GTA
Airguns by Make and Model => Diana Airguns => Topic started by: dtdtdtdt on September 30, 2020, 01:30:21 PM
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My 20 caliber D54 built by Hector-Medina was provided with his harmonic tuner(HT). I've used the 20 caliber successfully for over two years without monkeying with the tuner. A few months ago Nitrocrushr posted his results with his D56TH that were spectacular. That led me back to the posts that Hector-Medina made during his development of the Harmonic Tuner.
Since I can't ever leave well enough alone, I just have to tinker with the HT on my 20 caliber and will follow up with tinkering on my .177 D54 that I purchased the Diana HPM (high performance muzzle weight ) for. So here we go!!!
Since my outdoor range is a minimum 50yarder and my vision makes shooting in the sunshine problematic, I am starting at the 50' 17yd indoor range that is readily available. I can shoot from inside my kitchen to about 30yds and will do that soon.
First experiment - establish a base line for the current set-up.
I shot 5 consecutive 10 shot groups under the same conditions before making ANY modifications to the setup. They are first target shown below. Since the rifle was zeroed for 50yds from my last outdoor foray the groups center about 0.4" high at 12 o'clock from the POA. This is nice as I didn't shoot my POA out. Average group size measured as a rectangle: 0.452" High x 0.570" wide. The width is probably a bit wider than it should be. The range has substantial ventilation for gun smoke and the targets are hanging from a carrier that flexes. I try to wait until the target quits swaying but the difference is pretty small.
Second experiment: Change the number of O-rings to see what impact they ave on accuracy.
I started with 9, then 7, then 5, then 3 and finally 1 again. All 10 shot groups.
I shot 3 groups with 1 o-ring to compare to the baseline. Average was 0.44" High x 0.57"wide. Statistically identical to the baseline. HOWEVER: the point of impact moved sustantially to about 1" at 10:30 o'clock.
9 o-rings group 0.45"H x 0.77"W (note the table on the target is backwards - dyslexia??) POI 0.55"at 10:30o'clock.
7 o-rings group 0.45H x .42"W POI 0.42" at 10:30o'clock.
5 o-rings group 0.42"H x 0.52"W. POI 0.25" at 12 0'clock.
3 o-rings group 0.50"H x 52"W. POI 0.40" at 10:30 o'clock.
I suspect the change in POI from the 12 O'clock position was my not paying attention to whether I put the stabilizer in exactly the same alignment on the barrel. Next series I will take that into account.
Preliminary results:
At this short range the accuracy was little different except in the 9 o-ring group that may be statistically different.
Positioning of the stabilizer on the barrel and may have some impact on POI that would be eliminated in the zeroing process.
SORRY THAT PICTURES ARE UPSIDE-DOWN. I WISH I COULD FIGURE OUT WHY MOST OF MINE END UP THAT WAY WHEN POSTEDD!!!
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Dave,
Could you please post a picture of the contraption that you are talking about?
Upside down is fine... ;D
-Y
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Yogi:
Here are the pictures. For whatever reason my computer is being truculent and didn't want me to make them small enough to post. I finally beat it into submission!!!
The blued steel muzzle weight is Hector's harmonic tuner. It is bored out so that 0-rings can be put on the barrel so that the device can be adjusted forward and back to the chosen spot. He put it on my 20 caliber D54 among others I guess. It's purpose it to manage the barrel vibrations to help with accuracy. Nitrocrushr has the D56 version of the same thing and posted a discussion of his results with it back in March. That post also has a link to Hector's site where you can see much more detail.
The shiny aluminum version is Diana's commercialization of Hector's design. Same concept and same method except a bigger aluminum piece that has the same weight.
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Thanks Dave,
Are all the o-rings the same size? I figure if you change their location on the barrel, maybe having a thicker or thinner o-ring, maybe even ones that have a slightly different ID, or even different shore numbers would also be varables that would increase/decrease effectiveness?
Sorry to be long winded... ::) ::)
-Y
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They are all the same size and apparent diameter. I don’t think a few thousandths difference is significant. Look to be about 1/16th” in diameter. I’ll measure when I get home
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The O-Rings are all the same size. More O-Rings extend weight further out on barrel.
Hector sent me one to test on my Model 48 and I returned it to him.
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The O-Rings are all the same size. More O-Rings extend weight further out on barrel.
Hector sent me one to test on my Model 48 and I returned it to him.
Hey Robert,
If you tested Hector's Harmonic Tuner on your Model 48, what were your conclusions as to it's effectiveness?
Inquiring minds would like some feedback ;)
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Only shooting off hand - I was not able to shoot accurately enough to be able to test it.
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Only shooting off hand - I was not able to shoot accurately enough to be able to test it.
What a JIP .......... ::)
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What a JIP .......... ::)
Sorry, Non-native English speaker here, exactly what is JIP?
Apologies, but searches in Google lead to various possibilities.
TIA and TLA's rule!
;-)
HM
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My 20 caliber D54 built by Hector-Medina was provided with his harmonic tuner(HT). I've used the 20 caliber successfully for over two years without monkeying with the tuner. A few months ago Nitrocrushr posted his results with his D56TH that were spectacular. That led me back to the posts that Hector-Medina made during his development of the Harmonic Tuner.
Since I can't ever leave well enough alone, I just have to tinker with the HT on my 20 caliber and will follow up with tinkering on my .177 D54 that I purchased the Diana HPM (high performance muzzle weight ) for. So here we go!!!
Since my outdoor range is a minimum 50yarder and my vision makes shooting in the sunshine problematic, I am starting at the 50' 17yd indoor range that is readily available. I can shoot from inside my kitchen to about 30yds and will do that soon.
First experiment - establish a base line for the current set-up.
I shot 5 consecutive 10 shot groups under the same conditions before making ANY modifications to the setup. They are first target shown below. Since the rifle was zeroed for 50yds from my last outdoor foray the groups center about 0.4" high at 12 o'clock from the POA. This is nice as I didn't shoot my POA out. Average group size measured as a rectangle: 0.452" High x 0.570" wide. The width is probably a bit wider than it should be. The range has substantial ventilation for gun smoke and the targets are hanging from a carrier that flexes. I try to wait until the target quits swaying but the difference is pretty small.
Second experiment: Change the number of O-rings to see what impact they ave on accuracy.
I started with 9, then 7, then 5, then 3 and finally 1 again. All 10 shot groups.
I shot 3 groups with 1 o-ring to compare to the baseline. Average was 0.44" High x 0.57"wide. Statistically identical to the baseline. HOWEVER: the point of impact moved sustantially to about 1" at 10:30 o'clock.
9 o-rings group 0.45"H x 0.77"W (note the table on the target is backwards - dyslexia??) POI 0.55"at 10:30o'clock.
7 o-rings group 0.45H x .42"W POI 0.42" at 10:30o'clock.
5 o-rings group 0.42"H x 0.52"W. POI 0.25" at 12 0'clock.
3 o-rings group 0.50"H x 52"W. POI 0.40" at 10:30 o'clock.
I suspect the change in POI from the 12 O'clock position was my not paying attention to whether I put the stabilizer in exactly the same alignment on the barrel. Next series I will take that into account.
Preliminary results:
At this short range the accuracy was little different except in the 9 o-ring group that may be statistically different.
Positioning of the stabilizer on the barrel and may have some impact on POI that would be eliminated in the zeroing process.
SORRY THAT PICTURES ARE UPSIDE-DOWN. I WISH I COULD FIGURE OUT WHY MOST OF MINE END UP THAT WAY WHEN POSTEDD!!!
Dave, thanks for the effort!
POI moves because the barrel moves. EVEN if you make it a point to insert eh HPM EXACTLY in the same position every test, POI WILL move.
And this tells you how much our barrels vibrate when we shoot. And also why these little gizmos work.
Now, I have found a periodicity of about 5 ORings. Meaning that if a barrel shoots well with 1 ORings, it will shoot more or less as well with 6. And so on and so forth.
Each ORing is nominally 1.5 mm's, and there is no way to make them finer because they also need to fit between the space of barrel and HPM. The HPM I am building for the 430L uses 1 mm's ORings, but that is what is allowed intrinsically by the rifle to HPM difference. They do pose other problems, LOL!
As it is, the 1.5 mm's is a bit COARSE of an adjustment, but it is what is possible. So, doing two at a time, MAY create too expanded a view of the situation where you cannot see the trees for the forest.
Go 1 by 1.
Lastly, you are missing one step in your tests, and that is to shoot THREE pellets into a "waste bullseye" to SETTLE the HPM in place through the gun's recoil.
Once you shoot three somewhere you do not mind, then shoot a 5 shot group, or even better a 10 shot group. The fact that ALL your groups are more or less the same height tells you that you are missing something in the procedure.
Again, thanks, keep well and keep us posted!
HM
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Thanks for the suggestions Hector.
I do shoot a few pellets into the backstop before starting. I just didn't say it in the notes.
Regarding the step size of 2 rings per group: My intent was to do a scoping experiment first covering the range of 0 - 9 O-rings. (That's how many that there the baggie you sent! I may have some more but didn't see it as critical to go further at this time. I didn't do zero as the range was closing and I had to stop. The 5 group baseline was as I found the rifle when returned from your last work on it. It is the way it has been from the beginning as far as I know. However, The symmetry of 1,3,5,7,9 seemed to work for me on that day. I will do the zero base when I shoot next.
If I found a marked difference between the steps. I would have bracketed the interesting result one at a time for at least three. That is: if 5 had a marked change from the others I would do 3,4,5,6,7 to see if there was anything going on.
The group sizes were effectively the same for each 10 shot group. Number 9 being wider was because I pulled one shot left. Note it is the only one not in the main group. I knew I had pulled it when I shot it. Also in one of the three followup groups with 1 ring was to verify that it returned to the original baseline. By the way they look a little weird on the target as I didn't wanted to keep the data on the same target so I turned to target over and used the numbers as aiming points again. As you mentioned the positioning of the group is not really relevant as taking it apart, changing rings and re-setting the tuner certainly would have impact on the POI. I was not concerned about that just noting that it happened. Returning the tuner to the same arrangement in future groups as I plan to do is just minimizing another variable.
As for shooting 5 or 10 shot groups, 5 may be more indicative of performance while 10 is more indicative of pellet variability and my ability to remain focused. I also mentioned that the target may be swaying a bit from left to right and increasing the width of the groups relative to their height. Air flow in the range is designed for powder arms, not air guns. I try to get there when no one else is on the range but can't that at all times. I saw several groups as they developed that were quite small with 3-5 pellets that opened up a bit when 10 were shot.
My interpretation of group size was that my range is too short to effectively demonstrate the harmonic tuner's effects. That's why I am going to redo the experiment at 30yds and continue from there. I am, in oil-field terms, WOW (waiting on weather) to improve so I can shoot out the kitchen window without raindrops....
I didn't see the JIP designation anywhere in my notes or in the string??? Am I going more blind?? If it is mine, it could be a typo or the spellchecker effects? I did see elsewhere that some people refer the tuner JOHN IN PA as JIPA but that doesn't seem relevant????
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What a JIP .......... ::)
Sorry, Non-native English speaker here, exactly what is JIP?
Apologies, but searches in Google lead to various possibilities.
TIA and TLA's rule!
;-)
HM
Sorry Hector,
My bad English :P.
Even though the past tense is spelled Jipped, the present tense is spelled gyp?
Go figure, but I guess I should have looked it up first before using :(.
Anyway, I was suggesting, having something tested using a process that results in nothing conclusive.
- Like testing water volume using a sieve; one can conclude nothing from the results.
aka - A pointless endeavor.
However, I would love to understand more about their effectiveness; also where such a device can be purchased ;).
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I should have said - I did not test it because my results would have been inconclusive since I could not shoot accurately enough to provide any useful data.
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I should have said - I did not test it because my results would have been inconclusive since I could not shoot accurately enough to provide any useful data.
Sorry Robert,
Didn't mean to hammer you :(.
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What a JIP .......... ::)
Sorry, Non-native English speaker here, exactly what is JIP?
Apologies, but searches in Google lead to various possibilities.
TIA and TLA's rule!
;-)
HM
You of all people use more acronyms and abbreviations that anybody I know, except my alma matter... ;)
-Y
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Interesting Topic. I have played with muzzle weights and Brakes for a while.
I have one rifle, a Webley and Scott with a long and probably flexible barrel. Without anything on the end it shoots very very poorly. With 150 grams of steel brake screwed on it shoots very well.
I also have a Diana 34 short barrel that came with a very heavy steel brake held by grub screws. What a disaster. The first and considerable improvement was to get rid of the brake. The brake and the grub screw attachment were unsatisfactory.
Other rifles I have I experimented with brakes. Trying different sizes and weights Sometimes I think they are beneficial and sometimes I think they are not. I think the skill of the shooter, modest in my case, has a bigger influence on accuracy.
I await developments in this thread to add something more than amateur trial and error to my efforts.
PS. I recall that at one of the recent Field Target championships in Germany I think. Hector will know about it. Anyway the springer title was won by a chap shooting a Prosport. He had adjustable weights along the length of the barrel. I can't recall if he had anything on the muzzle. Hector may be able to comment on that.
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@ Dave. -
One of the things I forgot to mention is that HPM's work best when the gun is rested at the far end of the forend (from the shooter's perspective). If you are not resting it at the far end, but somewhere more closer to the middle, results are not as they should be.
@ Hugh.- You are right, Linas Burvis (Lithuania) is one of the great shooters of modern times. He did use a Pro-Sport in Germany (2013), but the more important part is that he removed completely the short barrel/shroud arrangement and replaced it with a solid, and rather long, barrel. So the weights were actually mounted ON the barrel, not on a shroud. Contrary to predictions, his solution worked VERY WELL. He got more than 10 points on the 3rd place. Brian Samson was real close to Linas on that occasion.
BTW, he has a really gruff "façade", but he is a really nice guy. His wife, Regina Burviene is also a champion shooter, usually placing top 3 in the Women's and often Top 10 in the general springers.
Thanks for bringing back the memories: https://www.ctcustomairguns.com/hectors-airgun-blog/the-worlds-2013-a-beautiful-experience (https://www.ctcustomairguns.com/hectors-airgun-blog/the-worlds-2013-a-beautiful-experience)
Keep well and shoot straight!
HM
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Hector,
Would just plain o-rings be of any help in reducing "harmonic distortion"-maybe not the right term, but I like the sound of it. ;D
Or do the o-rings need to to be in contact with something to reduce vibration?
-Y
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Hector,
Would just plain o-rings be of any help in reducing "harmonic distortion"-maybe not the right term, but I like the sound of it. ;D
Or do the o-rings need to to be in contact with something to reduce vibration?
-Y
ANY mass will alter the vibration patterns of a barrel. Even the weight of an ORing. You CAN get rather thick ORings, and so, it is possible to tune a barrel like this.
Now, the REAL question is "How long will those ORings stay in their place?" simply putting the gun away may move them, and then you are back to square 1.
HTH
HM
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It springs to mind that if you use something flexible as a muzzle weight such as an o ring or a group of them or stuff like heat shrink plastic tube then you introduce another barrel deflection by way of the weight moving as the barrel flicks about.
That is one of the problems I encountered with my experiments using weights held on the barrel of a Hatsan 99. The grub screws bit into the relatively soft steel of the barrel and loosened the grip. The same with my Diana barrel. No such problem with a threaded muzzle.
I notice that Hectors muzzle brakes are secured with grub screws and I assume that the o rings are really a packer to move the weight away from the muzzle in a controlled manner.
I look forward to further reports of how that works out. The other factor is that Hector and Diana know what they are doing.
I have had some success making muzzle brakes out of Delrin plastic and securing them with a hammer fit. If nothing else the plastic brake makes a good rust proof handle.
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Next verse.
I have been playing with different muzzle brakes on my CO2 CR600 rifle. There is no appreciable recoil but it is there. Different muzzle brakes of different materials and weights alter the point of impact substantially. It is complicated a bit by temperature and gas level at the end of the cartridge charge.
It entered my dim wit that I could fashion a muzzle weight that screws on and has a threaded interior with a weight that screws in and out to vary the centre of gravity of the brake. The moveable weight to be secured by a grub screw. Off to the workshop to find something to try it out.
Well as soon as the grand children go home.
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Hector:
I generally use a Caldwell Tackdriver bag when shooting indoors. It is about 12" long and supports the stock from about 2-3" front the trigger guard to about the front screw hole. I have another rest that are less convenient to take to the indoor range. It is a Caldwell bench-rest with a separate bag holding the butt stock. It works well outdoors. I will fiddle with the rests to see what impact they have as I go along.
Your comment does raise the question of whether the harmonics of a break-barrel or straight-barrel without the recoil sledge mechanism is different and more pronounced that with the 54 style rifle??
You mentioned the European shooter taking the barrel shrouds off and putting his weights directly on the "real" barrel. The HT and HPM attach directly to the "real" barrel and only touch the shroud fairly lightly. Is it likely that that contact would impact the harmonics significantly. As we discussed above, it seems like a likely cause of the change in POI I saw. Obviously the POI change was caused by taking the HT off and then reassembling it but suggests that any stablizer should be directly attached to the "real" barrel as you have done?
I hope to do Round 2 with the 20 caliber today. Weather is good and wind is calm. I open the kitchen window and shoot across the backyard about 30yds. I will follow your suggestion to rest the front further out for a couple test groups before starting. Round 2 will be just as Round 1. 5 groups, 10 shots each with 1 0-ring followed by 9, 7, 5, 3 , and finally 1 again with 3groups of 10 shots. As I mentioned earlier, if I see something interesting I will go back and fill in the groups around the "interesting" bit.
One change that will probably have no impact is that I will mark the barrel and the stabilizer (bit of masking tape with a line on it so the stabllizer is uniformly positioned. Just being anal, I will torque the screws to a very low level for consistency (will report what I do after I figure it out.)
A question, you said that you "settle" the o-rings with three shots into the back-stop. Do you do that before tightening the screws? Is seems like the way to do it to me? "Settling" with tightened screws may be damaged or unproductive.
Nova Gun:
I am shooting a Hector Diana 54 that is a side-cock and the barrel isn't handled at all during the shooting process so the grub screws aren't a problem. Installation of the HT and HPM is simple. Remove the front sight base, Slip on the small o-rings as spacers to position the metal weight where desired, press in, and lightly tighten the grub screws. The only "damage" to the barrels might be a mark on the actual barrel that is invisible to all but those who take it apart. Actually, I haven't looked to see if there are any marks. I will today.
A suggestion for experimental weights that are cheap and easy to do before you get fancy! Wrap a known weight length of solder wire around the barrel where you want the weight and secure with masking tape to keep it in place. The idea comes from an very old picture in my gun club of a 1930's member who won the national championships in small-bore position with a light-barreled Remingtion that he wrapped solder around the whole barrel to add weight.
By the way, take a look at Hector's blog on harmonics for a lot of good information.
https://www.ctcustomairguns.com/apps/search?q=harmonic (https://www.ctcustomairguns.com/apps/search?q=harmonic)
Good luck.
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Dave;
Hope this answer reaches you in time.
The grub screws I include in the HPM are flat faced, so there is no chance of marring the barrel.
They are flat faced because the idea is that they are torqued down to about 12 in-lbs, and THEN you "settle" the HPM with three shots.
Because the ORings are ShA75, they DO have SOME elasticity, so setling the HPM without the final torque will allow the HPM to return to an "unsettled" state before you torque the screws.
If we accept reality, NOTHING in that size range can actually "AFFIX" the HPM to the barrel upon recoil. Forces are simply too big for any decent sized screw. And putting humongous screws would only add more variable masses all around.
So:
Add or remove ORings
Press the HPM into the barrel
Torque the screws
Fire three shots
Run test group
Repeat.
One more thing: As it was explained to me, Linas CHANGED the barrel of his ProSport to a L-W of conventional length. He did not only remove the shroud, he CHANGED the whole thing and threw away the AA parts.
Hugh.-
the problem with things that are elastic (ORings with ShA hardnesses larger than 30), is that they let the device act as a "loose weight", and that can AMPLIFY the vibrations.
Kirk.-
I am working on a design for smooth sided barrels, if you want one, let me know in a PM.
Keep well and shoot straight!
HM
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HECTOR:
Thanks for the input. Yes, it is in time. I spent the interim re-reading your series on harmonics and see better what you were doing.
That means that Round 2 will be done tomorrow rather than today at the indoor range. I will also use a better target style similar to the one you used. I will do the statistical groups that I mentioned but may reduce to 5 shots as the 10 shot group sizes may be impacted by eye fatigue and air flow more. I noted in several of the groups shot the other day that the first 4-5 were quite tight and the groups deteriorated as I went on.
I am grateful that you feel 19yds is good enough!!! I noted in my use of the Chair-Gun that the near zero was alway around 17-20yds and certainly makes good sense. My indoor range, a 50' (16/2/3yds) is MUCH more convenient than any of the other options for me. I can shoot in my backyard as I mention BUT I do have neighbors who aren't too thrilled with me doing any kind of shooting there and the bright sunshine really messes with my vision. Visualize looking through a smudge on dirty glasses and you have my normal vision. Light scattering adds to the problem with "fog over my whole visual axis when outdoors. So I will modify my plans to match the conditions you used as best possible. That is: 50' or 17yds. and I will do the steps one o-ring at a time as you describe. I will follow your regime on torquing the screws to 12in/lb. I had thought to go lighter!!
I haven't taken the screws all the way out for fear of losing them so didn't realize they were flat-ended.
I will report results tomorrow evening!!!
Dave
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Dave;
Hope this answer reaches you in time.
The grub screws I include in the HPM are flat faced, so there is no chance of marring the barrel.
They are flat faced because the idea is that they are torqued down to about 12 in-lbs, and THEN you "settle" the HPM with three shots.
Because the ORings are ShA75, they DO have SOME elasticity, so setling the HPM without the final torque will allow the HPM to return to an "unsettled" state before you torque the screws.
If we accept reality, NOTHING in that size range can actually "AFFIX" the HPM to the barrel upon recoil. Forces are simply too big for any decent sized screw. And putting humongous screws would only add more variable masses all around.
So:
Add or remove ORings
Press the HPM into the barrel
Torque the screws
Fire three shots
Run test group
Repeat.
One more thing: As it was explained to me, Linas CHANGED the barrel of his ProSport to a L-W of conventional length. He did not only remove the shroud, he CHANGED the whole thing and threw away the AA parts.
Hugh.-
the problem with things that are elastic (ORings with ShA hardnesses larger than 30), is that they let the device act as a "loose weight", and that can AMPLIFY the vibrations.
Kirk.-
I am working on a design for smooth sided barrels, if you want one, let me know in a PM.
Keep well and shoot straight!
HM
Hector,
Have you ever used either silver tipped or bronze tipped grub screws? Nylon tipped ones?
Just wondering, would be even more non-marking... ???
-Y
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@ Yogi.- Nylon is slippery by nature, so there is no guarantee that the HPM will not move under recoil. Steel is, up to a point, elestic. So as long as you keep to a reasonable torque, things should settle and then stay put. The principle by which ORings work is how and why the HPM works:
HPM moves a little when the settling in shots are fired
ORings compress and expand sideways
This blocks further movement and compression
HPM cannot move BECAUSE
Screws CAN keep the HPM from "Re-bounding" at low axial forces
ORings won't get "out of adjustment"
Everything is stable.
As is usual, the best ideas are the simple ones.
;-)
Keep well and shoot straight!
HM
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"Speaking from ignorance with authority!" - one of the two Thomas Clan mottos.
It seems to me that torquing the screws that tight with steel to steel contact will probably keep them in place. Also, the small amount of movement that may occur is probably insignificant.
I will put a bit of tape on the HT as mentioned earlier and will examine for any movement after each group. I'll report on any movement.
Second Clan Motto: "The first liar doesn't have a chance!"
Dave
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Round 2 of O-ring numbers testing. 5 shot groups, 50' indoors. Started with zero o-rings up to 7. Stopped there because performance started deteriorating (both mine and the rifle!!)
The first comment is that testing 1 step at time with more care did show the impact of the tuner in the 4-5 ring range that Hector mentioned seemed to be a harmonic node.
Measured the position of the end of the barrel to the front end of the Harmonic Tuner. A table is below. Did measurements before and after shooting group.
Each test:
O-rings inserted and pushed firmly toward stock.
Allen screws tightened but not fully torqued as on screw head seemed damaged and didn't want to further damage it. Depth of muzzle in the tuner measured.
(Hector - could you let me know what the screw size actually is? I tried 6x32 6x40 and 6x48. All seemed to screw in but didn't want to damage the tuner so stopped.). (Yogi- you asked about marking on the real barrel from the screws. Yes, there was some. Nothing serious and not visible to the user.)
Settling shots: 3 into waster target before any test shots.
Group: 5 shots with POA center of smallest ring. Zero intentionally off so the aiming point remained clear of shots. Depth of muzzle in tuner measured.
Data:
O-ring Number. Depth Before Depth After. Group Size Edge to Edge
0. 0.000. 0.001. 0.48"
1. 0.010. 0.011. 0.62"
2. 0.055. 0.015. 0.41"
3. 0.163. 0.160. 0.48"
4. 0.180. 0.130. 0.25"
5. 0.190. 0.180. 0.32"
6. 0.242. 0.210. 0.42"
7. 0.270. 0.270. 0.48"
Test of repetitive groups with 4 o-rings
1. 0.180. 0.58"
2. 0.60"
3. 0.52"
4. 0.110. 0.58"
I suspect that the o-rings will need substantial shooting to compress to their final state. 5 shots is clearly not enough. #1 o-ring was "pushed". space between the barrel and the shroud almost completely. The last o-ring appears to squeeze into the shoulder area that is not a perfect right-angle. This suggests to me that a minimum of two o-rings might be necessary to reliably move the tuner forward in reasonably constant increments. This is interesting but not too relevant because the shooter will keep adding o-rings until he gets the desired results.
This may explain the difference between the initial 4 ring test and the subsequent 4 groups. I probably didn't have consistent pressure on the tuner when I tightened the screws. Also, accurate torquing is needed as Hector suggested. My next step will be to work on the 4-5 ring region using headed screws of the correct size and pitch so I can get the torques right without damaging the original screws or the tuner itself.
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Hector:
I understand the point about the torquing but I am concerned about the threads in the tuner getting damaged with 12in-lb of torque and as I said one of the screws Allen wrench hole was a bit buggered. I think that may have happened from an older Allen wrench with somewhat rounded edges. I found another new one of the same size in my tool drawer that may work better.
A couple questions about the o-rings. Do you have a part number for them? Did you try others?? Deldrin? Ever considered metal o-rings or annealed copper wire?
My plan for the next step is to be more accurate on the measurements of the position of the tuner relative to the "real" barrel muzzle. I didn't have my depth micrometer with me at the range.
I'm going to shoot into my pellet trap at measurement purposes to see how long it takes to stabilize the o-rings and the position to stop moving. I'll do some with the level of tension that I used yesterday but also cautiously torque them to the 12in-lb that you recommend.
Dave
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Regarding the screw sizes that I discussed above! The stupid English system of measurements got to me again!!! Did you all know that the US legalized the metric system in the US in 1871 but it is still roundly ignored!!!
After a bunch of careful measurements and testing with other screws, I found that, of course, Hector was using METRIC screws to go with the REST of the WORLD. From what I can see, the Allen screws (aka Grubb screws) are M4 size and thread. According to Fastenal 4mm screws with 0.7mm pitch can be torqued to 16in-lb so Hector's 12 is a good compromise.
I also found an error in my table above. The compression after 4 additional groups with 4 o-rings gave a depth measurement of 0.127". not 0.110" I couldn't read my own handwriting after it got cold and I got tired.
In any case, the next step it to shoot some pellets into the trap and measure the depth more carefully.
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Sorry Dave that I didn't get around to shipping you some screws. Yes they are M4; as the rest of the gun is metric, it made sense to use metric. IF I ever encounter a US made airgun with SAE screws I will use SAE screws. In the end it should be easier for the shooter to only needs ONE set of allen wrenches.
If you read my response to Yogi, the "Squishiness" of the ORings IS important. They need to squish and compress, but without enough force to FORCE the HPM out of position again after you're done shooting. SO that is why they are ShA75 M1.5X13
Lastly, the need to DE-compress to allow the extraction of the HPM whenever it needs. A harder material MIGHT permanently deform and then the whole thing becomes one piece. Change the pellet batch and you're in trouble.
IF (BIG IF), we could get precision cut rings from bronze or brass, then we COULD spec precisely the "steps", but each ring would cost at least $5, I can, and have made spacer rings for springs, those get used once every 15-20 k rounds, but the spacers for the HPM had to be DEAD CHEAP. and at $5 per hundred, they can be discarded if they get twisted, damaged, or otherwise less than perfect.
In a sense, it was THIS what defined the design of the HPM.
It is hard to see how much thought, experience and knowledge goes into such a simple-looking device.
I've just finished a version for smooth-sided barrels (like the D280-34, and many of the HW's), and, while different in many aspects, it still works on the idea of a mass that moves for tuning, and once moved, it STAYS there THROUGH the forward recoil of the rifle.
I'll post something on that end soon.
Thanks Dave for your hard work and dedication, keep well and shoot straight!
HM
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Going to try something on the settling shots and torquing etc. this afternoon in my trap at home.
I'll not get groups for these tests as I am inquisitive about the compression changing during shooting and the depth of the muzzle from the HT changing as shooting proceeds.
First using your standard method: insert 4 o-rings, torque, shoot settling shots, then group. I'll measure after each shot then shoot multiple 5 shot simulated groups Depending on results, I may try 5 too. As you saw 4-5 seemed to give best results in my test.
Second: insert rings, shoot 3 settling shots, torque, shoot 3 more settling shots, retorque, then shoot several groups and measure after each group.
Incidentally, I browsed the Internet a bit and found that HOBBY-LOBBY sells metal rings with gaps that are nominal 15mm in diameter. If they are close to the right size, I will buy a pack to see what happens. $4 for 35! I also thought about 14-16 gauge copper wire trimmed to the right length - all that for later.
cheers!!
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BOTH are most EXCELLENT ideas!
Keep us posted.
If you are going to try that two stage method, then I would try:
add/delete ORings
insert HPM
SNUG screws
Shoot 3
Torque screws
Shoot 2 more.
At least in Steve's tests, snugging the screws down was enough to MAINTAIN after a few shots a final position.
One of the reasons this may be so is that all things have a bit of tolerance, whenthe HPM moves back a little, the screws change angle and everything gets "clamped" in place.
In general I do not torque those screws, just go by feeling. After years and years I've found I can repeat a setting fairly well.
Screws used are a soft stainless steel. They SHOULD slip the wrench (and therefore they cannot be tightened, but they can be extracted to change) before they sltrip the threads, though that is theoretical, LOL!
Thanks for all your hard work, we're all learning here.
HM
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Things got out of control yesterday when I planned to do the tests so this morning is it!!! Wife will be gone and 91+year old brother-in-law is deaf enough the clanging in the trap won't bother him. The dog will hide under a bed somewhere!!!
I found my stash of odd Allen wrenches and have about half a dozen NEW 2mm wrenches and the 2mm that will go with my torque wrench so I should be able to safely torque them. I was a bit concerned on the level as there are only 3-4 threads in the HT and the screws and didn't want to cowboy them! On the other hand most scope bases and actions only have 3-4 threads too. In any case, I will go lower than 12in-lb. I will try your tightening routine too.
Later!
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I did three different installation methods.
ss
Most important conclusion: Torquing to 10in/lb or using a Allen wrench tightened just enough that the wrench flexes enough to be felt sets the Harmonic Tuner so it won't move more than 0.001". It would be worthwhile to check the depth occasionally.
I think Method 1 makes good sense to settle the rings tightly in the HT and compress them. The friction of the the HT on the barrel sleeve is likely enough to hold it while you tighten the screws.
Measurements were taken from the outside flat edge of the muzzle crown to the flat outside of the harmonic tuner.
Installation of the HT for tests. Push barrel sleeve firmly towards the action to seat it. Insert O-rings by stretching sideways to oval shape, slip over barrel to the edge of the barrel sleeve. Take care to not roll the ring so it twists. Repeat for each ring. Push rings together so there is no space. Slide the HT onto the barrel all the way until it mates with the sleeve. Adjust position so one screw hole is aligned with the top of the barrel and action. Check to make sure the barrel sleeve is firmly set against the action, push firmly on the HT to hand seat it on the barrel and barrel sleeve. This was done for each of the following tests.
Test 1:
1. Add rings and install HT as above. Measure the barrel setback: 0.126"
2. Shoot three settling shots. Measure: 0.118"
3. Torque to 10in/lb. Shoot three settling shots. Measure: 0.117"
4. Shoot 3 five shot strings measure after each: 0.117", 0.116",0.117"
Test 2:
1. Add rings and install HT. Measure barrel setback: 0.124"
2. Torque to 10in.lb. Shoot three settling shots: 0.124"
3. Shoot 3 five shot strings measure after each: 0.123",0.123",0.123:
Test 3:
1. Add rings and install HT. Snug screws with Allen wrench. Measure barrel setback: 0.127"
2. Shoot 3 settling shots. 0.124"
3. Torque to 10in/lb. 0.123"
4. Shoot 2 more settling shots. 0.123"
5. Shoot 3 five shot strings. 0.123",0.123",0.123"
Next step it to go back the range and confirm that 4 rings is the "right" number for my rifle. I will do 3, 4, 5 to bracket the number.
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Morning dtdtdtdt. Down here Repco, an automotive supply shop sells copper washers. Expensive but everything here is. Copper as you know is very easy to work with simple tools. Might be just the thing you need.
You mention having a sleeve on the barrel. Is there a sleeve between the barrel and the brake/HT or is there a sleeve over the D54 barrel that is cut short to accommodate a brake for direct contact with the barrel.
Tried the internal threaded weight on a brake. Complete failure; a weight interferes with the gas flow and who knows where the pellet went. It might work with an external threaded weight. An airstripper works but the position of the internal cone is important so not much use.
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Morning dtdtdtdt. Down here Repco, an automotive supply shop sells copper washers. Expensive but everything here is. Copper as you know is very easy to work with simple tools. Might be just the thing you need.
You mention having a sleeve on the barrel. Is there a sleeve between the barrel and the brake/HT or is there a sleeve over the D54 barrel that is cut short to accommodate a brake for direct contact with the barrel.
Tried the internal threaded weight on a brake. Complete failure; a weight interferes with the gas flow and who knows where the pellet went. It might work with an external threaded weight. An airstripper works but the position of the internal cone is important so not much use.
The way this HT is designed it is NOT a muzzle brake at all. It is a weight to moderate the vibration of the barrel while the pellet moves down the barrel and the piston shakes everything around. You might look at videos on the Internet to see slow motion pictures of a barrel oscillating similar to a piano or instrument string. Hector's device is intended to dampen that vibration and control the barrel's motion.
Below is a pretty scientific analysis of barrel vibration for powder arms but the same rules apply. Just look at the first graphic and visualize adding weight to the end to modify and reduce the vibrations.
https://www.varmintal.com/amode.htm (https://www.varmintal.com/amode.htm)
The o-rings are a simple, cheap and elegant way to incrementally move the weight on the barrel to managed that vibration. It is an excellent empirical solution to a complex problem at minimal cost.
I thought that metal rings might give a more accurate and reproducible way to set the weight in the desired position. Hector advised me that he had thought of the same thing but found the cost and complexity added was not worth the effort. As I said above there are rings that MIGHT work and I MAY go find some to tinker with.
My real objective in these tests was to figure out how to fix the harmonic tuner in the desired place and satisfy myself that it will stay where I put it and keep it there! These results show that Hector's method is pretty darn good.
The Diana 54's barrel is about 15mm in diameter. It has a shroud that covers the barrel about 90% of its length that appears to have an inside diameter of about 17mm. In the original configuration the shroud attaches to the front sight base. Hector's design fits snuggly to the barrel and covers about 5cm of the shroud also snuggly. It makes a strong and attractive addition to the rifle.
You can find a diagram for the D54 on the Internet that shows the original parts fairly clearly. Here is such a diagram. The barrel and shroud are shown at the upper left.
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pyramydair.com%2Fmodel-schematic%2Fm%2FDiana_54_Air_King%2F398&psig=AOvVaw276-OXSxuQb8dA1BbsT59-&ust=1602369873592000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNja3orLqOwCFQAAAAAdAAAAABAD (https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pyramydair.com%2Fmodel-schematic%2Fm%2FDiana_54_Air_King%2F398&psig=AOvVaw276-OXSxuQb8dA1BbsT59-&ust=1602369873592000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNja3orLqOwCFQAAAAAdAAAAABAD)
A good machinist could apply straight threads to the exterior of the barrel and make a device that looks like Hector's with internal threads to allow you move it back and forth but at great cost. Much like a long threaded bolt with a nut on it. The cost would be substantial and far beyond its value!!!
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I did three different installation methods.
ss
Most important conclusion: Torquing to 10in/lb or using a Allen wrench tightened just enough that the wrench flexes enough to be felt sets the Harmonic Tuner so it won't move more than 0.001". It would be worthwhile to check the depth occasionally.
I think Method 1 makes good sense to settle the rings tightly in the HT and compress them. The friction of the the HT on the barrel sleeve is likely enough to hold it while you tighten the screws.
Measurements were taken from the outside flat edge of the muzzle crown to the flat outside of the harmonic tuner.
Installation of the HT for tests. Push barrel sleeve firmly towards the action to seat it. Insert O-rings by stretching sideways to oval shape, slip over barrel to the edge of the barrel sleeve. Take care to not roll the ring so it twists. Repeat for each ring. Push rings together so there is no space. Slide the HT onto the barrel all the way until it mates with the sleeve. Adjust position so one screw hole is aligned with the top of the barrel and action. Check to make sure the barrel sleeve is firmly set against the action, push firmly on the HT to hand seat it on the barrel and barrel sleeve. This was done for each of the following tests.
Test 1:
1. Add rings and install HT as above. Measure the barrel setback: 0.126"
2. Shoot three settling shots. Measure: 0.118"
3. Torque to 10in/lb. Shoot three settling shots. Measure: 0.117"
4. Shoot 3 five shot strings measure after each: 0.117", 0.116",0.117"
Test 2:
1. Add rings and install HT. Measure barrel setback: 0.124"
2. Torque to 10in.lb. Shoot three settling shots: 0.124"
3. Shoot 3 five shot strings measure after each: 0.123",0.123",0.123:
Test 3:
1. Add rings and install HT. Snug screws with Allen wrench. Measure barrel setback: 0.127"
2. Shoot 3 settling shots. 0.124"
3. Torque to 10in/lb. 0.123"
4. Shoot 2 more settling shots. 0.123"
5. Shoot 3 five shot strings. 0.123",0.123",0.123"
Next step it to go back the range and confirm that 4 rings is the "right" number for my rifle. I will do 3, 4, 5 to bracket the number.
Thank you, thank you, thank you!
Great results.
I'll make a note ro recommend just 10 in-lbs of torque on those screws.
Again thank you for your hard work!
HM
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Thanks for the nice comments, Hector!
This morning, I completed this series on the 20caliber Hector D54. Used it set as at the end of the previous set of tests on the theory that lots of shots to settle everything down followed by retorquing to 10in/lb. So the muzzle set back is 0.123" with 4 o rings.
Fired 10 5 shot groups at 17yds from the Caldwell Tackdriver bag with the bag centered at the midpoint of the stock forward of the trigger guard. Luckily no one else was on the range so conditions were the best they could be. 10-15 settling/warming shots ahead of measurements. I called pulling 4 shots in the whole string of 50+ and noted the results below. A picture of the groups followed the table. Groups were measured edge to edge on maximum diameter.
Results:
Group All. w/o pulled
1. 0.60. 0.50
2. 0.43
3. 0.40. 0.30
4. 0.46
5. 0.52
6. 0.46
7. 0.48
8. 0.70. 0.35
9. 0.48. 0.39
10. 0.43
Average group size without called pulled shots: 0.42"
Average group size with pulled shots included: 0.49"
Average group size 1 o-ring baseline 5gp10sht. 0.56"
Conclusion: At this range (17yds, 50' at the NEAR zero, the HT improved the average accuracy by 0.14" in group size that is about a 25% reduction. An observation: the groups appear more round than with the OEM setup. It is likely that longer ranges will benefit more from the HT. However, the average shooter would probably not see a significant difference in field shooting
Final 20cal test will be at 50yds. Baseline group sizes, 10 shots are approximately 1".
I plan to repeat this test with my 0.177" OEM D54 with the Diana HPM.
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Hector:
Regarding the 10 or 12 in/lb torque settings. No significant difference. Fastenal table for soft SS M4 grub screws quotes 16in/lb as the correct torque. I wanted to remain conservative so I don't bugger the HT or HPM threads. 10-12 is well below the destruction level in either case. The six-sided hole in the Allen screw fails first (found that out the hard way in the past!!) I would consider using cup-head screws to get more of bite at the risk of dimpling the barrel exterior though. That would stop any sliding around and give more leeway to the user. I believe the Lothar Walther barrels are hardened as I saw a picture on line from one of the plants with a batch of barrels being heat-treated in an induction furnace.
By the way, after torquing, I tried to increase the tension using just the Allen wrench and was not able to move the screws at all without getting really really vigorous so hand tight is probably in the 10in/lb range.
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Good results, Dave!
Thanks again.
Just one more thing, whenever you have the time:
Try resting the gun's forend as far forward as you can in a series of tests.
Thanks!
HM
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Good results, Dave!
Thanks again.
Just one more thing, whenever you have the time:
Try resting the gun's forend as far forward as you can in a series of tests.
Thanks!
HM
I actually do the forward resting at the outdoor range with a benchrest type of rest. I'll shoot a few groups with both the Tackdriver bag and the br rest soon.
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Hector asked me to test resting the rifle further forward on the theory that it would impact the work of the harmonic tuner.
Today I tried it. I set the tackdriver bag as far forward as feasible. The front action screw rested on the back edge of the bag. For the rear hold, I "cuddled" the stock and used the web of my left hand to steady the stock. I have used this method for years with powder arms and am comfortable with it.
Normally, I center the bag between the action screw and the trigger guard. In that case, the rifle balances on the bag with ease.
I also was testing a new target type that hopefully would help me hold my POA more precisely. I think the new target does help in that regard.
I shot a total of 9 groups. The first was the "warm-up" that Hector recommends because the rifle starts cold and the heat of compression will warm the action and piston to some equilibrium level and change the POI. Group sizes were measured edge to edge.
Results:
One 10 shot warmup: 0.42"
Eight 5 shot groups: 0.35, 0.35, 0.58, 0.41, 0.42, 0.56, 0.36, 0.38
Average 8 groups: 0.43"
Group 3 and 6 suffered a bit from the guy in next lane shooting a 45acp just as I was squeezing off. A hot 45acp case down my neck was an unwanted surprise in the first case.
Analysis: The group sizes obtained with the "center" hold averaged 0.42" versus 0.43" for the forward hold don't feel the D54 is sensitive to hold position. This makes sense as the 54 has the recoilless sledge system and the hold on the wood stock shouldn't be a significant issue. Without the two groups affected by the next door shooter the average group size was 0.38"
Target attached:
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Interesting and THANKS for humoring me.
That's some good shooting.
Keep well and keep having fun!
HM
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Interesting and THANKS for humoring me.
That's some good shooting.
Keep well and keep having fun!
HM
Thanks. Now all I have to do is get the 1-2click adjustments to split the center of the target. :D
Next step is to do the same thing on my .177 with the Diana Version HPM. With luck that will be next Saturday AM or Monday? It should go quicker as I now know what I am doing.
Dave
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I installed the OEM Diana HPM (High performance Muzzleweight) on my 0.177 RWS 54 following the process discussed above. Pellet used is Kodiak Match 10.6gr that has been this rifle's favorite for years. 5 shot groups at 50'. I started with 1 o-ring and continued adding o-rings until performance was degrading. After this series, I shot a total of 13 groups with the preferred number of O-rings.
Comment on the HPM. It wasn't finished as well as it could be. Machined edges were sharp enough to cut skin (twice.) I have a tumbler with steel pins. An hour of tumbling made at HUGE difference.
#orings. Group Edge-to Edge, inches
1. 0.48
2. 0.48
3. 0.52.
4. 0.68
5. 0.60
6. 0.70
Reinstalled 1 o-ring. Torqued HPM screws to 10in-lb. 5 shot groups.
0.52 0.38 0.38 0.52 0.45 0.60 0.48 0.34 0.38 0.33 0.52 0.50 0.48
Average: 0.42"
Best: 0.33"
Worst: 0.60"
Old records show that the average without the HPM for the past 10+years is about 0.4-0.45"
This shows that the OEM setting is close to the NODE for barrel vibration with this pellet.
I may try a couple other pellets to see what happens.
Dave
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Thanks for your continuing hard work!
HM
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Hector, does this work like the barrel devices used by 22 lr shooters?
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Hector, does this work like the barrel devices used by 22 lr shooters?
Dunno WHICH devices you are thinking about. There are several things RF shooters add to their barrels, from bowstring dampeners, to huge rubber grommet-like bulges, to steel weights that are positioned in different places.
If you are interested in RF's then you should reaf Geoffrey Kolbe's paper: http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm (http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm) , but even the Subsonic RF cartridge is so far away from our airguns that the complications he deals with are huge and we are better off simply testing by shooting into targets.
In CF rifles, there are two things that are used: The BOSS type system, and the SmartStock system, one works essentially the same as our HPM, the other works by moving the point where the barrel is pressure bedded in the stock.
In GENERAL, all harmonic tuning devices work on the same principle, which is the "tuning fork" principle:
You have something that vibrates, then you add a small mass and move that mass, in order to reach the frequency you want.
I just so happens that we are not interested in the frequency itself, but in the vibration's peaks and valleys, because at those, the transversal velocity of the muzzle (perpendicular to the bore's axis), is near zero, and so, SMALL changes in MV, will still allow the pellet to exit the muzzle when the muzzle is pointing in the same, or very close, direction where it was when the pellet exited in the last shot.
We may not have enough energy to create BENDS in the barrels, but we do have enough energy to MOVE the muzzles of our barrels by more than 3 thou' in any direction.
And if you calculate what the angle of 0.003 over 16" will cause at 55 yards (1,980") , it comes to 3/8", when you think that is just one half of the possible total, you come out to 3/4".
So, "tuning" the barrel's harmonics makes sense. Reducing them also makes sense. Doing both is leaving no stone unturned in our quest for the best possible accuracy from our rigs.
;-)
Keep well and shoot straight!
HM
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When I shot small bore prone with a very tight sling, hard hold, and strong cheek weld. Subsonic ammunition. Winchester 52C with a free floating barrel 28" long about 1" in outer diameter.
I could feel the vibration in my cheek bones and ear as sort of a twang. Hard to describe but real.
I also have a Rem 40x .22LR with screws that apply pressure to the barrel as Hector describes. I have not shot it under the same conditions as the 52 but understand the purpose was to modify the vibrations of the barrel as described above.
I think I've gone far enough down this rabbit hole for now.