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Shot cycle Dynamics in 3 Spring-Piston Airguns.- Preface

4/1/2021

11 Comments

 

A nine+1 entry series by John Cerne, Yogi, and Hector Medina

Another title could be: "Conversations between three passionate airgunners: a scientist, a profound observer of life and great admirer of beauty", and an engineer.

Or, we could even have a joke: "A scientist, a 
yogi and an engineer enter a bar . . "

Truth is these blog entries (we THINK we will stop at 9) that we plan on publishing every fortnight, started as a casual conversation; not in a bar, but in a forum; were then taken to PM's, and when the project really started to flesh out, formal EMail's started flying all around.

We formally convened on Valentine's Day 2020, and it was truly an auspicious day because everything has gone reasonably well. It has been a pleasure, and a great privilege, to work with these two gentlemen over the last 13½ months.

So, let me introduce my friends to you.

The originator of all this was my friend "WL", who chooses to use ONLY the nick/handle "Yogi", both here and when posting in the GTA forum; he had some very pertinent questions about transfer port (TP for short) geometry (diameter, orientation, length) and when I explained my theories, he ventured the idea of underwriting the effort to ship different guns to different people that could study and explain the possible relationships.

At about the same time, John Cerne, who uses the nick/handle "JohnC" when posting in the GTA, came up with the idea of looking into the overall dynamics of the shot cycle in spring-piston guns.
Now,
John has a PhD in experimental condensed matter physics and is a physics professor at a well known research university so, his participation was an opportunity that was too precious to let go.
He was very enthused with some experiments by Jim Tyler on measuring recoil motions in airguns, which were published in the British "Airgun World" magazine..

On my side, I had recently finished the collaboration with Steve Herr (NitroCrushr) about the Four Part "Saga of a DIANA 56 T/H" and, as closure of that report was the receipt of Steve's sled. I hadn't had time to study in detail how to expand its functionalities, so the project proposed by John seemed a suitable vehicle with the ideal candidate. I proposed the joining of forces to all three parties, with the caveat that the TP geometry aspect would be looked at just tangentially, still, Yogi was generous enough to help us get everything underway.

And so it is that we (99% John) have been working in these ideas, developing the tools to START interpreting and understanding the REALITIES behind the APPARENTLY simple mechanical devices we love (and sometimes hate) that are spring-piston airguns.

We FULLY REALIZE this is just the beginning of a new conceptualization. And we realize that we will not do it all on our own. So, part of the intention of this NINE part series is to give (in the spirit of the 1950's "Popular Mechanics" magazine) almost anyone with a modicum of common sense and practical skills, the knowledge and understanding to make up HIS/HER OWN research devices/apparatus, and enable them to start researching into the phenomena that actually make our airguns what they are, what gives them "character", what makes them "tick".

We also HOPE that the industry realizes that the shooters are becoming more and more sophisticated, and that some "Benchmarks" CAN be set that are quantitative and hard-data based enough to dispel all the mystery and "dark-arts" atmosphere that surrounds the "tuning" of spring-piston air rifles, or the qualities of a design.

Now, regardless of how much science you want to put into anything, NOTHING regarding human interaction with machines is written in stone (or parchment / paper). It is not a dogma of faith. Because we, humans, are vastly different. So, we don't purport to have arrived to the ideal recipe for a gun that will work for everyone, but we do think that measuring some key aspects of the shot cycle should enable users to select better the gun that will suit them; and allow manufacturers to come up with better products.


I know that, in a way, we cheated. Why? because we chose for this exercise three of the best examples of spring-piston airguns of all times (Walther LGU, Walther LGV and FWB 124). We know that the dynamics in these three highly tuned airguns are as good as they can get, AND we had the added advantage that the Walthers are basically the same rifle, just one uses the barrel as a cocking lever, the other has a fixed barrel and a separate cocking lever.
​BUT, in our defense, we will say that this also allowed us the tangential look into the TP geometry, since one (the LGV) has a long transfer port and the other (the LGU) has a short one.

The nine parts of this series are:
Chapter 1. Diagnostic equipment: How can we understand better what our air rifles are doing? 
Chapter 2. How do the Walther LGU, Walther LGV and FWB 124 compare?
Chapter 3. Group statistics: What can target groups tell us about the accuracy of an air rifle?
Chapter 4. LGU/LGV powerplant swap: How does swapping airgun pistons and springs in an LGU and LGV affect performance? 
Chapter 5. Does Krytox improve performance?
Chapter 6. Does more mass in a springer air rifle result in better accuracy?
Chapter 7. Does a higher energy spring decrease accuracy in a springer air rifle?
Chapter 8. What happens when you remove the LGU’s muzzle cap?
Chapter 9. Conclusions: What does this all mean?
​
So, without further ado, I yield the floor to John Cerne.
11 Comments
Bob (Springrrrr on GTA)
4/2/2021 07:28:56

Looking ahead to your results. I too am in the LGU crew and some years ago modified my trigger by placing the second stage screw further away from the pivot point to gain leverage and thus making it easily as good as any Rekord or TX200 out there.
I also installed a sleeve around the spring to reduce vibration. The spring guide on my gun fits quite tight so the need to change that was secondary and the original remains.
Your input will be closely followed by all of us that still are attracted to our spring guns and have not closeted them for PCP's.

Reply
Hector Medina
4/2/2021 07:56:19

Bob;

While I admit there are tried and true ways to tune a spring gun, this series about going MUCH FURTHER than the usual "tinkering".

We aim (pun intended) to provide advanced airgunners like your goodself with the wherewithal to BUILD an INSTRUMENT that will allow you to experiment and "see" phenomena that are too fast for the human to see, feel, hear, or even fathom in many cases.
And then we try to provide you with the tools to analyze what you find, as well as giving some examples of how to use the tool to compare airguns on a scientific basis.

Thanks for reading and stay tuned!






HM

Reply
Steve Cox
4/2/2021 14:00:40

Do you know if Jim Tyler's work has ever been republished in a single volume? If so, do you know where to obtain one? Many thx for all you . SC

Reply
Hector Medina
4/2/2021 14:46:17

Not to my knowledge.

Actually, this series of articles will expand on Mr. Tyler's great pioneering work.

Thanks for your interest!




HM

Reply
Bob
4/2/2021 15:20:43

Thanks, keep the research going.

Reply
RidgeRunner
4/3/2021 07:17:16

Awesome!

Reply
Efrain Z. Rivera (ER00z on GTA)
4/13/2021 22:50:17

Looking forward to the results also. Always you provide good information and I'm sure many are tuned into the upcoming presentations.
Unlike most, I went from gas rams, to pcp's, to springers. Their simplicity and reliability make them great and always I'm looking to learn more about them.

Reply
Michael Adams
4/18/2021 21:24:29

Hi,
I did numerous postings on the old Yellow around 2003-4 regarding this topic. I think used a 200 or 500g accelerometer and a dual trace Fluke DSO to captured both piston motion as well as the precise point of pellet exit for many spring and gas ram air guns. I may or may not have some of the data on a drive somewhere as it has been some 18 years and several computers ago, Regardless, I still visit the forum occasionally so I look forward to reading your work.

Best Regards
Mike Adams

Reply
Hector Medina
4/19/2021 09:52:23

Hello Mike!

Thanks for reading!
Hope you have already read the 1st chapter.
There are some interesting results there.
BACK in 2003, a Fluke memory scope would have costed as much as a Whiscombe!
;-)
If you have the data, and if you care to share it, I will gladly do some comparative analysis.

I have also used professional grade accelerometers, but my main peeve with those is that they are still outside the realm of what a typical "home gunsmith" can spend in insrumentation.

There is an interesting discussion going on here:

https://airgunwarriors.com/community/airgun-talk/a-scientific-look-into-the-dynamics-of-the-shot-cycle-of-three-spring-piston-airguns/#post-47169

And, yes, while I agree that the numerical values are not precise, the value of having an analysis tool at the home gunsmith's level is enormous.

Like the advent of the inexpensive chronograph changed the shooting industries in the 80's, I hope this will change the tuning industry. A much less ambitious goal, but important, none the less.

;-)

Thanks for reading!






HM

Reply
Michael Adams
4/20/2021 14:02:29

Hello Hector,

I did some looking and found some of the data summarized in a word doc from 2005. If you shoot me a e-mail I will send it along to you.
I applaud the work you are doing.

Best Regards,
Mike

Hector Medina
4/20/2021 15:40:01

@ Michael Adams;

PLEASE contact me through the contact page because there is no way I can find out your Email from the blog page.

Contact page is here:

https://www.ctcustomairguns.com/contact-us.html

THANKS!





HM

Reply



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    Hector Medina

    2012 US National WFTF Spring Piston Champion
    2012 WFTF Spring Piston Grand Prix Winner
    2013 World's WFTF Spring Piston 7th place
    2014 Texas State WFTF Piston Champion
    2014 World's WFTF Spring Piston 5th place.
    2015 Maine State Champion WFTF Piston
    2015 Massachusetts State Champion WFTF Piston
    2015 New York State Champion WFTF Piston
    2015 US National WFTF Piston 2nd Place
    2016 Canadian WFTF Piston Champion
    2016 Pyramyd Air Cup WFTF Piston 1st Place
    2017 US Nationals Open Piston 3rd Place
    2018 WFTC's Member of Team USA Champion Springers
    2018 WFTC's 4th place Veteran Springer
    2020 Puerto Rico GP Piston First Place
    2020 NC State Championships 1st Place Piston
    2022 Maryland State Champion WFTF 
    2022 WFTC's Italy Member of TEAM USA 2nd place Springers
    2022 WFTC's Italy
    2nd Place Veteran Springers

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