projectile testing - any volunteers?
Posted: Wed Mar 30, 2011 11:37 am
This thread raised some interesting questions regarding streamlined projectiles and it would be good to have some practical results to back up the theories
What I am proposing is that someone with a lathe, reasonably powerful pneumatic launcher capable of high subsonic muzzle velocities, and a distance over which to shoot. The projectiles illustrated should be manufactured, using a light tube (PVC, aluminium etc.) that fits closely in the barrel as the central body, with a heavy nose component (steel, lead etc.) and a lightweight tail component (foam, balsa wood etc.) in the following configurations:
1) identical nose and tail profiles
2) flat tail profile
3) elongated tail profile
4) "boat" tail profile
5) no tail cap
The test would have two principle objectives:
a) determining which shape is the most stable in flight, without the aid of fins or rifling
b) determining which shape allows superior velocity retention over distance
For the first objective, I propose that the projectiles are fired at large flat targets (such as sheets of thick cardboard) set out at various distances (say 5 or 10 metre increments out to 50 metres). A number of shots would have to be fired per shot type (projectile shape and distance) in order to determine an average patern. The targets should be examined for evidence of tumbling, which should be fairly obvious by the appearance of keyholing. This should also allow the degree of tumbling to be determined.
The projectile shapes found to be stable (exhibiting little or no tumbling out to 50 metres) are then selected for the second objective. Ideally a commercial chronograph is used to determine velocity after 50 metres of travel, but in practice it would be difficult to align the shot. Using the laptop/microphone method is probably the best option available to those without a professional testing range. For this test it would also be useful to fire a spherical projectile of similar weight to see what advantage if any is gained by using streamlined projectiles.
I realise that the different amounts of tail material would alter sectional density and therefore change a parameter beyond simple aerodynamic shape, however in practice this should be negligble in terms of results.
It would be great if someone could take the trouble and do a reasonably rigorous test like this one. Why don't you do it yourself, I hear you say - the answer is simply space, I don't have enough room to shoot over that will give me meaningful results. I am however willing to make a pengun/markergun or similar as an incentive of sorts to anyone willing to conduct this expertiment.
Any takers, or comments as to what other parameters ought to be tested?
What I am proposing is that someone with a lathe, reasonably powerful pneumatic launcher capable of high subsonic muzzle velocities, and a distance over which to shoot. The projectiles illustrated should be manufactured, using a light tube (PVC, aluminium etc.) that fits closely in the barrel as the central body, with a heavy nose component (steel, lead etc.) and a lightweight tail component (foam, balsa wood etc.) in the following configurations:
1) identical nose and tail profiles
2) flat tail profile
3) elongated tail profile
4) "boat" tail profile
5) no tail cap
The test would have two principle objectives:
a) determining which shape is the most stable in flight, without the aid of fins or rifling
b) determining which shape allows superior velocity retention over distance
For the first objective, I propose that the projectiles are fired at large flat targets (such as sheets of thick cardboard) set out at various distances (say 5 or 10 metre increments out to 50 metres). A number of shots would have to be fired per shot type (projectile shape and distance) in order to determine an average patern. The targets should be examined for evidence of tumbling, which should be fairly obvious by the appearance of keyholing. This should also allow the degree of tumbling to be determined.
The projectile shapes found to be stable (exhibiting little or no tumbling out to 50 metres) are then selected for the second objective. Ideally a commercial chronograph is used to determine velocity after 50 metres of travel, but in practice it would be difficult to align the shot. Using the laptop/microphone method is probably the best option available to those without a professional testing range. For this test it would also be useful to fire a spherical projectile of similar weight to see what advantage if any is gained by using streamlined projectiles.
I realise that the different amounts of tail material would alter sectional density and therefore change a parameter beyond simple aerodynamic shape, however in practice this should be negligble in terms of results.
It would be great if someone could take the trouble and do a reasonably rigorous test like this one. Why don't you do it yourself, I hear you say - the answer is simply space, I don't have enough room to shoot over that will give me meaningful results. I am however willing to make a pengun/markergun or similar as an incentive of sorts to anyone willing to conduct this expertiment.
Any takers, or comments as to what other parameters ought to be tested?
)
