Reverse enginerding, does it work?



Author Topic: Reverse enginerding, does it work?  (Read 3879 times - 1 votes) 
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #40 on: March 13, 2018, 09:43:32 PM »
Pistol shrouds shouldn't be too much work but this one was, I started with 30 mm bar stock, most of it is gone now. Had to use every trick in the book since it has t-grooves, round bottom slots in a strange angle, serrations, million holes, angled ports, long holes, internal & external radius and all that stuff.
Guns internal parts are mostly removed, trigger guard chamfers had to be filed in there, lots of alu powder. Black part on top is the first rear sight part, it contains the ramp for elev. adjustment and moves back and forth to change sight radius.
Finally a comparison between my second homemade target pistol and this one, I do believe that the grip material for the newest is that same wood.
« Last Edit: March 13, 2018, 09:45:43 PM by Finn »
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Offline Rob M

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Re: Reverse enginerding, does it work?
« Reply #41 on: March 13, 2018, 09:43:55 PM »
looks awesome, and from you I'm not surprised !!   ;D
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Re: Reverse enginerding, does it work?
« Reply #42 on: March 14, 2018, 02:15:41 AM »
Oh my that is going to be one fine looking pistol. Time and patience to build it, outstanding!
Could I do it, yes and no. I dont have enough time.  ::)
I'm more of a funktion over beauty kind of guy.
Albert if you ever want to try and shoot the 20mm, it can be arranged.  ;)

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Offline Rob M

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Re: Reverse enginerding, does it work?
« Reply #43 on: March 14, 2018, 02:50:18 AM »
what model is the bottom one ?>
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #44 on: March 14, 2018, 07:08:58 AM »
I don't have a name for it but it is basically a mix of Walther LP line of pistols and my own ideas built back in 2013 if my memory serves me right.

Oh my that is going to be one fine looking pistol. Time and patience to build it, outstanding!
Could I do it, yes and no. I dont have enough time.  ::)
I'm more of a funktion over beauty kind of guy.
Albert if you ever want to try and shoot the 20mm, it can be arranged.  ;)

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Form comes from the fact that I am building a 1:1 scale model of a gun, my own designs are usually a bit more utilitarian.
Shooting the 20 mm beast would be once in a lifetime experience (I mean who wouldn't like a good beating ;D). If I start weight lifting today, I may be able to handle it when the time comes.  I will probably never build anything like that, can't even think of a range nearby where I could actually shoot it.
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Online AmBraCol

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Re: Reverse enginerding, does it work?
« Reply #45 on: March 14, 2018, 11:12:31 AM »
I like that grip.  Need something similar for my IZH-46M.  :-D  Thanks for sharing this build with us!
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #46 on: March 16, 2018, 06:26:27 AM »
Worked the grip yesterday, it not worthy oil like a sponge.
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Re: Reverse enginerding, does it work?
« Reply #47 on: March 16, 2018, 06:35:02 AM »
That is really beautiful, nice work man!
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Offline Rob M

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Re: Reverse enginerding, does it work?
« Reply #48 on: March 16, 2018, 08:46:51 AM »
Worked the grip yesterday, it not worthy oil like a sponge.

this is outrageous lol..the factory will be calling you for woodcarving  tips
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #49 on: March 16, 2018, 11:20:16 AM »
Just saw what I posted, this is an outrage, I wasn't politically correct when using the s*ck term to describe the oil absorbing capacity of the wood. Normal words should not be turned into hebrew by forum censorship software, I hope that people could behave so that automatic censorship could be omitted, but that never happens when one can anonymously express thoughts.

Enough with the rant, time to check if the gun still shoots with the grip on. If it does I will test a couple different diameter valve stems I have and start designing the regulator and air tube.

Grip will receive a new coat of oil whenever the last one has been absorbed, it has two coats in the photos.  Might just be the best grip I ever made, it's not like holding a pistolgrip it's more like putting your hand in lukewarm water.
« Last Edit: March 16, 2018, 11:28:54 AM by Finn »
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Offline farmerjoe99

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Re: Reverse enginerding, does it work?
« Reply #50 on: March 16, 2018, 01:37:34 PM »
Truly amazing work Albert!! Thank you for sharing your builds, they are a joy to follow and inspiring as well.

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Offline Rob M

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Re: Reverse enginerding, does it work?
« Reply #51 on: March 16, 2018, 02:57:01 PM »
hows the semi auto function now ?
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #52 on: March 16, 2018, 04:33:28 PM »
Seems that I have lost the original sear spring but it did work with poorly fitting spring. In fact it was difficult to adjust the mechanism in such way that it wouldn't work, fired 40 pellets and it worked well if the pressure was kept between 65-80 bar. I feel it works better and has more velocity with tight valve stem (0.025 mm radial clearance). Next I would try to find the best length for valve stem, it will be simple if I make a piston with small adjustment screw, no need to cut the valve. However it is best to do those things last as the hammer will be heavier when right hand cocking lever is done.
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #53 on: March 16, 2018, 10:48:45 PM »
The day is over, it currently 3:40 am and I have been making parts six hours straight with no breaks.
Parts that I made:
- Regulator housing
- 3 sets of regulator springs (0.4 mm, 0,5 mm and 0,6 mm)
- Regulator piston and seat
- Retaining part for piston seat
- Part that attaches the reg to gun.

Now it is time to relax and crack open a beer and watch some pbs space time, tomorrow is the air tube day and maybe I get to shoot the pistol with mock up sights on Sunday. Some 500 crosman destroyers have been destroyed while testing the action, really they are almost good enough for that.
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #54 on: March 18, 2018, 11:31:36 AM »
Almost there, now that I can actually shoot the gun I am starting to see and feel what I have made. It is just incredible experience, trigger is absolutely match grade, light 200 gram pull with short clean reset and the gun points itself to the target with no effort.
  Air tube is steel and sets the CG nicely. Shot the gun with 65 bar fill, as I forgot to make the test connector to check reg. output so I have no idea what the set pressure is but it is over 70 bar. Shot a couple of 5 shot groups from 5 meters away (to save the furniture) without sights as fast as the finger moves and they were all about 1 inch.  Also had a couple of goofs, forgot to tighten the barrel setscrews and to my surprise it shot fine even when the barrel had slid 4mm forwards.
Also had a bad idea about using M3 screw on the shroud front screw hole as temporary front sight. I
t would have worked but as I shot the screw turned further in and soon the pellets started hitting windows 1 meter away from target. Had to cut that screw off with dremel diamond burr because it was bent 90 degrees and pointing outwards from the muzzle, luckily no damage was done to the shroud.
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Offline Rob M

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Re: Reverse enginerding, does it work?
« Reply #55 on: March 18, 2018, 11:49:48 AM »
amazing... awesome job
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Re: Reverse enginerding, does it work?
« Reply #56 on: March 19, 2018, 12:56:18 AM »
That is truly amazing, something that no other can say at the range. "I just wanted this pistol so bad that I decided to make it"  ;)

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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #57 on: March 19, 2018, 08:15:13 PM »
I have thought about that, but nobody at the indoor shooting range where I go has any interest in what guns someone has, neither are they very knowledgeable about air gun tech in general. So I don't tell anyone I made the gun unless they ask, you guys are the only people getting to see this gun being built and have all this in depth information about it.

Wasted half a tin of pellets today, it didn't take too long. I made temporary rear sight from sheet metal, M3 setscrew serves as front post. Accuracy is good enough I think, it is likely to improve when I get those sights done and proper crown on the barrel. Tested pellets were RWS R10, RWS meisterkugeln LP, Exact 8,44gr and Crosman domed.  Regulator was set at 60 bar, used 7 0,4mm bellevilles, chrono was set up just front of the target at 9 meters. Only pellet that gave readings was exact 8,44 gr and it clocked in at 110 m/s at the target. Velocities were really stable over 20 shot test series, it was always 110 or 109 m/s, I should mention that I took my time shooting as the chrono is picky about shot placement and larger velocity spread is expected when rapid firing.
 Pressure must be changed if more speed is required, if mainspring adj. screw is out of setting range by 1/2 turn, auto loading doesn't work anymore. There is a range of one complete turn (0,8 mm pitch)where everything works perfectly, that is only +-0.4 mm more or less tension on the spring. Heavier pellets are more reliable, JSB exacts worked every time no matter how fast the trigger was pulled, Crosman domed on the other hand barely worked at all, they almost fall through the mag. RWS pellets all worked but they must be pushed into magazine properly or the skirts will rub in the mag housing.




 More testing tomorrow, I want to check how the mainspring screw effects velocity vs auto function. Accuracy will also be tested more, it might be a good idea to make a removable rail for red dot sight while iron sights are WIP, really want to take my time and make those sights perfect.
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #58 on: March 25, 2018, 07:56:21 PM »
Made more parts, rear sight is almost done. Air stripper is also done, don't have any data if that changed anything else than looks of the muzzle area. Upped the regulator pressure and spring tension, V0 is now 130 m/s and I am astonished by the accuracy of this thing, took 5 shots (rested) in approx two seconds and got 7 mm hole in the paper 9,5 meters away!  Only the first shot after refill hits low, I guess something has to be done with the regulator to fix that, need to think about it.
 I used reflex sight for accuracy testing, it would be difficult to use open sights shooting from tabletop where the eye is closer to the gun, grip also is only good for offhand shooting.
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Offline Finn

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Re: Reverse enginerding, does it work?
« Reply #59 on: March 25, 2018, 08:23:07 PM »
Reflex attached to the shroud rail, really horrible position for offhand, works ok for benchrest shooting. Had to install some filters inside the sight to get rid of light streaks and reduce the dot size, now it is really small on the lowest setting and light artifacts are gone.
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