Q:

Tophat adjustment for nice curve… how?

Hello,

Went back to the stock hammer and started finally adjusting tophat for curve – no go. Here’s starting situation. Starts to go down from first shot. I tried opening tophat more and more but still nothing

I tried to read all tips for tuning but none of them seemed to describe how to achieve the curve i.e. how to make it raise from start and then start to go down. Any ideas?

btw, Here’s another example what you can achieve with proper setup with SoftChrono 😉

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Viewing 14 replies - 1 through 14 (of 14 total)

quote Shadoh:

LOL, Mike, it sounds like you need a regulated valve in your rig. You know anyone who has specs on one or who has enough talent to machine one out? 😀

😀
Well I actually have gotten little more knowledge on that area and during long winter that project just might be lifted back to live. Few people in Finland has already made relatively similar regulators but for different guns. I believe our newcomer FinnishVisitor might have something more to tell.

I am waiting for field test results to get more accurate information of required minimum regulator chamber size. So far it looks like it needs to be little bigger. With 20ccm regchamber and 150-160bar pressure fed from 250bar tank should provide ~100 40J+ shots with flat velocity curve.

LOL, Mike, it sounds like you need a regulated valve in your rig. You know anyone who has specs on one or who has enough talent to machine one out? 😀

Leel; great tips. Thanks to you and for the rest as well.

I was under impression that all Talons could and should provide bell curve but thanks for clearing that out. I think I will first try the lighter hammer – made only from Delrin or more likely PTFE. (Easy and quick).

I am not after highpower. But balance between shotcount and flat trajectory. I blindly trusted ballistic software and choosed 275 m/s for my velocity which looked like a nice compromise. Then I learned that the BC and other data on those software are not accurate. So I have to make some field tests myself to see what is real drop on 50meters. For my application I can accept ~15 mm maybe even more during string.

This leads to another question. Has anyone performed field tests about POI drop? What are the REAL numbers? (start pressure, FPE, velocity, end pressure, POI drop, range). I would appreciate very much if someone has that data for any pellet/velocity combination.

Oh. It is 18″ barrel – not 12″.

Lorrin, will you marry me?

A flat curve would be desireale but this is only possible with a regulated valve. What we see with a talon valve/hammer setup is full power on shot 1 or 2 then a gradual decline. One hopes to loose as little velocity by keeping the shot spread close but it is still a loosing battle. A curve would be most desireable and yield the most shots.

quote Benzin:

This might be a pretty dumb, newby question, but…
Why in gods name is a “bell shaped” velocity curve desired, over a flat one????
i mean, the way i see it, it would be GREAT, to know that from shot one, till shot X, i get almost the same velocity, instead of having to take into account that my first X shots will be slower, then from shot Y they will go faster, and finally from shot Z they will slow down again!
Whats wrong with a nice flat power line for X number of shots?

Benzin, the idea of a power curve is so that you can get more shots. The key is to obtain a tight curve, so that when the velocity rises early in the curve, the POI only increases only about a pellet diameter (or a bit more depending on the shooter) then low about another pellet diameter. With this, the shots increase as opposed to without a curve, whereas the POI drops at each subsequent shot.

This might be a pretty dumb, newby question, but…
Why in gods name is a “bell shaped” velocity curve desired, over a flat one????
i mean, the way i see it, it would be GREAT, to know that from shot one, till shot X, i get almost the same velocity, instead of having to take into account that my first X shots will be slower, then from shot Y they will go faster, and finally from shot Z they will slow down again!
Whats wrong with a nice flat power line for X number of shots?

I see that three or four of you had time to reply while I was typing my long one. Oh, well, typing it out committed it to my memory.

Lorrin

Mcmike,

I’m going to assume that you have a 12 inch barrel.
(In other words, an 18 inch Talon, not an 18 inch barrel)

I just did a bunch of re-reading on the yellow forum to refresh my memory, and here is what I was trying to say in less words. I’m just going to ramble a bit, so this might sound a little unorganized:

Guns which do not have a very well balanced setup between hammer spring and valve spring strength may not have a well defined curve in velocity. The idea is to raise the fill pressure to the point so that it’s harder for the hammer/hammer spring to open the valve enough for the first few shots so that you know you are about at the top end of the “correct” fill pressure for your gun’s setup. If the spring ratio between the hammer spring and valve spring strength are not “correct” enough, you may not be able to raise the fill pressure high enough to get into the “curve” area safely before you get to the maximum recommended fill pressure for that gun. With a 12 inch barrel, 916 fps for 16 grain pellets is probably close to max velocity, so you are using your air pressure up pretty quickly. You are getting about 36 shots before your velocity drops about 60 fps, which I think is about normal for a Talon adjusted for high power. I am using the 60 fps number because that is about the fps drop that you will start to see a drop in impact at 40 yards. I have adjusted my top hat down to where I am getting only about 750 fps for the same 16 grain pellets, and my curve looks exactly like yours, its just that I get over 60 shots before my velocity even drops 30 fps. I could probably get at least 75 shots before I lost 60 fps and saw a change in impact at 40 yards. So, adjusting your top hat will probably NOT change the shape of your curve, but adjusting it to lower your power will “flatten” out the curve so that you would have many more shots in the acceptable range. A lighter hammer spring would probably have the same affect as raising your fill pressure because the higher pressure in the valve on a 3000 psi fill would make it harder for the lighter hammer spring to open the valve fully. Another way to think of it is that the Talon comes with a strong enough hammer spring that it might require a fill pressure of 3200 psi before a curve begins to show up (since the lighter hammer spring will get “slowed down” easier by the 3000 psi in the valve pushing back against the hammer). Since you shouldn’t over-fill your gun, installing a weaker hammer spring would lower the fill pressure that is required for that change to happen.
Some guns don’t always a power curve like you are talking about, and I think that stock Talons are probably one of those guns.

I think that you probably have these options:

o Adjust the top hat for less space so that you are opening the valve less, resulting in less velocity per shot, less air used per shot, and therefore more shots per fill. Lowering the pellet weight you use, and then adjusting the valve so that you drop back down to the original velocity would also increase the number of shots you would get before the point of impact changes. This is because of the increased velocity you would get with lighter pellets for the same amount of air used.

o Experiment with different (probably lighter) hammer springs so that you can get the “curve” that you are looking for. If you have your “power wheel” maxed out, you might want to try lowering it to mid-range to see if that changes your curve for a 3000 psi fill, but that would probably not make enough difference in the spring pressure to accomplish that.

o Adjust your top hat down in small increments until you see your velocity start to drop to verify that you are not wasting air. In other words, you may be be releasing more air per shot than your 12 inch barrel can use, and the pellet is exiting the barrel while you are still expelling air. By adjusting the top hat down to just when your velocity starts to drop you will be using the optimum amount of air for that velocity in that barrel with that pellet, and no more.

Hopefully some of the experts here on the Talon will chime in with ideas also.

Good luck,
Lorrin

Lighter hammer, quicker locktime. There is no curve with the talon tank and a 3000psi fill w/stock hammer 45-50g. On the other hand a lighter valve spring and lighter hammer will give you more shots as the tophat can be dialed in further if you have the threads to allow this. I just did a valve mod and found the best tophat setting at .058 stock hammer and its fullpower from shot 1 or 2 then 1.8fps loss per shot on avg. from there. A lighter hammer will give you the curve your looking for.

Keep in mind that you can also change out the valve spring to one that is a bit stiffer. This, almost always, will give you a curve.

Mike, Leel has it right. The older valves had this problem as well as most of the Condors. Folks just learned to turn a flaw into an asset by using the curve to their advantage. The newer guns and valves dont do this, at least mine doesnt with a 3000 psi fill. I believe we would have to go even higher in pressure to see that type of shot string.

I know some have tried it to little or no success but it sure seems like you should be able to use the power wheel to get this same kind of curve. Start at a lower wheel setting and turn it up a fixed amount after so many shots. If you did it right you should be able to “regulate” your shot string.

Thanks.

That’s .22 (18″ std. talon) 16 grain pellets starting from 200 bar and 275 m/s (40J or 29fpe). Ending somewhere 130 bar (can’t check accurately).

You had interesting theory about fill pressure but as I see it I am already filling to max. So I am interested if OPENing the tophat more or CLOSING it will bend the left side of curve downwards?

I know that someone will correct me if I’m wrong, but I thought that you adjust your FILL PRESSURE to achieve the curve you are seeking.

In other words:
1. Adjust the top hat to get the air efficiency/shot count versus velocity that you can live with
2. chart your velocity curve starting from a fresh fill with different initial fill pressures

When you fill the gun with a pressure that is too high for your valve/preload/tophat settings you will get lower velocities until the tank pressure drops enough to allow the valve to open more easily.
You then continue to get good velocities until the pressure in the tank drops enough that your pellet velocity drops also. I’m not near as knowledgable as a lot of people on this forum, but I would guess from your graph that you are not filling at a high enough pressure to start at the “other end” of the pressure curve. Of course, don’t exceed the fill rating of your equipment…

It would also help to know what caliber you are shooting and what weight the pellets are for your graph. 71 shots for heavy pellets would be a lot while 71 shots for light .177 pellets would mean something different. Also, is your gun a 12 fpe model?

Now let’s see what the experts say…

Good luck,
Lorrin

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