If that was the first video he removed it because he used a slug at a much lighter weight then first described giving a false representation.
I must apologize. There is an error in the results of the test. I've recovered one of the spent bullets and realized I was using lighter bullets for the test. I've machine those bullets in small batches of various sizes and the 23 grams was mixed with the 18.5 grams bullets. So the weight used in the video was 18.5 gram (293 grain). Consequently the energy is 1055 ft/lbf (1430 Joules).Please forgive me. I was away from the shop for some time and eager to start the testing. And in some way fooled myself by the excitement. I will make anew video - including all the technical details - to replace the current one.
Quote from: Insanity on October 30, 2019, 08:41:06 PMIf that was the first video he removed it because he used a slug at a much lighter weight then first described giving a false representation. Matt, I think you must have missed Bill's explanation, 3 days ago, of his mistake with the weight of the bullet.Lloyd Quote from: billzweig on October 27, 2019, 07:32:06 PMI must apologize. There is an error in the results of the test. I've recovered one of the spent bullets and realized I was using lighter bullets for the test. I've machine those bullets in small batches of various sizes and the 23 grams was mixed with the 18.5 grams bullets. So the weight used in the video was 18.5 gram (293 grain). Consequently the energy is 1055 ft/lbf (1430 Joules).Please forgive me. I was away from the shop for some time and eager to start the testing. And in some way fooled myself by the excitement. I will make anew video - including all the technical details - to replace the current one.
For the sake of an academic argument, this experiment will help clarify if and how much heat is being added by the arc or combustion. Simply eliminate additional heat, or combustion by using an engineered full bore cold rupture disc:Find or make a 4000 PSI burst disc. Install in the system without the capacitor charged. Aim the barrel at the backstop over the crony and fill slowly with air pressure until the burst disc blows from over pressure.Firing needs to happen at 4000 PSI, so a series of burst discs may need to be constructed, starting with 3000 PSI to ensure the rupture pressure VS thickness is understood.Now; compare the projectile velocity obtained with a 4000 PSI cold rupture disc against that obtained with the hot rupture disc.What makes this a potentially bad idea is if the burst disc does not rupture at 4000 PSI and there is no other way to fire or depressurize the system... There must be a safe way to bleed the system, else a system that sits on the point of failure at 4000 PSI is a big problem. After a period of material creep, or a slight increase in storage temperature, then boom...I would imagine that such a rupture disc as I describe above would not just be made from thin aluminum or brass shim stock (something that won't hurt the bore), but that there would be a sharp "scored" anular ring to make it rupture in such a manner that the free disc can pass down the barrel in predictable fashion. A definite stress raiser that functions a bit like the notch in a Charpy Test specimen...
I am still bothered by not seeing any significant air blast...
Even at 10 feet, the diffusers and the support wires wobble all over the place....
I have blown the diffusers clear off a Chrony at 3-5 feet
Quote from: rsterne on October 31, 2019, 12:33:17 AMEven at 10 feet, the diffusers and the support wires wobble all over the place.... Maybe at 10 feet the air blast is wide enough to hit the crony supports and screens, but a 4 feet it passes through between them Fair question. While there may be jumbo shrimp; there are no pocket nukes...
I this a PCP or is the pressure made by the "high voltage discharge"? If the latter, then this is essentially a firearm, not an airgun. Right?
If this is true, then the BATF would, IMHO, probably classify this as a firearm and not an airgun.One could argue that there is no "explosive" (as per BATF definition of a firearm) involved, but if there is combustion there is fuel.
Quote from: BackStop on November 03, 2019, 01:57:38 AMIf this is true, then the BATF would, IMHO, probably classify this as a firearm and not an airgun.One could argue that there is no "explosive" (as per BATF definition of a firearm) involved, but if there is combustion there is fuel.Why not declare it a single cylinder, disposable piston, internal combustion engine? I don't think the ATF recognizes sheet brass as a propellant or accelerant; or even a fuel. Metal powder, yes. Solid bits that you could not light with a match, no. Perhaps the burst disc is acting as a "heating coil", transferring the stored energy in the capacitor to the compressed air volume: Acting both as a resistance and as a heat exchanger. Melting the disc turns part of it into metal vapor and metal droplets, with lots of surface area. This should be effective for heat exchange and oxidation. If these particles or vapor are being burnt, where are the products of combustion? Is there any of it left on the remainder of the burst disc that can be examined?
I would think the oxygen in the compressed air is the real source of fuel.
QuoteI would think the oxygen in the compressed air is the real source of fuel.By definition; oxygen is the oxidizer that takes the reducing agent's (fuel) electrons.You need three things for combustion:FuelOxidizerActivation energy of sufficient magnitude.Activation energy required can be reduced by means a catalyst (as in catalytic converter); or by increasing the pressure. That is why pure high pressure oxygen is so dangerous. You don't need to increase the temperature of 3000 PSI oxygen to start combustion, with a fuel such as oil or grease present.
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