XS60C PCP Repeater project

[stalwart]

Bob, I'm wringing every ounce of energy I can out of this system.

[rsterne]

Nice !

Bob

[stalwart]

It will take a modded F trigger frame mount to clear the striker, but we are in at 30mm stroke, and 90+g of striker.

Double the pleasure... double the fun!

 

[rsterne]

I like the shortened up valve / striker block idea.... but how are you sealing the back side of the exhaust port?....

Bob

[stalwart]

I'm going to epoxy these together, and put a 016 ring in like the later Bobcats. Given that the DOM tube is far more precise, and will be polished internally, I don't think this is going to require a fat ring. I have to put the (2) 1/4 x 28 backup screws in, then I'll glue, true, and size the combo.

What kind of FPE numbers can we get from this setup?

[rsterne]

I was just looking at the location of the two screw heads.... They are so close together that the tubing wall separating them will effectively have no bearing ability for the front screw, right?.... Imagine if you will the front screw moving back and bending the thin web between as it stays in contact with the rear screw head.... I realize that the shear load from a tear-out point of view is, in theory, lined up with the ODs of the screws, and that is just over one head diameter.... but I can envisage the web between the screws bending to the rear because the only part resisting the valve moving back is the cradle behind the rear screw.... Even if the tube doesn't shear, I can see the valve setting back under load.... Also, where is the O-ring going to seal, there are now 3 holes in the tube?.... (or is that only in the receiver?)

As far as FPE numbers, that will depend more on port sizes, caliber, and bullet weight.... What you are trying to achieve with the striker is enough hammer energy and momentum to allow as much dwell as you need at 3000 psi to develop that....

Bob

[stalwart]

The 2 screws are going to be left with all their inherent slop. They will settle under pressure, as they do stock... but it will be into the (2) 1/4 x 28 screws fully set through the sides of the tube, into the block. Those will have 4.25" of solid tube behind them. This leaves the stock screws to serve as mounting (as well as the 2 back CS screws) for the tube. That's (4) 5mm screws... when I said you could mount a bayonet, I wasn't kidding.

As the entire power plant will be self contained, in the full length tube, I don't have to worry about any extra holes... could swiss cheese the receiver... and as an ex go fast guy, I'm quite tempted to do so, just to see how much weight I can lose. Someday.

Please tell me I have this right: We have all the oomph to do anything that can be done with 3K?

I was just looking at the location of the two screw heads.... They are so close together that the tubing wall separating them will effectively have no bearing ability for the front screw, right?.... Imagine if you will the front screw moving back and bending the thin web between as it stays in contact with the rear screw head.... I realize that the shear load from a tear-out point of view is, in theory, lined up with the ODs of the screws, and that is just over one head diameter.... but I can envisage the web between the screws bending to the rear because the only part resisting the valve moving back is the cradle behind the rear screw.... Even if the tube doesn't shear, I can see the valve setting back under load.... Also, where is the O-ring going to seal, there are now 3 holes in the tube?.... (or is that only in the receiver?)

As far as FPE numbers, that will depend more on port sizes, caliber, and bullet weight.... What you are trying to achieve with the striker is enough hammer energy and momentum to allow as much dwell as you need at 3000 psi to develop that....

Bob

[rsterne]

Ahhhhhhhhhh, yes.... side screws to do the heavy lifting.... I didn't want anyone viewing the thread to think that just those two screws, as located, were good for 3000 psi....

Please tell me I have this right: We have all the oomph to do anything that can be done with 3K?

Well knowing what you (we) have in mind, yes, I think we'll be just fine up to a .30 cal.... Slinging 150 gr. .357 cal bullets at 300 FPE ain't gonna happen with that hammer setup, though.... My Hayabusa .308/.357 uses a 145 gr. hammer with 1.45" of travel.... and the .410/.457 uses a 250 gr. hammer with 2" of travel.... There are two limiting factors that require more hammer strike.... The first is the pressure, the second is the diameter of the valve seating surface.... The force required to open the valve is the product of the two (pressure x area = force).... The 82 gr. hammer with 3/4" of travel I have in my Disco Double will handle 3000 psi and a 1/4" throat or a bit more now that I've gone to PEEK, and bullets up to about 70 gr.... On the other hand a 145 gr. gram hammer with 1.45" of travel is maxed out with 150 gr. bullets and a 5/16" throat in the Hayabusa....

Bob

[stalwart]

Thanks, Bob. For the near future, we are "fat and happy". There is no more stroke possible, without stretching... but the weight can be increased quite a bit ( I made a lot of room). I'll get into that more when we run out of punch... could be a while.

We are just a tiny change (CrMoly + 1 more 1/4" x 28) from 4.5K, right? The 3rd block screw could be converted from 5mm to 1/4" and the block floated... the pin slot needs to be elongated in the receiver only, that 3rd screw could be left with 40mm of backup in the tube itself. Got plans for the Winter of '15? 

[stalwart]

As we have far more energy than needed to make the .25s hum, I'm going to limit their stroke to 20mm (and eliminate the need to customize the trigger frame mount) and use the extra room to try an adjustable striker. There is a possibility that I can make one adjustable through the floor of the mag slot. Remains to be seen...

[rsterne]

4.5K?.... I think you need to slow down and get things working at 3K first.... Every change you make causes 2 problems (then 4, 8, etc), and pretty soon you can't find solutions fast enough....

Bob

[drewciferpike]

I'm almost crying with joy.

I've been so busy with work that I haven't checked any gates for close to two months. I knew I had to come here, first chance I got.

This thread always makes me happy. I love seeing people come together to make magic.

Now for the negative: You punks are making me want a new rifle... 

[stalwart]

I'm not going to 4.5 for a while... but it makes no sense to develop a part number, just to add another later. I'm going to set up the tube design to take 4.5 in CrMoly, or whatever comes along... and continue to work with steel at 3K pressures. It's cheap insurance, and allows me to cut a bunch, if I want... and not be sitting on a pile of an early version when the time comes to go big.

IIRC, (3) 1/4 x 28 screws, riding on their heads, will hold 4.5K. No?

Negative? I thought it was written into Law here, that "Ye shall enable, at every opportunity, despite the lamentations of friend and foe..." Or, something like that. Just playing by the rules....punk!

 

Wondered where you were...

[avator]

Ya know.... sometimes just reading is funner than modding or shooting or machining or developing or whatever the heck you magicians are doing.

[rsterne]

You're pushing it.... Safety margins are 2.4:1 to yield on the tube and 2.3:1 on the bearing area.... but yeah I think it'll live.... but only because the SM to burst on the tube is well over 3:1.... I was more referring to what would be required to knock open a valve against 4.5K of pressure.... Even with 1/4" ports and a slim seat, you are talking 277 lbs. force just to crack the valve.... Got room in there for a balanced valve design?.... and the time to machine it?....

Bob

[stalwart]

Those answers remain to be seen, but we sure have a high ceiling to work under.

What would the longest useful range of travel be, for an adjustable striker?

[stalwart]

Ya know.... sometimes just reading is funner than modding or shooting or machining or developing or whatever the heck you magicians are doing.

You're right... and I do a ton of it here. Just wish more would stick in my withered bean.

 

[rsterne]

IMO there is no need for an adjustable travel except to tune a bstaley setup.... Since the #113 O-rings are 0.103" thick, then about 0.10" is all the travel you need.... Since you can get "backer rings" which are half thickness, you really only need half that.... and since you have the option of using a #016 (which is 0.070") and some #113s, in various combinations, you might get away with even less.... A more important question is how much room do you have for the O-ring buffer with the longer striker?....

I will never build an adjustable striker again unless it's to tune a bstaley setup.... Every time you reduce the striker travel you just have to wind in more preload, so why bother?.... Set the gun up with the striker weight and travel to do the job you want with a reasonable spring and use the preload for all your tuning.... KISS....

Bob

[stalwart]

I have 10mm more to work with. The Wolverines (.25 and .22 bullet) will be limited to 20mm stroke. We don't need more, and why increase the lock time? I have room for far more weight than they'll ever need.

I think I can make this happen.

[rsterne]

A three x #113 O-ring stack (0.31") is all you need, or two plus a backer ring (total of ~1/4").... maybe 1/8" travel on the striker to be able to easily tune it.... For the Wolverines I can't imagine you will ever want to decrease the power by going bstaley, but sounds like you have the option....

Bob