You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
G
Guest
Guest
Interesting that both "dressed and seated" and "seated" showed lower velocity than "from the tin" or "dressed". Dead air space from the seating depth??? Something else???
I am sorry, I missed this question
I don't think it is dead air space as much as it is the pressure build up while the pellet is being swaged into the barrel.
With gasses if you halve the volume you double the pressure/temperature. So on a 70f day after the piston has moved 1/2 the stroke the temperature of the air in the cylinder has risen to 140f. This is where it gets interesting. It only takes 1/4 of a stroke to double that again so at 3/4 travel of the piston the temperature has risen to 280f. And again at 1/8 more travel the temperature doubles to 560f. So at 7/8 (1/2+1/4+1/8) of the stroke the temperature is high enough to cause dieseling because the temperature combustion of petroleum based oils is about 500f.
This pressure/temperature excursion builds a pillow of air at the cylinder head which catches the piston and stops it from slamming into the end of the cylinder thus destroying the piston. No pellet, no pillow. No pillow, no bueno.
So the pellet which is already seated into the forcing cone will start to move sooner than the one which needs to be swaged into the barrel. This relieves the pressure before it can hit the maximum. There will be some optimal amount of obstruction which produces the highest velocity in a specific power plant with a specific pellet.
Upvote 0