1.375 dia "2240" valve volume?

[A.Brown]

Are there any engineer/ mathematicians who could figure the volume of a valve identical to the stock 2240, except the diameter raised to 1.375" or 35mm?
I'm mulling over the capabilities and usefulness of a custom tube for a 2540 that would hold an 88/90 gram co2 (in the same manner as a 12gram)and bolt up to stock grips and reciever.
I'm neither a machinist nor engineer and don't want to waste the money machining a custom 1off if the performance is going to be lackluster.
After all it would also require a new threaded cap, hammer, power adjuster,etc.
I think springs and seals , the stock piercer, hammer pin, sear, screws, could all be reused or easily sourced.
ANY THOUGHTS WOULD BE GREATLY APPRECIATED!

[Rob M]

that sounds awesome actually... anyway , if the tube is 1.375 i.d , the valve exterior is 1.375 o.d .. Assuming you go thicker wall based on on the fact its a larger diameter pressure vessel , lets assume the valve threads front to rear are 1.125 or 1-1/8th ..
my estimation is  less than 16cc based on 1.125 i.d and 1 inch length of full bore volume.. .thats assuming the rest of the interior of the valve is the same I.d as the thread root , so its more likely to be 12 cc because that wont be the case with the front cap plugged in.

if the interior is more a reflection of the thread crest like the 2240 valve , the volume would be down to about 9 cc and could be as low as 6cc.  that all being said it would be quite the bang were it working similarly to a 2240.. ( even at 6cc

[Rob M]

i often thought about this same concept on a 1377, scaling up evrything ..in your case, to take advantage of the added volume youd want a longer barrel , and possibly largr caliber.. The one thing that would not scale up is the poppet, but the porting certainly could go up.

[A.Brown]

I of course intended to increase the diameter of the air channels to allow for more efficient airflow. If the OAL of the valve doesn't change then the pierce  and it's spring and the orange seal at the front could all be reused.
  ANY ideas on the transfer port? I have a larger than stock on my 2240. Is there a port say off a disco or something that could promote better flow and still be used with the stock receiver?

The tube would be 330mm/13" with a standard cap. 40mm OD, 1.5mms wall, 37 mm ID. I think the 10" barrel would be a minimum. The 14 an excellent choice. Any longer and you're building a carbine.

[A.Brown]

I should say this is intended to be a.25 cal handgun.

[Rob M]

well i was just working on a big bore 2240 myself , .266 is about max throat ( credit bob sterne) so .225  or less is max transfer port.. theres a lot of machining involved with your idea..the stem itself could be taken from a marauder , 760, or discovery. but again , stems like the marauder have different diameter shafts so ud need to plan ahead as to what stem to use. As a piston , with steel tube and a 88 gram loaded up front , it would be very front heavy..were the valve only as long as a factory one , plan on the 5-6 cc estimate.a challenge might be getting the valve to actuallly dump that 6 ccs, not a big challenge , but its there. a 10 inch 25 cal barrel has a volume of 8cc , so the 4-6 cc range in the valve would be ideal. its alot of work when all the same power can be accompished with an elongated 2240 valve, and a regular 12 gram co2 .

[A.Brown]

The elongated valve may be the way to go, but I was also considering shot count in the field. Besides, there's always the "no ones ever done it before " and " it's the only one of its kind" and " I built this " factor.

[Rob M]

certainly , i agree.. ill Pm u a pic of my recent 2240 build. even on the 88 gram build , while using some stock components , id still elongate the valve slightly... Better to have 10 ccs in the chamber than 5, so if you decide on a longer barrel or higehr caliber, there are options.

[rsterne]

Here is a sketch of what might be possible....



If you exactly copied all the dimensions inside of the 2240 valve, you would end up with a lot less volume, because it is only about 3/4" long inside.... You would end up with about 7 cc, or less depending on what you used for the ID....

The valve shown above used the same threads as the front of an MRod tube.... The seat is moved forward inside the valve to allow for an angled exhaust port, which requires a different poppet, of course.... As drawn, it is 0.9" long inside.... The taper at the front, to miss the front trigger screw, is in the same place relative to the port and valve screw as a 2240 valve....

For CO2, I would use about 50% of the barrel volume, going larger than that won't gain much power, but will use more CO2 in direct proportion to the volume.... assuming you are using enough dwell for the pellet to exit before the valve closes....

Using an O-ring as shown, around the outside of the 1/2" stem on an 88 gr. CO2 tank, would result in a force on the valve screw of 353 lbs. at 1800 psi (the design pressure for CO2)…. That would certainly require an upgrade on the valve screw.... A high tensile 10-32 low profile SHCS should be OK.... 

Also, make sure the front tube that contains the 88 gr. is vented in case of a CO2 leak.... You don't want to end up with 1800 psi pushing on the valve.... It would likely leak out fast enough around the sides, but if it didn't, the end force on the valve (and front plug) would be 2700 lbs.... 

Bob

[A.Brown]

Where would one find this elongated 22xx valve you speak of? If it's a double threaded extension where can I get one?  So, what is the volume of a standard valve and the volume of the extended valve? I may want to test one of these with 25 and 30 cal barrels to see some real life results.

[Rob M]

really theres no such thing off the shelf.. its all custom stuff that been done before more than once/... Wyoman has a 25 or 26 fpe pistol based on a 2240 , it uses the cothran balanced valve ( powerhouse, those are pricey 125 to 185 for the valve )
BoB who posted the diagram above has also built a big bore co2 pistol , also in 30 cal as i recall..anyone with a lathe could make the entension , but being dual threaded on both sides , u lose some volume initially.. the longer it gets, the further displaced the 12 gram is torward the front of the tube so its commonly done with a longer tube to start with,.Lot of complexity involved for all these ideas, even when you have a full machine shop the planning is paramount and often the downfall of most ideas.

[rsterne]

The valve extension I made was exactly the length of the difference between a 2240 tube and a 2250 tube.... You screwed it in between the two valve halves, lengthened the piercing rod, and used the 2240 front cap on the 2250 tube.... It was a great solution for a .25 cal pistol....





Here are the results....



There was probably a bit more available but I changed over to a .30 cal barrel once I hogged out the ports....

Bob