Medusa Structures Bolt Calcs

Summarized Table of the minimum diameter for bolts:

Bolt Min Diameter Calcs

Two cases: 

• a=0 at deployment (only piston force)

• Max acceleration = 1066.5617 ft/sec^2 = 325.088 m/s^2

• Does not need to be calculated for internal members

Notes: 

Max shear stress of 316 steel is 3.447 *10^8 Pa for all

Piston Mount (Under the force of the piston):

a=0

Notes: Force is divided by the number of bolts being used: 8

Force = 316.93 N

S= 3.447 *10^8 Pa

using

D=(4F/S(pi))^(½)

Calculated min D is 0.001 m

Mission Package tube (Under the force of the piston):

a=0

Notes: Force is divided by the number of bolts being used: 8

Force = 316.93 N

S= 3.447 *10^8 Pa

using

D=(4F/S(pi))^(½)

Calculated min D is 0.001 m

Max Acceleration

Mass of av bay and deployment: 3 lbs +2.25 lbs = 2.381 Kg

F=ma=2.381 Kg*325.088 m/s^2=774.035 N

Force=774.035 /8 N

S= 3.447 *10^8 Pa

using

D=(4F/S(pi))^(½)

Calculated min D is 0.0006 m

Diaphragm cup:

a=0

Notes: Force is divided by the number of bolts being used: 12

Force = 316.93 N

S= 3.447 *10^8 Pa

Using 

D=(4F/S(pi))^(½)

Calculated min D is 0.0001 m

Thread Stripping Calculations for U-Bolt:

yield stress of 316 stainless steel: Y = 290 MPa

piston force: F = 477 lb-F = 2121.8 N

dimensions of threads in U-bolt:

• height = 0.0301"
• minor diameter = 0.2458" = 0.00624 m
• major diameter = 0.306" = 0.00777 m

number of threads on each end of U-bolt: 0.2675" * 18 threads/1" = 4.7 threads

surface area of threads on each end of U-bolt: 4.7 threads * pi * ((0.00777 m/2)^2 - (0.00624 m/2)^2) = 7.911*10^-5 m

the threads on each end will experience half of the piston force: F = 2121.8 N/2 = 1060.9 N

stress on the threads on each end of the U-bolt: 1060.9 N / 7.911*10^-5 m = 1.341*10^7 Pa = 13.41 MPa

the stress on the threads on each end of the U-bolt is less than the yield stress of stainless steel, so no thread stripping should occur

assumptions and simplifications made during calculations:

• the force is distributed uniformly on the surface of the threads
• the pitch angle is 0 degrees (in reality, it is 30 degrees)