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PostPosted: Wed Nov 18, 2015 12:48 pm 
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Location: Coalmont BC
I have most of the materials coming to start work on this project.... I do need, however, a small block of aluminum for the front bipod mount.... I need a piece 1.5" x 2" x 2".... and 6061-T6 would be suitable, no need for anything fancier.... Anybody have a piece kicking around their shop you can spare?....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Nov 18, 2015 4:39 pm 
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Many Thanks to Watertown for the generous offer.... address on the way....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Nov 18, 2015 5:02 pm 
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Location: Coalmont BC
I have been looking at my supply of hammer springs for this project.... I needed a long, rather weak spring for the captive spring guide concept, and it turns out that using two QB (like) hammer springs riding on one guide should work perfectly.... The ones I have are actually 0.36" OD x 0.051" wire x 2.4" long, but they have the same spring rate and length as a QB spring.... Stacking two of them end to end gives a spring of the following specs....

LOA 4.80"
Rate 9 lb/in.
Max. travel 2.70"
Max. force 24 lbs.

There are two adjustments, the preload on the spring (set by the length of the spring guide, which is adjustable).... and the distance the end of the guide is clear of the inside of the hammer when uncocked (which sets the distance that the spring is compressed when the gun is cocked), also adjustable.... The hammer pulls back 1.50" from touching the valve stem to being cocked.... Here is a table of the various combinations....

Image

The columns, left to right, are (distances in inches, forces in lbs.):
The distance the spring is compressed by the guide (preload);
The force required to do that (also the force at the beginning of the cocking stroke);
The distance the spring is compressed during cocking (the guide is clear of the inside of the hammer by 1.50" minus that distance) ("D") ;
The total distance the spring is compressed when cocked;
The force required to do that (force when cocked);
The average force over the travel of the hammer ("F") ;
The energy given to the hammer during the firing stroke (F x D / 12) ....

As you can see, I can vary the hammer energy from 1.0 - 2.0 FPE, and I am expecting to need about 1.4-1.5 FPE, so I should have no problem finding a setting that will work.... When I actually make the spring guide and adjuster I will post a photo of it....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Nov 18, 2015 7:21 pm 
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Location: P.G. B.C.
rsterne wrote:
It has been done already, I believe it was a bullpup, loaded through the butt....

Bob


An AC DC gun?

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Daryl


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PostPosted: Wed Nov 18, 2015 9:03 pm 
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IIRC, the gun with the reservoir around the barrel was called the "Uni"? ..... I am not aware of it's preference.... :lol:

Well, I made the first part today.... Amazing how something as simple as a spring guide and adjuster takes so long to make.... Here it is....

Image

The spring guide is made from a piece of 1/4" drill rod 6.5" long.... It is threaded 1/4"-NF for 1.25" at the back, and carries two nuts, locked against each other, and a bumper made of a 90D # 108 O-ring.... The guide is also threaded at the front for another nut, which is held with Loctite bearing mount and then turned to provide a spring seat and fit loosely inside the hammer.... The adjuster is a 9/16"-NF bolt 2" long (which I had to anneal before machining) drilled through 1/4" and then counterbored to 3/8" for a depth of 1/2" to accommodate the length of the two springs, which total 4.8" long.... They are 0.36" OD x 0.051" wire.... As pictured, the spring is under 0.8" of preload (4" fitted length) and it takes about 7.25 lbs. to move it.... That is how hard the hammer would have to hit it on rebound to store any energy in the spring, so I think the chances of hammer bounce are very small.... It will take about 20 lbs. of force to cock the gun, which is high but certainly manageable.... The chart in the previous post shows the large range of adjustability....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Nov 18, 2015 9:21 pm 
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Location: Canada
Magair 1180


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PostPosted: Wed Nov 18, 2015 9:36 pm 
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Nope, the one I was thinking of was the "Uni".... http://www.gatewaytoairguns.org/GTA/ind ... ic=78088.0

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Nov 18, 2015 10:20 pm 
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Location: Canada
Well that's cool too. 8)


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PostPosted: Fri Nov 20, 2015 1:08 am 
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Location: Alberta Canada
Early 18th century was the first. Bbl incased in a copper containment vessel. Built by IIRC an Austian. Cant find my file on it at the moment. Wee bit of history lesson.

Interesting chart Bob.

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May the cry of the pack be with you upon your hunt

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PostPosted: Fri Nov 20, 2015 12:03 pm 
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Thanks for the history lesson, Kim.... Never anything new under the sun, it seems.... 8)

With the two adjustments, one for preload on the spring, and the other for the clearance between the end of the guide and the hammer (which also governs the cocking distance) there is more than one way to get a desired hammer energy.... My thoughts are that having minimal clearance (e.g 0.1") for the hammer to rattle around in is the best, because you get a greater cocking distance, but it may be that increasing the preload and allowing more clearance may reduce hammer bounce, if any still occurs.... I can't imagine that is possible with this design, that is the whole idea behind it, well that and to reduce the maximum cocking force....

I have found in the past that the worst possible arrangement for hammer bounce is when the preload is minimal, with the hammer spring either just touching the hammer when uncocked, or barely compressed.... Using a lighter spring with more preload, seems to bounce less.... Going the other way, using a short stiff spring that rattles around loose, generally greatly reduces (or sometimes eliminates) hammer bounce, but then the gun gets hard to cock at the end of the cocking stroke, for a given hammer energy requirement.... I came up with this idea, and tried it on my Grizzly (.30 cal XS-60c HPA conversion) and I really liked it, so decided to incorporate it into all my future PCPs where possible.... The downside is that it requires a lot of length.... but in this design that is hidden inside the extended main tube....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Nov 21, 2015 6:15 pm 
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Location: Coalmont BC
My Christmas present from my dear wife came in today....

Image

Millet 6-25 x 56mm SF.... Just another scope you say?.... well, yes, but this may give you a hint about what is different about it.... those are 1" rings for comparison....

Image

Yes, the tube is 35mm, and the scope is 22" long with sunshade and weighs 2 lb. 13 oz. with the rings.... Here is it sitting beside a Leapers 3-9 x 32mm AO with sunshade.... :shock:

Image

The scope is very bright and clear.... It focuses down to 15 yards, and has 140 MOA of Elevation adjustment.... I will be machining the Picatinny rail it mounts on to a 20 MOA angle on the bottom, which should put me on target at 100 yards with the scope still on optical center.... The 1/2 MilDot Reticle is calibrated at 25 X, and there is a mark at 12.5 X, which makes each 1/2 MilDot work out to a full MilDot, so that works out to a lot of holdover just using the dots....

Bad part is, I have to put it away until Christmas.... :lol:

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Nov 21, 2015 7:40 pm 
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Joined: Sun Jul 15, 2012 10:49 am
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Location: Victoria, BC and Clarkston, WA
Monster scope, eh! Not listed on Eric's sight so you must have bought the last one?
Have you looked through it much compared to your old Leapers? Do you know what % light comes through?

Your valve looks very interesting!

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-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Sat Nov 21, 2015 9:08 pm 
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Location: Coalmont BC
That photo is not the valve, just the hammer spring, guide, and adjuster....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Nov 26, 2015 12:22 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8972
Location: Coalmont BC
The bulk of the materials arrived yesterday, and I spent the day finalizing most of the design.... It doesn't look much like an airgun at the moment....

Image

Plastic pipe is for the forestock and cheek piece.... 1 1/4" OD CrMoly tubing for the monocoque upper tube (0.065" wall) and air reservoir (0.095" wall).... The 1 1/8" 2024-T3 Aluminum round bar is for the breech block, valve, front plug, and all other internal mounts.... The rectangular aluminum barstock is for the external parts; the spacer between the tubes, the adjustable stock mounts, and the front bipod/stock mount....

Soon to be converted into a pile of chips, and usable parts, I hope....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Nov 26, 2015 2:23 pm 
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Joined: Sun Jul 15, 2012 10:49 am
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Location: Victoria, BC and Clarkston, WA
Sorry I couldn't get you more scrap aluminum material Bob. I haven't worked at that company since June 2014.

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-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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