# Q & A: Force due to an accelerating piston

Q:
I am operating a large V-12 gasoline engine. The pistons weigh 8 pounds each, have a 6" bore and travel a 6.6" stroke. If the engine is running at 4,000 RPM, what are the computed G forces on the pistons as they reverse direction at the end of each stroke?

Thank you.

Ken Nott
Mach2@Rogers.com
- Ken Nott (age 56)
A:
f = 4000/60    =   66.67             Frequency in revolutions per second
w = f*2*pi       =   418.9            Angular frequency in radians per second
x = 6.6*.0254  =  0.168             Stroke in meters
a = w^2*(x/2)  =  14705            Acceleration in meters per sec^2
M = 8/2.2         =  3.64              Mass in kilograms
F = Ma             =  50350           Force in Newtons
g  = 9.8                                      Acceleration due to gravity
P = F*g/2.2        =  11319          Equivalent Force in pounds

That seems like a lot of force but if I havent made a mistake thats what it comes out to.

LeeH

(published on 10/27/2007)