Yes! That's what my Technical Report is all about. I need to design a line shaft with 3 pulleys and 1 gear. I am required to determine the diameter of the line shaft (just one diameter of the whole shaft). What if I already known the maximum torque in the line shaft? Should I ignore the other torques in each section of the shaft?Dr.D said:If there is power entering and leaving the shaft at several different points (such as a drive pulley on a line shaft powering several machines), you need to find the torque in each segment (between entry and exit locations) to determine which is the largest.
Thread moved to the schoolwork forums.CWatters said:Perhaps this should be in the homework section.
CWatters said:Perhaps..
Design: Line ShaftDr.D said:The source quoted at that previous PF article seems to indicate that the shaft can be properly designed by considering torsion alone. I think that is in error.
Any shaft with transverse loads (such as belts or gearing) that is not continuously supported (i.e. bearing support at every section) must be designed for combined bending and torsion as both are present at every location along the length. My old machine design book (Mechanical Engineering Design, Shigley, 3rd ed) discusses this topic at length in Ch11. There are many different situations involving combined static and dynamic stresses in combination, but it is simply not safe to look at torsion alone.
Yes, it is in my textbook (Design of Machine Elements by V. M. Faires). And I have a copy of Shigley's (9th Edition) pdf.Dr.D said:I don't know what ASME says about such things, so I cannot address that. Is it in your textbook?
You need to apply a failure theory, such as the maximum shear stress theory, and test this at every point along the length of the most highly stressed section. I'd program this, and test it in small steps from one station to the next because it is usually not possible to eyeball the location of the worst condition. You may also want to do some on-line research for the Westinghouse formula, the Sines approach, and the Kececioglu approach. I suggest getting a copy of the machine design texts by Shigley or the one by Spotts if your own text is inadequate. This is a great problem, and you will learn a lot if you carry it through.
My copy of his book is the 4th Edition, date 1962 or 1965? I'm not sure.Dr.D said:Ah, V.M. Faires! He was on the faculty of North Carolina State and his book was used at Texas A&M. Some of my Aggie friends have told me that a common quiz question was to ask students what the V.M. stood for. My copy of Faires' text is the 3rd ed., date 1955. I looked there, and sure enough, there was a reference to an ASME Code for Shafting, but no information about what the Code says. I hope your copy has more information.
Thanks. But I already searched for it. And it is also in my textbook (Design of Machine Elements by V. M. Faires), that tells it is based on Maximum Shear Theory.CWatters said:A quick google suggests that the ASME methods says something like..
"..the permissible shear stress for shaft without keyways is taken as 30% of the yield strength in tension (Syt), or 18% of the ultimate tensile strength of material (Sut), whichever is lower."
No, you cannot simply add all the torques in a shaft and use it as the Tmax. The maximum torque, or Tmax, is the highest amount of torque that a shaft can handle before it starts to deform or break. It is determined by the material and dimensions of the shaft, and cannot be calculated by simply adding all the torques together.
The formula for calculating the Tmax of a shaft is Tmax = (π/16) * (d^3) * σ, where d is the diameter of the shaft and σ is the maximum stress that the material can handle. This formula takes into account the dimensions and material properties of the shaft to determine its maximum torque capacity.
It is not recommended to exceed the Tmax of a shaft, as this can lead to permanent deformation or failure of the shaft. It is important to carefully consider the maximum torque requirements and choose a shaft with a suitable Tmax for the application.
The Tmax of a shaft can be affected by various factors, such as the material and dimensions of the shaft, the type and magnitude of the applied torque, and the operating conditions (e.g. temperature, vibration, etc.). It is important to consider all of these factors when determining the Tmax for a specific application.
Yes, the Tmax of a shaft can be increased by choosing a material with higher strength and/or increasing the dimensions of the shaft. However, it is important to note that increasing the Tmax may also result in a heavier and more expensive shaft, so it is important to carefully consider the trade-offs for the specific application.