Keeping valve warm to avoid rapid firing freeze?

[wahoowad]

I often get rapid back to back shots on rats, and running on CO2 has me paranoid about accuracy issues from valve freeze. How would something like a disposable handwarmer work to try and keep the temp up? I could wrap it around the bottom of the tube with a rubber band or something and would expect it to keep the area metal warm to counter CO2 cooling.

Yeah, yeah, I know the valve is inside but this warmth would act as a cold sink so to speak to counteract cooling. The metal should conduct the heat pretty good during slower periods of firing.

[beejwest]

The handwarmer is not going to work.  It won't conduct enough energy transfer to do you a single bit of good in the time frame you are worried about.  You won't freeze your valve.  I promise.  You can however shoot fast enough to change your POI.  That said, two shots followed by a period of inactivity is probably not enought to change POI enough to matter.  Unless you're ratting at 100 yards or something.  Within 30 you're still gonna kill a rat. 

Run yourself an experiment over a chrono.  Fire one shot, wait 1 minute. Fire again.  POI should be the same.
Second series, fire one shot immediately followed by another, check chrono, check POI.  This should tell you what you need to know on how your rig shoots.

[quickster47 †]

Great answer from beejwest.  When I started working on my 2240 Lite project, and after I had opened up my main tube for lightness, I also did some testing of valve temperatures by connecting six thermocouples as various places around the gun.  Conclusion was that heating up the main tube and the valve was a total waste of time and energy and effort.  The valve will get really, really cold but in my testing never did freeze up and stop working.

Shoot one or two or three fast shots and then pause for a minute or so and repeat.  Your POI will be okay and your rats will be dead.

Carl

[quickster47 †]

Forgot to mention that I did modify a battery powered bottle warmer to fit snugly around a 2240 in hopes that it would keep the 2240 warm enough to keep the Powerlet pressure up.  Waste of time but lots of fun experimentation.

Carl

[WyoMan]

Not sure what gun you have w-wad but I second and third the comments above. A Co2 setup, however,  can be made to self regulate. You need a large enough (volume) valve and a hammer strike that just takes "a sip" of the gas from the valve.
As temperature and pressure drops, the valve will stay open longer...just like a pcp. Bob Sterne built one to shoot in cold temperatures and the velocity was consistent over a large temp range. Can't find the link to the gun...
But there is one key to get consistent velocity when rapid firing, cooling, or temperature changes. The shot has to take a small amount of gas relative to what's available.
You'll get a good consistent velocity. Almost forgot...you will also use more gas when it's colder...hth

[CraigH]

Wyoman,

I read that topic with great interest.   Definity want to do that.  Here it is:

http://www.gatewaytoairguns.org/GTA/index.php?topic=59537

[WyoMan]

Thanks for that, Craig. There was also a thread on the Green but your link covers the gist of it.