BAM B50/51 Pressure Gauge

[Taso1000]

Hi All,

I've been wanting to get a pressure gauge for my B51 air reservoir but am unsure of a safe method.  Eric from Stalwart Arms had made me a fill adapter with a gauge for my FD PCP.

I was thinking I could replicate something similar in form with a high pressure street tee fitting but I am unsure of the thread sizes and what pressure rating the fittings have to be for safety.  I have seen tee's rated at 3000 and 6000 psi.  Are these the max pressures or is it like the B51 is rated at 2900 but has safety factor built in?

I think the gauge and foster fill fitting are 1/8 npt.  I am not sure what the threads on the B50/51 fill cap are and what do I do for the dowdy seal?

Thank you all in advance.

Taso

[rsterne]

If a fitting is rated for a working pressure of 3000 psi, it should be good for at least 3.5 times that before failing, at least in theory, as that is the ASME standard for pressure vessels.... I would not be concerned using a 3000 psi rated fitting in a B-50/51.... provided you have proper thread engagement for the material you are threading it into.... and the threads are compatible, of course....

Bob

[Taso1000]

Bob,

Thank you!  I'm just not sure what the threads are on the end cap where the stock foster screws in to.  The dowdy seal makes me think the threads aren't tapered.  But I could be wrong.

Taso

[Motorhead]

Bob,

Thank you!  I'm just not sure what the threads are on the end cap where the stock foster screws in to.  The dowdy seal makes me think the treads aren't tapered.  But I could be wrong.

Taso

There NOT tapered and WHY the dowdy seal.

If your T is 1/8" NPT on the male end, and the thread pitch is real close on the cap you could RE-TAP the cap to make the FM threads 1/8 NPT that would allow a snug attachment, eliminate the dowdy seal & allow use of teflon tape.

[vigilandy]

Taso,  hit up Rocker1 for some advice.  He recently set me up with dual gauges on a regged B50. 

[Rocker1]

Made these gauge blocks. David

[Taso1000]

I have a naïve question due to my inexperience.  I have tapped straight threads before.  You just go all the way through till there's no more resistance.

How do you know where to stop cutting tapered threads?  Do I test fit with the fill fitting and keep cutting till I have adequate thread engagement?  Also is there a recommended torque number on tightening?  I have split pvc connectors in the past from over tightening.  Unfortunately I'm an over tightener and over lubricator lol.

Thanks,

Taso

[YEMX]

Made these gauge blocks. David

This is perfect for my rifle!   

[rsterne]

Basically tapered pipe threads are a cut and try, IMO.... The minimum engagement (with your fingers) is given in the thread tables, usually about four full turns, although it varies with pipe diameter.... According the this chart.... http://www.engineersedge.com/hardware/taper-pipe-threads.htm .... for 1/8"-27 NPT the finger tight engagement 0.162" minimum, which for 27 TPI is 4.4 turns.... I'm pretty sure I use 5 turns with my fingers when I'm tapping a hole for that, but it's been a while.... 1/8"-BPP threads (which is often what it used on airguns) is 28 TPI, so in 5 turns of engagement the error is only 0.007" (about 0.2 threads).... In my experience, you can install a tapered 1/8" NPT male fitting in a 1/8" BPP female hole ONCE with Teflon tape without leaks.... After that, depending on materials, you may have a problem.... I have not tried retapping a hole from BPP-28 to NPT-27, but by the time you run the tap in 1/2", you will be completely peak to valley on the tap, ie no threads left at the bottom of the hole....

Bob

[Taso1000]

Ugh    Bob, is there an easy way to measure the threads on the male foster fitting from the B51 endcap to find out what kind they are?

Are there 1/8 BPP-28 adapters to 1/8 npt?  I'm pretty sure they won't hold 3000 psi but could a 1/8 npt helicoil seal that pressure and would the aluminum material removed from the cap make it unsafe at 3000 psi?

Nothing can be easy   

Thanks in advance for all your help.

Taso

[Voltar1]

IIRC they are 10mmx1.0mm threads. Will confirm asap

Checked one here and that is the thread. Confirmed!

[Joe Brancato]

I miss  your Jeff Dunham puppet as your avatar.

IIRC they are 10mmx1.0mm threads. Will confirm asap

Checked one here and that is the thread. Confirmed!

[MichaelM]

I was going to wait for my b50 build thread to show how I did mine but its on a back burner while I finish up work for customers right now so I will put in a sneak peak for you

I am building a regulated b50 for FT work so what I did was remove the rear plug of the valve, Then machine a longer rear section and replace the spring with a much softer conical spring... this makes the valve and plenum one piece.... then I machined a gauge stand and put it together..... looks like this

Stock rear valve plug and new longer one


valve assembled


Valve assembled with gauge and standoff


and a view of the inside showing how full the flow is with gauge installed into extension



Dont have any pics of the final assembly with the oring groove and such... but you get the idea... not a cool duel gauge setup like Rocker built but will read the regulated pressure which is all I care about..... would also be amazing for an unregulated power valve as it has great  unrestricted flow to the poppet seat....

[Taso1000]

Hi All,

First of all SAFETY is my highest priority in this project.  I just saw this post and I have some questions:

http://www.gatewaytoairguns.org/GTA/index.php?topic=114164.0;topicseen

That fitting looks like it's one piece where neither the male or female fill fittings are removable.  Would it be safe to leave the female foster attached continuously for months on end?  I am a little leery of it being bumped.

If something like that setup is safe I should be able to assemble one with higher quality 1/8 npt parts.

Obviously it will not be removable unless the entire gun has zero pressure.  I would also leave the check valve out of the guns fill fitting and rely on the new assembly's check valve.

I would have rather done my initial idea if I can solve the thread compatibility issues.   

Taso

[Taso1000]

I was going to wait for my b50 build thread to show how I did mine but its on a back burner while I finish up work for customers right now so I will put in a sneak peak for you

I am building a regulated b50 for FT work so what I did was remove the rear plug of the valve, Then machine a longer rear section and replace the spring with a much softer conical spring... this makes the valve and plenum one piece.... then I machined a gauge stand and put it together..... looks like this

Stock rear valve plug and new longer one


valve assembled


Valve assembled with gauge and standoff


and a view of the inside showing how full the flow is with gauge installed into extension



Dont have any pics of the final assembly with the oring groove and such... but you get the idea... not a cool duel gauge setup like Rocker built but will read the regulated pressure which is all I care about..... would also be amazing for an unregulated power valve as it has great  unrestricted flow to the poppet seat....

Michael,

That's pretty slick!

Taso

[cca50]

Hi All,

First of all SAFETY is my highest priority in this project.  I just saw this post and I have some questions:

http://www.gatewaytoairguns.org/GTA/index.php?topic=114164.0;topicseen

That fitting looks like it's one piece where neither the male or female fill fittings are removable.  Would it be safe to leave the female foster attached continuously for months on end?  I am a little leery of it being bumped.

If something like that setup is safe I should be able to assemble one with higher quality 1/8 npt parts.

Obviously it will not be removable unless the entire gun has zero pressure.  I would also leave the check valve out of the guns fill fitting and rely on the new assembly's check valve.

I would have rather done my initial idea if I can solve the thread compatibility issues.   

Taso

If you are talking about the Air Venturi Inline Air Pressure Gauge, it is made to go on Air Venturi Tank Adapter Assembly, 4500 psi, for High-Pressure SCBA Tanks
https://www.pyramydair.com/product/gold-plated-trigger-for-webley-raider-tomahawk-or-longbow?a=401 other words, it fits the end of your female foster fitting fill hose, and attached to the male foster fitting for filling. After normal filling, you bleed the pressure off the fill hose and remove it. As far as I can tell, it is not designed to be left attached. Or that is how I understood your question about it. I just would like to see a much better gauge is my issue with it for filling. I am trying to find the parts to assemble basically the same setup with a much better quality glycerin filled gauge... and the individual parts for that matter.
Charles

[Taso1000]

Charles,

Since I don't want to make any permanent modifications to the rifle I has been considering a gauge fitting that worked off the end of the air tube.  But yes, I wanted to leave it on semi permanently.

Thanks to Voltar1 for identifying the threads on the BAM B51 fill adapter.  I did find this street tee, RGA-33, but it doesn't list the working pressure:

http://www.mscn.com.au/oil-pressure-tees

Taso

[cca50]

A site to remember, when in doubt about any hardware type products    http://www.mcmaster.com/#gauges/=140ivn
I can spend days wandering around that site looking at everything they stock. I have already been there today looking for parts...lol

[Voltar1]

Could take that tee and cut off the npt threads, drill and tap to 10x1.0mm. Use a section of suitable rod with a hole drilled through, seal with the same Dowty washer and in business.