Yes, with a 1/2 cc per FPE plenum, you may be getting a 20% drop in pressure inside the valve during the shot.... That, plus a rise in pressure due to the poppet compressing the air inside the poppet chamber could give you a 30-50% pressure differential, depending on the volume of that chamber and the lift of the valve....Bob
I’ve ordered a pile of mikuni carb jets ranging from .020 to .045” for eBay as a kit . I hope to be installing a cobra tube in my highly strung BT65 and get rid of the anti hammer bounce device . It’s going to need some creativity to cram it all in the Vale housing something like rallyshark did with his AT44. Yet another project on the go .
My first attempt. This is my gauntlet valve, up until now it had factory porting. Now it's .233 bore with the cobra mod. Once I get the SSG done I'll give it a go!
Quote from: Kerndtc on October 19, 2018, 11:37:40 PMMy first attempt. This is my gauntlet valve, up until now it had factory porting. Now it's .233 bore with the cobra mod. Once I get the SSG done I'll give it a go! Perfect gun to try it on. I would try it Cameron before SSG so you know what percentage each device contributed
Quote from: oldpro on October 19, 2018, 11:47:21 PMQuote from: Kerndtc on October 19, 2018, 11:37:40 PMMy first attempt. This is my gauntlet valve, up until now it had factory porting. Now it's .233 bore with the cobra mod. Once I get the SSG done I'll give it a go! Perfect gun to try it on. I would try it Cameron before SSG so you know what percentage each device contributedI have such a hard time not doing things all at once. Luckily the SSG I like to put together arevery simple to install after removing the rear tube cap and the spacer. Maybe I'll shoot it with the new valve then drop in the SSG. Cam
If there is the slightest drag on the oring and the inside of the brass tube is smooth, the oring should be sealing. You could test this by temporarily putting some silicon grease on the oring. Could there be a leak elsewhere else in your cobra assembly?Once the Cobra is working you should notice it both in shot cycle and velocity. You should have to lean on the hst a little more to get the velocity back to where you were previously tuned .
Having the tubes vent WELL INSIDE the valves internal space will IMO require you to use a very small vent size. I would start down in .020" range or smaller. ( * wire drill sizes from the 60-80 sets )because of the large pressure drop within the valves body the captive pressure within the tube gets sucked right out if vent is too large & effectively has the valve act as if a MUCH lighter poppet spring is in place which would cause valve to over dwell somewhat if indeed a heavy poppet spring was in place previously.
Just replying to keep up with this valve's development. May also need to order when they are up for sale. CaseyP.S. I have a couple of potential uses, have you made anything close for the Air Force valve in bottle type guns yet? And I have a 30 cal Disco tubed gun, that may get switched to an M-Rod tube and breech with the same barrel,so that may be a better candidate for this valve.
Mike D, have you made any more progress on the cobra install on your P15?? I'm really curious to see if you made any headway there.Sadly, I've made almost no headway. I made changes to have it vent outside of the valve body, into the regulator plenum. I drilled out the screw that secures the tube to the cobra chamber, and inserted a tube from a small Triflow bottle. A #68 bit is a very snug fit in that tube, so the vent is right at .031. All I managed to accomplish was needing my HS turned up,lol! I'm pretty sure the cobra spring is working, given the fact that I had to increase the HS to reach the same velocity. I gained a couple of shots from my last attempt, but I still can't beat my best tune with a conventional valve spring set up. Just thinking out loud here, but I think it would work better with a higher reg set point. Right now, it is at 125 bar. I wonder if turning it up to 130-135 bar will increase the effectiveness of the cobra tech. That would likely give a larger pressure differential between the tube and the rest of the valve. Of course, the extra pressure would make the valve close faster too. I feel like I'm just at the point of diminishing returns with it right now. A larger plenum sure wouldn't hurt either, but I'm only working with a 165cc cylinder before the regulator. Either I'm missing something, or the cobra tech just isn't the best option for a .22 Flash at 30fpe. Any input or advice is most definitely welcome from anyone that wants to chime in! I made the cobra tech work in the gun, but it may be better suited for a lower power tune in this case? Currently, I'm thinking I'm at the point of going back to a conventional valve spring for this gun.
Advertise Here
Share This!