Re: [PSUBS-MAILIST] jettisoning battery pods or other ballast

["Jens Laland" <laland@artematrix.org>]

Jon

If you use a trapezoidal (acme) threaded bolt (as the vertical rod in the
drop keel arrangement) having a nominal diameter of 3/4" (or even 7/8"),
then the pitch of the said thread would be 0.2"

I used he following equation (please correct me, anyone, should this be
wrong!):

Torque [in-lbs] = (axial force [lbs] * thread pitch [in]) / (2 * PI)

So, when I put the 0.2" thread pitch, plus your 280 lbs required axial
force, that is, the force needed to turn the hook, into the above
equation, we get:

Torque = (280 lbs * 0.2 in)/(2 * 3.141592654) = 8.91 lbs.in which is the
same as 0.74 ft.lbs

Even with a 10,000 lbs drop keel, such an arrangement should only require
10.6 ft.lbs torque to release....

Please note, however, that all friction has been ignored!

Best regards,
Jens Laland





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