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PostPosted: Sat Dec 12, 2015 5:41 pm 
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Posts: 1079
Location: Calgary, Alberta
Jeez Bob, you burning midnight oil on this?
Forget spring, I'm starting to think this will be done by the new year....(If Russia can hold off on nuking the Turks :shock: )

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The flaw with experience is, it causes us to forget what we were like when we didn't have any.


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PostPosted: Sun Dec 13, 2015 7:14 pm 
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Location: Coalmont BC
I couldn't put it off any longer, so today I did most of the machining on the Monocoque Tube.... all the holes for the various bolts, plus the loading port and transfer port are done, plus the additional 10-32 tapped hole for the front of the Picatinny scope rail.... Here is the top view....

Image

Everything fit really well, all the bolts fit into the holes, but a couple were tight enough to require a touch with a file or Dremel bit to make them easy to assemble.... Careful deburring was the order of the day to make sure that the Breechblock didn't hang up when slid inside.... I was particularly proud of how well the loading port lined up.... Below is the bottom view, and you can see that the transfer port and mounting bolts also line up with the Spacer....

Image

All in all, I am very pleased.... The key to the accurate machining was using the 5/16" hole behind the loading port where the heads of the screws are that take the tension and compression loads of the barrel and tube.... Using a 5/16" pin in the chuck of the lathe through that hole, both for setup (measuring everything from that point), and for indexing 180* for the holes on the bottom, did the trick....

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: Mon Dec 14, 2015 3:28 pm 
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Location: Coalmont BC
Today I machined the top of the PRod trigger group to fit the 1-1/4" OD x 0.095" wall tube.... It normally fits a 7/8" OD x 0.065" wall tube, so one of the concerns is that the sear projects far enough into the thicker tube I am using to safely hold back the hammer.... I used the 1-1/4" diameter router bit I have to cut the larger radius, and at the point it barely touched the center of the recess I stopped and checked the seat engagement.... It was about 1/32", which although I feel was perfectly safe (after all, the hammer can't raise up by more than the clearance in the tube), I decided I wanted a bit more.... I noticed that the boss in the casting that holds the sear pivot pin was about 0.010" below where the router cut, so I mounted the trigger group back in the milling attachment and milled down until I just touched the edge of that.... The arrow in the photo below points to that shiny mark, right beside the sear.....

Image

With the trigger group machined to that depth, there is over 1 mm of sear engagement (I'll get an exact measurement after I cut the slot in the tube), and I'm happy with that.... One other thing that is important is that the slot in the tube to clear the sear must be slightly more than the full length of the sear.... The parts of the sear in front and behind the actual sear now project slightly above the bottom of the tube recess in the trigger group, so if the slot is too short, it would affect the engagement depth, and in fact could even prevent the sear from cocking properly.... All the other parts (the trigger and the intermediate link) are still well below the tube and do not interfere....

The PRod trigger is very strongly built, and I see no problem with it easily withstanding way more than the 20ish lb. maximum load I will be asking it to hold....

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 Dec 16, 2015 6:11 pm 
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Location: Coalmont BC
Today I made the front half of the Valve, and cut the O-ring groove in the Fill Fitting while I was set up for that....

Image

You will notice that I am using a conical valve spring to eliminate any restriction on the inlet side of the valve poppet.... I hope to work on the back half of the Valve tomorrow....

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: Fri Dec 18, 2015 10:05 pm 
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Location: Coalmont BC
I worked on the Valve today, and completed the machining on the body....

Image

While the rear half was in my square Collet holder so that I could index it 90* to drill and tap the four 1/4"-28 mounting holes, I also drilled the port and the two 8-32 screw holes beside that which hold the two tubes together at the front of the Breechblock.... In addition, I screwed the valve front into place and drilled and tapped 1/8"-NPT for the gauge which mounts on the left side.... I was extremely pleased with how well everything lined up.... Here is a photo of the assembly (without the tubes)....

Image

The two long 8-32 screws which hold everything together dropped right through the holes and screwed in with my fingers.... I still have to make the poppet, and install an O-ring seal for the stem in the back of the valve, but this is the last major internal part.... It won't be long I will be able to machine the lower tube to hold the valve, hammer, and fill fitting.... Unfortunately, I am still waiting for the 1/4" long 1/4"-28 SHCSs which hold the valve and fill fitting in place against the air pressure, so I won't be able to pressure test it until they arrive....

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 Dec 19, 2015 7:38 am 
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Looking great. I can count the number of times things have lined up that well for me on the fingers of one hand. Actually, I exaggerate, I don't need the fingers. I really need to take my layout and setup skills up several notches.


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PostPosted: Sat Dec 19, 2015 1:16 pm 
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its coming along nicely Bob... 8) 8)

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PostPosted: Sat Dec 19, 2015 3:15 pm 
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Location: Coalmont BC
I made the rest of the valve parts today.... Here is the finished poppet and stem seal....

Image

The poppet is made from 3/8" diameter PEEK, and I threaded the end of the 1/8" drill rod stem to 5-40 thread, drilled the PEEK with a #38 drill (tap size for 5-40) and counterbored it 0.10" to 1/8" and then just wound the stem into the PEEK, letting it cut its own threads until it stopped.... It was so solid I couldn't back it out.... I then cut the head to length and turned it for the spring seat right on the stem.... It sealed first time.... The stem seal is a #006 70D O-ring sitting in a 1/4" diameter recess in the valve body, held in place with a short piece of 7/16" bolt faced off flat on both ends and a screwdriver slot ground in the end for installation.... It has only enough drag to barely hold the weight of the valve body, so considering the forces on this valve shouldn't even be noticed.... The inside of this valve is huge....

Image

The throat (visible in the bottom of the rear section on the left) is 5/16" ID, so the seat margin is only 0.030".... The valve is drilled 11/16" ID, leaving a 5/32" gap all the way around the poppet head (4 times the throat area).... The front of the valve is drilled 13/32", the same as the front ID of the conical valve spring, and so has twice the area of the throat, allowing the air to enter the valve from the reservoir much easier than it can get out.... I don't think there should be any problem with this valve flowing air....

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: Sun Dec 20, 2015 7:12 pm 
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Location: Coalmont BC
Today I worked on the Thimble which contains the Barrel Port and Loading Tray.... The 3/8" diameter stub on the barrel fits into the front of it to insure alignment with the bore, and the joint is sealed with an O-ring, which also seals it into the Breechblock in front of the Transfer Port.... I haven't yet machined the O-ring groove behind the transfer port in it.... The barrel port in this part was machined with a 3/16" end mill starting at 30* to match the transfer port at the back of the port, and then angled to 45* to make the front of the port longer to match the bore area.... The port ends up just over 3/16" wide x 5/16" long at the boreline, but blends into the 17/64" round transfer port.... The finishing touches were done with a Dremel....

Image

The hole at the back fits over the head of an 8-32 screw in the bottom of the Breechblock, that takes the end load from the barrel screwing against it, and the air pressure inside it.... You can see that screw in the bottom of the loading tray in the photo below....

Image

Once again, I am extremely pleased with the way everything fits and lines up.... This relative small part took about 6 hours to make.... Next up is the Bolt, which will carry the O-ring that seals the breech inside this Thimble.... It is the retractable style I developed a while back, with no probe to restrict the airflow.... Then comes the complicated job of machining the "J" shaped bolt slot in the Breechblock and Monocoque tube.... I'm not looking forward to that....

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: Sun Dec 20, 2015 8:46 pm 
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Joined: Sun Feb 10, 2013 1:16 pm
Posts: 1787
The effort you put into the transfer port is amazing. That should certainly breathe well!

My brain must be addled - I'm not following how the parts line up. If the hole in the back of the thimble came over the screw in the loading tray, surely that would block the the tray? I must have got completely the wrong end of the stick :oops: Any chance you could show the two parts side by side so I can see how they line up?


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PostPosted: Sun Dec 20, 2015 8:56 pm 
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Location: Coalmont BC
The lower photo shows the tray installed in the Breechblock.... The top of the head of the screw is a few thou below the bottom of the groove in the loading tray.... It doesn't hold the tray down (it can't come up, it fits in the 1/2" hole through the Breechblock at both ends).... it just keeps it from sliding back.... If you look at the photo at the top of this page, you can see the screw head in the slot in the Breechblock....

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: Sun Dec 20, 2015 9:53 pm 
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Ah, I think I've got it now. Thanks.


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PostPosted: Mon Dec 21, 2015 4:34 pm 
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Location: Coalmont BC
Today I made the Bolt, except to fit the handle, and cut the O-ring groove in the Loading Tray / Thimble behind the transfer port.... The Bolt still has to be cut off about where the line is drawn, which will be flush with the back of the Breechblock when fully open....

Image

The Bolt has a very long travel, when it is fully forward the shoulder on the Bolt is up against the Loading Tray.... This is necessary because of the long bullet, necessitating a long loading port, plus the nose of the bolt has to go past the transfer port, which had to be far enough from the front of the loading port to allow for the O-ring to seal when retracted so that the nose of the bolt clears the back of the transfer port, without the O-ring dropping into the port when fully forward.... It will retract about 3/8" from the full forward, loading position to the firing position....

It's time to do some more thinking to make sure I don't forget anything before I continue machining the tubes.... The Monocoque tube and Breechblock both need the slot machined for the bolt handle.... and the Reservoir tube has yet to have any machining done.... although all the internal parts are now complete....

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 Dec 23, 2015 8:45 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
Only got a few hours in the shop today.... but I got the holes in the top and bottom of the lower tube machined.... That allowed me to bolt together some of the sub-assemblies for the first time.... It actually is beginning to look like something other than a pile of parts....

Image

The barrel and Monocoque tube are not in place in the photo, because I wanted you to be able to see the general arrangement of how the parts fit together.... It was great to actually be able to shoulder it and see how the ergonomics work.... I'm quite pleased, although the gun is definitely long.... The LOP as shown in the photo is 14".... I still have to machine the side holes for the valve screws, the hole on the left for the gauge, and the slot on the right for the cocking handle for the hammer.... Then it remains to machine the slot for the bolt handle in the Monocoque tube and the Breechblock.... The next time I put it together it should look close to the finished product.... Long, thin, and heavy....

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 Dec 24, 2015 7:49 am 
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Joined: Wed Sep 14, 2005 8:47 pm
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Location: 123 gun street Nova Scotia
i finally understand the butt / breech . looking great


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