The SAGA of a DIANA 56 T/H

[TonyL]

But just wondering, I'm no expert but shouldn't these 150 gram-ish pistons and softer springs in these kits actually produce less recoil/shock that could harm scopes? The shot cycle seems indicate that there's less recoil going on. Guess we won't know for sure unless someone has an accelerometer and some spare time out there but yeah, shouldn't light piston = less recoil?

The recoil and surge is less, the physical speed of the piston is a little faster, this can translate into sharper movement even though its less overall travel. I have found the speed is more pronounced in shot feel in light weight guns, so my light weight HW50S experiments showed a harshness that you could feel, the weight of a TX and 54 etc looks to soak up the movement well and less is transmitted into the scopes, hence you can watch pellets fly easier, attach scope cams and they work like they do on PCP's etc.

Regard how much faster the pistons fly, i know my guns here (Tx rifles and 77's) have a locktime around 9 to 10ms, a HC can have 8 to 8.5ms which is like a pcp in speed but this is down to shorter barrel. Normal 77's weigh in around 12ms, the older 25mm guns 10 to 11ms so not much slower than my 22mm TX. I have never seen a 54 stock measured at 12fpe BUT i would imagine its around 12ms total locktime which puts piston flight time very close to 22mm. There is a lot of energy going into a stock 54 piston, big heavy brick that needs a good shove to get going.

[HectorMedina]

Since the idea of high speed photography is being discussed, has anyone considered running experiments with a compression tube made out of plexiglass? It would allow filming of the piston in action rather than guesstimating it’s dynamics from recoil measurements.

I’m definitely not a material scientist, but perhaps a plexiglass compression tube could be made on a mini-lathe and matched with a regular barrel/breech in a vise.  Filming the piston and any associated flash from air combustion would be an amazing experiment. The first guy to do it first could be called (insert deep voice) - The man with the plexiglass gun! - Kind of catchy don’t you think? 

-Marty

Marty;

Sorry to have skipped your post.
The Cardews already did that and the problem was that the flash is so intense that there is little chance of seeing any detail.
If you look at this video:



You will see that it would have to be a VERY expensive photographic setup to be able to see the difference in temperatures between the walls and the center of the compression chamber.

Thanks for reading!




HM

[Mossonarock]

I have an acrylic see-thru fire piston. Really cool device.

[MartyMcFly]

Since the idea of high speed photography is being discussed, has anyone considered running experiments with a compression tube made out of plexiglass? It would allow filming of the piston in action rather than guesstimating it’s dynamics from recoil measurements.

I’m definitely not a material scientist, but perhaps a plexiglass compression tube could be made on a mini-lathe and matched with a regular barrel/breech in a vise.  Filming the piston and any associated flash from air combustion would be an amazing experiment. The first guy to do it first could be called (insert deep voice) - The man with the plexiglass gun! - Kind of catchy don’t you think? 

-Marty

Marty;

Sorry to have skipped your post.
The Cardews already did that and the problem was that the flash is so intense that there is little chance of seeing any detail.
If you look at this video:

You will see that it would have to be a VERY expensive photographic setup to be able to see the difference in temperatures between the walls and the center of the compression chamber.

Thanks for reading!

HM

No need to apologize, I knew you would get to it in good time! Indeed I was aware of the Cardew experiments, so I have no doubt that there is combustion/plasma being generated within the chamber. My reason for suggesting the transparent chamber was aimed more toward the idea that it would be easier to measure how much piston slap or bounce was occurring given variations in pellet weight, TP diameter, spring settings and piston mass - capturing the combustion would be just icing on the cake. That said, if the equipment to perform the observation is out of reach of a hobbyist then scratch that idea  and move on to the next.

-Marty

[HectorMedina]

Marty;

Sorry for the long post:

It is often the case that we need to search alternative methods first.

Galileo didn't have a way to measure very short times when researching into free-falling objects. So, he used ramps to "slow" down the motion enough so that he could see.
Galileo was reasoning that if the theory held true for different degrees of inclination; from the very light inclination, very observable experiments; to the more inclined, and hardly noticeable by eye, ones; then the theory had to hold true for the vertical case.
Where the myth of deducting things from the leaning tower of Pisa came, I do not know, but we do know from his notes (impounded by the Inquisition and only fairly recently released for study by the Vatican), that the way he came to the conclusion was to study the fall of objects (spherical) down differently inclined ramps.

In this instance, Galileo was only following PREVIOUS researchers techniques and methods.
Because we do not have written records past the 7,000 BCE time, it is hard to decide to whom to ascribe the "invention" of what the French Enlightenment scientists decided to call the "Scientific Method" that is, essentially, what Steve did in all this process:

Changing ONE thing at a time.

For the hobbyist, sometimes this presents the problem that to change ONE thing (like TP diameter) it means either devising a "test bench" airgun, developing it from an established and well know platform, and then devising a way to be able to change that ONE thing.

To give you an example: this is what I did when designing the breech seal that is now standard in all my builds:
Used a platform that I knew well, and adapted one to look into the effect of different TP Diameters in the case of the different calibers and power levels. So, the steel insert that goes in the composite seal can have, basically, 4 different diameters, one for each caliber and one for the special 12 ft-lbs/ 0.177 " case.
How many experiments it took to arrive to these 4 numbers? about 50 different cases. Once "trends" can be established, then you start "bookending" the goal and you narrow down on both sides till you get the result you need. Which may not be the result you want, LOL!
Again, talking about this seemingly simple device, when the optimal diameter for energy transfer was found in one case, it conflicted with the need to make the piece perform the other duties assigned (pellet alignment and seating), and so the LENGTH was changed just enough for that particular caliber. It was somewhat of a challenge to change the length of the TP without changing the seating depth. But it was necessary to achieve an OVERALL OPTIMUM, which may not be the optimum for one purpose, but by compromising in one aspect, a better result overall could be achieved in ALL aspects.

The OTHER problem for hobbyists is that once they get good results, if someone asks them to create a duplicate part for THEIR needs, the answer you often get is "Sorry it's expensive for what it is".
Most people do not realize, or do not want to accept, that the person making things is not charging for the 5 grams of steel and the 2 grams of plastic that go into the piece, the value of the part is in the KNOWLEDGE that took to make it work the way it does, and the cost of all the tests and tries that were needed.

On the industrial side the problem is different: Boards (of directors) do not like to see what their bean-counters think of as a "too large an R&D budget". Specially in technologies that they consider "mature" and at the "end of the development".
All corporate boards are happier with "cash cows".
And it is difficult for a non-airgunner to understand the extremely fine nuances of what a "finely tuned", as opposed to a "highly strung", airgun is. Needless to say that absolutely none of the CEO's, CTO's, and COO's of airgun-making companies is truly an airgunner.

But within all this bleak picture, the users are taking the lead. And that is another aspect that is truly worthwhile about airgunning.

There is a very generous offer from one of the friends here to help defray some costs that would be associated with the research into the location (and therefore length and shape)  of the TP in breakbarrels. I greatly appreciate that offer, now I need to find someone like Steve willing to do a number of experiments, and carefully document the results in the case of breakbarrels.

Hopefully we will find our person soon enough, but it is also an ongoing process that takes time.

To close this: Do not be afraid to experiment. It is always wise to ask if someone has done the experiment before and what were the results, but by all means, dream of something and go for it.

;-)

Keep well and shoot straight!






HM

[Mossonarock]

Hector,
That is so true. I got into airgunning specifically to experiment. I wanted to learn what these new adult airguns were capable of, how they operated and all that. Target shooting and hunting came later. Hunting was much later and rarely at all actually.