Regulator for BAM B51

[Taso1000]

Hi All,

I'm sorry I haven't updated you on my project in a while.  I didn't realize I would have such a hard time locating parts.    I did get very lucky though.  Scott had time over the holidays and was gracious enough to make me 3 nylon hammers.  Thanks Scott!

Kirk was also great in that he was able to locate and send me the conical valve springs.  Thanks Kirk!

I was able to find a 1/2" od light hammer spring from Menards.  Scott recommended the 10# Marauder hammer springs from WAR, so I've ordered 2 and waiting for them to arrive.

I had to open up the valve cap id to 1/2" as the conical springs were too tight and kept hanging up on the wall.

Scott recommended I also polish up the reservoir tube where the nylon hammer will slide with 600 grit.  There are still factory machine grooves but Scott said not to worry about them.

I tapered the valve poppet to make it easier to lift off the seat.

Next I needed to vent the rear of the hammer chamber because vacuum is created when the hammer is  released forward.  I drilled a 3/8" hole but when I went to put it back on the air reservoir I noticed I made a mistake.  I thought the end cap extended past the trigger frame.  Oops!  Then I figured I can file away some material from the end cap to allow the pressure to escape.  It came out better than I thought.  Good save Taso!   

The pictured spring is mostly temporary unless it works awesome.  I cut it so it had about a half coil of preload per my measurements.  I didn't have any 1/2" od washers to keep the spring pigtail from going into the air vent and changing spring rate.  I will get some from Lowe's tonight.

Hopefully I can get the rest of the rifle together tonight, pump it up and shoot it!  I will keep you updated!

Thanks for your patience and help!

Taso


 

[Taso1000]

It's a BAM B51 air rifle again! It was apart way too long.

I hope there are no leaks and get some shots at different fill pressures to post.

Taso

[Taso1000]

So I was able to shoot the rifle from 800 to 1500 psi to find the pressure to set the regulator.  I don't remember which post Bob Sterne mentioned it but I'm glad I found it.  Bob's way, pumping to 800 psi and taking a couple shots to see where you were velocity wise.  Then pumping to 900 psi and recording your shot velocities.  I used the gauge on my Xisico pump for the pressure readings.

I was going to pump up to 1500 psi and then shoot down from there.  I planned to connect my pump after about 5 shots and pump till where the fill valve clicked open and record that pressure off the gauge.  I like Bob's way better.  Thanks Mr. Sterne!

So now for the issues.  Remember this rifle was basically unfired.  I probably put 10 pellets through it before I took it all apart to perform my lightweight plan.  So it was never broken in.  All the o-rings were replaced with polyurethane ones except for the transfer port o-rings which I used 70 durometer buna-n.

First issue:  the valve poppet would not seal as I tried to pump up the rifle from empty.  I tried to grab the poppet stem on the fully assembled rifle from the bolt probe notch on the left side but it was too narrow for my needle nose pliers.  So I had to remove the stock, back cover and hammer to grab the poppet stem with the pliers while trying to pump.  Yes, my feet came into play, almost like Twister but I got it done!    I will keep an eye on the poppet but hopefully it will break itself in and mate better with the valve seat.

Second issue:  after I pumped the rifle to 1100 psi I heard air leaking from the foster fill fitting.  I quickly shot my 3 shots before I lost too much air so maybe those shots are skewed and should be disregarded.  While pumping to 1200 psi I was able to get a couple drops of silicone oil into the fill valve and the leak was almost gone.  I put another 2 drops when pumping to 1300 psi.  I will have to keep an eye on it too.  If it doesn't go away I'll take it apart again.  I'm almost positive there's a new poly o ring in there.

Now for the velocity results.  I used Crosman .177 Domed 7.9gr Premier Pellets from the brown cardboard box.  The end of the barrel was about 7 feet from the first chronograph sensor.  I'm listing the velocities in the order they came out of the rifle.

  800 psi  751, 761, 767
  900 psi  740, 737, 735
1000 psi  672, 673, 677
1100 psi  621, 642, 655
1200 psi  571, 560, 569
1300 psi  507, 506, 505
1400 psi  455, 445, 440
1500 psi  398, 412, 417

It's obvious from my results that the higher the pressure goes the harder it is for the lighter springs and hammer to open the valve.  Since my goal is around 550 fps as a regulated 10 meter target rifle I think I'm on the right path.  Tomorrow I will take velocity readings starting at 400 psi. 

If, for example, I hit my 550 fps goal at 400 psi Is it normal for a regulator to be set this low?  Milo74 did say his regulators can be set as low as 100 psi.  Or would it be better to shoot at the 1200 psi level?

I'm thinking the 400 psi level should be more efficient.  More shooting and less pumping would be great.  I don't plan on pumping to 3000 psi.  I think 1500 or 2000 psi will suffice. 

I have a feeling other issues may pop up running at so low a pressure.  Would it be harder to keep the poppet sealed or under control if there is less seat pressure due to low psi and lighter poppet spring?

I remember reading the first page or two of Bob Sterne's SSG, maybe that can help, but I would have to re read it as I don't remember what I read back when he first posted it.  Tomorrow is another day.  :-)  And besides, my brain is mush right now.

Thanks to everyone for your help,

Taso


 

[Motorhead]

Actually the HIGHER pressure is more effecient.  In a low power tune as you wanting experience tells me 1100-1500 psi range for reg set point will be where to start.

Also on the BAMs ... poppet diameter is WAY TOO LARGE and can be reduced to @ .320 or even a tad less.  Poppet spring needs to be replaced as well with one much softer when utilizing those light hammers.

Burnishing in the poppet to body by spinning with an electric drill works quite well.

have fun !!

[Rocker1]

 Don't over power the poppit spring with to much hammer spring , it will make you dance.  David

[Taso1000]

Hi all,

First off I'm going to answer your questions.

Scott,

I did turn the poppet down a bit toward the sealing end.  I initially removed material too fast and I think I heat warped it from too much friction on my files and sandpaper.  So then I had to "true" the warped part.  I cut a 3/8" strip of 600 or 800 grit sandpaper, poked a hole in it for the valve stem to pass through and put the poppet in the valve body.  I figured it would keep my angles correct and only remove material from the mating surface.  Then I connected my drill to the valve stem and held the sandpaper so it wouldn't turn in the valve body.  I sanded the mating surface of the poppet slowly till all the warpage was gone.  I am also using the #86 Hillman conical spring.  It's much lighter than stock.   There is a picture of both assembled together in my last set of pictures. 

David,

Thanks for the heads up.     I am using a 1/2" x 3.5" spring I found at Menards.  It's much lighter than stock at about 6.5 pounds per inch of travel.  I should test the force again as I basically cut the spring in half since then.   I am not a very good dancer lol



So now for today's update:

This morning I checked the gun with my pump gauge to see if it leaked air overnight.  It was down to around 950 psi from around 1400 psi from last night.    So when I got home today I took the stock and the barrel off and checked the transfer port, valve body and fill fittings for leaks.  The only place I saw leaking was the fill fitting out the foster end.

So I release all the pressure in the tube and remove the end cap.  The little valve has a new polyurethane oring so I must have replaced it when I went through the gun initially.  So I checked for burrs or junk that would interfere with the seal.  I didn't find anything so I put some new silicone grease on the orings and put the gun together again.  I start pumping and the poppet valve hisses. It's losing less air than I'm putting in and stops leaking after 2 or 3 more pumps. 

So I stopped pumping around 400 psi so that I can start taking velocity readings up to 800 psi.  I start releasing the pressure on the pump and all the air comes out of the rifle.  I close the relief valve and figure 400 psi may not be enough to seal so I pump up too 800 psi, like I did yesterday and it held pressure.  Upon opening the relief valve as quick as I can, all the air leaks out of the rifle again. 

So I pull the endcap off and think there may be a thin casting line in the polyurethane oring. So I stretch it over a rod and I spun it about 10 times on some 800 sandpaper.  I put it back together, pump up to 1000 psi and same thing.  The valve won't seal.  I got the same results with a buna-n oring too. 

Am I doing something wrong?  Is there a better foster fitting to use with a spring assisted valve like the FD PCP's have?  I see the sintered filter is threaded and moves.  Does that need to be a certain distance from the valve?  I have the valve inserted so that the slot faces the rear of the gun also.  Is that right?

As always, thanks in advance for your help!  I am going to search the internet for possible solutions too.

Taso

[Motorhead]

Yea the BAM oem Foster can be a MAJOR PITA !!!
many times had to polish the bore where sealing spud moves.  Worst case manufactured another altogether changing it to a more conventional T stem and o-ring configuration.

[Taso1000]

Okay,  I'm a dummy lol.  I found out what I was doing wrong with my fill valve.  I, the genius (sarcasm), was pushing the little valve into the bore of the foster fitting.  I "believed" that is how it was when I disassembled it.  So tonight, as I thought about that design, I couldn't figure out how the valve was supposed to get back into the bore to seal. 

So from searching the internet I read that the valve should rattle in the fitting and is designed to seal against the bevel on the end.  I make the adjustments and now the rifle holds air after pumping.

Ta Da!

[Taso1000]

Here are my velocities shooting from 400 to 800 psi:

400 psi  634, 616, 614
500 psi  701, 694, 690
600 psi  720, 724, 715
700 psi  755, 768, 761
800 psi  741, 753, 749

And a graph of the velocity averages versus psi below.

Taso

[Taso1000]

Hi All,

I received the 10 pound Marauder hammer springs from Wicked Air Rifles on Monday and I had time to swap one in and shoot some pellets at rising pressures like my prior posts from 500 psi to 2500 psi.  Everything is the same except for the new hammer spring.  I only shot one pellet after 1500 psi because the rifle was so loud.

2500 psi  1138 fps
2400 psi  1124
2300 psi  1104
2200 psi  1101
2100 psi  1083
2000 psi  1066
1900 psi  1056
1800 psi  1044
1700 psi  1024
1600 psi  1008
1500 psi  984, 984, 970
1400 psi  973, 959, 951
1300 psi  955, 942, 933
1200 psi  924, 917, 907
1100 psi  905, 890, 878
1000 psi  870, 866, 851
  900 psi  847, 838, 831
  800 psi  812, 808, 802
  700 psi  775, 760, 755
  600 psi  726, 714, 710
  500 psi  623, 619, 612  After this last shot the gun dumped the remaining pressure in the tube.  The poppet spring couldn't keep the valve closed against the hammer spring.

So now I have to figure out what pressure to set the regulator.  This is where Bob Sterne's "knee" comes into use.  I need to read that post again.  Milo set one of the regulators to 1200 psi and the other to 1500.  Does anyone know what type of regulators they are so I can read up on them?

I also need to figure out how much plenum I need for the 10 meter setup shooting 7.9 grain wadcutters between 550 and 600 fps.  I also need to know what to use as a plenum that won't crush.  I also don't know which end is which on the Milo regulators.   

But tomorrow is another day.  :-)  Thanks to all for your help!

Taso

[MartyB]

You're looking for about 6 fpe at that weight and velocity.  plenum is normally 1cc per fpe so a 6 cc plenum.  you'll have to do the math.
flat end of the milo regulator is the plenum end.  I've got 4 from him now.
And I think I've got a length of the plenum spacer that he uses for the B50/51 that i can send you.
it is thick walled aluminum tubing its OD just smaller than the air tube ID.
use the 1200 set regulator.  the plenum calculation is based on 1000psi.
tie a wire loop onto the stem end so you can pull it back out later if needed.
then play around with lighter/clipped hammer springs, striker adjustment and a restricted transfer port.  5/16 delrin rod makes easy transfer ports for these rifles.

[Taso1000]

Marty,

Yes, that's my goal for this first rifle.  I think my first spring, the cut down spring from Menards, may work.  On that pressure/velocity graph, the first one I posted, the setup was hitting around 566 at 1200 psi.

Thank you for your offer on the plenum spacer!  If it's something I can source locally I'd hate to inconvenience you.  But if I can't get it from home depot etc.  I will take you up on your offer.  :-)

Do you have the ID of your thick walled aluminum tubing so I can calculate the 6cc's length? 

Yes I agree, I will tweak preload, striker and transfer port one at a time to see what effect they have on my power and efficiency. 

I am using the shortest of the three nylon hammers I have.  The other two are longer so I can see how they affect power after I get the regulator installed.

Mike Melick sent me some delrin for transfer ports with the extra parts I ordered from him.  I think I will play with that last.

I have attached a picture of my regulator.  From your explanation, the side I labeled with "1" goes towards the muzzle and "2" towards the valve?  The plenum will go between the regulator and the valve.

Do these regulators need to be vented to atmosphere?  I'm assuming the vent needs to be placed between the two orings.  Can you tell me what type these regulators are so I can read up on them and their design?

Thank you for your help!

Taso

[Motorhead]

Direction is as stated, adjustment end towards muzzle.
Plenum between Valve and Reg.
YES needs a vent hole in main tube between o-rings.  * Do so as far forward as you can once plenum size is known ... so if wanting more power later a longer plenum can be fitted and vent hole still falls between o-rings ( tho would be at other end of reg body )
That is a MILO74 regulator ... Excellent units made by a fellow GTA member " milo74"

[Motorhead]

Forgot to add .... MAKE SURE the I.D. area of tube where regulator ends up is smooth and free of drawn tube marks.  O-rings need a good surface to seal against.   Using a 3 stone brake hone maybe required.

[MartyB]

Plenum spacer I've got is 0.895" ID.
Running through the math, a .75" spacer would give you a 7.7cc plenum.
You have a little more volume in the valve as well.
A little larger than needed, but a good spot for your goals.

[Taso1000]

Thank you Marty!   

Scott,

What size does the vent hole need to be drilled?  I can match it to the vent hole size on the regulator or does it have to be bigger?

I'm pretty sure it's not possible but I'm going to ask anyway.  The hole cannot be sealed if drilled wrong correct?  I'm thinking the heat created from an arc welder will change the tube properties and weaken it.

I think I'll measure 4 times and drill once lol.

Taso

[MartyB]

You are welcome!

[Motorhead]

Thank you Marty!   

Scott,

What size does the vent hole need to be drilled?  I can match it to the vent hole size on the regulator or does it have to be bigger?

I'm pretty sure it's not possible but I'm going to ask anyway.  The hole cannot be sealed if drilled wrong correct?  I'm thinking the heat created from an arc welder will change the tube properties and weaken it.

I think I'll measure 4 times and drill once lol.

Taso

I do mine with a 1/16" tip starter drill, stop short of breaking threw, finishing hole with a .040"
Run a hone within tube where reg will sit to BOTH deburr hole and make sure o-rings will seal.

[Taso1000]

Hi All,

Sorry for the delay in my project to those that are following.  I had time tonight to degas and disassemble my first B51 so that I could drill the vent hole for my Milo74 regulator.  I used Motorhead's recommendation and it came out well.  I started the hole with the 1/16 drill bit and completed with the .040 drill bit. I've never used a drill bit so thin and I broke it before the hole was all the way through. I was able to clamp the cutting end in my drill chuck and finish the hole. 

I ran my 600 grill flex hone with 30 weight nd oil to remove any burrs from drilling.  Surprisingly my tube had a mirror finish from the factory so I shouldn't have any problem with the regulator orings sealing.  I rinsed the tube out with 91% alcohol to get the flex hone grit and oil out.  I didn't remove the valve because I have a hard time removing the cross pin that holds it in.  Maybe I'm doing something wrong.  If there's a proper way to do it please let me know.

So I'm going to let the tube air out so I don't have a flame thrower and hopefully I can get it all back together tomorrow and start shooting it!   

Thank you to all who have helped.  You know who you are!

Taso

UPDATE:  I forgot the pictures!

[Taso1000]

So I got the rifle all together and roughly adjusted to shoot around 550 fps with 7.9 grain Crosman Premiers.  I have never had or shot a regulated rifle before and the prior configuration didn't have 50 pellets through it to break in.

Later I will try tuning it for better efficiency via striker length and maybe an ssg.

I know things should smooth up and settle down.  My question is how is a regulator supposed to work?  The reason I ask is right now the rifle with the regulator starts at a lower velocity, 490's, and then comes up to the 540's after 5 or 6 shots and pretty much stays there.  I pumped it back up to about 2900 psi and it did the same thing. 

I also think if I let it sit for an hour and then shoot it I get the same pattern.  Is this normal?  Does the regulator need to break in?  I asked Milo74 to set at 1200 psi.

Thank you,

Taso