P10221: Baja 1 (Baja Driveline Test Development)
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Stand FEA

Stand, Method of Analysis:

• Weight of engine = 45 lbs
• Connections that transmit the weight in the Y-axis are modeled as "bonded."
• Connections that are prone to slide or are bolted were modeled as "no separation."

FEA versus Calculations - Bolt:

Calculation Assumptions:
• Rockers take the weight of the engine
• No friction between clamped faces
• Use 5/16 bolt with min diameter=.260"
• Use Max Shear Stress Theory (Conservative)
• Steel Sy=36,259 psi
• Shear Tau max = (.5)*(Sy) = 18,129.5 psi

Calculations Explained:

• Friction force between rocker and side
• Ff = Mu* N
• Ff = ( .7 * 45lb) / 2
• Ff = 15.75 lb

Sum moments about point 0.

• -(200 in-lb) +2 * (F * 7") + (15.75 * 6") = 0
• F = 7.5 lbs

Max Shear Stress

• Tau = (4 * F) / (Pi * (dia)^2)
• Tau =(4 * 7.5) / (Pi * (.260)^2)
• Tau = 141.3 psi

Factor of Safety

• FOS = Sy / (2 * Tau)
• FOS = 36,259 / (2 * 141.3)
• FOS =128

Calculation Results:

• Shear Stress of bolt= 141.3 psi
• Factor of safety = 128

Fea Results:

• Shear Stress of bolt= 278.57 psi
• Max stress = 2440.3 psi in side
• Factor of safety = 15 (Ansys max)

FEA versus Calculations - Base:

Assumptions:
• Weight of engine is supported by 2 sides
• Bolts are in complete tension
• Weight of engine = 45 lb
• Use 1/4"-20 bolt with min diameter=.1876"

Sum moments about point 0:

• -(200 in-lb) -F1*(-5.45") + F2* (5")= 0
• 200=5.45(F1) + 5(F2)
• 200= 5.45 (F1) + 5 * ( 22.5 +F1)
• 200=5.45(F1) + 112.5 +5(F1)
• 87.5=10.45(F1)
• F1= 8.37 lb
• F1/ (2 sides)= 4.2 lbs

Sum forces in Y axis:

• -F1 + F2 -22.5lbs = 0
• F2=22.5 + F1
• F2= 30.87
• F2 / (2 sides) = 15.4 lbs

Max tensile stress at F2:

• Tau= 4* (F Bolt) / (Pi*(dia)^2)
• Tau=(4*15.435) / (Pi*(.1876)^2)
• Tensile stress= 558.4 psi

Calculation Results:

• Tensile stress= 558.4 psi

Fea Results:

• Tensile stress = 461.4 psi

FEA Deformation: Max deformation occurs at 30 degree tilt and is equal to .0001 inches.

FEA Stress at Tilt Titled away from dyno 30 degrees, shear stress of bolt equal to 1074.4 psi.

Conclusion

Overall the stand is proven a safe concept, giving a green light to move toward the building process.