Regulator for BAM B51

[Taso1000]

I think that is where my brain get confused.  My thinking is that if I still have a thousand pounds per square inch, 1000 / 1 = 1000.  If we reduce the area to .5 square inches the force becomes 2000 pounds per square inch.  1000 / .5 = 2000

See what I mean?  So there is now more pressure on the seat.  Or is air pressure applied in all directions versus one direction like a weight or spring?  Sorry, I don't remember much from my physics class 30 years ago 

Taso

[nervoustrigger]

The way I like to think about it is like this...

There's high pressure in the tube.  There's low pressure in the outside world.  The high pressure wants to escape to the low pressure side but the poppet is in the way.  The pressure is acting on one end of the poppet.  There's virtually no pressure on the other side of the poppet (only 1 bar / 1 atm).   It's the difference in pressure between those two sides that establishes the direction the poppet "wants" to go.

To draw a comparison, an object placed inside the tube--say, a small steel mass the size and shape of a sugar cube--does indeed have pressure acting on it from all sides.  If that object were compressible, it would shrink in size but it has no impetus to actually move within the tube because the pressure is acting on it equally in all directions.  One side of it would have to be exposed to the atmosphere (or some lesser pressure) in order to make it want to move.

[Motorhead]

I think that is where my brain get confused.  My thinking is that if I still have a thousand pounds per square inch, 1000 / 1 = 1000.  If we reduce the area to .5 square inches the force becomes 2000 pounds per square inch.  1000 / .5 = 2000

See what I mean?  So there is now more pressure on the seat.  Or is air pressure applied in all directions versus one direction like a weight or spring?  Sorry, I don't remember much from my physics class 30 years ago 

Taso

Actually other way around.

If you have a vessel with 1000 PSI within it, and your poppet to release pressure had a surface area of 1 sq in, it would take a force of 1000 LBS to break it loose.
Reduce poppets area to 1/2 sq in it would take 500# to break it loose .... 1/4 sq in at 250# on down the effort falls as the area pressure is exerted against keeps getting reduced.

This is why we speak of reducing poppet diameter so it takes LESS hammer/spring energy to open it.

[Taso1000]

Hey guys,

I got the poppet springs yesterday!     Hopefully I will be able to get the first B51 up and running with a goal of 500 - 525 fps in .177 this weekend.

I bought a little dc inverter stick welder, I've always wanted a welder  , to fix the hammer I cut too far.

I also found an 8" drill press for $60 shipped.  I'm going to try drilling out the hammers from the side to lighten them.  Hopefully that will work out better than the rotary tool.

What diameter do you recommend turning the poppet down to for the first rifle?  Or should I use the spare conical valve as is?

Thank you all for your help!   

Taso

[SpiralGroove]

Hey Taso,
The taper on my B50 poppet is about 35 degrees.



Hope the pic helps ............ Kirk

[Taso1000]

Kirk,

So you recommend the conical valve, from your picture, sealing on the edge of the flat valve seat versus a slimmed down flat valve poppet on a flat seat like Garththomas posted?

This is for the low powered B51.  I haven't started on the high powered rifle yet.   

Thanks,

Taso

[SpiralGroove]

Hey Taso,
I chose to taper poppet's end.  The (large) outside diameter of the whole poppet was not reduced.
My valve spring is conical; this is the heavier valve spring I sent you.  In Later versions, I used the lighter spring.
IIRC, I drilled the throat of the valve slightly larger too.



Garth Thomas's poppet looks to be a slightly smaller diameter, with a taper near the sealing surface of the poppet.  Since the poppet is unused, it's hard to see if the poppet seals on the taper or with the flat end?

[Taso1000]

Kirk,

From his post here:

http://www.gatewaytoairguns.org/GTA/index.php?topic=79971.80

It looks like he tapered the poppet to 5/16" but I haven't found if his valve seat is flat or angled. 

The seat passage/area around the valve stem, in my valve seems to be around .236" with a slightly rounded edge.  So .3125 - .236 = .0765    .0765 / 2 = .03825 sealing ring. 

Will that be enough to seal?  I guess if there's abrasion/wear, with the taper, it may wear to an equilibrium point where the spring/air pressure balances with the delrin physical support properties.

Kirk, do you remember what your delrin hammer weighed?  I like your tapered poppet solution the best so far.  How did your poppet wear?


OR, am I worrying about stuff that has minimal effect and I should stop worrying and just shoot the rifle?  lol

Thanks,

Taso

[GarthThomas]

The seal is on the flat face, the reduced diameter allows for less force to open as discussed. That is a factory poppet by the way, I'm still waiting for it to fail.
This setup is for what ever power level you want as a matter of fact it suits higher power especially with the thinner washer which reduces spring preload in the valve.

[Taso1000]

GarthThomas,

Thank you for the clarification!  I'm off to go get welding rods.   

Taso

[Motorhead]

Hey Taso,
The taper on my B50 poppet is about 35 degrees.



Hope the pic helps ............ Kirk

If your going to go with a tapered contact seat configuration, Angle as shown ( Or flatter yet ) is going to be required IMO.

Using a shallow contact angle is kin to a cork in a bottle ... The poppet head as it gets hammered into the seat will start going down the throat effectively CORKING IT !
The lift of poppet required to clear throat will become higher as the portion of poppet within throat of valve increases in depth.

[SpiralGroove]

Hey Taso,
So GT's poppet seals on the smaller flat surface of the original poppet, while my poppet taper has a higher pitch and seals on the taper (as can be seen in the pic).
I believe, sealing on the taper requires a lighter hammer strike than the flat, but obviously both methods work fine.  I used the taper seal because a very light hammer was being used.  I don't know the combined weight of my delrin hammer & spring guide - maybe in the 40+ gram range.

You can use the light or heavy conical springs I sent you to further lighten the force needed to break the poppet from the valve seat.  The lighter valve spring just allows you to use a lighter hammer/spring guide set-up and or a lighter hammer spring.

The goal of using the lighter hammer/spring guide/valve spring/tapered poppet & lighter hammer spring was to reduce stress on the popper, which has been a known failure issue with the BAM B50/B51.  I have never checked a poppet for wear, but assume it will last much longer than OEM.

This "lighter" tune process is the Motorhead method using some  tweaks copied from others.

Taso, much like I "DO" you are beginning to ruminate too much about this and just need start working.  However, you don't want to get so caught up in "process" that you forget to be present while your working (I do this ). 

Good Luck

[GarthThomas]

Thank you for the clarification!  I'm off to go get welding rods.   

Don't get me wrong but you may want to trash that broken hammer, they are a precise fit and welding may distort it and without say a lathe or some tooling that could true things up it may not fit back in the tube or slide properly. Since it was a spare just move on to your next idea or try the less invasive steps and shoot it you may like where your at before doing all the other stuff. JMO

[Taso1000]

Garth,

I tapered the poppet to about 5/16" like yours.  I learned a lot about delrin last night lol.  First, it takes a lot longer to remove material than I thought.  Second, have to keep the drill at a slow speed so the friction doesn't create enough heat to melt the delrin.  It created a warped lip, kinda like a candle.  So I slowed down, kept going and it came out well. 

As for the welding, it went ok.  I was able to mend the gap.  I cleaned it up with a file and put it in the rifle but I found out the hammer was doomed from the start.  I don't know if you can tell but the tail end of the hammer I posted pictures of had material removed from the diameter in the center portion.  This change in diameter, step, causes the hammer release to catch and the hammer can't be pulled back enough to set correctly.  I tried to radius the forward edge of the hammer release so it could pass the step but it won't work.  So I filed the step out of the hammer.  Tried it out and now the material is too low to catch. 

So I'm done with that hammer.  As for the new hammer I think I can get away with just drilling one .8 hole all the way through the side.  Will a regular high speed steel bit work or should I look for a carbide tipped one?

I also noticed that there are two different length hammers.  The one that came out of the new rifle is shorter than the unmodified one Mike sent me.

Thanks,

Taso

[GarthThomas]

Yes there is not a lot of room for play with those hammers as far as drilling I wouldn't know, I've never tried cutting into the hammer. I put my valve stem in a drill press and set it for low rpm so that helps with the heat, then I set the table so I can hold the file or emery paper on a block to shape what ever I'm working on, its a poor mans lathe but I have had a lot of practice with it. Even shaping the poppet takes precision I don't know if I could do a good enough job like Motorhead's taper with my method.
Also if I might add, since doing the work shown by rsterne I have tuned my rifle to below 6fpe and right now I have it at 17fpe just using the stuff shown in his post so that was what I liked about that post, nothing radical or permanent. For the lowest power I used the MC spring, the Delrin guide with 1/4" stop and a 3/32 Transfer port and some shims for the hammer spring to fine adjust as well as the valve work and that put it just below 500fps.

[Taso1000]

Hi All,

I apologize for not giving an update for a while but I haven't done anything with my project till today.  Well today I tried to drill my 3/4 inch hole through the side of the hammer. 

The Bosch high speed steel drill bit I bought only made it half the way through the one side and stopped.  It was going good until then.  I guess the interior is hardened or the bit wore out that quickly?  I was using oil to help the drilling. 

Oh well, I need to find a carbide drill bit now.  I'm going to skip the cobalt drill bits unless anyone has had success.

Thanks,

Taso

[Taso1000]

Hi All,

Tonight I was able to lighten the hammer with my drilling through the side idea.  It honestly came out better than I expected.  The final weight ended up being 93.63 grams. 

So after my small victory I started searching for optimum hammer weight after I saw this recent post:

http://www.gatewaytoairguns.org/GTA/index.php?topic=101679.0;topicseen

So in my search I found this post:

http://www.gatewaytoairguns.org/GTA/index.php?topic=48892.

I have only read the first page but it seems I need a much lighter hammer.     That or sorcery lol

Until any of those two things happens I'm going to put the rifle together and start shooting is and see what happens.   

Thanks,

Taso

[Motorhead]

I shoot my .25 caliber regulated B50 at @ 45 to 50 ft lbs with a 100% nylon hammer with a steel screw contacting poppet stem weighting JUST 30 grams total weight. ( Reg set at 2000# )

[Rocker1]

 Wow, those hammers are hard, for sure something wore out doing that.  David

[Taso1000]

Rocker1,

I never would have thought they were that hard.  I have read many times that these rifles are built like tanks and now I'm seeing why.     I am so glad I picked this platform to tinker with.

My little, cheap drill press was chattering and groaning.  I couldn't find a solid carbide drill bit in 3/4", that was budget friendly, but I did find a carbide tipped drill bit that's made to drill granite counter tops that had a sharpened edge versus concrete hammer drill bits that are pretty dull from the factory. 

All in all it was $13.20 well spent.

Rocker1, are you still making B51 LDC's?  I may need your services in the very near future.   

Thanks,

Taso