Author Topic: Hatsan Air Stripper Adjuster  (Read 1044 times)

rsterne

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Hatsan Air Stripper Adjuster
« on: October 14, 2016, 03:57:35 PM »
Quite a long time ago I made some alignment tools (pilots) out of wood to allow me to set the stripper cone parallel to the bore on installations where the alignment wasn't great, and I had drilled out the outer stripper housing and installed six setscrews to allow me to move the cone around....



While these did a great job of what they were intended for, adjustment of the gap was primarily an eyeball thing.... A few months ago, when I changed over my Hatsan AT-44 S-10 Long to shooting the 34 gr. JSB Heavies, I checked the alignment of the stock Hatsan Stripper with one of my pilots, and found it was virtually perfect.... At the time, I had been reading up on Barrel Harmonic Tuners, and several people told me that just a few thou change in the position of the adjusting weight can drastically affect group size.... Simultaneously, I read a few articles about Air Strippers, and the opinion is split about which is the operative factor, the gap between the muzzle and the stripper cone, or the effect of moving the weight of the cone back and forth.... I think it may be a combination of the two, but in reality DOES IT REALLY MATTER?.... I mean surely the goal is to reduce the group size as much as possible by moving the cone back and forth until you find the sweet spot where the group is the smallest.... So, I decided to design an adjustable version of the wooden pilot above, that would allow me to change the position the cone by just a few thou at a time, and would also be repeatable.... I came up with the following design, but it had to wait until the Motel wasn't so busy and I had some time to get into the shop to make it....

Instead of all wood, the core of the new pilot is turned from a 1/2" steel rod.... The mid-body is a precise slide fit in the stripper cone, which will vary with caliber.... There is a shoulder above that which is just under 12mm (the OD of the brass cone) so that it can push the cone into the hole in the stripper body when required.... Behind the mid-body the steel shaft is turned down to 3/16", and a piece of hardwood dowel, drilled out to 3/16", is pressed onto it.... The OD of the dowel is then turned down until it just slides into the muzzle.... The center hole in the end of the steel shaft insures it remains concentric with the midbody of the pilot that slides into the cone while turning the OD of the wooden bushing.... This insures the cone and bore are concentric and parallel....



The aluminum "nut" and the front of the steel shaft are threaded 1/4"-28, so that each turn is 0.036" of travel.... That works out so that 10 deg. of rotation is 0.001".... There is an 8-32 setscrew pushing lightly on a short piece of 1/8" Delrin rod against the threaded shaft to act as a brake to keep it from self-adjusting, and a screw slot in the end of the shaft for adjustment.... Turning the shaft changes the position of the shoulder on the shaft relative to the end of the aluminum collar, which in turn pushes the cone deeper into the body of the stripper when the aluminum collar is pushed against the end of the stripper body.... In the photo below, the cone is at the deepest position, with about a 1/2 caliber gap between the muzzle and the end of the cone....



In the photo below, the cone is slid out far as it can go, and the gap is about 2.5 calibers.... The cone has a slot which limits it's travel before it hits the setscrew in the stripper body.... There is a 1/2" diameter milled pocket that is 0.4" deep in the aluminum collar to allow the shoulder on the pilot a place to go when the collar is screwed in to retract the cone position.... The gap you see between the collar and the stripper body is the total adjustment range, which is 1/2"...



With the collar threaded down until the cone has the largest possible gap, it looks like the photo below.... You can see the shoulder on the pilot up inside the aluminum collar, and the center hole in the end of the steel pilot shaft with the wood bushing to protect the bore.... If you look closely, you can see a center punch mark at the end of the screwdriver slot, so I can tell full turns from half turns, and of course I can also measure how far the threaded shaft sticks out of the aluminum.... This is not a difficult tool to make on a lathe, but it is surprising how much time even a simple project can eat up.... about 4 hours in this case, plus the design time.... and then the time to write up this report of course....



I hope the photos and the description make it clear how it was made, and how it works....  My plan is to start like this, with the cone fully out, with the screw slot and center punch mark pointing at the set screw hole in the collar.... I will slide it in until the collar touches the end of the stripper body, snug the setscrew holding the cone in place, slide out the tool and shoot a group at 50 yards.... I will measure and record the group size, screw the threaded rod in one turn, slide the tool back into place, loosen the setscrew until the cone moves in 0.036", snug it up and shoot another group.... I will keep doing this until the cone is as far in as possible.... That will take 14 turns, so the initial test will be 15 targets.... Graphing the results should quickly narrow down the best position of the cone, and at that point I plan to repeat the process with 1/4 turn adjustments, or less if required.... If there are two (or more) sweet spots, I can explore them both, possibly at different ranges.... I think you could spend a whole day (or a few days) just tuning with this device.... I hope it's worth it....  ::)

Bob


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Re: Hatsan Air Stripper Adjuster
« Reply #1 on: October 14, 2016, 11:01:35 PM »
Strippers are best seen in person  ;D
Wildly misaligned strippers can be quite entertaining  :o

In all seriousness .... Great thread Bob having much useful FYI
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Scott

calinb

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Re: Hatsan Air Stripper Adjuster
« Reply #2 on: March 25, 2018, 10:31:22 PM »
I'm making progress with my Hatsan Air Stripper and my copy of your tool, Bob. For anyone arriving here for my sequel to this old(ish) thread, I mistakenly posted about my fabrication of Bob's tool on his older older thread (http://airgunguild.com/pcp-c02-and-helium-powered-airguns/aligning-a-hatsan-air-stripper/msg20074/#msg20074).

It looks like I will need at least a couple more set screws in the air stripper, because I've learned that after repeated firing of my LGV springer, the brass insert can cock in the holder. I get it nicely centered with the tool and the single set screw remains tight with no discernible play anywhere, but it's definitely cocking (rotating) on the single set crew. On several occasions I've shot a couple of rounds into the same hole and then the POI shifted and I shot two or three more rounds into the offset hole! I started to check the air stripper alignment with the tool after every shot and, sure enough, the tool reveals that the POI shift correlates to an air stipper mis-alignment. I guess I'll try installing two more set screws in the air stipper, but I noticed that you installed a fourth set screw next the original one too. Is it useful?

I honestly don't know how anyone can get much out of a Hatsan air stripper without your tool, Bob. Hatsan should include one (and three set screws) with every unit shipped!
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rsterne

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Re: Hatsan Air Stripper Adjuster
« Reply #3 on: March 26, 2018, 08:21:10 AM »
I actually used 6 screws, in two rows of three, and the bore of the stripper was drilled out from 12mm to 1/2" to allow the cone to be moved more.... It is held only by the screws.... If your stripper is aligned well with just the single screw, then stay with that....

Bob
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calinb

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Re: Hatsan Air Stripper Adjuster
« Reply #4 on: March 26, 2018, 09:20:41 AM »
I can easily get my single set screw stripper aligned well using the tool. The problem is its doesn't stay aligned under the recoil of my springer. It stays tight (set screw and brass piece) to a "finger" and allen wrench test, but the brass insert is rotating / cocking on the set screw.

I tried twisting the brass piece just before my last tightening turn of the screw so that the edge of the milled slot in the brass piece is hard up against the side of the set screw. That seems to help somewhat, and I think and it's actually more effective when I twist it clockwise (when viewed from the muzzle) to the milled slot edge, but I will still need more screws. The fact that abutting the set screw against one side of the slot than the other also indicates that the recoil of a springer is probably at play here!

Thanks very much for your reply, Bob. I'll go to six screws if I must, but perhaps I'll try three screws first. Until this set screw issue is well-known, I can check alignment in my testing with the tool after every shot.


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calinb

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Re: Hatsan Air Stripper Adjuster
« Reply #5 on: April 02, 2018, 12:55:51 PM »
UPDATE: Two more set screws (three screws total) solved the problem for me with my LGV Master springer. I'm not getting POI shifts anymore and checks with the alignment tool prove the brass cone is staying put! :P
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