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Old 03-28-2013, 11:02 AM   #1411 (permalink)
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When we keep the actual valve design, then I see the biggest problem in valve entrance location (near cup seal), too.

Pehaps will be the "logistically" and "economically" best solution manufacture simply new valve nut and powertube... and solving the problem more than with construction with (manufacturing) technology:

Very precisely manufactured powertube and valve nut with smallest possible clearance in between them to reduce the leaks without seal on the smallest possible rate.

Manufacture powertube from best high-strength alloy (some tool steel for forging tools? or Tungsten?) to allow make the tube really thick and have really big holes on end.

Use hard material for powertube seal to be able reduce thier overlap and thickness.

Last edited by 3022; 03-28-2013 at 11:08 AM.
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Old 03-28-2013, 11:18 AM   #1412 (permalink)
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Tymcneer makes very high density pt for just thst reason ive already commissioned it
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Old 03-28-2013, 11:30 AM   #1413 (permalink)
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Theoretically there will be possibility reduce the dimensions even so that the powertube will have only reduced lifetime - some hi-end sport wear is not designed on longer lifetime than one race.

When you take CNC machined powertubes then, with consideration of price paint and CO2 it will be perhaps economically effective have powertube for one season.

You can recycle them like powerlets : -).
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Old 03-28-2013, 01:56 PM   #1414 (permalink)
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You guys are right about compromising on powertube strength, I have yet to have a tube fail inside a gun but have ruined many while machining. The biggest drawback to the Nelson design is the delicate powertube. There's very little meat to play with inside, btw Mike@CCI grinds his tubes, and reams the retainer nuts to a very close fit. Typically .2465OD on the power tube and .247" ID on the retainer nut. These "odd" sizes are because of the nickel plateing.

The place to make gains with the standard Nelson valve train is in the valve body. Especially if you want a drop in kit.
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Old 03-28-2013, 08:07 PM   #1415 (permalink)
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When we talking about limited lifetime:

Powertube of ZXS-200 / Winchester Laredo 80:



center hole ID 4,8mm = 0,189", two holes on end ID 3,6mm = 0,142"
OD of the plastic part of powertube is 7,4mm = 0,291"

In the arangement with the nut has the powertube space for openning 1,6mm = 0,063".
BTW the hammer weight is here 26g = ~0,92 oz, it is the lightest hammer what I have seen on factory marker.



...the powertube has been broken after ~200 shoots. Surprisingly not in the plastic part but on other side, the metal part has been broken off in the place where on she reduces the biggest diameter in the small what goes in the valve nut. Theoretically the biggest stress should be really here - here colides the full power of hammer from out and the power of gas from inside, and here is the force concentrated by the edge. The metal from whitch is this part looks be crappy, coarse-grained, looks even not like steel.
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Old 03-28-2013, 08:24 PM   #1416 (permalink)
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There is imho the optimal construction if you will have something like classic nelson:

- still fairly simple construction / instalation
- still only two key seals (fail of other can hurt only efficiency but not function)
- capability be used in different nelson bodies
- the hammer integrates now the front part of the classic powertube like Trracer
- both ends of the powertube are now sealed when firing (hammer needs be sealed in bolt - but it is easy now)
- pressure ballanced valve allows use bigger valve face seal
- force of the valve closing spring can be externally adjusted while is marker pressured
- the whole construction can be scaled = the powertube ID can be entlarget until the paintgun frame allows




...it is hard for me to resist the temptation modify ZXS-200 to be more efficient than Grey Ghost...

Last edited by 3022; 03-28-2013 at 08:33 PM.
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Old 03-29-2013, 10:27 AM   #1417 (permalink)
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Quote:
Originally Posted by 3022 View Post
There is imho the optimal construction if you will have something like classic nelson:



Looks pretty similar



The main issue with a system like that is still getting high enough closing forces without a stiff spring. It doesn't bias as badly as other examples of balanced poppets have in the past, but it would benefit from higher closing forces still.

And now for something I had mentioned, but don't think I had showed. Very similar to the above, but with a twist. I haven't built one in a Nelson, so the potential is theoretical. I believe Lurker may have a bit more physical experience with this concept though.



Air is not only allowed through the powertube, but allowed to act on the rear balancing surface to further drive it closed.
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Old 03-29-2013, 11:42 AM   #1418 (permalink)
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Yoda,
This intrigues me.If I am reading this correct you intend for some of the air pressure to circulate to the rear of the valve and close it before the ball leaves the barrel. Is a spring used as well? I have been able to work without springs on some of my guns but this looks like is should work better for that.
As a side note, since you are working with smaller things like valves, I have a Puma valve seat that has become damaged and I need a new one machined. Would you be interested in such work?
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Old 03-29-2013, 12:02 PM   #1419 (permalink)
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Originally Posted by y0da900 View Post
Looks pretty similar

The main issue with a system like that is still getting high enough closing forces without a stiff spring.

...
Air is not only allowed through the powertube, but allowed to act on the rear balancing surface to further drive it closed.

The system can be pressure balanced less or more - how do you will, so there is imho no problem to ensure the similar closing forces like normal nelson has, but with sightly larger sealing diameter - and that was the only goal to use here the ballanced valve system.

Other thing is that I take the shifting of the closing force from gas to spring as advantage - one thing that I do not like on nelsons is thier common inability to cock depressurized.


Your system is clever in principe, but imho more difficult for manufacturing and his parts will be hightly stressed in places, where they are weakened in material amount and even in stress concentration. At least I think that the threading on your powertube is useless. Use only pipe, let the outer diameter of the powertube go in and press them only on the diameter a little. Something like this:



And I have doubts about the real gains and losses of such like design in nelson style valve with tight and long powertube - you using the gas in powertube to closing the valve, but disturbing the flow of the gas to barrel more... at least in first time and in second time you will have the same limitations like in unbalanced valve to control the dwell.

I think that "suboptimally timed" valve will be work in the same way. Combination of conventional system with lightened hammer will perhaps do the same job.

Last edited by 3022; 03-29-2013 at 12:21 PM.
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Old 03-29-2013, 12:30 PM   #1420 (permalink)
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The springless design works for the phantom, heres the second generation that i've been working with. Props to Silentnuke for the flash of inspiration, this uses the stock(enlarged) air passages.



The cup seal is pushed backwards into the valve port when fired, sealing the valve chamber off. The full input pressure then acts on the end of the cup seal pushing it closed once the difference in pressures between valve chamber and valve input is great enough.

Im using it at 400 PSI(CO2) and getting 270+FPS with a good paint/bore match, SilentNuke has gotten to 270+FPS using an otherwise stock phantom but with 450 psi input(HPA)

3022: I like your idea, I can tell it would flow a lot but its fundamentally changing the basis of the nelson valve train. You have a lot to share, and by all means please do! But this thread is dedicated to updating the mechanical pump action nelson, not to turn it into a single action semi.

That being said, take care in the design of the sear mechanism. Your going to put a tremendous strain on it, and if it moves backwards even the tiniest amount your going to leak down the barrel. Have a look at how an automag sear works, you may be able to adapt the idea to work in your concept.
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