Air Gun Home :: View topic - New Old Project - Hayabusa PCP

69Hotrod69 · Veteran Member

Like I said the graph is messy, I was rushing, the diamond is actually burried under the other PSI Marker.

My idea for the Port adjuster is to incorporate the barrel and valve seal in the adjuster it would then slide into the breech with an alignment pin allowing proper timing with a cross hole in the breech for adjusting. This would allow me to try ones with different diameter tranfer ports. I havent tested it yet but I think the idea of using a needle more designed for regulating airflow like a carburetor needle will produce finer adjustment than a hemispherical end like the MRod. Very old carburetors used hemispherical adjusters then as engineering progressed they started using tapered needles. I'm going to run some experiments with them soon since I have a bunch of carb needles the same diameter and pitch as the MRod I just need to drill and broach them for the hex, or I may just slot them for now. It won't allow me to completely cut off flow but I think it will allow for much finer adjustment where its needed in the mid range. Time Will tell.

I'm no help on the .25 MRod Clip but somebody here must have one and a set of callipers.

69Hotrod69 · Veteran Member

I forgot to mention. I was considering the barrel, bolt, and magazine swap until I started working on the MRod. It is so easy and quick to swap the Breech, Barrel, Shroud, Bolt, and Magazine as a unit. That I decided two breeches is the way to go for me. I'm saving for the .25. The new .22 MRod has a sleeved Valve so if the sleeve is removed the volume is suited for .25.

rsterne · Moderator

Swapping out the entire top end is, of course, an alternative.... If I designed it correctly, I might even be able to leave a scope mounted on each "top end" and not have to re-sight after swapping.... More cost, of course.... The valve volume isn't an issue as I only have the "back end" of the valve.... the volume is over 100cc....

I'm trying to visulaize how the needle would be positioned.... Most needles are arranged parallel to the flow, not across it.... so that the flow moves from the point of the needle through the metering orifice past the sides of the needle and then makes a turn.... Do you really think you need that fine an adjustment?.... On my .22XX PCPs I found that changing transfer ports from .125" to .140" to .156" to .166" (a total change in area of 76%) didn't make HUGE differences in velocity.... nowhere near as much as hammer spring preload.... What restricting the port did was smooth out the middle of the bell-curve in a non-regulated PCP.... The FT guys tend to "lean on the hammer spring and choke up the transfer port" to get as flat a shot string as possible.... Since the Hayabusa is regulated, I don't have to worry about that, at least not to the same extent....

Bob

69Hotrod69 · Veteran Member

Probably don't need that fine of adjustment just curious if it would make a difference, the MRod hemepherical goes in at an angle similar to the old stromberg 97 carb airflow around 30 degrees the tip of the cone leaning towards the venturi same direction of flow as the MRod just curious more than anything. Their are obvious huge differences in the two designs.

I was just mentioning the valve issue for my situataion, I understand you won't have any of the issues I'm dealing with because you can design them out, unfortunately until I get some machines I'm stuck with altering factory stuff.

Would be really cool to be able to leave the scopes sighted in on each barrel breech combo.

I love regulated PCP's as soon as I get a lathe I'm building a regulator for the MRod I don't like the design of the one from the Albanian(I think). If I can make it two stage with out taking up too much room I would like to try that. I built a cell disruptor for the Salk Institute that used a two stage regulator and each stroke pulse was less than 2 PSI differnece. Although the valve was an electric solenoid operated it was very similar to an air rifle firing, it just did it many times at around 2.0hz cycle.

My FT will be regulated with 13CI bottle simple and very effective and best of all cheap. Have you seen the R3 2260 Carbine I put together, it will be very similar to that with a 24 inch .177 barrel. I will omit a tranfer port adjustment since it will adjustable fall and more importantly regulated. Oops off subject sorry my mind wonders a lot.

I can't wait to see your Hayabusa.

rsterne · Moderator

Just bear in mind that if you are going regulated and don't have enough volume between the regulator and the valve outlet you will restrict your power level.... I use 1cc of plenum per FPE expected as a design point.... It has to do with the AVERAGE pressure during the shot cycle....

Bob

69Hotrod69 · Veteran Member

Ive done the same with all of my regulated set ups as per your older posts.
I made an aluminum block off for gauge on the Disco tube I'm using for My FT rifle for the same reason. I was thinking of doing the same for the MRod By pinning the regulator in the tube at the desired volume for that particular valve. I have a new born so the regulator will probably be a ways of anyhow. My first regulated rifle used the 2400 tube with regulator atached the end with a disco end cap S.S. fittings and a ASA on/off The tube was completely unrestricted. It's now in a 2260 Tube with the ASA on off attached to quage port I also used Joes valve cap a little more streamlined by me. The bottle is the foregrip. That set up is really good. It has more power than my Disco hammer spring can provide. I was actually getting 907FPS with JSB heavies using a 1377 Spring. It has the disco spring now but I havent had time to chrony it but it hits way harder now. Did I mention my barrel is only 19" long. Very Happy

This is the one recieving Jays breech that uses the Marauder clip. I'm also using a Marauder shroud for it as well. The valve is a direct copy of your disco valve. Which by the way completely outperforms the B&A valve, but I think that Might be because the valve face is moved back but the valve stem is not shortened. I put it in just to compare the two no mods to it. It will push the pellets at 825FPS with the 1377 Sping. Not Bad, but I think it will jump up significantly with the stem shortened and thinned and the valve port a Little larger. I love the way it performs!!

rsterne · Moderator

I got some needed materials and finally had time to get back to this project over the last couple of days.... The breech is now about 90% done with just the slots for the cocking pin and bolt handle yet needed.... In addition, last week I had the chance to shorten the Marauder stock and fit it around the tank/trigger band.... so I was able to fit the breech/trigger assembly into it today for the first time....

The breech is machined from a piece of 1" x 1.3" 6061-T6 aluminum 6.4" long (which is the longest cut I can make on the milling attachment on my Atlas lathe).... It has a standard 3/8" dovetail milled into the top, and the breech cutout is milled to fit a .25 cal MRod 8-shot magazine.... It will also accept a .22 cal 10-shot MRod magazine by using a 0.1" spacer.... The hole in the side just in front of the breech notch is threaded 10-32 for an adjuster for the transfer port.... and the vertical hole above that is for a 6-32 set screw which will press on a plastic rod to act as a brake for the adjuster.... allowing it to hold the selected adjustment.... The notch on the underside at the front fits over the tank/main tube band which also locates the front of the trigger group....

You can see in the above photo how the trigger group mounts at both ends.... at the back to the RVA..... and at the front to the tank band assembly.... When the two top screws are tightened up, the tank and main tube are both drawn up into place and held securely against the bottom of the breech.... The stock mounts with the original 1/4-20 hole near the front of the trigger group.... Since the entire front of the stock was removed to make room for the air tank.... in order to mount the stock securely, it was necessary to add another mount at the rear of the trigger group.... A hole was drilled and tapped 8-32 just behind the trigger box, in front of where the trigger mounts to the RVA.... This lines up with the rear screw location for the trigger guard.... A hole was drillled up through the stock so that a long 8-32 bolt could be used to attach the stock rigidly....

All in all, I'm pleased with the progress I made this week.... I'm delighted that I was able to figure out how to make the one breech fit both .22 cal and .25 cal Marauder magazines.... The bolt will be made from 3/8" steel with the front portion reduced to 1/4" diameter for the .25 cal setup .... and 7/32" diameter for the .22 cal version.... Those diameters feed properly through the MRod magazines.... and then a conventional extended probe will load the pellet forward of the transfer port.... I need about 1.3" of bolt travel to be able to retract the probe far enough for magazine removal.... and have allowed for that.... The rear breech mounting screw is recessed below the bolt, which allows for a longer bolt, and the bolt handle to be moved further back away from the magazine....

Bob

rsterne · Moderator

I made the spacer for the .22 cal magazines today, slid the stubs in place, and took some pics....

The above photo shows the .25 cal magazine and the 1/2" diameter stub that locates it.... You can just see a part of the 1/4" ID O-ring that will seal the bolt.... There are two tiny bumps top and bottom in the groove in the magazine that "clip" onto the stub to hold the magazine in place....

Since the .22 cal magazine is narrower, a spacer is required.... and the stub is 0.100" longer (the same as the thickness of the spacer).... Functionally, with the spacer in place, the magazine sees the same 0.060" stub.... although it is 7/16" diameter for the .22 cal magazine and carries a smaller (7/32" ID) O-ring.... The spacer is held in place by a single 6-32 SHCS....

Bob

rsterne · Moderator

Had a chance to get back into the shop today and make the bolts and finish off the breech....

The two bolts are interchangeable.... the one with the bolt handle in it is the .22 cal and the other one is the .25 cal.... The middle section is the correct size to pass through the Marauder clips and seal in the O-ring between the stub and the end of the barrel.... In order to move the bolt handle back as far as possible, I needed a way to activate the cocking pin in the hammer without having it ride on the end of the bolt.... In the assembled bolt, you can see a 6-32 screw half way between the bolt handle and the front of the 3/8" section.... That rides in the slot in the bottom of the breech and draws the cocking pin backwards with the bolt.... The wide area near the front of the cocking slot allows the head of the screw to rotate opposite the bolt handle when the bolt is closed.... It was a lot of measuring, bit I'm confident it will work perfectly.... By using this system, I was able to move the bolt slot right to the back of the breech.... This allows lots of room between the bolt handle and the magazine....

You can see the 10-32 button head SS screw which will be used to adjust the transfer port.... The end of it will be turned down to remove the threads and shaped as a hemisphere.... It will enter the 3/16" ID transfer port through a close fitting hole in the side of the brass port (yet to be made) and when turned fully in will choke off about 90% of the port area.... It will take 6 turns to fully withdraw it to give 100% flow.... I plan on shaping the head of the screw like an "arrow" to aid in counting turns..... There is a "brake" in a setscrew hole on the top side to keep the adjuster from turning by itself....

It's getting close to the point where I will have to start machining the main tube.... I still have to fit the cocking pin into the hammer.... and harden the hammer and pin.... There are still a few other small jobs to do as well.... but I'm beginning to see the day when it will be assembled for the first time.... Mr. Green

Bob

rsterne · Moderator

Finally got a chance to get back to this project the last couple of days.... I have now done the machinining on the main tube.... The valve and tank block are installed with three 10-32 low-profile SHCSs with the heads set flush into the main tube to spread the load on the tube wall.... The slots for the cocking pin and sear are done, and the rear mounting holes for the breech, trigger group, and RVA.... The tank band supports the rear of the tank, the front of the trigger group, and the front of the breech and everything is rock solid when tightened up....

I have also made the barrel band, which mounts to the top of the tank block.... It uses an O-ring to locate the barrel and yet allow linear expansion and contraction of the barrel and tube relative to each other with changes in temperature and/or pressure.... I purchased a sling swivel that fits on the picatinny rail on the bottom of the tank block and there is still room for a bi-pod in front of that....

I'm getting really close to being able to pressurize the gun to test for leaks.... Stay tuned.... Mr. Green

Bob

yourdaddyjoe · Supporting Member

Looking Awesome Bob! Mr. Green

rsterne · Moderator

YAHOO !!!.... No leaks.... Mr. Green

Bob

yourdaddyjoe · Supporting Member

Phew! I get it now... First thought... I was going to offer to send ya some Depends... Wink

rsterne · Moderator

Bob