- #1

tthree

## Main Question or Discussion Point

Please bear with me, I am trying to design a shaft that will be under torsion. I do not know the diameter of the shaft and I would like to be able to calculate it by the things that I do know about the system.

There's a 15HP 3 Phase motor running at 85RPM [there's a gearbox]

This will be putting out 1255Nm of torque.

I have medium carbon steal with these mechanical properties:

Hardness, Brinell 201 - 269 201 - 269

Hardness, Rockwell C 13.8 - 27.6 13.8 - 27.6

Tensile Strength, Ultimate 686 MPa 99600 psi

Tensile Strength, Yield 490 MPa 71100 psi

Elongation at Break 17 % 17 %

Reduction of Area 45 % 45 %

Modulus of Elasticity 205 GPa 29700 ksi Typical steel

Poissons Ratio 0.29 0.29 Typical steel

Machinability 55 % 55 % Based on AISI 1212 steel as 100% machinability

Shear Modulus 80.0 GPa 11600 ksi Typical steel

Impact 8.0 8.0 kg(f)/cm²

Leaving off safety factor for now, just for simplicity sake.

My question is; can I calculate the the diameter of the shaft based on the above information? What I can say so far is:

T = 1.255x10^6Nmm

G = 80GPa

Hz = 1.42

RPM = 85

If so how can I do it?

There's a 15HP 3 Phase motor running at 85RPM [there's a gearbox]

This will be putting out 1255Nm of torque.

I have medium carbon steal with these mechanical properties:

**Mechanical Properties****Metric****English****Comments**Hardness, Brinell 201 - 269 201 - 269

Hardness, Rockwell C 13.8 - 27.6 13.8 - 27.6

Tensile Strength, Ultimate 686 MPa 99600 psi

Tensile Strength, Yield 490 MPa 71100 psi

Elongation at Break 17 % 17 %

Reduction of Area 45 % 45 %

Modulus of Elasticity 205 GPa 29700 ksi Typical steel

Poissons Ratio 0.29 0.29 Typical steel

Machinability 55 % 55 % Based on AISI 1212 steel as 100% machinability

Shear Modulus 80.0 GPa 11600 ksi Typical steel

Impact 8.0 8.0 kg(f)/cm²

Leaving off safety factor for now, just for simplicity sake.

My question is; can I calculate the the diameter of the shaft based on the above information? What I can say so far is:

T = 1.255x10^6Nmm

G = 80GPa

Hz = 1.42

RPM = 85

If so how can I do it?