Paintball

[CJOttawa]

From our very own self-described "retro grouch" B, posted to the Nelson Owners Group (NoG) here:
Nog -> Nelson Valve 12 Gram Efficiency Tuning

I was thinking of posting this to the general pump section but let's face it: the only guns on the market that really take advantage of this are Ducks and Boxguns.

For reference, I've also posted power tube dimensions from B, here:
http://www.mcarterbrown.com/forums/p...imensions.html
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Nelson style valve tuning for efficiency with 12 grams

First off forget any notion of getting maximum efficiency from a vertical or bottom line layout. The key is to have the CO2 gas take the shortest path to the valve and remain in a compressed state. These techniques will also work on other set up but will not be as efficient as a direct and shot path to the valve.

Things you may need to arrive at the most efficient set up.

• Nelson Spring Kit
• Valve body back bottle, bobbed, or drop out any one of these will do.
• Power tubes of at least two different sizes these are not necessarily necessary but will make for an efficient set in the long run, I suggest a Lapco #4 & #6. (P is for Phantoms)
• A couple of valve seats with o-rings and a couple of cup seals put them together to have ready to go jet sets. These will make for easy tuning down the road but are not necessary.
• Nylon spacer 5/8” long x 1/2 “ OD x .375 ID can be found at your local mega home center in the hardware aisle. These usually come three to a bag we will make three different lengths.
• A light weight hammer Taso or Lapco will also be a nice addition but not necessary, both are out of production but with some hard work can be found on the internet.

Tools and such needed:

• File, (small half round and one flat),
• hack saw (to cut the spacer down)
• Crocus cloth (rouge paper) for polishing the power tube some sort of drill to spin the power tube to ease polishing the power tube,
• oil,
• 12 grams plenty or a dummy set up for constant air,
• paint,
• chronograph,
• note book

First thing clean every thing bolt & hammer, body of the gun, valve.

Next polish the power tubes to make them smooth, don’t go over board just want smooth and shiny.

Now assemble you jet sets if you have them (power tube, valve seat, o-ring, cup seal)

The next step is to cut down the nylon spacers the first I cut a 1/2” next at 3/8” and the last a 1/4". The first length may need a bit of trimming to allow the full travel of the power tube you will need to confirm this on the valve body. I cut the spacers down with a band saw but you may also use a hack saw. Try to keep the spacer as square and true as possible, use the files to clean up the ruff edges.

Next come the arduous part tuning, I start with the largest power tube, heaviest spring for the valve, and the lightest main spring with a light hammer.

In general a heavy valve spring will be the most efficient one. Put a drop of oil on the valve seat o-ring and the power tube where it intersects. Make sure to set the velocity adjuster to its midway position of adjustment, and the bolt & hammer have some lubricating oil on them.

Now starts the long process of tuning for efficiency, remember to let the 12 gram not chill too much; take your time between shots, don’t rush.

You may need to go through all the combinations of tubes, springs and valve spacers you made to get the best combinations for you set up. This is what the note book is for so you can know if you are making progress.

Remember to remove your gas source before opening up the valve to do adjustments.

In my tuning I go for a velocity of about 265fps to 275 spikes will and can happen due to paint and ambient temperature.

Generally the largest spacer will give the most efficiency but rapid shots will suffer low velocity.

There is always a bit of a balancing act that needs to be done to fit your style of shooting / playing.

The most efficient set up may not work for your style of play just make sure to have fun and continually adjust to the game.

[ironchef97]

Nice! Where do you put the spacers?

[CJOttawa]

Originally Posted by ironchef97

Nice! Where do you put the spacers?

I'm scratching my head about that myself. I can't figure if they're intended to go in front of the valve behind the collar the hammer hits or if they go behind the valve spring as a shim.

B's post pushes me to try lighter valve and main springs and a smaller power tube in the Redux.
Maybe the the smaller tube diameter would help increase efficiency and reduce liquid getting to the ball. (I'm destroying Marblizer and X-Ball Gold in the Redux, in the breech, due to liquid CO2 getting out)

[Greenmtnphantom]

B knows his stuff when it comes to Nelsons. The spacers were IIRC shims, basicly used to "bob" the valve without perminately modding it. The valve inserts in the Gargoyle are of the same idea I believe.

[CJOttawa]

Originally Posted by greenmtnphantom

B knows his stuff when it comes to Nelsons. The spacers were IIRC shims, basicly used to "bob" the valve without perminately modding it. The valve inserts in the Gargoyle are of the same idea I believe.

A plus with the Redux is the valve is already significantly devolumized.

The only issue is liquid going directly from the 12-gram through the pierce-pin assembly to the power-tube openings, which is where either a diffuser sleeve or smaller power-tube come in.

[Greenmtnphantom]

Yeha I'm working on bringing an old Nelspot (pre 007) back to life and some kind of diffuser sleeve is going to have to be part of that project. Already have full Lapco internals, battle frame, and in-grip lever changer. Got lots more work to do but it's one of only two projects I have going right now

[sniper42]

CJ, What size powertube do you have in your redux right now? What were you thinking about bringing it down to?

In my nelspot, I have run stock vavle spring with a blue main and the stock powertube which is about .160" and I am having trouble getting the velocity up past 200fps. Maybe I need to get a bit lighter of a valve spring though.

[ASKA]

what actually happened to B?

[CJOttawa]

Originally Posted by sniper42

CJ, What size powertube do you have in your redux right now? What were you thinking about bringing it down to?

In my nelspot, I have run stock vavle spring with a blue main and the stock powertube which is about .160" and I am having trouble getting the velocity up past 200fps. Maybe I need to get a bit lighter of a valve spring though.

I'm running a #4 bored-out to #6 specs.
Main spring is red (heavy), valve spring is blue (medium).
I max out around 300fps with the TPC dialed strong. Dialing the TPC down I can get 275fps.
This assumes a slight underbored paint/barrel setup.

Try a heavy main spring in your setup and/or wider power tube.

Originally Posted by ASKA

what actually happened to B?

Not sure but I got the feeling there was some kind of falling out or drama. Maybe not...? Too bad. I see a lot of wisdom in his posts.

[ASKA]

I hope I'm not touching a sticky topic. Just curious