GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: uragan.25 on October 28, 2020, 07:26:20 PM
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Hi Bob & Lloyd
My rifle shoots consistently on my 3% tune of 793 fps max for 70 bar set point, then reduced HST to 770 fps as required. The tune works well and was achieved using a 180-200 bar HP. But,, when i fill the HP to the max fill of 300 bar my required 770 fps drops down to 730 fps . It then gradually rises to 750 fps as the HP lowers to 200 bar. I dont require any more power than this so i dont want to open up the reg any more and it would also foul my tune.
Could i reduce the plenum size and then possibly open up the reg to get the tune and power im at... or is there another reason for the power drop at higher HP.
Please help, what can i do.
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It sounds like poor input regulation. That is, high input pressure causes the output pressure to increase. That is producing a condition of partial valve lock when you go to the full input pressure. As others mentioned in the initial thread in the darkside gate, that may be the result of operating the regulator at a setpoint outside of its optimal adjustment range. The Bellevilles may be barely compressing and being influenced disproportionately by the input pressure.
To address it, you don’t need to reduce the plenum volume. Instead, restrict the transfer port (and increase the setpoint as you described), then readjust the hammer spring tension to the knee as before.
Huma makes regulators intended for 65-110 bar or 110-170 bar. Which one do you have?
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Not sure which reg i have and i dont recall an option so i may have the wrong reg i suppose, although i have had it in my Huma reg tester to set at 70 bar and would the stronger reg actually drop to 70 bar in the tester ?..
I believe AGT have pre fab restrictors for use on export sales so i will contact them.
Would you know what size port i would require... may be 6mm-6.5mm at a guess for a .25 cal = 33 fpe.... :P
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Sounds like a SIDE INTAKE Reg issue ? When you have the storage pressure bearing on the outer most end of the spool outside the seat, it feels the added pressure and reacts as if the bevel washer spring rate in greater having set point actually rise. As pressure in storage falls, so does the pressure on end of spool at seat and reg will once again drop the set point slightly.
Generally these type regulator designs only show this ugly trait when the tune has hammer spring energy / hammer weight balanced near the top of bell curve.
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Hi Scott,
Yes you mentioned this as a possibility before but im sure you said that Huma were a top center fill reg ?
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yes the Huma is top fill, center seat bleed hole. HP only contacts spool within the center of bleed hole.
Is the regulator correctly vented ? and is this a HuMa your having issue with ?
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Yes Scott, its a huma reg but as far as correctly vented then i wouldn,t have a clue about that. As a guess would that be the tiny screw inside the adjustment head that has to be 2 turns out from closed according to Huma instructions ?
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Venting comes from the hole in the side of regulator ALSO HAVING a hole is side of air tube where the regulator sits within the tube. The bevel washer space must be vented to atmosphere.
The little grub screw in adjustment end plug is just flow a controller that keep seat from hammering. Yes a few turns out from bottomed out is correct.
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Yes the Huma is vented and also the reg chamber on the rifle is vented BUT the original AGT reg and chamber vent holes are the same size and the Huma reg vent hole is tiny, about a 1/4 of the size. I can try to send you a pic if i knew the best way of doing so. I tried the photo bucket but having problems trying.
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I can try to send you a pic if i new the best way of doing so. I tried the photo bucket but having problems trying.
Grant,
You can attach images to this forum directly:
Below the window used for posting a new reply is "+ Attachments and other options". Click on that.
Scroll down and click on "choose file". Direct the file manager to the image file you want and hit "open".
If you want more images (up to 10 per reply), click on "more attachments"; then on "choose file" again; one at a time.
I randomly chose an image to attach in this manner - below
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I can try to send you a pic if i new the best way of doing so. I tried the photo bucket but having problems trying.
Grant,
You can attach images to this forum directly:
Below the window used for posting a new reply is "+ Attachments and other options". Click on that.
Scroll down and click on "choose file". Direct the file manager to the image file you want and hit "open".
If you want more images (up to 10 per reply), click on "more attachments"; then on "choose file" again; one at a time.
I randomly chose an image to attach in this manner - below
right, I've got the wife to try for me :).
i did as you said but no matter what picture i try to send i keep getting this message ..
Your attachment couldn't be saved. This might happen because it took too long to upload or the file is bigger than the server will allow.
Please consult your server administrator for more information.
tired cropping the photo as it reduces the KB size but again nothing works??
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Biro for comparison,
Bottom reg is the huma one.
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Vent hole size does not matter. So long as the vent in pressure tube falls between o-ring on REG the air will equalize fine.
OK ... NEXT, anyone else want to take a stab at what may be going on ?
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You have a regulator tester. How does the output pressure change as you increase the input pressure?
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I dont have a dive bottle to test but i use the buddy bottle from my R10 which i fill first, i open and close the bleed on the tester a couple of times to assert the press reading. Thats about the best i can do under the circumstances.
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An up date from Huma just in after suggesting bevel strength or configuration to them as they are as confused as ourselves with the issue,,
WE ARE DOING EXTENSIVE TESTS TO THE BEVELS RIGHT NOW I WILL BE IN TOUCH SOON AS.
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Jolly good.
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It sounds like poor input regulation. That is, high input pressure causes the output pressure to increase. That is producing a condition of partial valve lock when you go to the full input pressure. As others mentioned in the initial thread in the darkside gate, that may be the result of operating the regulator at a setpoint outside of its optimal adjustment range. The Bellevilles may be barely compressing and being influenced disproportionately by the input pressure.
To address it, you don’t need to reduce the plenum volume. Instead, restrict the transfer port (and increase the setpoint as you described), then readjust the hammer spring tension to the knee as before.
Huma makes regulators intended for 65-110 bar or 110-170 bar. Which one do you have?
Just had a look at the huma site to double check and it seems that the AGT Uragan reg is a one size fits all however they do offer a service for set point pressure of your choice. But this reg certainly aint doin what their desciption of capability is thats for sure..
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As a TUNER here in the USA ... honestly over the last 8 years have installed or serviced likely a 100 or more HUMA regulators.
There a solid product.
More times than not when an end user has had an issue with one is was one of two things generally ....
Adjustment screw had been screwed down CW bottomed out by the customer to see how far it was turned CCW from bottom. THIS RUINS THE SEAT DISK requiring it be flipped over. DON'T do it again !! Use a test pressure fixture !!!
Or ... Reg has been in use a few years and needed to be resealed ( new O-rings threw out X3 )
Scott S
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You have a regulator tester. How does the output pressure change as you increase the input pressure?
I have been racking my brain about this question and doing the rounds on the web. I came across a fella that recons he had to set his reg under full press for the rifle ( in my case 300bar) to get the reg to bed properly . I have been setting my reg using my R10 buddy bottle as i dont have any other source of pressure and its only about 210 bar. So i think the set point may be shifting due to this once i crank up the pressure after setting. I must admit that it sounds plausible.
So i think you may be onto it here Nervoustrigger.
Q is now, how to do it without a 300 bar input source ?
Maybe set to 60bar and fill up to 300bar so to push open the reg to 70 bar and then tune up.
Whats the thoughts guys ?
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I just done a test on the set point. I filled the tester with my buddy again and the gage went to 70 bar and then i tested with my compressor and took it to 300bar and the reg rose to 76 bar. So, ive now set the reg at 70 bar under 300 bar pressure and i will test the rifle shortly to see how the performance pans out..... Fingers crossed ::).
Just to put minds at ease my compressor is a Hills EC-3000 with digital output pressure settings and auto cut off at selected pressures with a max of 300 bar. Must admit i was a bit nervous about using this method, i even left the room and put my fingers in my ears ;D.
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Ok, Some more info to share here, basically the problem still exists so i tested the reg against various pressures to see what happens and as follows....
Set reg set point to 70 bar under 300 bar input press and let settle and it held at 70 bar. reduced input press down to 105 bar and the reg press dropped down to 60 bar...
Set reg press to 100 bar under 300 bar input press and left to settle and it held at 100 bar. Reduced input press down to 105 bar and the reg press dropped down to 90 bar.
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Share this with Huub at HuMa regulators
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Already done so Scott.
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Hi folks, after a very busy period i now have some time to pick up where i left off.
So i contacted Huma and arranged to return the reg for inspection on their request and Huma sent out a tested replacement at the same time as to save time on the whole turn around.
The new reg works fine and the rifle runs sweet.
Huma said that they would contact me with their findings, this they did and are returning the original reg to me ,rebuilt & tested... BUT... they forgot to examine the components before the rebuild and binned them, so i guess we'll never know for sure .
This is the first issue ive ever encountered with a Huma product and ive had lots of products from them! They have been extremely helpful with marvelous customer service and not one penny asked for!
So we have it concluded, and i have a new chrony with new light system, a spare regulator, and 20 empty tins of pellets "frustratingly fired" ;D
:D
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Excellent service!