Regulator for BAM B51

[Taso1000]

Thanks Scott,

I will try to pull it out of the rifle tonight to verify.

Dumb question, do the internals of the regulator need to be lubricated?  I recently bought some Ultimox and can use that if applicable.  Besides obvious damage in the regulator, is there anything else I should look for?

Thank you,

Taso

[Motorhead]

Thanks Scott,

I will try to pull it out of the rifle tonight to verify.

Dumb question, do the internals of the regulator need to be lubricated?  I recently bought some Ultimox and can use that if applicable.  Besides obvious damage in the regulator, is there anything else I should look for?

Thank you,

Taso

You can use ultimox IF YOU THOROUGHLY DEGREASE all the parts first.  Krytox based lubricants DO NOT PLAY WELL when mixed or in contact with petroleum or silicone lubricants.

 

[MichaelM]

I have been following this thread on and off for a while now... I have a gut feeling that reducing your reg pressure that far is causing you more trouble then its worth..... I would be willing to bet that with the lightweight hammer and such that you have in it now you should keep the reg set around 12-1400 psi and use a severely restricted transfer port.... if I had to guess somewhere in the .07-.08 area (heck maybe smaller) and removing any plenum you may have in the setup because there is plenty of room in the valve itself to supply enough air.....  heck in the 500 fps range you may even think about stuffing the valve a touch to remove even more space so that there is enough pressure drop for the reg to work effectively between shots....

I know if I was going to build a low fps all week on a single fill shooter thats probably where I would start.....
light weight hammer
fully internal through hammer SSG setup
regulator around 1200 psi
restricted transfer port around .07 (drill#50)

start from there and see where it needs to go......

 

[Taso1000]

Michael,

To be honest, Scott said the rifle would be more efficient running at a higher pressure way early when I was planning the project out.

I did a lot of reading and weighed pros and cons.  I decided to go low pressure. I wanted low fill pressure since I pump.  I wanted lighter hammer cocking because I don't think the hammer cocking lever screwed into the bolt is a strong design.

I was also inexperienced. I thought strangling the transfer port did not increase efficiency or shot count compared to less air from the get go.

If it doesn't work in the end many will still benefit.  I have with all the experience I have since aquired. People can point to my thread and say, "Taso tried this and this and it didn't work."

Or it may not be the perfect setup but good enough for 10 meter practice.

We will find out eventually. 

Thanks,

Taso

[BigTinBoat]

Zooming in on this pic sure makes those bellvilles look like they have very little bevel, almost like they have collapsed.

[Taso1000]

Rob,

Thank you.  I will check that the washers are still convex/concave.  It may be the angle of the picture because those washers are from the brand new in bag, never been installed regulator.

Taso

[Taso1000]

I found the transfer port thread I keep referring to:

http://www.gatewaytoairguns.org/GTA/index.php?topic=105564.0

They are Bob's, RSTERNE'S, reply's numbered 11 and 19

Taso

[Taso1000]

Hi All,

I didn't get a chance to pull the rifle apart tonight but the never installed regulator does not have any holes around the smaller diameter intake side.  Since they both came together I am 99.99% confident they are identical.   

As soon as I get the rifle apart I will update the thread as to the condition of the regulator in question.  I'm gonna contact milo to see if he has any suggestions.

Thank you,

Taso

[Taso1000]

Hello All,

I was able to swap out the first "Taso adjusted" regulator with the second unmodified regulator that was pre set with a 1500 psi set point.  I also installed a delrin transfer port with a 2.5mm opening.  This is the graph of the merged strings in order.

[rsterne]

The huge bump in velocity at the right hand end indicates insufficient hammer strike for the setpoint pressure.... Either reduce the setpoint pressure until that bump disappears.... or increase the hammer strike to bring the velocity up on the plateau to the left.... Ideally, a bump of less than 1% of the velocity will give you a good balance between velocity and efficiency (shot count)....

Bob

[Taso1000]

I know the big spike at the end is because I have too much hammer tension so I need to adjust that out.  I am impressed that my thinking was wrong and Motorhead was right.  The setup was more efficient at the higher set point pressure because of the more shots it produced.

I shot a string last night with one preload washer removed but it wasn't enough to remove the spike.  I'll post that graph when I get home tonight. 

Once I get rid of the spike I will work on a smaller transfer port size.  I soldered the stock brass transfer port and will try opening up the port size and see how it works to trim down the high points.

I still don't understand why I'm getting the velocity dips and rises.  I wanted to think the regulator was not reacting quick enough to the small sips of air per shot.  But from the last graph the dips are around 100 shots peak to peak.

I am puzzled as to what's going on.

These are the first 400 shots on a brand new regulator.

Taso

[rsterne]

You have insufficient hammer strike, not too much, for the setpoint pressure.... That is what is causing the spike....

I have no idea why you are getting the large ES on the part of the curve above the setpoint.... I have never seen that before....

Bob

[Taso1000]

Thanks Bob.  For some reason I thought I had to reduce hammer spring energy.  I'll have to re read my notes.

It's seems we were both replying at the same time to my post.  :-)

Taso

[nervoustrigger]

My guess is the high ES is precisely because the hammer strike is too weak.  It's barely enough to knock the poppet off its seat so minor variations appear amplified.

[rsterne]

I suppose that is possible.... The big spike does mean that the hammer strike is very light for the setpoint pressure, and any slight irregularities would therefore be emphacized, resulting in varying velocity.... You see the same thing sometimes in unregulated PCPs, with a zig-zag string on the initial upslope part of the bell-curve, which then settles down across the top, and nice and smooth on the downslope.... Quite common, actually, although only in guns tuned for high shot count, where the pressure drop per shot is tiny.... or tuned for a very wide ES.... That would be the case here, of course.... the ES of the spike is over 30%....

Yeah Jason, I think you nailed it.... I learned something new today.... 

Bob

[rsterne]

You know what?.... I actually HAVE seen this before, but didn't recognize it.... Here is a low-powered setup I had on a regulated QB.... High setpoint pressure, very light hammer strike....



The green line is the AVERAGE velocity, the red line the maximum, and the blue line the minimum.... Note that for shots 1-30, the ES was very large, nearly 40 fps, which dropped for shots 31-60 to about 30 fps, and for shots 61-70 (near the setpoint) to less than 15 fps.... Once below the setpoint, the ES was only about 1%, shot to shot.... The maximum velocity stayed a constant from shots 1-70, but there was a bigger ES when the tank had more pressure in it, just like taso is seeing.... The differential across the regulator is larger, and the downstream pressure probably varies just a whisker, and when it's higher, the very light hammer strike doesn't open the valve as far, resulting in a lower velocity....

So there you go, it DOES happen when you have way too light a hammer strike for the setpoint pressure.... Thanks Jason, for the solution, and to taso for bringing this to light....

Bob

[nervoustrigger]

Well, Bob, it is truly reason for celebration to contribute a little brain dropping to you today.  In fact, I think I'll have some ice cream tonight

Actually I thought this was something that had come up at least a couple of times in past threads we were replying to.  I too had noticed it on detuned regulated rifles.  The extraordinarily small lift and dwell makes for both great efficiency and sometimes giggle-worthy report but at the expense of a higher ES.  But the cool thing is if you're taking, say, a 30+ fpe .22 cal 70 yard rifle down to 10fpe for all-day discreet backyard plinking at 25 yards, a 10% ES isn't really a problem. 

Same thing applies to suburban pesting at modest ranges.  I once took a 30fpe rifle dialed down to 13fpe over to a buddy's house to thin out his gray squirrels and it went 6 for 6 that morning at distances out to 30 yards.  And nobody in the neighborhood even knew I was there

[Taso1000]

Hi All,

Here is the chart for the string I took last night.  I've tried to scale the second graph to approximate the first graphs x axis scale.  The first graph was shot from 3000 psi down to where the poppet dumped the remaining air.  In this this graph I started at 2000 psi and removed one washer I used to increase preload.  They are .5" in diameter and about .04" in thickness.  So 2000 psi to poppet dump.

Taso

[Taso1000]

Gentlemen,

I am glad to be able to bring things to light.     I don't expect to shoot it further than the 17 yards.  That's the difference from the back porch to the fence in my back yard. 

So my ES doesn't need to be that tight as long as it doesn't really affect my groups.  It would be nice from a perfection standpoint but maybe not necessary if the difference isn't apparent in shot grouping.  My goal was to build an accurate and quiet regulated paper puncher to hone my skills with.

It looks to me that last night's string may be a little flatter and the right hand peak wasn't as high.  It is very similar to the first graph in this area.  But it seems the wider velocity swings happen from 3000 to 2000 psi as shown in the first graph.

So what do you gentlemen think I should try tonight?  At this time I'd like to leave the regulator alone to see how it compares to the first one and to remove one variable from the tuning, for now.   

Do you think if I tune the spring rate and preload I can flatten out the velocity curve?  I could then use a transfer port restriction to lower the velocity average?

As always, thank you all for all the help and insight you have offered!

Taso

[rsterne]

When you say you reduced the preload, I assume you are talking about the hammer spring?.... To me, that is going the wrong way.... Are you trying to tune for ~ 600 fps or more like ~ 800 fps?....

Bob