Weird Idea again

[YEMX]

This remote line idea is looking better and better!!

I'm going to have to get in touch with Mr. Brancato and talk to him about some kind of set up with his tethering reg and long fill whip.  Oh man...  This is getting interesting!!

What's the calculation for converting cubic inches to cubic centimeters at 4500 psi?  I'd be interested to see how many cc's of air a Guppy (118 cu in) tank has... 

Okay- I'm pretty sold on setting up this rifle with a remote line... 

[rsterne]

If you decide to tether, here is what I do.... I mount the regulator on the output of my 4500 psi SCBA tank, with a bleed valve and pressure gauge in an aluminum block.... You can also use a commercially made tethering regulator.... I build the gun unregulated, which allows you to use a 3000 psi bottle for tethering up to that pressure (or a 250 bar for up to 3600 psi)…. I then tune it for a short, (ie 1% ES) string off tether, which when tethered puts me on the upper side of the sweet spot, giving good efficiency and high shot count.... I tether from the reg/bleed valve to the gun with a microbore hose with a 90 deg. elbow at the gun....

Bob

[YEMX]

Could you not use the the bleed valve on the bottle and disconect the hose with a forster fitting?

Not exactly- we're talking about 2800 psi here... or less.  In the line.  If I were to set up a traditional remote line, there is no on/off at the tank valve.  Hence my concern.

[YEMX]

So as far as feeding the gun air, here's the plan:

Guppy tank
Tether reg
40" fill whip

All from Airtanksforsale.  I'm hoping the tether reg will direct-thread to the tank valve.  If not, I'll have to find or make a pack that will store the tank and tether reg together so I can easily carry the set up and/or hang it from a tripod hook or even set it on the ground... 

Thank you for the idea/push gentlemen!   Keep them coming!  It's going to be a long road, but I may see a dream gun come to fruition yet!!

If you decide to tether, here is what I do.... I mount the regulator on the output of my 4500 psi SCBA tank, with a bleed valve and pressure gauge in an aluminum block.... You can also use a commercially made tethering regulator.... I build the gun unregulated, which allows you to use a 3000 psi bottle for tethering up to that pressure (or a 250 bar for up to 3600 psi)…. I then tune it for a short, (ie 1% ES) string off tether, which when tethered puts me on the upper side of the sweet spot, giving good efficiency and high shot count.... I tether from the reg/bleed valve to the gun with a microbore hose with a 90 deg. elbow at the gun....

Bob

That's exactly the plan Bob- Even with just the primary reservoir, that'll be a good bit of air- more than a Mrod at least.  The USFT main tube dimensions are O.D. 1.885", I.D. 1.610" so what, .1357" wall?  Call it 19" for the reservoir length...  Not sure how to calculate how many CC's that is...  I don't think it's as simple as calculating volume of a cylinder (is it?)...  Either way, I should have enough air for some off tether tuning. 

Note:  I know that the USFT is designed to run at lower psi than 3k.  For now, this is all talk, and no machining is being done any time soon!  I'll get to figuring out actual material dimensions and types later on when I'm closer to actually getting some metal cut.  I'm not trying to disregard any safety issues. 

[Jim Holmgren]

Could you not use the the bleed valve on the bottle and disconect the hose with a forster fitting?

Not exactly- we're talking about 2800 psi here... or less.  In the line.  If I were to set up a traditional remote line, there is no on/off at the tank valve.  Hence my concern.

Ok I don't think I follow..

Is this not a traditional way for regulated tethering? In this order first to last.

Tank
regulator
on/off valve
bleed valve
hose
checkvalve/airgun

This is what I use at least when I tethering...

[Jim Holmgren]

A tube with I.D. 1.610", 19" long have a volym of ~630cc

[YEMX]

Ok I don't think I follow..

Is this not a traditional way for regulated tethering? In this order first to last.

Tank
regulator
on/off valve
bleed valve
hose
checkvalve/airgun

This is what I use at least when I tethering...

You're absolutely correct- When I said "traditional", I meant "traditionally with paintball set ups".  Very stupid of me.  My initial mental picture of tethering the gun was to use a JSAR adjustable tank regulator (similar to a Ninja type paintball regulator in size/shape) and use available paintball remote lines to connect the gun and JSAR reg.  Paintball tank regs (whether Ninja or JSAR) don't have an on/off per se.  The Ninja regs have a pin valve, but I don't think the JSAR reg will.  That still wouldn't solve the problem of up to 3k psi in the line w/no way to bleed it.  The problem with my first statement regarding tethering was that I hadn't thought of using an actual tethering reg and fill whip to air the rifle.  Basically I was trying to get the job done as cheaply as possible with readily available parts.  I see now that I won't be able to do that.  Which is fine, I'd rather spend the money and be safe. 

[YEMX]

A tube with I.D. 1.610", 19" long have a volym of ~630cc

Wow, that's about double an Mrod's reservoir... yeah, I'll be fine to tune the gun off tether for a few shots...  Thank you for that calculation! 

[YEMX]

Just a quick re-hash of the tethering plan- same parts, but I'm just gonna leave the tethering reg "floating" instead of trying to connect it directly to the Guppy.  This way I can also use it on the Great White if I need an extended shooting session (like bench testing).  More versatile this way.  Easier to find/use a off the shelf back pack.  Only thing that I'll need to get extra is maybe a shorter fill whip to connect a tank (Guppy or Great White) to the tether reg...

[Motorhead]

I'm somewhat lost on this thread on what platform you will actually working with ... or doing a One-Off complete custom

As one who services USFT's and Very familiar with design etc ..... Any of there Pellet shooters won't convert well to big bore without a different valve body, MUCH larger poppet and a hammer with MUCH greater weight.
Unless a machinist, the OEM valve body is Stainless Steel and near impossible to rework with hand tools.  Hammer I saw on Tim's ( Mac1 ) big bore a few years ago had a big weight brazed on it.

Just some FYI for your thoughts ....

[YEMX]

I'm somewhat lost on this thread on what platform you will actually working with ... or doing a One-Off complete custom

As one who services USFT's and Very familiar with design etc ..... Any of there Pellet shooters won't convert well to big bore without a different valve body, MUCH larger poppet and a hammer with MUCH greater weight.
Unless a machinist, the OEM valve body is Stainless Steel and near impossible to rework with hand tools.  Hammer I saw on Tim's ( Mac1 ) big bore a few years ago had a big weight brazed on it.

Just some FYI for your thoughts ....

This is going to be a one-off build that will have a rotary breech and an internal hammer that is cocked via side lever or a cocking knob on the side.  I'm just here bench building/brainstorming.  I'm definitely not trying to design a rifle for production or anything.

The USFT not converting to a big bore well is the reason for this build.  I also really don't like the exposed hammer that the USFT uses.  I feel that a USFT type rifle with an internal hammer set up like the Thomas Rifles would be a great combination.  I'm hoping to have a balanced valve of some kind to be developed to work with the rotating breech design, as that is the only way to achieve enough air flow and ease of cocking I want/need for the larger calibers.  Personally, I'm not going to go larger than .357 with this build.  What others do with the info here is up to them.

The reason for the overall design choice is because I LOVE the freedom and ability to choose caliber and projectile without the need for cumbersome degas and disassembly.  I love how solidly the barrel mounts into the receiver, and the fact that you don't have to worry too much about projectile length due to loading port size.  You could also fiddle with barrel clocking easily.  I also like the smooth action of a rotating breech.  For testing new barrels and projectiles, the ease of the USFT/Thomas Rifle actions allow would be awesome!!   

[YEMX]

I wonder if there's a single TP diameter that would work well across the board for up to .357?  Likely calibers will be 6mm, .257, 7mm .30 and .357.  .30 and .357 will include pellets.  Not sure of what energy goals would be, since I'd be testing a wide variety of bullet lengths weights and twist rates...  For .357, I'd be looking for 130-250 fpe range, w/cast boolits for the higher fpe of course...   6mm-7mm max fpe around 120-ish fpe.  .30 is an odd-ball- maybe 100 fpe?  Honestly, I'll probably stick to pellets for .30... 

The T.P.'s for my .30 Mrod bullpup (will end up being 80-100 fpe), and my .357 Brod pellet shooter (130 fpe at 2100-2200 psi)  are both .250".  Would a .250" port be fine for all those calibers, and for more power, just adjust the psi of the tether reg?  It would be far easier to have just one port for all calibers, and adjust reg pressure than to have different ports for different calibers.  I'm not too concerned with spring tension, as I'm going to attempt to build a balanced valve for the rotary breech.  As Bob puts it, it's either on or off.  The key is the pressure regulation.  Thoughts?

Also, I'm having a time trying to figure this out, and I don't want to bother TJ, as I know they stay pretty busy- what are the O.D.'s available from TJ?  I know .5" O.D. is available, 9/16"? 5/8"?  I'm hoping he can do 5/8" O.D. barrels...

[Sbak]

Go .28 tp if you have the available hammer energy and let the restriction in the porting be the port in the barrels. It won't make any difference in the smaller calibers and .28 porting in the 357 is good for 180-250 fpe depending on barrel length and pressure

[YEMX]

Go .28 tp if you have the available hammer energy and let the restriction in the porting be the port in the barrels. It won't make any difference in the smaller calibers and .28 porting in the 357 is good for 180-250 fpe depending on barrel length and pressure

Nice!!  Thank you!  There won't be a port in the barrels though:

[rsterne]

My last build/change was to my .357 Hayabusa when I fitted my simplified balanced valve.... I made the porting as large as I could, for the .357 cal, and then used a tapered transfer port to cone it down to the barrel port, just to get rid of the step, for the smaller calibers.... It works perfectly for .224, .257, 7mm, .308 and .357 cal.... I hardly even need to adjust the hammer strike, as long as I keep the SD of the bullets similar....

The maximum OD of the TJ's barrels depends on the caliber.... but I have had him make 14mm OD (0.551") in .172 through .257 and I know he can do 9/16" (0.563") in .308 and .357, so no reason they can't all be made the same....

Bob

[gabi.nechita]

I saw a screw on the upper side of rotating breech.
You can use it like a flow restrictor. You can also cut to 45 degree the end of screw to redirect flow to pellet back .
But again I have some reserve about sealing rotating breech against the barrel at 150-200fpe. Maybe if you will made a longer rotating breech at 1.2 or even 1.5 inch to add stifness when pressure will push the breech back. In this mode you can made an angled transfer port for better flow.

[YEMX]

My last build/change was to my .357 Hayabusa when I fitted my simplified balanced valve.... I made the porting as large as I could, for the .357 cal, and then used a tapered transfer port to cone it down to the barrel port, just to get rid of the step, for the smaller calibers.... It works perfectly for .224, .257, 7mm, .308 and .357 cal.... I hardly even need to adjust the hammer strike, as long as I keep the SD of the bullets similar....

The maximum OD of the TJ's barrels depends on the caliber.... but I have had him make 14mm OD (0.551") in .172 through .257 and I know he can do 9/16" (0.563") in .308 and .357, so no reason they can't all be made the same....

Bob

So was that tapered transfer port "one size" for all your calibers?  If so, what were the dimensions?  That could very well work in this build!  I'm trying to design the gun so that it will work with no changes (other than reg pressure change and hammer strike) across multiple calibers. 

I may have to just call TJ and see what he can do-  I'm hoping I can get the same O.D. barrel for different calibers...  That way, I can make all the barrels the same, regardless of caliber.

I saw a screw on the upper side of rotating breech.
You can use it like a flow restrictor. You can also cut to 45 degree the end of screw to redirect flow to pellet back .
But again I have some reserve about sealing rotating breech against the barrel at 150-200fpe. Maybe if you will made a longer rotating breech at 1.2 or even 1.5 inch to add stifness when pressure will push the breech back. In this mode you can made an angled transfer port for better flow.

That top screw in the rotating breech is in fact a tuning jet:



But I wonder, would it really be that simple for the big bores?  Even if it is as simple as using jets, the other question is, what should the "parent port" size be?  I don't see why a jetting screw wouldn't work though...  But deciding on a "parent port" size is the hard part...   

Yes, I will absolutely be discussing breech thickness w/the machinist...  Other than being hard to manufacture, there has to be a reason for the rotating breech not being common in the market.  But I feel, that as long as you pick the right material for the job it'll be fine.  The USFT breech is .5" thick and 1" wide.  Again, the USFT is built for low pressures, so of course my version will have to be bigger. 

[rsterne]

The TP was the size for the .357 at the bottom end and smaller at the top to match the barrel port.... a different TP for each caliber....

Bob

[YEMX]

The TP was the size for the .357 at the bottom end and smaller at the top to match the barrel port.... a different TP for each caliber....

Bob

Ah, that's what I was figuring...

I think, after combing through more than a few threads, for my needs- I think a .281" port, with a 28" barrel and variable pressure will suit my needs across all the calibers I want to shoot...  Plus, for a caliber change, I'd only have to swap out the barrel.  Maybe adjust the hammer tension and pressure setting. 

 

[YEMX]

Bob- to try and figure a "off the cuff" estimate for prechamber size- don't you use a "1cc per fpe" rule? 

-  Assembled/sized similarly to a USFT
-  Balanced valve
-  .281" TP
-  Internal MDS hammer (either side lever or side cocking actuated)
-  Simple stock design like this:


-  28" barrels, sleeved in CF (still have to get with TJ to see what the largest O.D. barrel I can get)
-  Not sure which trigger to use:  Mrod, Prod, maybe even a regular or e-trigger from some paintball gun... 
-  Picatinny scope rail

That's where I'm at right now...  Just narrowing down what I want.  My machinist/tuner is busy at the moment.  It doesn't help that he's already working on a few of my projects!    But as soon as he's able, I'm going to talk to him about a balanced valve with a rotating breech configuration...  That's the one part I'm concerned about.  Whether or not a balanced valve can be adapted to work with a rotary breech.  I NEED the valve to be a balanced valve so that the cocking effort will be easy, and I can get the air flow I need for the larger calibers.  If I can't adapt the balanced valve tech to a rotary breech, this whole exercise really will just be a pipe dream.  Looking at some available pictures though, I'm pretty confident we'll figure something out.