A few notes on DIAN...
 
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A few notes on DIANA's HPM / High Performance MuzzleWeight  

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Hector J Medina G
(@hector-j-medina-g)
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Mark.in.AZ
(@mark-in-az)
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Posts: 125
April 28, 2020 19:45:34  

Well written and easily understood.  After the experiments that you and Steve did, it is not hard to see the benefit and subsequent tightening of groups.

Looking forward to adding one to the muzzle of my D54 (Miss Diana) along with the new piston.  Wondering now if the 22mm piston, working in concert with the HRM is more beneficial to the "standard" CCA piston.  I really like those one hole groups!

Stay safe, stay healthy.

Mark


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Hector J Medina G
(@hector-j-medina-g)
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May 1, 2020 09:25:19  

@mark-in-az 

 

I've been asked why I don't answer here this question, and I must apologize because I did answer it to Mark, in private, but since there seems to be some level of interest, I'll answer here again:

Sadly, you cannot use a short stroke with the 22 mm's piston. There is simply not enough volume to drive the 12 ft-lbs.

The 22 mm's piston, by definition, needs the full stroke, and that precludes the change of the fulcrum point in the lever that means that the cocking force (and therefore the "work" you perform to do the full cocking cycle) cannot be reduced to the levels that you can when using a short stroke concept.

As in all aspects, there is a tradeoff, and it's up to each shooter to decide what is important for HIM or HER.

It is, theoretically, possible to achieve a "happy medium" where everything would be in line: Bore, stroke, leverage, spring force, etc. but it would take quite some time to find it and then it would be a "single application" airgun, so, not feasible as a production item.

Hope this clarifies the issue, and thanks to all (2,731) readers!

 

 

 

 

HM


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RockDoc65
(@rockdoc65)
Joined: 2 years ago
Posts: 78
May 10, 2020 18:33:55  

Hector, I have to admit to being slightly fascinated by these types of devices. I'm a scientist, not an engineer but I'd like to think I can think a bit like an engineer if I try hard enough. I once referred to a (geotechnical) engineer as an "applied scientist." He got my meaning and took the compliment.

Correct me if I'm wrong but these work on the same principle as a pendulum. By changing the length of the string of a pendulum you change its period. By effective changing the length of the barrel (by moving a mass longitudinally) you change its frequency. Being a visual learner, I always imagined the end of the barrel tracing a sine wave on a spool of recording paper. The goal was to get the bullet to leave the muzzle at a peak or trough when the barrel was motionless for an instant as it changed direction.

Browning/Winchester marketed the B.O.S.S. in the 1990's that worked on the same principle. A weighted muzzle device attached via fine threads and a lock-nut, with a decimal scale engraved along the end of the barrel. There were two versions; ported and non-ported. The ported one reduced recoil noticeably but was LOUD and would blow all your stuff off the bench. I once owned a Winchester Model 70 Super Grade with the B.O.S.S. system on it and it worked as advertised which is to say very well. I think the only reason it didn't really catch on is that people didn't understand it or thought their accuracy was "good enough" and didn't want to fiddle with it.

I am assuming that the reason you use the washer system instead of threads is because it's was simpler and less expensive to manufacture on a prototype and just as effective, the engineering trifecta or holy grail.

As I was writing this post I had an idea for a threaded, weighted moderator for airguns that both quieted and accurized. Given the preponderance of threaded barrels these days I don't know why someone hasn't tried to market one yet.


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Mark.in.AZ
(@mark-in-az)
Joined: 2 years ago
Posts: 125
May 11, 2020 12:39:50  

@rockdoc65

I just got my tuner for my D54 along with the new piston.  I have to wait until I can get some range time to start working with it, but I also remember the BOSS system.  This is similar but simpler with the O-rings as spacers.  I plan on documenting the progress and posting my results on the forum.

Mark


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Hector J Medina G
(@hector-j-medina-g)
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May 13, 2020 08:55:41  

Thanks for your kind words.

RD.-you're close. Not a pendulum but a metronome.

Moving a mass changes the location of the CoG. And therefore, the oscillation parameters.

Our experiment showed that barrels vibrate in every possible sense, not just up and down.

And it's a very fast phenomenon.

Problem with threads in Springers is that the same vibration you are trying to change will also loosen up any adjustable device.

Using spacers makes it discreetly adjustable, but impossible for the device to go completely out of adjustment.

 I'm an engineer, but also hold post-grad degrees, one of them in applied physics.

Thanks for reading!

 

 

 

HM


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Hector J Medina G
(@hector-j-medina-g)
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May 13, 2020 13:37:28  

Mark;

I am sure the friends would like to see how you do it.

You only need between 15 and 20 yards to tune your HPM.

At 15 yards the differences are smaller, but beyond 20 other external factors start creeping in, from wind to hold consistency. If you know your "First Zero" use that distance.

It is also important that you shoot from the same position and with the same equipment/hold that you are going to use in competition. Tuning the HPM with a different support geometry is  a headache waiting to happen, LOL!

Keep well and shoot straight!

 

 

 

 

 

HM


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Mark.in.AZ
(@mark-in-az)
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Posts: 125
May 14, 2020 23:32:35  
Posted by: @hector-j-medina-g

Mark;

I am sure the friends would like to see how you do it.

You only need between 15 and 20 yards to tune your HPM.

At 15 yards the differences are smaller, but beyond 20 other external factors start creeping in, from wind to hold consistency. If you know your "First Zero" use that distance.

It is also important that you shoot from the same position and with the same equipment/hold that you are going to use in competition. Tuning the HPM with a different support geometry is  a headache waiting to happen, LOL!

Keep well and shoot straight!

 

 

 

 

 

HM

Working on it, Hector.

Shooting from 25 yards from a sitting FT position.  it may take a little time.

Mark

 


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Mark.in.AZ
(@mark-in-az)
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Posts: 125
May 30, 2020 20:44:14  

I finally got some range time to sit and work with this harmonic tuner.  The range is 25 yards and shot from a sitting, open piston, field target position.  The temperature here in Phoenix is rapidly approaching 100 degrees F today, but I am (so far) still sitting in the shade.

I started with the tuner attached to the muzzle with zero o-rings.  I shot on a sighter target to adjust the POI and was using the center dot as my hold point.

The tuner has set screws both fore and aft and positioned at 120 degrees around the circumference.  Mine is positioned with set screws along the centerline of the barrel underneath and splitting the set screws on top.  I took a piece of masking tape and using a sharpie, made a mark on the tape and a corresponding mark between the set screw locations on the tuner.  This way I could align the marks to keep the same orientation.  Just trying to eliminate variables.

My first target, marked “O” started out with my shot absolutely dead center.  I thought to myself, this isn’t going to take long.  Subsequent shots showed the group to be ¾” c/c.

Moved to target marked “1” and added one O-ring and shot 5 shots.  Group reduced to 5/8” and shifted down a bit.

Moved to target marked “2” and added a second O-ring and shot 5 shots.  Group moved further down and registered 9/16” c/c.

Added another O-ring for target marked “3” and noted a dramatic drop of POI, but group tightened to ½” c/c.

Shifted to next target marked “4” and with 4 O-rings and POI moved to the top of target, still using center dot as my point of aim.  Group size is still ½” c/c.

Next target marked “5” and using 5 O-rings is centered and just a shade over ¼” c/c.  Things are looking good!

I added one more O-ring for target marked “6” and noted a shift in POI with group size of ½” but below center of target.

My last target, marked “7” has 7 O-rings and has opened back up ¾” c/c and below point of aim.

At this point I stopped.  I was running out of shade and was already baking with the heat.

After each O-ring addition, I tightened the set screws the same amount and the same way; a little bit on one, move to the next, a little on that, and so on until they were all EVENLY tightened.  It is time consuming, but I was striving to get consistent results each time, again trying to minimize variables.

For my barrel and velocity, 5 O-rings seems to be ideal.  Again, I was shooting from a seated position, using a harness, and sitting on a bum bag, the same way I shoot in competition.  Granted, I was only shooting 5 shot groups, but this still took about 2 hours to get set up, settled in, and after shooting some sighter shots to settle the gun.

I am using QYS 8.48 grain pellets at average of 825 fps with the new piston.  At this velocity the pellet registers a SD of just under 8 fps and this pellet has a BC of .026!  So far things are looking good and I will continue to work with it.  I was amazed at how much the POI moved and how tight the group got.  I am confident that I can better that group and am anxious to see what it will do at 50 yards.  Range availability, my available time, weather, and wind will dictate when that will happen.

I will keep plugging away.  As far as I am concerned, this harmonic tuner works pretty good if you the time to work with it.

D54 tuner test (2)

Above is my target; 1" outer circle, 1/2" inner circle.  Below is a pic with the tuner alongside the barrel, then attached to the barrel, and finally, Miss Diana.

Tuner off
Tuner on
Miss Diana

 


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Hector J Medina G
(@hector-j-medina-g)
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May 31, 2020 09:28:56  

@mark-in-az

Very nice, Mark!

Thank you.

Just a few notes that may be useful in the future:

When adding or removing O'Rings, you need to shoot 2-3 shots into a "waste" bullseye to settle in the HPM.
The HPM is designed to settle INTO the shot cycle of the 54, the more you shoot it, the more it settles down. Contrary to other devices that depended on threads to adjust and got out of setting with the vibrations, the recoil and the surge, the HPM USES the motions to settle in firmer and firmer, it;'s also a reason why we use flat point/flat faced grub screws and not the "cup points" that are more traditional for grubs.

You should ALWAYS use one line of screws at the bottom. This is because of the slant that you show in your picture. At extreme settings (10-12 ORings), if you used a line of screws at the top, the topmost screw would land on the slant and the dimple created by the OEM grub screw (a cup point) CAN yield erratic results.

You should NOT rotate the HPM, just move it forwards and aft. If you rotate it, then you need to start again. To this date, no one has told me that rotation has an effect in the final setting, but it DOES have an impact on the POI (pun intended).

The POI's change location BECAUSE the barrel is vibrating differently for each location. THIS is precisely what confirmed to us that "barrel flip" was not only an up-down thing, but that the motions were all over the place, sort of like a butterfly's flight, just less random.

Now that you have found several "settings" that are useful, and since you were smart enough to document it, you can now choose the one or two settings that seem most promising and return to them, fire the 2-3 settling shots into a waste bullseye and shoot 10 shot groups at 25 yards. Shoot several, with rythm and calmly. Take your time.

Shooting 10 shot groups at 25 yards will give you a better picture of what each setting will do for your gun than 5 shot groups at 55 yards. There is a solid statistical methodology for that that we will discuss in an upcoming blog entry, but we have found that 10 shot groups give you a VERY good idea of what we will call the Point of Impact Envelope (POIE), which is the area where you can count 99.9% of ALL shots to fall. For FT shooters, this is an essential bit of knowledge.

Again, THANKS, great job!

 

 

 

 

 

HM


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Mark.in.AZ
(@mark-in-az)
Joined: 2 years ago
Posts: 125
May 31, 2020 13:25:06  

@hector-j-medina-g

Hey Hector,

One thing I failed to mention was that when adding an o-ring and reinserting the HPM, I would push lightly to the rear when tightening the set screws.  this was done in order to "seat" the O-ring.  This was not meant to compress them, just seat them without minute gaps.

Still a lot of work to do, but am aiming for those 1/2" 50 yard groups.  If this fat old guy can do it, anyone can do it.  Problem is that I like eating as much as I like shooting.  Last years' Cajun Spring Classic and subsequent exposure to Cajun BBQ shrimp have done me in.  I love that stuff and make my own.....frequently.


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Hector J Medina G
(@hector-j-medina-g)
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May 31, 2020 20:44:07  

@mark-in-az

 

Understood, Mark, but no amount of pushing will replace three shots. You may be saving a first or a second, but not the third, and if the first shot or two gave evidence of being "wide", then you have your answer.

 

Eating is not a problem. Just make sure you take 1,000 shots every day in the sun, and you'll see how you can eat all you want.  😉

 

Keep well and shoot straight!

 

 

 

 

HM


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