Lucky Ego Air Assist valve

[Strawb]

Update time

I made a new bolt pin that is far more reluctant to let go of the rammer

So the good news is now i can shoot without the bolt becoming detached from the rammer after every shot.

Not so good news is that the max velocity i managed using my 21g bolt was 150fps
After changing to a nexus bolt with my new pin (29.5g) and removing the valve spring ( i really don't like having to do this, imagine getting to an event and having to strip you marker because the exhaust valve poppet is now rattling round in the lower tube ) i managed 210fps. This is with the LPR flush and HPR set for max velocity, slightly higher or lower HPR resulted in a drop in velocity.

Dwell is at 7ms, anything more than this made no difference at all.

All this testing was done with a stock 0.693 shaft barrel with reballs 0.679? or there abouts so with paint fitted to the barrel i could possibly get another 20fps.

Conclusion is that whilst a delrin rammer might stand up to the job it just isn't heavy enough to achieve the required velocity.
I guess the Lucky Air Assisted valve is not as balanced as the Newton kit for angels and simply cannot operate with such low mass in the rammer/bolt assembly.
To achieve the 210fps the weight was 5.6g rammer and 29.5g bolt+pin so we now know that 35.1g is too light. (Stock is 28.6 rammer and 39g bolt/pin = 67.6g)

Next is to figure out what weight is required is required to consistently achieve the required velocity.

Any guesses?

Steve

 

[robof9]

dont forget the valve has to bed in.

im using a 3inch stock bolt, delrin pin, stock rammer. slightly lighter than stock spring(till it beds in), 300psi hp, 70psi lp, dwell at 10 on tadao, getting 260fps.

if u let me use your delrin rammer ill report on what my results are at those settings

 

[Strawb]

Another test complete, this time added a large capscrew to the back of the bolt just to get the weight up.
Total weight now 44.6g bolt, pin, and rammer and the new record velocity is [Drumroll please].................................260fps still not there but getting closer. The good news is that it still only takes 7ms dwell to achieve max velocity.

Now we seem to be getting very close to what is achievable with the stock rammer and a light bolt/pin combo ( 51g or so), so that being the case how do i get this thing consistant?

So unless there are any sugestions as to how to achieve a higher velocity without adding weight [looks for inspiration from John C] then i guess the delrin rammer idea is dead

Steve


Edit* What i will do is rig up a guage to check what pressure i'm getting out of the LPR, never know i might be down on pressure

 

[Strawb]

Completed testing with different weights to find out what we need.

Testing done with both the stock rammer and a delrin one (5.6g), a couple of different bolts, different pins and various other ways to adjust the weight.

Tests done with LPR springs in stock configuration and LPR flush so basically the max LPR pressure available. Is that 100psi? Not had chance to rig up a gauge yet.

Dwell and HPR adjusted for each test to achieve max velocity and no spring on the exhaust valve.

Weights quoted are for rammer, bolt and pin combined as this is what really matters.

26g 150fps
35g 210fps
44.6g 260fps
51g 320+fps Didn't try to get the max velocity as i got 320 straight away.

From this we know that the required weight is somewhere around 45g to 51g .

To achieve this we could use a stock or nexus bolt, stock pin and the NDZ rammer? Around 48g

Or the stock rammer with modified bolt and delrin pin. Around 50g to 60g depending on how the bolt is modded.

By the time a spring is added to the valve so that the poppet cannot fall out when not under pressure i would guess that 55g to 60g should be the target weight?

Haven't run out of ideas just yet, but it's getting close.

Anyone else done any extensive testing yet?

 

[Strawb]

Just to add i have now got it shooting fairly consistantly at 270 -275 with reballs, not actually tested the max velocity i can get with this setup.

This is with the stock rammer, a custom bolt and delrin pin weighing 21.7g so 50.3g in total.
LPR 1 turn from flush
Dwell at 8
Valve spring is the ram return spring from a BKO
05 EGO, it may be possible to run with a lower mass on an 06 due to the lower operating pressure.

Thread on pbnation about NDZ testing an ally rammer, they won't release much info at the moment. My guess is because it's too light and doesn't work properly .
What it does show is that an 06 ego may be able to run with a reciprocating mass of 44g possibly due to the lower operating pressure. Or possibly just because it's a Dark EGO so it must work better right?

http://www.pbnation.com/showthread.php?t=1505493

I guess that's me about done on this as i can't see what else can be done.
Just need to test it with paint before the masters on sunday

Steve

 

[John C]

It is worrying that the valve is so hard to open.

In any balanced valve the piston has less surface area in contact with the firing pressure than the valve stem, so that the air pressure is holding the valve closed more than the air pressure on the piston is opening it.

With the newton valve, when the adjuster is dialed all the way out, you have a hard time getting the velocity under 350 From this point you would screw the adjuster in, increasing the valve return spring force until air does not get blown up the feedtube. This gives the lightest possible force holding the valve closed that is capable of closing the valve properly.

In your case it seems the force holding the valve closed is quite high, as you need quite a punch to knock it open.

Finding the ideal weight with the stock LPR setup (as you are doing) is the best course of action.

When you chrono remember to set the firing pressure alot lower than stock and dial it up as you chrono, reducing the firing pressure will reduce the force holding the valve closed and may actually help increase velocity with the ligter mass.

 

[Strawb]

Thanks John that's pretty much what i did, at each weight i found the highest hpr setting possible before raising or lowering the hpr resulted in a drop in velocity. Also found the highest dwell before it made no difference.

Guess this is why they call it an Air Assist Valve and don't mention ballanced in any way.

I'm now running LPR exactly the same as i did with the stock valve, reciprocating mass is 9.5g lower than before and dwell is 2ms lower than before so it's not all bad news.

If it works with paint tomorrow (all testing done with reballs) i'll use this setup at the masters on sunday.

Steve