My Field Target Project

[Bent]

The best for moving parts are wiper rings. O-rings have a tendency to get stuck when they aren't used/moved. You just have to change the high pressure side of the groove so you can mount them.
http://www.m-seals.dk/da/shop/hydraulik/skraberinge

[michaelthomas]

Bob, you are correct on the flow path.

I see what you are saying about the Oring grooves.  I just pulled the specs right from the Parker book for dynamic Orings.  On the next round I will make them as you suggested.  I'll probably pick up some 90 durometer urethanes for the spool as well.

After my gun sat in the 65 degree heat of the house.....it functions exactly as it did before I went to shoot outside yesterday.  I think that, maybe, the boost converter is sensitive to cold.  It was supposed to be 47 degrees where I was at, but in the shadows......there was still lots of snow.  I'll have to set it outside and measure the voltage after it has cooled down. 

My logic when designing this was to keep the small end of the spools' area as small as possible to keep the HP influence, due to fluctuation,  to a minimum.

Ant thoughts about my idea of making the low side piston diameter smaller to put the stack in a more favorable (linear) condition?

Bent......I don't think I can get wipers small enough for my needs, here.  The spool oring is a 004.

Mike

[Bent]

I think you are right about that.... smallest I could find is 3mm/7mm but I've seen them smaller in some of the machines we made in my former job (Shambanrings they were called, but I think that was just the name of the maker).... but they must have been custommade....

It is possible to make yourself in PTFE...

[Motorhead]

In playing with various seat types and air path routes ....
Found those seats which take HP air in at end of the spool / adjustment cap routing air once passing under the open seat threw a side hole in small end of spool under the seat that upon closing has the ENTIRE spool under the lower regulated LP pressure are the more stable.

Those seats and designs that allow HP to access small end of spool from the side and when seat is open travel up and threw seat at the top of spool always have influence to a small degree on the spools bevel stack because the HP present bears against the o-ring. * as HP side pressure changes ever so slight is the pressure felt on the bevel stack from pressure exerted on small end of the spool. 

Next is seat size & material used
Larger the diameter, less the contact pressure exerted over its area ( Tho with this greater area comes a far greater chance for it to leak from contact pressure inconsistency if not VERY square and true.  Smaller the seat diameter easier it is to seal quickly and accurately. 

Because the bevel washers move so little when the seat opens and closes, ANY yield in the seat surfaces and you have changed travel distance spool travels and there for it's set point.

Delrin is far to soft finding PEEK hands down the best material as the seat base.
Also find in seat designs that isolate the HP air once shut do best with very small diameter seats under high contact pressure are very fast to settle, recover very fast and generally very stable shot to shot.

Hope this helps ya some more ...

Scott

[Motorhead]

One more little snippet ....

Once you have the HP flow into seat area being shut off upon closing, No longer do you need to worry about HP influences on the small end of spool.  Now you have MANY more options to seat design.

Regulators set up in this way go about sealing in these noted ways ...
Audrius / Ninja and some others bring air to the seat via a small diameter soda straw tube whose end rests on a seal material placed on the end of the spool.
Huub uses a floating disk that is sandwiched between the spools end & a raised seat on the end cap.

generally found the I.D. of hole feeding seat between .050" and @ .070" with the seat diameter being .100" or less.

** Likely reason we see such small diameter seats is because greater the area seat has, greater the HP side air bears against it attempting to open it.  A small seat only getting contact of .050" - .070" with HP in storage, less this overall influence regulator feels dealing with changes in storage pressure.  Less valves sealing surface feels in tank pressure changes more accurately it will continue to seal off by what LP side is exerting against it.

All these successful regulators have spool drilled from LP end NOT going all the way to the LP end, but stopping a short way from the end being intersected by a cross drilled hole.

Scott

[michaelthomas]

I suspected that PEEK might be a better surface, and ordered a 1/2" round from McMaster yesterday.  Good to now that it will likely be a better seat material, and that I didn't waste my money.  Stuff is kinda pricey.

I see the reasoning behind a side entry hole being better than a straight through like mine......on paper.  When mine is sealed....the HP air is bearing on is the small Oring channel of the spool.  This equates to about 20 pounds of difference in the HP influence on the spool.  That would seem to suggest that the pressure should vary by 100psi or so on the low side......but I have not been able to witness that with a gauge and a test rig over the pressure spectrum that my gun sees on the HP side (2100-3000).  I see about 50-60. 

My gun seems to deal with the 50-60 psi variance well enough that the shot strings are pretty tight over the spread.

I suppose putting the small spool oring on the ID of the body, instead of the OD of the spool would accomplish the same thing.....actually it would be better, since the HP air would not be acting on anything when the valve was closed.   That was my original intention, but I didn't want to buy an expensive little ID groover that could do it.

I really just want to fix the sluggish top up rate for now.  If I could knock it down to under 15 seconds.....I'd be plenty happy.

I'll see what the PEEK seat and the change in the spool diameter will do......and I guess I'll go from there.

Thanks for sharing your findings.

Mike

[michaelthomas]

Actually.....what I said about the HP side pressing on the oring channel wasn't right.  It presses on the front and back of the channel equally, so they cancel each other out.....so its just the difference in diameter between the spool and the body that presses on the ring itself.  If this isn't correct......someone please say something.  I see it as air pressure being applied to all surfaces.

That works out to around 1lb or so.  So overall maybe 5 psi difference in the LP side due to the oring alone.

It must be just the HP pressure requiring more force to keep the valve closed at the seat juncture that makes the fluctuation.....and that would seem to be equal no matter what the design....provided the seat diameter isn't huge.

I guess a more prudent question would be......what sort of fluctuation between 2000 and 3000 psi is noticed with the Ninja, or those other brands of regulator?

Mike

[Motorhead]

Michael,
What I find odd is the TIME it takes your regulator to stop creeping and settle in.
Places to look would be o-ring compression amount ( Groove depth too little ) causing excessive drag on spool within body.
A seat that is actually closing at a lower pressure, is leaking until sufficient LP side pressure is built up having seat yield enough to finally seal.
* Here a Harder seat will make matters worse if there is a mismatch of seat contacting squarely / evenly around it's circumference.

Would also suspect the HP bearing down on the small end of spool o-ring has it further being expanded outward adding to the drag preventing accurate and speedy settling in at pressure set point

My Audrius and both my Huub regulators recharge and settle within seconds of the shot being taken.  This just an FYI   
 

[rsterne]

In any design (such as yours) that has the small O-ring on the spool exposed to the HP air all the time, even after the seat is closed, you are going to experience a variance in output pressure with tank pressure.... It wouldn't matter if the O-ring itself is static or moving, it's the pressure on the area of the stem that causes the changing force.... If the HP inlet is closed off once the regulator seat closes, then the only force on the spool that changes is in proportion to the diameter of the sealing surface of the seat.... As Motorhead states, in a Ninja reg, the inlet hole is very small (I think under 1/16"), so that change in force is likewise very small.... However, it is still noticable, I find about 50 psi difference between a full tank and one that is just above setpoint....

Bob

[michaelthomas]

I'm going to make another body and turn the big end down tomorrow.  At least that will tell me if an improvement can be had from the belleville's working in their proper range.

Thanks for the suggestions.

Mike

[Sfttailrdr46]

  Michael this thread has opened my eyes to just how tec savvy you need to be once fully immersed in playing with toy guns can become. Now I need to go back to school and take some mechanical engineering classes next year when I retire

[michaelthomas]

Don......just get yourself a small lathe and mill with the money you would use to take classes.   Then get on Practical Machinist and read everything you can......ask a lot of questions, and make a lot of parts.  You'll be learning hands on.....and a lot faster than by going to school.

When I was fooling around with my reg a few days ago, I went outside and did a bunch of shooting at 56 yards.  I wanted to see the practical operation of the gun with the regulator in it.  I didn't have a bench where I was at, so I laid out a mat and some blankets in the snow and shot from the sitting FT (off the knee) position, and the prone position rested on a front bag. 

The wind was varying from 0-3mph, and was not changing direction very much.  I didn't have any sorted pellets, so I just shot them out of the tin (JSB Exact Heavies).

Nothing really all that consistent from the sitting position......lots of strays here and there.  One notable sitting group is #24......with a core group of 4 at .255" c ot c, then some serious fliers.  Definitely need a lot more practice sitting. 

I had a wind flag at the target......and when I was paying attention to it and timing my shots with repeatable conditions I got my best groups.  Big surprise, there.   I could see the mirage coming off the top of the target box, to back up the flag.  I have been studying the wind for the last few months using a wind meter and observable signals such as specific movement of leaves, etc. and mirage.  I test myself by looking around at anything I can use to get an idea of wind speed, then going and actually taking a wind reading with the meter to see how I did.   It's been kinda fun.....and a very good learning experience.

Anyway.....there are some decent prone groups spread around.....but one that really stood out.  The fourth group down in the sighter column is a keeper at .150" c to c for 5 shots.  Wind was about as calm as could be outdoors for those 5 shots......and it took me a good 5 minutes to get the shots off waiting for the exact conditions.

Pretty fun stuff.

Mike

[Sfttailrdr46]

56 yards amazingly tight group it can be suprising when it all comes together

[michaelthomas]

I made a new reg body and turned down the spool.  It really didn't make much difference.

I then decided to machine the seat to a concave form.  That made a dramatic difference.  Now it settles in 10-15 seconds.  I'm OK with that, but I'm gonna make another seat when I get the PEEK in.  Maybe that will improve the recovery time further?

I'm getting really nice spreads now......whether I pull the trigger at 15 second or 15 hour intervals.

Mike

[Motorhead]

Very good ..... nibbling away and sorting it all out !!!

[michaelthomas]

Although I'm getting great strings with very small deviations......it seems that a shot after an overnight sitting is on the higher pressure side of the bell curve, and a shot taken quickly (although they produce nearly identical FPS readings) is on the downhill side of the bell curve.  The latter is certainly consuming more air.

The curve without a reg on my gun is very narrow.....maybe 10 shots within 1%.  This would seem to indicate some creep after a long sit.

I contacted Huub, and he may have a reg that I can easily fit into my coupling.

I would like to see how they perform side by side.

 I'm definitely not married to the idea of producing my own regulator......just didn't see one that would work in my small space between the valve block and the tube.

If his can maintain better pressure spreads, I may be able to tune for better efficiency.

Mike

[michaelthomas]

I was still waiting on the regulator that I ordered from Huub, so I decided to work on mine a little more.

Since mine seemed to work very consistently at lower pressures......I thought I would attempt to get my gun to operate in it's peak at a lower pressure.  I was wanting to do this anyway since the old peak was around 2050-2100 psi.

I opened up the throat from .140" to .160".  I also enlarged the exhaust, transfer port and the barrel port fro .100" to .136".

This effectively lowered the peak from 2050 ish to 1400 psi.  I also lowered the capacitance from 600uf to 500 since I was anticipating the solenoid having a much easier time opening the valve at the much lower operating pressure.

I shot a few strings without the reg to verify the bell curve and help me decide where to set the reg.  I was peaking at about 905fps at 1450 or so.

I set the reg to 1550 and gave it a go.

I got 21 shots on my mini test cylinder that is 43.5cc. Filled to 3000psi........ Hi of 883.... low of 876....average of 879....extreme spread of 7....and a standard deviation of 2.  I shot down to 1450psi.  17.8 FPE average and an efficiency of 1.3 FPE/CI.  I think I can back the hammer out a little more, too.  This is the first time I have seen my CE chronograph with 5 duplicate shots in a row.

My normal reservoir is 220cc, so it's 5.15 times bigger.  I haven't run a full string with the normal reservoir, but mathematically speaking......I should get 105 shots at this power level and spread.

I was told by Huub that a plenum volume of 8cc for my gun would give the tightest spreads.  I lowered mine from 20cc to 12cc and that is where I tested it.  I may try a spacer inside the plenum to reduce it even further and see what happens.

I'm pretty happy with this, though.  The reg tops up very quickly at the lower pressure......you can even hear it.  Takes maybe a second or so.

It seems to hold pressure without the creep at 1550.

I have not changed out the seat material, yet.

Mike

[Motorhead]

Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.

Hope you get your Huub soon and install it ASAP .... smile time 

[michaelthomas]

I'm definitely looking forward to trying it.  Hopefully sometime next week, although there probably will be a lag in shipping due to the holiday.

Mike

[Sfttailrdr46]

Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.

Hope you get your Huub soon and install it ASAP .... smile time 

Huub regulator for Mrod??