Revisiting the HATSAN AT-44 valve mods .... For a Regulator conversion.



Author Topic: Revisiting the HATSAN AT-44 valve mods .... For a Regulator conversion.  (Read 1197 times)

Offline Motorhead

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Thanks to the previous work by fellow member rsterne, took his info and applied it to .22 Hammerli Pneuma.
See: http://www.gatewaytoairguns.org/GTA/index.php?topic=33903.msg315366#msg315366


Started out plugging 5 of the 6 valve holes ( This valve took 4-40 size grub screws BTW )
JB weld up the space between like Bob had done  ;)

Next having just the valve body in hand screwed it into main tube snug, then drilling down from the transfer passage opening up the remaining 6th hole to .165" being same size as the transfer passage. With a dremel tool slightly flared the hole outward into throat area behind seat.

Having pulled the seat earlier found it's I.D. hole @ .162" which was IMO going to be too small with the bigger passages down stream.
So ... gently held it in the lathe jaws carefully drilling it out to @ .175" which leaves the poppet a sealing margin @ .055 total ( .0275 contact width )

Drilled out the face of body with 3 holes as Bob had done using .125" diameter at the 20* inward angle converging holes just under the spring retention cup.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reassembling rifle for a few test shots changing nothing in hammer tension from previous strings headed over to the Chrony    ;D

** As spring tension was set from earlier, rifle was shooting CPHP 14.3 pellets @ 835 fps for just a tad over 22 ft lb power.
( @2000# in tube )
** After valve mods with SAME settings, rifle was shooting CPHP 14.3 pellets at 965 FPS for just under 30 ft lb power  8) 8)
( @2000# in tube )
So indeed valve responded to some massaging and flow management 

Now why this is all fine and dandy, quite likely rifles a bigger air hog than it already was  :P which gets to the reason for these mods with no interest in efficiency numbers quite yet  :o :o

REGULATION on the way
... Wanted to get the preliminary mods that would have rifle making the @ 30# power I was after at the @ set point pressure regulator will be used at. ( Actually @ 1800# ) which will have valve opening easier yet ... then allowing less spring pre-load to be used lowering dwell and air use  ;)

** Now we wait for the Huub AT-44 regulator from the Netherlands to arrive so we can finish up and see if concept = reality ???

Stay tuned ..........

Scott
  • Northern California ... Old Hangtown
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Offline rsterne

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Re: Revisiting the HATSAN AT-44 valve mods .... For a Regulator conversion.
« Reply #1 on: November 28, 2013, 10:10:17 PM »
Well done.... you should be all set for when you get your regulator....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline Motorhead

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Re: Revisiting the HATSAN AT-44 valve mods .... For a Regulator conversion.
« Reply #2 on: November 29, 2013, 02:10:26 PM »
Here the body with the additional holes feeding poppet cavity. * Also note flattened sides of spring retention cap allowing you to wedge cap off for future service chores.



Valve discharge area with plugged and JB filled holes with 1 discharge passage at .165"



  • Northern California ... Old Hangtown
** Home of MOTORHEADS AG Tuning Services **

RAW TM-1000 Bottle Hybrid *Reg .177 & .20
M-rod .22 Bull Pup *Reg
M-rod .177 HFT * Reg
Evanix G1 Rainstorm .22 *Reg
Crosman 1701P .177 *Reg
FD-XS60C PCP .177
AA TX-200 Mk-III .177 Vortek FT
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Offline Motorhead

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Re: Revisiting the HATSAN AT-44 valve mods .... For a Regulator conversion.
« Reply #3 on: December 10, 2013, 05:44:29 PM »
Hot Dang !!! .... Hubb regulator showed up today for the project  ;D ;D ;D

Got a shipping notice it mailed Monday Dec 2 from Holland .... Received USA west coast Dec 10
WOW !!! .... near 1/2 way around the globe in 8 days  :o .... impressive to say the least.

Results to follow .... But O'baby it's sooooo cold outside  :P
  • Northern California ... Old Hangtown
** Home of MOTORHEADS AG Tuning Services **

RAW TM-1000 Bottle Hybrid *Reg .177 & .20
M-rod .22 Bull Pup *Reg
M-rod .177 HFT * Reg
Evanix G1 Rainstorm .22 *Reg
Crosman 1701P .177 *Reg
FD-XS60C PCP .177
AA TX-200 Mk-III .177 Vortek FT
HW 35 .177 Vortek
Diana 75 HV TO-1 10M Match  .177 JM
FWB 124D  .177 JM
Barnett Spitfire .177  Tuned
Stoeger X-20 NP .22 
Benji C9A .20
Industry B3 .22
Crosman PC-77 & SSP-250 .177   
Shoebox 4.5K & Guppy

Offline Motorhead

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Re: Revisiting the HATSAN AT-44 valve mods .... For a Regulator conversion.
« Reply #4 on: December 11, 2013, 12:37:17 AM »
**Went in and changed spring pre-load lowering velocity with 2K in tank to be @ 860fps before installing regulator.

Got it installed .... Changing no settings 875 fps with 14.3 pellets.  *24.3 ft lbs
So velocity about where it was  ;)
Some warmer days and we'll shoot for some string data  ;) and see what shot count does on and off regulation.
« Last Edit: December 11, 2013, 02:00:15 AM by Motorhead »
  • Northern California ... Old Hangtown
** Home of MOTORHEADS AG Tuning Services **

RAW TM-1000 Bottle Hybrid *Reg .177 & .20
M-rod .22 Bull Pup *Reg
M-rod .177 HFT * Reg
Evanix G1 Rainstorm .22 *Reg
Crosman 1701P .177 *Reg
FD-XS60C PCP .177
AA TX-200 Mk-III .177 Vortek FT
HW 35 .177 Vortek
Diana 75 HV TO-1 10M Match  .177 JM
FWB 124D  .177 JM
Barnett Spitfire .177  Tuned
Stoeger X-20 NP .22 
Benji C9A .20
Industry B3 .22
Crosman PC-77 & SSP-250 .177   
Shoebox 4.5K & Guppy

Offline GARY T

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Any update?
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Offline bruce32466

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**Went in and changed spring pre-load lowering velocity with 2K in tank to be @ 860fps before installing regulator.

Got it installed .... Changing no settings 875 fps with 14.3 pellets.  *24.3 ft lbs
So velocity about where it was  ;)
Some warmer days and we'll shoot for some string data  ;) and see what shot count does on and off regulation.

New to this forum and just got a Hatsan at44 .22 long. I would like to install a regulator on it, but before going through all this trouble, It would be nice to see how you did on the pellet count. What I'm trying to achieve is as many consistent shots as possible @ 900 - 950 ftps using 21.14 grain beeman kodiak. with your mods and a Robert Lane regulator,  what could I expect in results?

Thanks,
Bruce.
  • CA

Offline Bwalton

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Looks like you went from 965 to 875 with the regulator, my mods were a little different...with out the regulator I tuned to 890fps for the AT,44 short....My mods were as follows..I plug two hole because the one did not line up, left 4 open..and went 3 1/2 turns out. With the regulator for 20 shots I got a  ES of 9 and a Avg of 824fps now...a whole lot less work. Same results or better, shooting 18.13gr , with 14gr I think it would be a much higher fps'...But with the 18.13gr you have more ftlb. Also Roy makes a very good regulator local no need to go outside the U.S
The Hatsan is very ez to tune. Bec even without the regulator, and just plugging two holes, I got a avg of 890fps shooting 18.13gr with a ES of only 13.
« Last Edit: June 28, 2014, 01:37:13 PM by Bwalton »
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Offline bruce32466

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bump ;D
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