Quote:
Originally Posted by Ether
I believe designs that do not use tubing or bungee or spring assist can exceed 80psi piston speed.
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I did a rough calculation to check this.
Assumptions:
- 1.5" bore 8" stroke cylinder latched at 3" stroke; extend side pre-charged to 60psi
- exhaust side (retract side) of cylinder left open to atmosphere*; assume no backpressure buildup during kick
- 2 pound mass equivalent load
- ignore energy lost due to sliding friction;
- assume adiabatic expansion of diatomic ideal gas (alpha=5/2 gamma=7/5)
Results:
I got a piston speed at end of stroke of 270 ips:
Calculations:
1.5 cylinder bore, inches
3 start stroke, inches
8 end stroke, inches
60 start gauge pressure, psig
14.7 atmospheric pressure, psi
2 weight of load, pounds
0.0381 bore, meters
0.0762 start stroke, meters
0.2032 end stroke, meters
515,057 start absolute pressure, pascals
101,357 atmospheric pressure, pascals
0.91 mass of load, kilograms
0.001140092 piston area, square meters
8.6875E-05 start volume, kiloliters (cubic meters)
0.000231667 end volume, kiloliters (cubic meters)
36.30 work done by gas, joules
14.68 work done against atmospheric pressure, joules
21.63 work done on load, joules
6.90 velocity of load at end of kick, meters/sec
272 velocity of load at end of kick, inches/sec
If vamfun or MattH are reading this thread I welcome your criticism.
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http://forums.usfirst.org/showthread.php?t=14218
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