Regulator break in

[txrpls]

FYI: When testing the prototype Huma regulator, I submitted 60 shot strings in a spreadsheet provided by Huub. The first string submitted was the factory regulator which was used as a benchmark. I was using a Labradar as the crony and did not wait more than about two second or less between shots. Delays only happened when changing magazines. The wheel was set on max and I set everything as close to factory as I could get it set. 

 

[weatherby]

Chuck, 

If I understand your point, VSA essentially fine tunes how long the valve is open, and not necessarily a primary way to adjust fps.

If this is correct, the the VSA should be the last adjustment made, and only to the point when the fps drops a little, thus increasing efficiency, and perhaps helping with harmonics.

Is this correct in your opinion?

Not want to speak for my turn, but in a nutshell this is true.

The VSA is a adjustable rubber end stop which acts as a limiter for valve (over)travel.

It creates a defined stroke length for the main valve, which as a secondary result also affects the time how long the valve will be open. A defined stroke is always preferable to a undefined stroke, because it partially eliminates the factor how hard the hammer is hitting the valve every time.

Your way of tuning is also the same way like I do it, adjust to a certain speed, and turn in the VSA until the speed starts to decrease. That is the point where the valve starts to make contact with the VSA's rubber ball, and defining the valve travel.

 

[AnimalHitman]

Regulators don't "break-in;" they regulate to a set pressure per se within the parameters of their design. Hammer springs, however, will lose load over their service lives. One physical phenomenon with metals is that at stress below the yield strength of the material, a very slow plastic deformation takes place. In the spring branch, this is called creep. A hammer spring, which is a compression spring, will start to lose load immediately upon use, and continue to to do throughout its service life. This is generally not an issue as long as the operation is still within the parameters of the regulator. It is recommended to periodically chronograph rifles with mechanical actions to monitor the effects of this spring creep. It can change fps and thus affect POI.

 

[nervoustrig]

Very good, it looks like we all have a common understanding of the role the valve adjuster plays in the tuning process.

Indeed, I think the quote "how far the valve can actually be opened" suggests it somehow only manipulates lift but you guys are correct that it will also change the dwell (how long it's open). That's because when the hammer runs into the bump stop, its momentum is arrested...momentum being the property that influences dwell.

This feature has an interesting potential--and Chuck, this goes to your question about the difference between a "low pressure/high volume" and a "high pressure/low volume" system. What it does is it allows one to use a somewhat high regulator setpoint and adjust for a high pressure/low volume type of tune. This tuning approach is generally regarded as better for at least a few reasons:

1. A quick burst of very high pressure is more efficient. That is, a small volume of very high pressure air continues to expand and accelerates the pellet until it leaves the muzzle.

2. It produces a softer report...more like a quick pop than a long boom.

3. It accelerates the pellet more quickly which gives a quicker lock time.

Those familiar with the strategy of using a light hammer will recognize these two approaches as being similar. Examples would be removing material from a factory hammer or making a new hammer from a lightweight material like MDS nylon (molybdemum disulfide impregnated nylon).

Just bear in mind that like most things, too much of a good thing is not good. Get the lift and dwell down too much and you'll start seeing inconsistent velocity. But in moderation, it's a good tool to use.

 

[Chuck26287]

Chuck, 

If I understand your point, VSA essentially fine tunes how long the valve is open, and not necessarily a primary way to adjust fps.

If this is correct, the the VSA should be the last adjustment made, and only to the point when the fps drops a little, thus increasing efficiency, and perhaps helping with harmonics.

Is this correct in your opinion?

Yes, as I understand things at this point, I believe that is correct. However, I'm new to this arena, and taking a lot in. A lot of good info coming in on these things to learn from, and I could certainly be off in some of my understanding. That's why I'm throwing it out there for some good old fashion brain-picking discussion.

 

[Chuck26287]

Very good, it looks like we all have a common understanding of the role the valve adjuster plays in the tuning process.

Indeed, I think the quote "how far the valve can actually be opened" suggests it somehow only manipulates lift but you guys are correct that it will also change the dwell (how long it's open). That's because when the hammer runs into the bump stop, its momentum is arrested...momentum being the property that influences dwell.

This feature has an interesting potential--and Chuck, this goes to your question about the difference between a "low pressure/high volume" and a "high pressure/low volume" system. What it does is it allows one to use a somewhat high regulator setpoint and adjust for a high pressure/low volume type of tune. This tuning approach is generally regarded as better for at least a few reasons:

1. A quick burst of very high pressure is more efficient. That is, a small volume of very high pressure air continues to expand and accelerates the pellet until it leaves the muzzle.

2. It produces a softer report...more like a quick pop than a long boom.

3. It accelerates the pellet more quickly which gives a quicker lock time.

Those familiar with the strategy of using a light hammer will recognize these two approaches as being similar. Examples would be removing material from a factory hammer or making a new hammer from a lightweight material like MDS nylon (molybdemum disulfide impregnated nylon).

Just bear in mind that like most things, too much of a good thing is not good. Get the lift and dwell down too much and you'll start seeing inconsistent velocity. But in moderation, it's a good tool to use.

Excellent response, and very educational as to the topic of HPLV vs LPHV tuning. It explains why it appears a general ballpark regulator pressure was set and the FPS adjusted from there, even using the VSA to achieve the goal FPS.

I think I want to start a new thread on the accuracy tuning process, picking up with these discussion points so as not to hijack this thread topic any further. Will probably title it something like "Gun specific accuracy-tuning process". Thanks for the replies, and sorry for taking this thread a little off-topic.

 

[Drumsnguns]

A very insightful discussion here and I've learned something.

I do have a question that has not really been touched upon concerning he tuning process and that's, where is the HS during the reg pressure determination?

Basically what I do for my .25 cal 600 mm X barrel is:

Set VSA all the way out past IV lines so it's out of play.

Then I have my HS somewhere close to spec which would be 18.00 mm

Then I start at 110 Bar on the reg and shot groups at around 75 yd.

After finding my tightest group to reg ratio I then adjust the HS to achieve max fps at that reg setting

Finally I adjust VSA in to the point of fps drop.

So my question is, where should the HS be when I start testing? At 110 Bar, 18.00 mm might be too high and might affect the groups?? and, at say 145 Bar, 18.00 mm might not be enough.

Or does it matter when determining harmony?........I just don't know

Right now I'm at 145 bar shooting 34 gn JSB Heavies for 1-1.2" groups at 100 yd. Seems pretty good to me but hey if I can get under an inch by re-tuning properly then I'm game.

KP

 

[Chuck26287]

A very insightful discussion here and I've learned something.

I do have a question that has not really been touched upon concerning he tuning process and that's, where is the HS during the reg pressure determination?

Basically what I do for my .25 cal 600 mm X barrel is:

Set VSA all the way out past IV lines so it's out of play.

Then I have my HS somewhere close to spec which would be 18.00 mm

Then I start at 110 Bar on the reg and shot groups at around 75 yd.

After finding my tightest group to reg ratio I then adjust the HS to achieve max fps at that reg setting

Finally I adjust VSA in to the point of fps drop.

So my question is, where should the HS be when I start testing? At 110 Bar, 18.00 mm might be too high and might affect the groups?? and, at say 145 Bar, 18.00 mm might not be enough.

Or does it matter when determining harmony?........I just don't know

Right now I'm at 145 bar shooting 34 gn JSB Heavies for 1-1.2" groups at 100 yd. Seems pretty good to me but hey if I can get under an inch by re-tuning properly then I'm game.

KP

It's my understanding the HST should be at MAX, and adjusted so the slider has no play or movement in it, to start the regulator pressure series testing.

I don't understand this step in your process: After finding my tightest group to reg ratio I then adjust the HS to achieve max fps at that reg setting. 

The purpose of shooting a series of groups at different reg pressures is to determine the velocity that yields the tightest groups via the harmonics of your particular gun. If you find that velocity, then use the HST to crank the velocity up as much as you can, you have just left your best accuracy/harmonics velocity for a lower accuracy velocity. Why are you striving to max the velocity once you find the optimum velocity? Incidentally, if you start with the HST at MAX, you CAN"T do this, as you can only DECREASE the velocity by turning the HST dial to a lower tension setting.

Take a look at the procedure I listed at https://www.airgunnation.com/topic/gun-specific-accuracy-tuning-process-fx-impact-or-impact-x/ and let me know if it makes sense to you. You are the second person who has indicated following a similar procedure, but not starting with the HST at MAX, so maybe I'm wrong about that being the starting point for regulator series testing.

While this is very generalized, my key take-away from this is the different factors which will cause a given velocity will produce a given harmonic vibration in the gun. So, by identifying the accuracy at various velocities, you can identify the favorable harmonic vibrations of your particular gun. Velocity is then an indicator for your harmonics, and can be used as an AIM velocity to achieve your best accuracy. (This is why I wasn't sure why you were changing your velocity with the HST after identifying the best accuracy velocity.)

 

[Drumsnguns]

Chuck,

First off thank you for answering my question. Now to your question. When I first start going up on the reg I'm only concerned with finding the best groups from achieving the best Harmony. At that point I'm not even checking the velocity. It's all about settling the gun down via the reg. 

When you get the best group you then need to sync your HST to the reg pressure you settled on and then out comes the chrony. The odds of it being perfectly matched to the regulator at that point are pretty slim. You're always going to have to tune the HST to the reg whenever you change the reg setting.

So what is said on the article you linked yes that makes sense. I'll try to explain my understanding of it all....

If you start with a HST too low for a certain reg setting and start to increase tension, you will see the velocity climb as you tighten. At a certain point, (for that reg setting), increasing the HST will do nothing to increase velocity, (in fact it might decrease a bit). Now if you start out with a maxed out the spring tension, (unless your reg is past 150 bar), its going to be too tight and will just waste air. Your max velocity point is somewhere below max. In that case you will want to drop the tension down until the speed just starts to drop and that's your sync point with the reg.

NOTE: We aren't talking about velocities going up 40 fps with the HST screw but more like 10, if that. It ain't much.

If someone like me who sets it to 18.00 mm, ( below Max), to start and I find that my gun shoots best at 145 bar, (where I currently have it), then I will have to tighten the HST in order to sync with the higher reg pressure and I will see my velocity climb then stop as I continue to tighten. I think it's now at 15.72 mm.

If, say, it shoots best at 120 bar then I might have to lower it because it's hitting too hard for the lower reg pressure and wasting air with no increase in speed. So again by starting with the HST maxed out like in the article, you will always have to lower the HST to get to the sync point with the reg unless you are going beyond 150 bar.

Too much HS tension and you waste air by keeping the valve open for too long; too little won't open the valve enough. 

Now about velocity....if the gun shoots best groups at a certain reg. pressure then I'd say as long as your within the speed range the pellet likes then you're good. Most of us .25 guys are shooting JSB MKII they like it around 860-910 fps. And even at 830. Yes some guys here have said that they get great results in the low 900's and I'm there and yesterday shot my best 8-shot group at 100 yd measuring 1.003."

But here's my question: I was wondering say if HST was maxed out and you start at low reg pressure, (110 bar), then as the pellet leaves the barrel the valve stays open and this continuous blast of air behind the pellet might cause a turbulence that might destabilize the pellet and give erroneous groups. Does that make sense?

Anyway, I found two reg pressures that have the tightest groups for my Impact:

One is at 120 bar where I get around 830 fps

The other is 145 bar where I'm getting around 900-905 fps. 

145 just squeaks by 120. I might drop it back down to 120 bar just to save air for punching paper.

Hope some of this makes sense...

KP

 

[Chuck26287]

Thanks, KP. It does make sense as I read over it a couple times. Very good info and I've learned from it. I guess my biggest question for you would now be when you have your regulator set to the pressure that gave you your best group, then you adjust the HST to match it to that regulator pressure, what happens to your group size? Does finding that spot where the velocity stops increasing with HST tighten or open your group? Or, does it merely improve air efficiency?

The process I've outlined really counts on the relationship of a given accuracy having a given velocity that it correlates to. It's very helpful in my keeping the theory straight and understandable, but in all honesty, I'm sure it not that cut and dried. There are so many variables that cause the harmonic response from the gun/barrel, I'm sure different sets of variables could yield the same velocity, but completely different harmonics. I guess this is why we all have to do this for our individual guns, and no two guns respond exactly the same.

With any luck, I'll have put a little of this info into practice by the end of the weekend.

Thanks again!

Chuck

 

[Drumsnguns]

Chuck26287, 

Hmmm, hard to answer your questions because groups sizes change from session to session even if you do nothing . But I'd say overall the groups didn't change with HST tune.

I think the thing here is to try it yourself and see if groups change once its all tuned. Like I said before, matching the HST to the reg wont result in a huge velocity change. Maybe 10 fps ...kinda depends where that spring lies in relation to where the reg. lies, you know?

It's mainly for efficiency between the spring and the reg. You don't want the spring too strong or too weak. 

Where the reg is set makes the biggest difference in group size, IMO. After that it's a matter of setting the hammer and perhaps fiddling with the valve knob in order to tighten up ES.

Give it a try and please let us know if it helps....also keep your eye out for two harmonic points. If you're a paper puncher I'd go with the best group, hoping it would be the lower reg pressure.

Cheers,

KP