Re: [DML] Open Invitational Door Strut Test

["Walter Coe" <Whalt@xxxx>]

How much dead weight does it take to compress a door strut?

Based totally on mathematics, I have two answers: a low of 270 lbs (122 Kg)
and a high of 315 lbs (143 Kg).

John Hervey supplied the seed figure of 1200 Newtons, and Tom Niemczewski
supplied 1400 Newtons. It is possible that both figures are correct
depending from where you take your measurements if the lower figure is the
minimum required to start to compress a relaxed strut while the maximum is
to completely compress it.

I was mistaken in my previous post stating that the door struts are charged
to 1400 psi. The "1400" was correct, but it was Newtons -- not psi. As for
what the charge really is, I have calculated this to be from 153 to 179 bar
(2225 to 2596 psi) which is a LOT of pressure. Can anyone verify this? The
next thing to try is calculate the change in strut charge according to
whether it is compressed or relaxed. A difference of 200 Newtons would help
test my theory, but I'm bored with it already. Maybe tomorrow.

So Rick, how are you doing measuring this experimentally?

For those of you who enjoy math:

1200 Newtons = 1200 Kg*m/s^2 = (convert to Kg by assuming gravitational
force is 9,80665 m/s^2) = (1200 Kg*m/s2) / 9,80665 m/s^2 = 122,4 Kg = 270
lbs

The rest of my calculations are based on the premise that the strut is in a
static mode. Therefore all internal force vectors mutually nullify each
other with the exception of the force exerted perpendicular to the
cross-sectional area of the rod. Assuming a rod diameter of 9,98 mm =
0,00998 m; therefore, the rod cross-sectional area = (0,00998 m/2)^2 * pi =
7,82E-5 m^2

So for the low end, 1200 Newtons applied over an area of 7,82E-5 m^2 =
1200 N / 7,82E-5 m^2 = 1200 Kg*m/s^2 / 7,82E-5 m^2 = 1,53E7 Kg/m*s^2 =
1,53E7 Pascals = 153 bar = 2225 psi (whew!)

And if you understand any of this, join the geek club. Two characters come
to mind: Anyone remember Poindexter in Felix The Cat from Romper Room or
the yellow chick in the Fog Horn Leg Horn cartoon in the Bugs Bunny Road
Runner Show?

Walt (the geek)