I liked the term Monotube, but since there is an air tube under it (making two tubes), it doesn't quite fit.... The upper tube takes all the loads keeping the critical parts (barrel, breech, and scope) aligned, like an Exoskeleton, so that makes it a Monocoque design.... From now on, I will be referring to it as my "Monocoque Design PCP"....
Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count!
Yesterday I got a piece of 1.5" black Delrin rod from Whitewolf (thanks, Kim!) and started turning it into a Buttstock today.... After a few attempts at trying to hold it, I managed to mill off both sides to leave me with a piece 1" thick, which I have drilled and tapped for the 3/8" threaded rod as shown.... It will soon look much prettier....
I usually use a 5C Collet in a square holder to drill holes at 90*, but the parts for this project are over 1" diameter, so they wouldn't fit.... The solution was to turn a 1" long x 1" diam. stub on the end of each part so that I could hold it in the collet as shown below.... The other parts below are the "Barrel Stretcher" which fits inside the front of the Monocoque tube, anchored by three 10-32 x 1/4" low profile SHCSs to stand the load of the Belleville washers that will put the barrel in tension.... and the mount for the Hammer Spring Adjuster which I made previously....
The upper (long) screw in the holder for the adjuster goes through the Breechblock, below the bolt, and the spacer, securing the rear of the two tubes together.... The shorter (lower) screw just mounts it into the lower tube, and will have a short piece of Delrin rod inside the hole pressing against the side of the 9/16" bolt that carries the spring guide, to lock the adjustment in place....
I also got the 10" long Breechblock turned to fit inside the Monocoque tube today, which prepares it for some of the machining to come.... I still have to make the Valve and Hammer.... Then comes the difficult job of machining the 4 foot long CrMoly tubes to hold everything....
Bob
Last edited by rsterne; Dec 10 2015 at 07:54 PM.
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count!
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....
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 to count!
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