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

• -(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"

• -(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.