 0.172". My original plan was to enlarge the bushing and the cylinder channel to 0177" to compensate for any minor misalignment with the valve spring port, so I drilled the damaged TP bushing and channel to .177". Just for the heck of it, I put the damaged bushing (the top o-ring face had pliar marks in it) into my mini lathe and took off the burrs. But when I reassembled the gun and shot it, the gun just made a putt sound, so I ordered a new Transfer Port bushing and 2 o-rings, as I assume it is not sealing. So my search for a 850fps with JSB 18.13 with regulator set at 120 Bar is on hold till parts come in.
The good that has come from this is that I found a way to safely remove a frozen transfer port bushing: just tap it with a 10-32 tap and pull away. The thread marks in the bushing disappeared when I is drilled to .172". Even if you were not going to enlarge it, the new threads would probably not adversely affect airflow to where it is noticeable, though I the added turbulence would have to decrease flow somewhat in theory.
I'll post results when the new bushing comes in & I drill it to .177"
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Summerfield FL
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #8 on:
February 26, 2017, 06:19:04 PM »
I'm sorry you had an "incident" there
Been there, done that.... I drilled out everything out of the gun myself. I actually used rolled up sandpaper to enlarge the transfer port to avoid damaging it. I also enlarged the hole the cylinder carrier, which is the brass piece that the transfer port sits in and the cylinder screws into. Try loosening the big screw on the bottom and the transfer port should normally come out easily then. I have seen a few cases lately where the tranfer was wedged in there and wouldn't come out with cylinder carrier loosened too though.
Whenever you do go to put everything back together test fit the cylinder with the cylinder carrier and transfer port in to make sure you still have the alignment. There is a little wiggle room there depending on where the cylinder carrier is in the trigger tube when the big screw is tightened on the bottom, FYI.
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Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
pllagunos
Sharp Shooter
Posts: 675
yes
Real Name: Pablo
Re: Update on AT44-10 Modifications
«
Reply #9 on:
February 26, 2017, 07:52:52 PM »
I would suggest as to trying to increase your efficiency, to get a short stiff spring, in mu at44 which has also the standard barrel, I was able to get 30 shots at 29ft-lbs with a 23fps spread. My valve only has 3 holes plugged and I run mine unregulated, I have also not made mods to the barrel or transfer port, so I think you could get even better results than I do. Like +30 shots at 29ft-lbs with 10fps spread.
Also for the accuracy clean your barrel if you haven't and check the crown. Mine I had the crown polished with some 600 grit sandpaper and can shot the 18.1 in a windless day in about half an inch at 50 yards (5 shot groups).
Hope this helps, good luck!
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Mexico
Hatsan AT44W-10 .22 (30fpe) SSS tune
QB79 HPA .177 (15fpe) SSS tune
Crosman Phantom .177
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #10 on:
March 10, 2017, 12:39:48 AM »
Hello All,
Graphs and data results for all mods to date are in attached file.
First, this is a summary of all the modifications to date:
Modifications:
A: Modification ver1
1) Plugged 5 valve holes & filled groove with epoxy
2) Drilled 6th hole (top) to 0.172 (OEM port of barrel is 0.166)
3) Added 0.036 spacer to valve spring (valve needle diameter measured 0.103)
4) Set Hammer to 1 Ύ turns CCW from minimum
B: Modification ver2
5) Installed Lane Regulator @ 120 Bar (also put groove into air tank threads of valve body & notched tank edge to match groove to vent regulator; also polished Valve body face which mates to regulator.)
6) Added another .065 of spacer to valve spring for tot. of 0.105 (actually the effective shim was .125 because the valve body face ended up .020 lower due to lathe mishap with polishing face for regulator mating surface, this caused the white plug which holds the spring to be .020 lower.) [*This configuration had a new knee of 8turns]
C: Modification ver3
7) Drilled cylinder channel to 0.177
Drilled Transfer Port bushing to 0.0173
9) Drilled barrel and frame to 0.173
10) Added 0.006 copper shim between air tank & brass cylinder channel to align valve transport holes.
C: Modification ver4
11) Tapped valve body plug, which holds the spring in, with M6 x 1.00 tap (no drilling required) for future removal without scratching polished face. (use M6 x 1.00 screw to pull out)
12) Removed 2 shims (totaling 0.070) from valve spring leaving an effective shim of .056 of shim (.036 + .020 face removal)
13) Drilled front edge of hammer set screw with a .096 bit and pushed in a piece of .095 weed eater string to make it self-locking
At last posting I was waiting on a new transfer port bushing as I thought the one i dinged and attempted to repair was not seating. i drilled the new out to .173" but as it turned out I had the same issue of the rifle just barely spitting the pellet out. In both cased the preset was out 1 turn. In desperation, I cranked in another 4 turns and the the chrono read 460 fps. The "knee" ended up being 8 turns out! I was expecting the knee at a much lower preset, but because I had increased the valve spring tension by 0.125", this reduced the power so much that I required a lot more hammer preset.
In the 1st mod ver1, I did the standard valve mods & added 0.036" of increased valve spring pressure. These results were already posted. Though encouraging, it produced "Mystery #1": The relationship (tested twice) between the change in preset and the change in FPS was inverse, ie, more preset (CCW turns) yielded less PPS.
In mod ver2, adding the Lane regulator requires a polishing the valve body face with its mating surface on the regulator. I had a mishap on the lathe in my attempt to polish it and ended up having to take off 0.020" of the valve face to remove the damage which gives me a permanent .020" shim effect on the valve spring. This initial regulated configuration yielded a 37 shot count with a 4% ES (14 shot increase over unregulated Mod ver1) but a decrease in FPS (from ave of 887 down to 784) and a decrease in ft-lbs (from ave of 31.6 in mod. ver1 down to 19.5 in ver2). Ver2 still had wacked out inverse relationship of Preset vs FPS.
In mod ver3, I opened up the transfer ports to 0.173". This caused "Mystery #1" to disappear, as there is now a correct relationship between preset and velocity. With the original transfer port bushing (which was a press fit) it was aligned with valve spring port allowing me to see the entire port and valve stem. The new transfer port bushing was a loose fit and with loosening the bolt holding the cylinder channel I still could not get them to align as they were about 1/3 closed. This caused me to make a 0.006" shim to get it right. [i remain quite certain that the transfer ports were aligned in ver1 & ver2.]
*The results of ver3 mod was a shot count of 37 -a 6 shot increase over ver2 within the 4% ES, with an almost unchanged average velocity (783fps) but a significant reduction in ft-lbs the average (from 25.0 to 19.50). So ver3 brought a "Mystery #2": how can the average velocity be unchanged (.5%) yet the ft-lb be reduced 22%? It is logical that if the shot count increases and the velocity remains constant, that the total power or ft-lb would have to decrease as both started with the same energy in the tank. However, I still can't see the same mass of pellet can have the same average velocity but different ft-lbs. Similarly, 2 exact velocities of identical pellets in two different strings can have different ft-lbs. Is my chrono results questionable?
In mod ver4 the only option to increase power without increasing 120 Bar regulator setting was to reduce valve spring tension, so I took out 0.070" of its spacers (a little more than 1/2 of what I added. Although this had significant increase in velocity and ft-lbs, and shot count, it did not change the preset value of 8 turns, as I was hoping the knee would come in at 4 or 5 turns from zero.
* The results of Mod. ver4 was a shot count of 38, a 1 shot increase from ver.3; an average velocity increase (of shots within 4% of Max. Velocity) from 784fps in ver3 to 806; and an increase in from 19.5 ft-lb in ver3 to 26.2 ft-lb in ver4. Reducing half of the valve spring shim netted me 22fps increase. I need another 44 fps increase. I am now forced to trade in some of those 38 shots for more power by increasing my regulator setting.
My goal is to get 850-870fps with a shot count of 30 within 4% of maximum velocity. So the big question now is how much can I go up and still hang on to 30 shots of 850+ fps all within 4% of max velocity? I really don't enjoy breaking open the air tank and getting it to seal again with hand pump, so I want to guess it right on the next try. I figure if I up the pressure, then the valve will have more to overcome so I will leave the last 0.036" of shim in place, hoping that I can crank down my present 8 turns of preset. That's my thinking anyway.
If anyone would look at the graphs and results attached and come up with a logical suggestion for the regulator pressure increase, I am open to suggestions, or if you have a .22 cal at44-10 with an efficient tune in the 85-870 range, what regulator setting did you end up with and what shot count did you achieve?
PS: The last attempt to fill my tank from empty, failed. I used grease on the valve seals as before, but it wouldn't take a seal. I admittedly am not capable of extended intense exercise due to health issues, so I duplicated a fill plug out of aluminum stock and threaded it with 1/8 pipe tap, then hooked it up to my 160 psi (10.9 Bar) air compressor. It then sealed & I finished with hand pump. If that didn't work I was going to hook it to my oxygen tank and regulate it down to 300 psi. Anymore than that and I would not trust the aluminum material in "emergency" fill plug.
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Summerfield FL
redlined_b16a
Expert
Posts: 1234
yes
Re: Update on AT44-10 Modifications
«
Reply #11 on:
March 10, 2017, 08:19:16 AM »
There is an article on the web somewhere,Some person used compressed oxygen in a pcp rifle.
The rifle tank exploded,some how ignited.
I don't know the whole story but please research before using compressed gases or oxygens.
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Louisiana
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #12 on:
March 10, 2017, 11:08:27 AM »
Redlined, your are right, one would not want to fill a pcp gun with oxygen. I was only thinking about using it with enough regulated pressure to slam the valve seat shut and seal the tank from leaking. The remaining 80-90% of the tank would then be filled with air from hand pump.
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Summerfield FL
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #13 on:
March 10, 2017, 12:34:44 PM »
Hello All,
I reread my post from late last night & realized I must have been half asleep. I need to correct the following:
My goal is to get 850-870fps with a shot count of 30 within 4% of maximum velocity. So the big question now is how much can I go up and still hang on to 30 shots of 850+ fps all within 4% of max velocity? I really don't enjoy breaking open the air tank and getting it to seal again with hand pump, so I want to guess it right on the next try. I figure if I up the pressure, then the valve will have more to overcome so I will leave the last 0.036" of shim in place, hoping that I can crank down my present 8 turns of preset. That's my thinking anyway.
I should have said "That' my late night foggy thinking anyway!"
If I increase regulator pressure, then the valve will be held shut with more force, thus requiring the even more hammer preset to open it. If I want to bring my high preset setting down from 8 turns, I will need to remove the remaining 0.036" shim from the valve spring so the valve can be opened with less hammer force. So the next step is to remove it and also up the regulator the minimum amount needed to provide the additional power to arrive at 850-870fps with the JSB 18.13 gr. Some might argue that I should 1st remove the last shim & see what it does before upping regulator, but if removing .065" gave me an additional 22fps, then removing the last .036 would give only half that, and I need to double it. So I am still hoping for some thoughts on how much to increase the regulator after also removing the valve shim.
I am also including a graph of mod ver4 showing the FPS of at specific tank fill pressures from 90-220Bar. By filling tank by hand to an exact pressure, firing 2 shots and record data, and doing this at 5 bar increments, you can see the knee of the power curve, what is happening below regulator cut-off point, and the effects of the regulator up to maximum tank pressure.
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Summerfield FL
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #14 on:
March 10, 2017, 10:48:38 PM »
I think you may be misunderstanding the term "knee". The knee is the point at which increasing the hammer strike no longer increases the velocity at the pressure you plan to shoot at. There is no need to go through all that trouble of plotting at different pressures. The only pressure you need to be concerned with is at the regulator set point and above. In other words, just adjust the hammer until you hit the knee when the pressure above the reg set point. After you find the knee, back the hammer spring off until you see a slight drop in fps(15-20).
You can remove that shim on the valve spring, unless you just like having more cocking pressure to overcome that stiffer valve spring. That brings me to another question, and I apologize if I missed it in an earlier comment. Are you using the factory valve spring, or a different stiffer one? In all of the regulated Hatsans I've tuned, I have never once had a need to increase the valve spring pressure or replace it. The only real benefit is to make it easier to get the valve to seat.
On that valve seating note... You can chuck the valve pin in a drill and spin it on the valve seat, and that may help with sealing once you put it back together. The idea is to get the surfaces to mate better.
I still think something is up somewhere on the gun. You shouldn't need 8 turns on the hammer spring to get the velocity you're getting. You should be getting that with 1 or 2 turns. Going by your measurements of all of the porting etc., the gun should be able to make more fps with the reg at 120 bar. A bone stock gun with nothing but a regulator set at 130 bar can make the 850-870 fps you're looking for. I can't tell you what is going on, but something just doesn't add up to me here
Could your valve spring possibly be getting fully compressed and having no more movement or something like that? The 8 turns of pre-load is a lot to get the fps you're getting. You shouldn't need any more than 3-4 turns at most on a regulated gun, but usually more like 2 turns. That is the kind of hammer spring pre-load needed for 45+ fpe tunes, and not 30fpe tunes. Either something is wrong somewhere, or you have an EXTREMELY stiff valve spring. I hope that helps.
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Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #15 on:
March 10, 2017, 10:51:51 PM »
Any of you other AT-44/Hatsan guys can jump in anytime here! Maybe you guys see something I don't
I know I'm not the only one reading this....
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Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
redlined_b16a
Expert
Posts: 1234
yes
Re: Update on AT44-10 Modifications
«
Reply #16 on:
March 11, 2017, 08:33:32 AM »
Is there a chance the the barrel port is mis aligned or had something blocking the transferport?
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Louisiana
d.lead.slinger
N.U.A.H. - Expert
Plinker
Posts: 242
yes
Real Name: David
Re: Update on AT44-10 Modifications
«
Reply #17 on:
March 11, 2017, 09:25:42 AM »
Never tuned an AT-44 but have tuned my Gladius. Just looking at all of the information here, I have to agree that 8 turns on the hammer adjustment is a lot. For me, 2 turns makes a drastic difference on velocity. Is it possible that the hammer was not "pinned" when making the adjustments? When first starting to tune mine, I would turn the hammer spring adjustment with little to no change in FPS. I noticed that even though I stuck an allen wrench in the hole to stop the hammer from turning, it didn't go in far enough and I wasn't doing squat!
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Louisiana
Happiest when squeezing a trigger!
.25 Taipan Veteran
.22 Custom Mrod
.22 Gamo Urban
.177 Beeman P17
.177 PP700S-A
.177 Ruger Blackhawk Elite
.177 JSAR Raptor
slingshot
Shooter
Posts: 49
yes
Real Name: Richard
Re: Update on AT44-10 Modifications
«
Reply #18 on:
March 11, 2017, 01:21:55 PM »
Thank you all for the responses. I am about to remove last shim and see what it does. I will report results.
Regarding responses:
1) The term "knee" as I have been using it is that as power is increased and velocity increases with it, there is a section on its graph where it transforms from a roughly diagonal line to a curve that ends up a horizontal line, ie, the velocity levels off and then stays the same, even as more hammer spring is turned in. All my results have been at the top of the knee or the beginning of the straight line. I don't know if that is the correct use if term, but that is how I have been using it in describing this data.
2) Regarding going through the trouble of plotting different pressures, that is a process Robert Lane (of Lane regulators)suggests to do as a baseline whenever you make a modification that effects power. The point being that some cases there is a spike in velocity just after the regulator falls off. If that is the case (it never has yet been for me) then you can adjust the spike down and thereby extend the shot count past regulator cutoff by a few shot. By doing this I can see that my configuration gives me several good shots past cutoff, but without loss or spike in velocity. The procedure is tedious & a pain for sure though. But it only needs to be done once for any modification.
3) I decided I will remove the shim before changing the reg as per suggestion.
4) The valve spring is the stock hatsan spring.
5) Regarding turns of hammer spring. I am befuddled by needing 8 turns. Modification ver1(plug 5 valve ports ect., & added .036"shim, no regulator) needed 1-2 turns for max velocity. Mod ver2 (went to .125" shim, added 120B reg) only needed 1 turn. Mod ver3 (drilled cylinder channel port to .177", transfer port to .173, barrel port & the frame port to .173; Also had to put .006 shim in front of cylinder channel as the transfer ports no longer aligned -I attributed this to the new TP bushing being now a loose fit & not jamming cyl. channel against its retaining bolt, but that is just my theory). is where the 8 Turn preset started. These ver3 changes (allowing more air through the transfer port) would if anything cause the preset to be a lower, not higher value, because less hammer strike would be needed if more air is getting in. What is curious about the hammer, when the gun is split open & the hammer & spring are in the frame & the set screw is full in, the the hammer is free to move back & forth at least 1/2", so much so, that the hammer spring can come out of its rear recess in the frame. I had to make sure the hammer spring was in the recess before reassembling the 2 halves. With all that slack it is logical that the setscrew would have to be turned out 4 turns before a pellet can be pushed out the barrel. I have only now put this together in my mind, but there probably isn't any reset tension until 4 turns. If this amount of slack at zero preset is abnormal, I do not have a clue as to what is causing it. I did not leave out the spacer in the hammer that is between the spring & set screw. To muddle this more: in mod. ver1 & ver2 where max. velocity was at 1 turn of preset, screwing it out further only decreased the velocity, so the whole time I have been recording the preset turns, it has always been out of the norm. I regrettably did not mess with or record preset changes in the stock configuration, only the velocity vs shot count.
6) I am certain the barrel port, the frame port, the transfer port bushing & cylinder channel ports are all aligned with the 6th port in the valve body.
7) And finally, I always double check that the hammer is pinned by wiggling the 4mm allen wrench & feeling it on the small phillips screw driver I hold to pin the hammer.
Thank you all again for your help.
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Summerfield FL
Rallyshark
GTA Senior Contributor
Posts: 4084
yes
Real Name: Donny
Re: Update on AT44-10 Modifications
«
Reply #19 on:
March 11, 2017, 03:50:11 PM »
Is your shim to get port alignment on the very front of the valve where the valve pin sticks out, or is it on the shoulder of the valve where the big o-ring is? A picture may be helpful. I wonder if the hammer doesn't have enough throw to strike the valve pin now. That would explain the need for a high pre-load setting. Maybe you should try taking the hammer stop screw out, and see if it changes the fps?
Logged
Dacula, GA
FX Maverick .30,.22,.177, 30-170 F.P.E.
Flash Rifle .177, 16 F.P.E Regulated(56+ shots)
PP700S-A .177 15 F.P.E. Regulated
(25+ F.P.E. unregulated)
Gamo Accu 177 pew pew pew F.P.E.
I may have Alzheimers, but at least
I don't have Alzheimers...
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