Canadian Airgun Forum

I have the tank blocks pretty much finished....



The 18 x 1.5mm studs are done to mount the bottles, the air passages are drilled to connect the bottles to the regulator, and the outer end of them is drilled and tapped 10-32 for plugs, which are a simple low-profile SHCS with a 5/16" OD O-ring under the head, fitting flush in a milled hole.... I have used these before and they work perfectly.... You can see one of the air passages in the right hand hole in the left hand block, and you can see the two 1/8" NPT threaded holes in the bottom of those, which allow a male Foster and gauge to be mounted on the front of the block.... The two tapped holes in the bottom of the tank blocks are to allow me to mount a Bipod, borrowed from my .257 Monocoque PCP, if I want to.... Here is a photo of it, mounted to the front tank band from that rifle....



It is adjustable for height and tilt (the pulleys act as handwheels), and has a level built in.... I probably won't need it on these rifles, because they will sit level on the dual tanks, but adding a couple of tapped holes to allow it to be attached just made sense....

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!

I finished up the tank block for the .183 cal today.... The tank mounting studs are fitted and loctited into place, and the regulator is also in place.... I removed the gauge and fill fitting, and moved them to the front of the tank block, and plugged the holes in the regulator with 1/8" NPT brass plugs.... I could then screw the bottles into place, pop the tank spacer in, and slide a tube into place to see how everything fits....



It all worked out exactly as planned.... .... I have to make the adapter to hold the regulator in the front of the plenum tube, but it looks like the whole idea is going to come together.... I will do the other tank block to the same stage before continuing....

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!

Air in the bottles as well as the aluminum tube?

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Best Wishes
Daryl

The bottles are the primary HPA reservoirs, two x 700 cc = 1.4 litres at 300 bar for the .183 cal, and two x 450 cc = 900 cc at 250 bar for the .22 cal pellet shooter.... The regulator is mounted between the "inverted V" shaped tank block and the tube, which is the plenum.... The valve and hammer will be inside the plenum, with the stock on the back of it, and the barrel above it.... The plenum in the .183 cal will be longer (because the bottles are longer) and be made from 4013 CrMoly, running at about 3600 psi.... while on the .22 I will be using 2024-T3 aluminum above the shorter bottles, running at about 2200 psi....



Dotted lines are for the .183 cal version.... where I will be using the adjustable scope mount to give up to 160 MOA elevation (dotted line) for long ranges....

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!

COOL! tks for the explanation.

_________________
Best Wishes
Daryl

I got the other tank block finished today, and both assemblies fitted together for the first time....



You can clearly see the difference in the size of the bottles.... One of the 3D spacer blocks my son printed for me is in between the long tanks near the back.... They are going to work great, with a simple clamp (or even duck tape) around the outside to hold the tanks aligned with the plenum tube and rigid....

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!

Looking good!

_________________
Best Wishes
Daryl

I finished the Regulator Adapters today, and drilled and tapped them for a (low-side gauge), and for the three 10-32 SHCSs to mount the plenums....



The front end of the adapter (made from 1.25" OD 2024-T3) is tapered to match the back of the regulator, and of course bored for the O-rings and tapped 1/4" NPS to accept the regulator output.... I lubed and tightened each regulator to its adapter, and then used the tapered sides of the tank block (they are at 60 degrees to the base) as a reference to orient the gauge and the upper plenum screws.... The lower screw is on the bottom, referenced off the base, and you can just access it with an allen driver between the tanks.... The drilling of the holes to mount the tube is so accurate I can orient the tube any of the 3 possible ways, which actually surprised me!....

Other than making the O-ring grooves (I will do them along with the ones for the valve, all at one time), the tank and regulator assemblies are now finished, and fitted to the plenums.... Here is the one for the .22 cal pellet shooter, on the 2024-T3 aluminum plenum....



and here is the one for the .183 cal slug shooter, on the (longer) 4130 CrMoly plenum....



I should get about 50 shots at 80 FPE with the 39 gr. BBT slug, and about 100 at 50 FPE with a 25.4 gr. JSB Monster pellet....

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!

Getting "there". Oh boy!

_________________
Best Wishes
Daryl

Pretty soon I will need some barrels!.... Still lots to do, though, I can make the valves, hammers, SSG spring adjusters, stocks....

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!

I started on the valves today by making the poppets.... These valves will be a semi-balanced design, similar to others I have made, but with the balance chamber reversed, with the "cylinder" being part of the poppet and the "piston" mounted on the front of the valve body.... Here is the basic design....



The position of the piston is adjustable to tune the volume of the balance chamber.... Smaller volume acts more like a conventional valve, larger volume "blows open" more, which requires less hammer strike but resists tuning via hammer strike.... Motorhead (Scott) uses this style, and the idea of adjusting it came from sb327 (David).... I decided to make the poppet from 2 pieces, a PEEK sealing portion and an aluminum sleeve/cylinder for the balance chamber.... I was concerned the PEEK may not be strong enough to resist the 3600 psi, and might "creep" over time to pinch the "piston".... Here are the poppets....



The one of the right is complete, the other one has the rough machining done, but it shows the internal O-ring to seal the two part together.... The 1/8" stem is threaded 5-40, and when assembled everything is glued up using Loctite 638 (green).... Final machining of the chamber is done after assembly, with the stem in the lathe chuck, to assure alignment.... The inside is done with a 1/4" mill, and the OD is 0.354", which reduces the force holding the valve against the seat by 50%.... At 3600 psi, it drops from 354 lbf. to 177 lbf.... The minimum clearance from piston the chamber will be 0.075", which is 1/4 of the valve throat diameter.... This means the valve can reach full flow without the poppet touching the piston.... That volume can be tripled if desired, to make the valve open easier.... The vent through the stem is 3/64" (0.047"), as is the hole through the side of the stem....

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!

Well, I got the valve bodies roughed out today....



You will notice that one of the poppets is now all PEEK, as one gun is only 2200 psi and others have reported no problems at those pressures with similar dimensions.... I had to replace the second poppet, as I drilled the vent hole off center.... .... If you look closely on that one, you can see the concave seat, machined with an 5 deg. undercut so that it only seals around the outer edge.... Also, I didn't have to drill the stem for the balance chamber vent, there was enough room beside the stem, through the PEEK....

Next is to machine the cage/spider for the front to fit in that recess, retained by a snap ring.... All the port, retaining hole and O-ring machining have yet to come....

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!

I made the rest of the valve parts today.... the cages/spiders that support the valve spring and balance chamber piston and allow air into the valve, through eight 5/32" holes (over twice the valve throat area).... and the adjustable pistons for the balance chambers....



I haven't cut the O-ring groove in the 1/4" pistons yet, but they are threaded and loctited to the 1/8" shafts, and are a loose fit in the 5/32" center hole of the spider, to avoid any alignment issues.... When the valve is closed, their normal position will be back towards the seat, with the distance between the end of the piston and the inside of the balance chamber in the poppet adjustable with the 5-40 Nyloc nut.... I filed flats in the piston so that I can use a 7/32" wrench on it to hold it when adjusting the locknut.... I can adjust the clearance from less than 0.070" to over 0.200", which varies the volume of the balance chamber, and so the amount of "blow-open" tendency of the valve....

The valve stem protrudes 0.200" from the end of the valve, and has at least 0.250" of travel before the spring goes coil bind.... The balance chamber has an O-ring for a bumper to absorb any impact and reduce the peak stress on the spider.... Under normal operation, the hammer will strike the valve stem, the lower pressure in the balance chamber will help to lift the poppet off the seat, the poppet will hit the end of the balance chamber piston and the two will travel together, against the spring force, and rising pressure inside the balance chamber, until the travel reverses and the valve closes.... It will be interesting to see how much affect adjusting the balance chamber volume has on the hammer impact required and the valve dwell....

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!

Good stuff, Bob.

_________________
Best Wishes
Daryl

Very nice.

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