Prod + HUMA regulator potential-Update

[cilami]

I purchased a HUMA regulator for my Prod mini-bullpup a few weeks ago and I am happy with it. It is really easy to install and I am getting 16 shots @ 19.4 fpe (avg. 695 fps with JSB's 18.1). The ES is around 10-11 fps. My first attemps were directed at getting 16 shots @ 22 fpe, but some distinguished members of this, and other forum, educated and convinced me that my goal was simply not realistic. The situation is even worst since I have  Jim Gaska barrel, which is supposed to slow down the velocity due to the tightness of the bore.

Well, now I am after a really nice shot string posted on the HUMA website: http://huma-air.com/wp-content/uploads/2015/06/shotstring-Prod-124-bar.pdf
The second string shows 31 shots @ 18.8 fpe, for a total of 582 fpe, with an ES of 11 fps. My best attempt at duplicating that tune has produced 17 shots @ 18.8 fpe, with the same ES. Still 14 shots away. Nick, from ASP, has been very kind, but he is really busy working with some other regulators he sells. He recommended trying a lighter hammer and maybe some valve/tp modifications. 

Now, this is my question: I don't pretend that the experts here tell me exactly what to do or try. I will be happy if someone could just tell me if that 31@18.8 string is realistic or not. If not, well, I'll learn to be happy with my current tune. 

[cilami]

Update:

I tested the Prod OEM barrel today and got an average of 725 fps (10 shots), compared to the 695 fps from the JG barrel. But the accuracy…no comparison.

I made a rustic aluminum light hammer (25 gr.and 34 gr. trials) and after using it with different springs and adjustments, could not get better results than with the stock hammer. Don’t know why… Anyway, in pursuing the elusive 31 shots @18.8 fpe shot string, my best results so far have been achieved with the stock hammer, all ports opened to 9/64″, weaker valve spring (no rate), 1 5/16″/.047″ hammer spring, and HT=0; HS=4. Still stuck at 20 shots@18.7 fpe. with an es of 10 fps. If anyone finds out how to achieve the 31@18.8 tune, please let me know!
 
I also got a string of 16 shots @19.8 fpe with the same setup but increasing the HS a bit, of course. My results, not the tune, are similar to the one in the following post, considering my slower JG barrel:

http://www.network54.com/Forum/79537/thread/1448492911/last-1448538857/Expand+Thread , in which the author achieved 16 shots@21.8 fpe with a spread of 3 fps, using a 3-oring Bstaley buffer. The HUMA regulators are proving to be very consitent.

I am running out of options…but having fun and learning, as usual with my PCP's .

[lloyd-ss]

I just installed a Huma regulator in my P-Rod and thought I'd throw in my 2 cents on the installation and results that I have so far.  I do plan on working with this some more with different tunes.
The quality of the reg is impressive.  Installation instructions on the website are good. I set the reg to 117 bar (1700 psi) just using the markings on the reg.  I did the installation using the sleeve that comes with the reg that replaces the original air pressure gage adapter block. So, I don't know exactly what the pressure is (at this time) but the performance certainly suggests something around 1700 psi. The gun is totally stock except I replaced the stock .086 dia T-Port with one of .110 dia. That seemed to help get decent velocity at the low pressure.

I didn't do a lot of testing, but the last string I got was 24 shots with a high of 701 fps and a low of 689 fps, which is a velocity spread of only 1.7% using the cheap 14.5 gn Crosman Premiers in the tin. That's an average power of 15.5 fpe for the 24 shots. By the 28th shot, the velocity dropped to 661 fps, so it was pretty clear that we had run out of air. (Tune info- .110 T-Port, hammer stroke in CW1/2 turn, spring in CW 3-1/2 turns).

Here are my thoughts on the performance of the Huma regulator.
24 shots from a 66cc reservoir at 15.5 fpe with an extreme velocity spread of 1.7% is very, very good.  That's a total of 373 fpe for the string.  Looking back at some of my old test data, in one non-reg example I got only 18 shots averaging 14.9 fpe and also with a much worse velocity spread of 3%.  With a different tune and again, no regulator, I got only 12 shots averaging 18.5 fpe with a 3% spread. Both examples of my old test data are nowhere near as good as what I got using the Huma reg.  But I have more tuning and testing to do.
cilami, I hope that gives you some info that might be useful.  Thank you for starting this thread and sharing your efforts on this.
Lloyd

[PBguns]

About time I get a huma for my prod it seems. 

[cilami]

Lloyd,

Thanks very much for your input. Assuming a fill pressure of 3,000 psi, your efficiency is around 1.03 FPE/ci, correct? Can that be considered very good for a regulated pcp at this power level? In terms of efficiency, how much room for improvement do you think is still possible?

I am sure many P-Rod owners will follow your tests with much interest. I certainly will. 

[FuzzyGrub]

FWIW: You are close to what can be obtained with a BSB and minor mods (0.110 TP, heavier hammer spring), ie 24 shots @ 16FPE.  Es is 3-4% though.  Following Scott's school of regulation, valve mods, lighter hammer, and lighter poppet spring, will probably make some gains on shot count.

[lloyd-ss]

There is definitely more efficiency that can be squeezed out of this set-up, and yes, Scott is the light hammer guru (and more!).  More work to be done! I am going to try this reg in  a Benjamin Discovery too, and I know that will definitely be a winning set-up.  And a Discovery with a Double tube ought to be ridiculous. 

cilami, I think the 1.03 fpe/cuin is ok but I have seen, and achieved, higher efficiencies, but mainly at pressures higher than 1700.  I kind of handicapped myself with this first tune by using a low pressure (1700 psi) with the short 12" barrel, while still trying to get reasonable velocity and power. And, like I said earlier, I need to check the actual pressure to see where the gun is operating.  I haven't done much work trying to tune a gun for a regulator, so it makes this quite interesting and fun.  It might be possible to get as many shots operating at 1900psi as you can get at 1700psi.    I don't know... yet.  That would make refilling easier, too.

[cilami]

Thanks Lloyd,

Please don't forget to included the 31 shots @18.8 fpe tune as part of your investigations . That is another interesting challenge, IMO.

[cilami]


I emailed Huub Andriessen, the person who originally achieved the 31 shots @ 18.8 fpe. He is a very nice guy and responded to my email in a matter of minutes. In case someone is interested, this is what he did to get the string:

"Hello miguel,

I have had a p-rod here to make and test the reg.
I only opened up the valve port and transferport.
Rest is nothing more or less as adjusting hammerspring and hammer stroke.
If i recall i did not do much with the stroke lenght.

Try not to much hammerspring tension, it will get huge air consumption.
Listen carefully to your pistol. More noise is more air use.

I thougt i had between 125-130 bar.
If the pelletspeed is ok and shotstring peaks at end then you have to much reg pressure and lower this and lower hammer spring.


My first shotstring was 15 shots. Second i readjusted the hammer and got 24 the last ones you have seen.

When you adjust the hammer you should see significant speed change with only bit adjustment.
If speed climbs very low the you have too much hammer spring and you have to get bit more reg pressure.

Trial and error
I think it is just "fingertip feeling"

Cheers huub"
Verstuurd vanaf mijn iPhone

He opened the ports to 3.5 mm, as indicated in the installation instructions of the regulator. For now, I'll keep using my current tune. I'll try this one after Christmas.

[lloyd-ss]

cilami, Thanks very much for making that inquiry.  What he says makes sense.  The stock barrel port in the P-Rod is .125, but the valve exhaust port is .110, and the stock T-port is about .079.  The valve throat is .201 with a .125 valve stem, so its effective dia is .157.
 
If you look at them as a percentage of the bore "area", the stock config is : .22 cal bore = 100%, barrel port = 32%, T-port = 13%, valve ex port = 25%, valve throat effective area= 51%,  so the areas are all over the place.

The Huma gentleman opened the valve exhaust port and T-port up to 3.5mm ( .138)  (39% of bore area) and used his tuning skills to tweak the velocity and shot count to what he wanted.  From his description of his method, I think his tuning skills with regulated guns are probably above average, LOL, so I am glad he shared his secrets.     I've got my P-Rod apart on the bench now, ha, ha.
Lloyd

[cilami]

Lloyd,

I hope your tuning skills are up to the task . Be gentle with the patient and good luck! 

[FuzzyGrub]

If either of you hit or come close to that mark, I'll be taking a much closer look in reg'ing my long tube prod. 

[cilami]

John,

If anyone can do that, Lloyd is one of them. I certainly can't, but thanks for your kindness .

[lloyd-ss]

The mods to the ports are done     and we are now into the tuning phase.  Gotta say, though, tuning with this Huma regulator is requiring a major paradigm shift in tuning techniques for me.      It responds differently than anything I have worked with before.  Maybe folks who use regs a lot could knock it right out, but it is a real learning experience right now.   
My first attempt before modding the ports was a super flat string of 24 shots averaging 15.5 fpe for a total of 373fpe. Decent for a 66 cc reservoir. Now I am at 32 shots averaging 16.4fpe for a total 524fpe (yikes !    ), but the string has a funny hump at the tail end that Mr. Andriessen mentioned.  I am working on getting rid of the hump now. This is a serious FUN challenge !!     I will post graphs after I get it figured out.
Lloyd

( For some reason, lots of smileys seemed appropriate this morning, LOL)

[cilami]

There you go!

[nervoustrigger]

Hi Lloyd, if it's rising as it comes off the reg, you either want to tune to a higher power level (e.g. more hammer spring preload and/or stroke) or reduce the reg set point to keep it at the same power level.

Basically the hump is an indication you are getting disproportionately more lift and dwell as the pressure falls.

[lloyd-ss]

Hi Lloyd, if it's rising as it comes off the reg, you either want to tune to a higher power level (e.g. more hammer spring preload and/or stroke) or reduce the reg set point to keep it at the same power level.

Basically the hump is an indication you are getting disproportionately more lift and dwell as the pressure falls.

Ahhhh, very good.  Thank you! I am working in the direction of reducing the set point with each round of testing and that seems to be working.  More iterations are need, though.  Creeping up on it.
Thanks,
Lloyd

[nervoustrigger]

No problem, always glad to help one of GTA's finest.

By the way, while I see you are targeting a specific fpe level, it may help others to know that if you are just trying to get a well-behaved regulated rifle, you can simply do the following.   Keep adding hammer spring preload until you find the peak velocity.  An RVA of some kind makes this super easy, otherwise add shims behind the spring until the velocity stops increasing.  If the hammer has an adjustable nosepiece, you can also (or instead) increase the stroke to achieve pretty much the same effect.  (Note: Balancing these two on an unregulated rifle is an often complicated trial and error affair critical to getting a good bell curve, but they are more forgiving in a regulated setup).

Once you know the max velocity, just back up to about 97 - 98% of that and you'll have a pretty efficient rifle that will have a gentle roll off as it drops below the regulator set point.  So for example, say you got max velocity of 900fps, something like 870 - 880fps would be a happy place to be.

If, on the other hand, you run out of adjustment before you reach max velocity, the easiest thing is to move to a heavier hammer spring.  There are many other approaches that can be taken, but the spring is typically the easiest.

Again, this is all about getting nearly the highest energy with good efficiency with minimal fuss.  No more porting or restrictors or grinding or drilling or adjusting regulators or all that jazz

[lloyd-ss]

Jason,
Thanks very much for the additional  info.  It is all starting to make more sense now.
Miguel also reminded me of this thread which will be helpful too.
   http://www.gatewaytoairguns.org/GTA/index.php?topic=74919.0 

Now, on to getting ready for the kids and grandkids this afternoon. 
Lloyd

[cilami]

I purchased a HUMA regulator for my Prod mini-bullpup a few weeks ago and I am happy with it. It is really easy to install and I am getting 16 shots @ 19.4 fpe (avg. 695 fps with JSB's 18.1). The ES is around 10-11 fps. My first attemps were directed at getting 16 shots @ 22 fpe, but some distinguished members of this, and other forum, educated and convinced me that my goal was simply not realistic. The situation is even worst since I have  Jim Gaska barrel, which is supposed to slow down the velocity due to the tightness of the bore.

Well, now I am after a really nice shot string posted on the HUMA website: http://huma-air.com/wp-content/uploads/2015/06/shotstring-Prod-124-bar.pdf
The second string shows 31 shots @ 18.8 fpe, for a total of 582 fpe, with an ES of 11 fps. My best attempt at duplicating that tune has produced 17 shots @ 18.8 fpe, with the same ES. Still 14 shots away. Nick, from ASP, has been very kind, but he is really busy working with some other regulators he sells. He recommended trying a lighter hammer and maybe some valve/tp modifications. 

Now, this is my question: I don't pretend that the experts here tell me exactly what to do or try. I will be happy if someone could just tell me if that 31@18.8 string is realistic or not. If not, well, I'll learn to be happy with my current tune.

Huma moved their website to another server. The new link for the Prod shotstrings is this:

http://www.huma-air.com/Files/6/87000/87843/Attachments/Product/6352i43Y989frn5b596p9E31N3I6H161.pdf