The Talon Tunes Top hat operation Question
Hello All-
First of all, hope everyone had a pleasant Thanksgiving.
A while back I purchased a TT one piece Top hat with inserts. I was able to crony it with the smallest insert yesterday. I am using Crosman Premiere Wal-Mart pellets.
I was getting a velocity spread with a 2900 PSI fill between 832 to 896 FPS across the full adjustment of the power knob. I am using the “O” ring regulator trick.
With the factory Top Hat, by using the 2 set screws I could adjust the setting to the point where the shroud did not hit the top hat with enough force to even open the valve to release; up to full blown open at maximum air release. I had adjusted the factory top hat to give me a pellet speed of 830 FPS at its lowest setting. I found that I still had enough adjustment in the power wheel to turn it up where I could get over 1100 FPS. I was counting the shots per fill at these settings. Of course at the lower setting that I use for target shooting I was getting many more ( about 120 to 160) shots until the pressure in the tank reduced 1500 PSI.
My question is ( and I do not know if I can word this clearly ) that with the TT top hat, and if I use the smallest insert or leave it wide open with no insert, the striking distance and force remains the same ( if I leave the power adjustment knob alone for each insert) and will hit with equal force. This translates to me that the valve inside the tank opens the same amount and allows the same amount of air to be released into the top hat assembly regardless of the insert used. With the TT with no insert, all the air is sent into the barrel, however with the restrictor in place only some of the air is allowed. Where does the excess air go since the valve itself is opening the same amount and the same amount of air is released from the tank? Is the TT unit actually sealed enough to stop the air from being released from the tank itself, or does it bleed off around the fitting?
The reason I was thinking of this was that today I was shooting with the TT and the smaller restrictor getting the same FPS as the factory one but the shots per fill were much less, almost half before the pressure went to 1500 PSI. This appears to me that I am using more air per shot even though I am going the same speed as when I adjusted the factory Top hat, so somehow I am wasting air somewhere else per shot.
Any one else ever see this happen or can explain this to me? Thank you all.
All Replies
Viewing 4 replies - 1 through 4 (of 4 total)
Jca,
I suspect that the the answer to this valve question involves considering a few more forces on the valve. Consider the following scenario:
The valve is held shut by spring force and force from the difference in gas pressure between the tank and firing chamber. This force due to pressure is greatest when not firing (chamber is at atmospheric pressure). This force goes lower as chamber pressure builds during a firing event.
Return spring force increases as the valve opens.
The O rings sealing the valve and breech create a clamp load that increases with chamber pressure. This clamp load opposes valve motion both opening and closing.
Then there’s the hammer strike trying to open the valve enough to do something interesting…
The open tophat probably allows almost the same pressure in the chamber and all the way down to the valve. The tophat with restrictor will give a somewhat higher pressure in the valve housing than in the chamber. This, in turn, would increase the clamp load of the O ring in the valve housing, which would keep the valve open a bit longer at a lower flow rate. (If I get some time I’ll draw a picture of all of this.)
In gas guns, high flow for a short period of time yields more FPS than the same amount of air metered out slowly…
So, before everyone razzes me for another headache inducing post, I just want to point out that there’s a lot going on in that little valve, even though the darn thing looks pretty simple…
There’s a lot of great experimental work posted in this forum that shows which designs work best and which tuning works best. All of these posts are the place to start with a tuning project.
-x356b
Sounds impressive to me. I think I know what you are trying to say with the restrictive back pressure. Either way thank you for the reply. No one else has offered any other explanation.
Take care,
Joe
Hi,
I am no expert in this, but the restricted insert changes the section the air travels through.
By some physics law a long forgot, having the same pressure in the back but a different section causes a different pressure drops on the breach side.
The different pressure established in the breach chamber by the two diffrent inserts is what changes the propulsion of the pellet.
Again, it was a while ago I last studied this stuff.
In the AF valve, you adjust the travel and keep a constant flow section.
This translates in air traveling at the same speed (due to the pressure drop) but for a longer time. So longer travel means more air and time to build a higher pressure in the breach chamber.
With the TT valve you leave the travel the same and increase or decrease the section. So same open valve time (likely) with more or less air depending on the insert.
The flow curves migh intersect somewhere based on the hammer energy (spring tension). So for certain power settings (especially if you have an o’ring mod) the difference between the two inserts might be minor. It will be more evident for higher power settings.
Wow, I either did a good job or pulled all this right out of my a$$ 🙂
Cheers
Chris
Viewing 4 replies - 1 through 4 (of 4 total)
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I suspect that the the answer to this valve question involves considering a few more forces on the valve. Consider the following scenario:
The valve is held shut by spring force and force from the difference in gas pressure between the tank and firing chamber. This force due to pressure is greatest when not firing (chamber is at atmospheric pressure). This force goes lower as chamber pressure builds during a firing event.
Return spring force increases as the valve opens.
The O rings sealing the valve and breech create a clamp load that increases with chamber pressure. This clamp load opposes valve motion both opening and closing.
Then there’s the hammer strike trying to open the valve enough to do something interesting…
The open tophat probably allows almost the same pressure in the chamber and all the way down to the valve. The tophat with restrictor will give a somewhat higher pressure in the valve housing than in the chamber. This, in turn, would increase the clamp load of the O ring in the valve housing, which would keep the valve open a bit longer at a lower flow rate. (If I get some time I’ll draw a picture of all of this.)
In gas guns, high flow for a short period of time yields more FPS than the same amount of air metered out slowly…
So, before everyone razzes me for another headache inducing post, I just want to point out that there’s a lot going on in that little valve, even though the darn thing looks pretty simple…
There’s a lot of great experimental work posted in this forum that shows which designs work best and which tuning works best. All of these posts are the place to start with a tuning project.
-x356b
Thank you for the detailed post. This information fascinates me. Sure, I like to load pellets and pull the trigger to see targets get accurately placed holes in them but the mechanics of air guns in general have always caught my interest. I enjoy shooting air guns, I have been doing it for 58 years on and off ( I still shoot the Crosman model 150 22 caliber co2 pistol I took my first shot on when I was 4) and I like knowing as much as I can about the things I enjoy, so thanks to both of you for clearing this up for me.
Joe
Kingsport, TN