Yeah, I need to re-read those as well. The thing I missed in the first reading was where they established that the Mach number in the TP was greater than one.I did a little more testing with my .22 Titan to try to capture the initial pellet motion. The Titan is a gas ram and it is a little longer/gentler shot cycle than my .177 Quest springer (comparison in image 1), though they are both in the 13-15 FPE range.The second image shows the results for several shots, both in terms of pellet position and the growing volume behind the pellet. My estimate for the TP in the Titan is 3.4 mm diameter and 17 mm long resulting in 154 mm^3 volume, though I need to take it apart to get better measurements.I hope to map out the motion over at least the surge spike, but some mods to the method are needed for that. (more details in the Titan thread linked earlier).
Yeah, I need to re-read those as well. The thing I missed in the first reading was where they established that the Mach number in the TP was greater than one....
That's interesting, I was not expecting a gas-ram to have a slower shot cycle than a springer.-Marty
... my problem is with the supposition that choked flow is occurring in a subsonic springer because of a knee in the bore velocity curve? That's a big leap I would not make based on the available data. Just a reminder to all readers that correlation is not necessarily causation.
Standard Air Arms SetupPiston Bore: 25mmPiston Stroke: 96mmPiston Cross-Sectional Area: 4.91cm^2Swept Volume: 47.1cm^3Piston Assy Mass: 249gTotal Dynamic Mass: 277gTony Leach 22mm ConversionPiston Bore: 22mm (-13.6%)Piston Stroke: 91mm (-5.0%)Piston Cross-Sectional Area: 3.80cm^2 (-22.6%)Swept Volume: 34.6cm^3 (-26.5%)Piston Assy Mass: 143g (-42.6%)Total Dynamic Mass: 167g (-39.7%)
My simulation is not perfect. It has several simplifications and estimates (like pellet friction)