Table of Contents
- 1 What is Lewis equation in machine design?
- 2 What is significance of Lewis form factor?
- 3 Where is Lewis equation used?
- 4 What is law of gearing?
- 5 Why are pinions weaker than Gears?
- 6 What is the effect of increase in pressure angle?
- 7 What is zero backlash?
- 8 What is the Lewis equation?
- 9 What is the Lewis equation for gear and pinion?
What is Lewis equation in machine design?
Lewis equation: WT = σw. b. π. m.y, WT= Tangential load acting at the tooth in N σw= bending stress in N/mm2 b= width of the gear face in mm m= module in mm y= lewis form factor.
What is significance of Lewis form factor?
The Lewis equation is used to estimate the bending stress in gear teeth (max. bending stress at the root of a gear tooth). Lewis equation forms the basis of the AGMA bending stress equation used nowadays.
Where is Lewis equation used?
Explanation: The Lewis equation is applied only to the weaker of the two wheels (i.e. pinion or gear). It is observed that m and b are the same for pinion as well as for gear. When different materials are used, the product (σb × Y) decides the weaker between pinion and gear.
What are the assumptions made for the Lewis equation?
Lewis Analysis is based on following assumptions: Only one pair of teeth takes the entire load (Load is often shared by more than on pairs). The effect of radial component, Fr, is negligible (Fr induces compressive stress). The load is uniformly distributed across the full face width.
How do you find the Lewis factor?
- The Lewis form factor is directly proportional to the width of the base and number of tooth on the gear and is inversely proportional to the pitch diameter.
- It’s more of a dimension less factor to make the formula for beam strength compact.
- The mathematical expression is 2*b*T/(3*pi*d)
What is law of gearing?
Law of gearing states that the common normal at the point of contact between a pair of teeth must always pass through the pitch point for all positions of mating gear. This is a must condition for the two gears to perform properly.
Why are pinions weaker than Gears?
When the different materials are used, the product of decides the weaker between the pinion and gear. The Lewis form factor is always less for a pinion compared with gear. When the same material is used for the pinion and gear, the pinion is always weaker than the gear.
What is the effect of increase in pressure angle?
The strength of the tooth is an important factor in the selection of the pressure angle. Figure 14-6 shows the variation of gear tooth geometry and pressure angle. The higher the pressure angle, the higher the tooth strength. The noise that the gears generate decreases with an increase in the contact ratio.
What is the face width of a gear?
The face width of a gear is the length of teeth in an axial plane.
What is tooth profile?
Gear Tooth Profile: One of the fundamental s of gear design is the profile of the gear tooth. Gears generally have an involute curve tooth profile. There are other types of gear profiles, but they are mainly utilized in specialty applications such as cycloidal gears in clocks and watches.
What is zero backlash?
These zero backlash gear units from Harmonic Drive LLC consist of a zero-backlash gear integrated with a housing and precision output bearing. This also eliminates the play between the gear teeth and thus eliminates backlash. Of course, the type of gears used can also have a large impact on the amount of backlash.
What is the Lewis equation?
Lewis equation is the method introduced by Lewis to calculate the bending stresses of spur gear tooth when gear tooth is subjected to bending forces. Lewis considers single spur gear tooth subjected to bending loads tangentially on the surface of tooth which leads to bending stress at the root portion of the tooth.
What is the Lewis equation for gear and pinion?
If gear and pinion are made of same material, pinion is the weaker member and design is based on its strength. But if those are made of different materials, it is evident from the Lewis Equation that the gear or pinion having lesser value of product [σb] X Y is weaker, as m and b are same for pinion and gear.
What is the Lewis theory of single spur gear?
Lewis considers single spur gear tooth subjected to bending loads tangentially on the surface of tooth which leads to bending stress at the root portion of the tooth. Lewis considered single spur gear tooth as a cantilever beam subjected to bending load its surface uniformly distributed over the facewidth of the gear tooth.
What is the Lewis form factor of gear tooth?
It was derived by Lewis in his research paper in 1893. It was based on the assumption of taking tooth as a cantilever beam. y = Lewis form factor. This equation is useful while designing gear tooth based upon beam strength (assuming cantilever beam).