THANKS MIKE , FOR THE FLYING DRAGON PCP , IT IS WONDERFUL .

[vigilandy]

The more I think about this, the more I am convinced that my gun leak is related to a seal or o-ring that is nicked or simply defective.
I think that the standoff and spring might be useful if a gun is leaking from the transfer port. My gun leaks from the thread of the tank. So it is probably the seal (urethane o-ring) that is bad. I know that a couple of other urethane o-rings that seal the valve are damaged. So they need to be replaced.
I will see if Mike is willing to send me those as I think it is the cheapest solution for both of us.

Seems like a bit of bad luck with your 22.  Fortunately mine are still holding original air pressure as delivered from Mike a couple weeks back!  Good thing too.  I know these are project guns,  but I'm not ready to open mine up yet.  I'm actively following everyone else's hands on learning in case I need to work on mine. 

Just as a side note: When I had my QB79 apart for minor surgery,  the valve seal started leaking even though I didn't touch it!  I didn't have a spare so I just rolled it over and reused it.  Works fine now.  Don't know if it's luck or what so I put in an order for a set of replacement o-rings!

[bocomomark]

"I think we need Mike to chime in and let us know what he thinks about this whole setup."

I think it was Mikes intention to release this gun into the wild first,  He does not offer a tune for this gun at the moment.  So I suspect Mike may be interested in what "we think about this whole setup".

"There is also an extremely small urethane o-ring on the valve pin itself. It would be nice if Mike would provide us with sizes and maybe even where we can get those o-rings."

I thought that someone already provided sizes and a source to you, in the thread you started for your gun?  Is there something wrong with the information they provided? (i.e. does it seem to be incorrect, or insufficient?)

[mouka]

Just go to Autozone and buy an O-ring kit. Every thread I see you complaining about your rifle not shooting. Try and fix it instead of posting on the forums, seems like time would be better spent trying to remedy the rifle.

Nick had specifically said not to use black rubber seals because of a very short lifespan. If you have a different opinion, I wouldn't mind hearing your take on rubber vs. urethane o-rings for the valve system.
I wish that someone could confirm that regular rubber o-rings would work fine. It would mean all i have to do is go to an auto parts store and get a whole set of o-rings and get what I need.
The "experts" think that urethane o-rings are what's needed. And there has to be a good reason why the manufacturer of these guns put urethane o-rings in the first place. Am I missing something?

[airgunwarriors]

Just go to Autozone and buy an O-ring kit. Every thread I see you complaining about your rifle not shooting. Try and fix it instead of posting on the forums, seems like time would be better spent trying to remedy the rifle.

Nick had specifically said not to use black rubber seals because of a very short lifespan. If you have a different opinion, I wouldn't mind hearing your take on rubber vs. urethane o-rings for the valve system.
I wish that someone could confirm that regular rubber o-rings would work fine. It would mean all i have to do is go to an auto parts store and get a whole set of o-rings and get what I need.
The "experts" think that urethane o-rings are what's needed. And there has to be a good reason why the manufacturer of these guns put urethane o-rings in the first place. Am I missing something?

mouka, please watch this video. There are many other videos on youtube in reference to Air-Guns and there inner working that are very informative and can answer many of your questions as well. They may not be the "right" answers, but again, very informative.



Al.

[airgunwarriors]

While we are on the subject of o-rings and seals, I thought you all might find this test interesting:



Respectfully,

Al.

[nervoustrigger]

Firstly to establish a context, we're talking about whether a polyurethane O-ring is needed for the -113 on the body of the valve.

In this application, regular variety Buna-N (nitrile) O-rings are fine.  We're dealing with air, not CO2.  CO2 will permeate through Buna-N; air will not. 

You want urethane when an O-ring is subject to either abrasion through continuously sliding back and forth on a surface (especially where buildup of heat is a complicating factor), or when the O-ring is subject to being nicked or torn on installation.  Polyurethane is tops for toughness if there is a slight burr or sharp edge that the O-ring passes when it is being installed.

The former isn't a factor here; it's a static O-ring.  I don't think the latter is either.  I don't have one of these rifles but if you install the valve from the end where the fill nipple was installed, I don't think the valve O-ring passes any sharp edges or holes.  That can sometimes be an issue with QB rifles that have a tank block because of the two holes cross-drilled through the tube so if there are any sharp edges, debur them before you reassemble. 

The way you install the valve is like this:  only screw the valve halves together loosely so as not to compress the O-ring.  Then slide the valve down into the tube and lock it into its home position by installing its screw(s) through the outside of the tube.  Then as a final step, you reach down into the tube with a wide blade and engage the slot in the face of the valve and tighten it to compress the O-ring and form a good seal. 

BTW for this step, I use a 3/4"W x 1/8" thick piece of bar stock from the hardware store.  I needed to just barely round off the edges with a file to help it fit snugly into the tube, and I used an angle grinder to reduce the thickness at the tip so it would fit into the slot in the face of the valve.  Works really well.

[vigilandy]

Firstly to establish a context, we're talking about whether a polyurethane O-ring is needed for the -113 on the body of the valve.

In this application, regular variety Buna-N (nitrile) O-rings are fine.  We're dealing with air, not CO2.  CO2 will permeate through Buna-N; air will not. 

You want urethane when an O-ring is subject to either abrasion through continuously sliding back and forth on a surface (especially where buildup of heat is a complicating factor), or when the O-ring is subject to being nicked or torn on installation.  Polyurethane is tops for toughness if there is a slight burr or sharp edge that the O-ring passes when it is being installed.

The former isn't a factor here; it's a static O-ring.  I don't think the latter is either.  I don't have one of these rifles but if you install the valve from the end where the fill nipple was installed, I don't think the valve O-ring passes any sharp edges or holes.  That can sometimes be an issue with QB rifles that have a tank block because of the two holes cross-drilled through the tube so if there are any sharp edges, debur them before you reassemble. 

The way you install the valve is like this:  only screw the valve halves together loosely so as not to compress the O-ring.  Then slide the valve down into the tube and lock it into its home position by installing its screw(s) through the outside of the tube.  Then as a final step, you reach down into the tube with a wide blade and engage the slot in the face of the valve and tighten it to compress the O-ring and form a good seal. 

BTW for this step, I use a 3/4"W x 1/8" thick piece of bar stock from the hardware store.  I needed to just barely round off the edges with a file to help it fit snugly into the tube, and I used an angle grinder to reduce the thickness at the tip so it would fit into the slot in the face of the valve.  Works really well.

Stupid newb question:  Can you distinguish between nitrile and polyurethane o-rings solely by color?  Black vs white?

Also, thanks for the info on valve installation.  On the QB-79 I screwed the pieces together tightly, lubed with silicon grease, and tapped it in with a hammer and dowel.  Now I see that's the wrong way to do it.  I didn't know any better.  Doesn't leak though.  I'll chalk that one up to beginners luck.   

[nervoustrigger]

Can you distinguish between nitrile and polyurethane o-rings solely by color?  Black vs white?

There's no sure way to distinguish by color.  Generally, polyurethane O-rings that I see are translucent or white or red but there's no guarantees because colorant can be added to make it pretty much anything you want. 

Nitrile is generally black but again, can be different colors.

There a whole host of other materials like Viton, PTFE, silicone, etc.  Just saying so no one gets the impression it's merely a matter of determining A or B.  There's also C, D, E, F and on through the alphabet.

Moral of this story:  keep your O-rings separated and labeled!

[mouka]

I don't know about other airgun rookies, but I am learning a ton here. And having a technical background, I am certain I will be up to speed in no time.
Keep posting your opinions and tricks, this is what us beginners are in desperate need for.

Thanks!

[mikeiniowa]

for the very best in the 113 O-rings for the valve and cap use the ones that Crosman has used for years, cost around a dollar each but will last for years...precisionpellet.com  has them, barrel orings can be just about anything and even if they look ratty will still seal, probe use the buna type....silicone grease applied after the o-ring is in place for installing...

[cwlongshot]

I have to say I have been using the Crosman rings too... they are easy to deal with and a flat 4$ shipping is great!!

CW

[Nick Hammack]

Thanks Mike :

I received the other two FDPCP rifles and the extra barrels , as well as the pump ,  I think I am going to have to buy one of the pumps for myself after putting this together and using it for a bit .

For those that want to put a drier on the pump ,  simply get some desicants and place in the handle on both sides and put breather back in and pump away ,  take out once in awhile and dry in oven and put back in and you have it .

Time will tell but I like this pump a whole lot better than my Airforce pump from what I have seen and used for a few minutes .

Regards Nick

[Nick Hammack]

The 2 guns and the hand pump I played with this evening ,   I love the pump is all I can say .

The first gun I pulled out of the box is I think valve locked ,  this is bad enough that I have to pull it down in order to tell it could be a couple of things ,  we shall see .

The second gun functions but the foster fitting on the fill port leaks like a sieve , will have to remove and put some Teflon tape back on it to replace the tape that is on it ,  but at least this gun will function .

3 out of 5 guns have little to no problems the other  two have lots of work to get em back up and running ,  this was to be a tinkerer gun and that has been proven ,  but they are so simple that a shoe cobbler can fix them so this is all the better ,   just a heads up as to what I have run into .

Regards,  Nick

[Nick Hammack]

I had a bit of time today and did some testing with the .22 cal FDPCP

Got 730 fps out of 28 gr. En jin pellet


The following was at a 2K fill and shot down to 1400psi using CP's 14.3 gr.

970,984,975,961,959,947,935,923,913,896  I could have used a bit more fill pressure on this to utilize the bell curve a bit .


This string was a 2K fill and shot down to 1400 using Kodiak Heavy @ 21.1 gr,


880,865,861,849,837,829,820,807,796,781.

I upped the fill pressure a bit to 2200psi and shot the following using the Kodiak 21.1,  looks very promising using the .22 cal and I think with a bit of warm weather and a bit of time is shall prove to be a very nice rig .

843,834,850,868,871,869,862,855,844,834,819,813,800,789,777.


The Kodiak's look like it is going to be very promising indeed we shall see how they shoot and I think it will be very consistant from the numbers I see with just a few minutes to play with today .

This takes the energy to 30.5 ftlbs  with the cps at 14.3 gr,   and 35.47 ftlbs with Kodiaks at 21.1 gr,


Regards ,  Nick


PS ,  DenSkin and I have been talking about what I should and can do on valve modification to this platform and I think I will be putting a .30 cal barrel on one of the ole girls and seeing what I can get out of it then ,  I do love this platform it is a wonderful 100 bucks spent ,  I can own a .177,.22,.25,.30 and still have no money in the project .
 

[Nick Hammack]

Hello fellow FD owners :

Now that Bob is onboard with his very own FD I will not worry about the tutorial any longer ,  for he is covering it in spades for everyone , Thanks Bob.

I changed out the Lead seal that I put in the .22 cal FD and machined an Acetal seal for the valve ,  the lead gave way after a bit and the Acetal once seated is working much better ,  I also like the fact that Bob is cautioning folks to keep the pressures down ,  I know that the M5 screws did not give me much comfort ,  so I installed the 10-32's at 90' to the M5's in the stop block to give me the comfort margin ,  I hate having a lot of pressure in my face with out some fudge factor involved .

I did finally strip out the barrel band screw and will take it back apart and drill out and tap to the next larger size , other than that I have things up and running 5 FD's later ,  I will be finishing out the others like the two guns as time permits .

I will be taking it to the bench one of these days to see exactly what can be done with the little guns .

Oh Mike my buddy I work with ( he is a Master Scientific Instrument Maker ) is very numbers orientated and I showed him my FD's and let him shoot them with open barrel and the extension I made for the other barrels and he has ordered a B-50 and a hand pump from you so please get them out asap he has not an ample supply of patiences  LOL  ,  I will keep on selling them for you ,  keep on shipping them out .

Regards,  Nick

[airgunwarriors]

Hello fellow FD owners :

Now that Bob is onboard with his very own FD I will not worry about the tutorial any longer ,  for he is covering it in spades for everyone , Thanks Bob.

I changed out the Lead seal that I put in the .22 cal FD and machined an Acetal seal for the valve ,  the lead gave way after a bit and the Acetal once seated is working much better ,  I also like the fact that Bob is cautioning folks to keep the pressures down ,  I know that the M5 screws did not give me much comfort ,  so I installed the 10-32's at 90' to the M5's in the stop block to give me the comfort margin ,  I hate having a lot of pressure in my face with out some fudge factor involved .

I did finally strip out the barrel band screw and will take it back apart and drill out and tap to the next larger size , other than that I have things up and running 5 FD's later ,  I will be finishing out the others like the two guns as time permits .

I will be taking it to the bench one of these days to see exactly what can be done with the little guns .

Oh Mike my buddy I work with ( he is a Master Scientific Instrument Maker ) is very numbers orientated and I showed him my FD's and let him shoot them with open barrel and the extension I made for the other barrels and he has ordered a B-50 and a hand pump from you so please get them out asap he has not an ample supply of patiences  LOL  ,  I will keep on selling them for you ,  keep on shipping them out .

Regards,  Nick

"4. The valve is located by two 5mm x 0.8 mm steel screws of unknown quality in shear.... Since one of the load-bearing screws is in the steel block behind the valve, is it critical that the valve bear tightly against that block, otherwise only the valve screw would be taking the shear load.... I would highly recommend that when you have your gun apart that you check that, and if they are not in firm contact, add a thin shim between them to insure both screws are doing equal load bearing.... The threaded portion of the screw is subject to the shear load, so I used the minimum listed minor diameter and calculated a total shear force of 1154 lb.f. for the two screws, assuming 1010 mild steel with a 53K tensile strength (32K in shear) .... With a 0.745" ID for the reservoir, at 1500 psi, the load on the valve is 654 lbs. which means the safety margin is 1.8:1.... If the screws were upgraded to high-tensile screws, this would increase, and I would highly recommend that anyone contemplating using more that the recommended fill pressure confirm that the screws are up to the job.... Where the valve screws penetrate the receiver, you could see faint marks from where the threads of the screws were pressing on the back of the hole.... However, the material is thick enough that I was not concerned about the bearing load at the recommended 1500 psi, but it is something to keep an eye on each time you have the gun apart...." Bob"

Nick,

I did the same thing you did, based on Bob's recommendations seen above for those wanting to exceed a 1500-psi fill, but based on the reply below, even that is not good enough. Maybe it just slipped his mind to mention the rest of the information in the write-up above about the screws; what he eventually educated me on in the reply below in addition to using better screws.?.

"Al, now that you addressed the screws so that you can increase the pressure, you have decreased the safety margin on the threaded portion of the tube.... Until we know what the material is, we have to assume mild steel, so at 2000 psi (using 44K to yield) you have reduced the safety margin to 1.9:1.... That means that every time you fill the tube you are "working" the steel past 50% of it's yield strength, which is into the area where fatigue becomes an issue.... Add to that the "stress riser" caused by the sharp vee at the bottom of the threads, and eventually I would expect the tube to fail at that point.... It might take 50,000 cycles, or it might not, and if the tube is CrMoly you might be just fine.... but exposing the threaded portion of the tube to pressure is the weak point of the design, IMO, once you address the screws....

Bob"

So, based on that fact that what we both have done really is not good enough, I have finally elected to go with a lower than 2000-psi pressure.

Your thoughts?

Respectfully,

Al.

[Nick Hammack]

Hello Al:

I deal in pressure vessels and metal requirments every day as a vocation.

That being said I will not go into details.

Liability permeate our society today,  with that being said folks should take the current path laid out before them.

I will not talk of fill pressures any further,  my comfort zone my differ from others so I would suggest everyone just take the safe road.

I have my FD'S figgured out to my satisfaction and then some,  good luck on your journey with your FD.

Regards. Nick

[RHytonen]

It's also well accepted, in official racing and aviation safety circles, that (round seamless) steel tube is far stronger than flat sheet or even square tube, and most spectacularly in sizes near and under one inch o.d., where the wall thickess to o.d. ratio is much stronger still. You can't use the same formulae, modulus or stress limits for round tube, as you would for flat sheet or even bolts.

[P.S.: There are places to get burst discs in the 'missing' areas around and just over 2000psi, if you're willing to tolerate a little more bulk from a 1/4" disc, holder, and an adapter from 1/8" NPT. ]

[RHytonen]

The more I think about this, the more I am convinced that my gun leak is related to a seal or o-ring that is nicked or simply defective.
I think that the standoff and spring might be useful if a gun is leaking from the transfer port. My gun leaks from the thread of the tank. So it is probably the seal (urethane o-ring) that is bad. I know that a couple of other urethane o-rings that seal the valve are damaged. So they need to be replaced.
I will see if Mike is willing to send me those as I think it is the cheapest solution for both of us.

Seems like a bit of bad luck with your 22.  Fortunately mine are still holding original air pressure as delivered from Mike a couple weeks back!  Good thing too.  I know these are project guns,  but I'm not ready to open mine up yet.  I'm actively following everyone else's hands on learning in case I need to work on mine. 

Just as a side note: When I had my QB79 apart for minor surgery,  the valve seal started leaking even though I didn't touch it!  I didn't have a spare so I just rolled it over and reused it.  Works fine now.  Don't know if it's luck or what so I put in an order for a set of replacement o-rings!

IME with other equipment/systems it's always the last place you look, or the first one you disregarded out of hand, as "couldn't possibly be it." And it's always the cheapest/simplest part, after you've replaced all the expensive/complex ones.

[RHytonen]

"4. The valve is located by two 5mm x 0.8 mm steel screws of unknown quality in shear.... Since one of the load-bearing screws is in the steel block behind the valve, ...." Bob"


Your thoughts?

Respectfully,

Al.

JFYI, not in the GEN II.

That block, like the trigger group stop, and the barrel band,
- is plastic.

Rod