Load Capacity Of Gears Research Articles

Friction and wear behaviour of acetal and nylon gears

The current paper will present an extensive investigation of polymer gear (acetal and nylon) friction and wear behaviour. First, a unique test method for polymer gear wear will be described in brief and later used in the extensive investigation of acetal and nylon gear wear. Initial tests were performed using acetal pinions with acetal gears, and nylon pinions with nylon gears, with further investigation carried out using dissimilar polymer gears. In this case the driver and driven effects on the gear wear behaviour was also considered when dissimilar materials were used. For acetal against acetal gears, it was found that the acetal gear wear rate increased dramatically when the load reached a critical value for a specific geometry and the gear surface showed slow wear, with a low specific wear rate if the gear was loaded below this critical value. It was found that the surface temperature was the dominant factor influencing the wear rate and an initial relationship between gear surface temperature and gear load capacity has been established and further developed. Experimental investigation on nylon gears was also carried out and different failures have been found compared to acetal gears, such as gear root and pitch fractures. The most interesting observation from the experimental work is the significant difference in wear behaviour when running acteal against nylon gears, especially the low wear rate when acetal is used as the driver gear.

Influence of oil supply on the scuffing load-carrying capacity of hypoid gears

In industrial or automotive dip lubricated gear drives, low oil levels may be used due to different design requirements or constraints. A variation of the sump oil level affects different working conditions of gears, such as the power loss, the heat generation, and the load-carrying capacity with respect to different types of damage. In particular, reduced oil levels decrease the scuffing load capacity of gears because of high bulk temperatures and reduced oil quantity in the gear mesh. Investigations were made in a back-to-back hypoid gear test rig to evaluate the influence of the bath oil level on the scuffing load-carrying capacity of dip lubricated hypoid gears.

A new approach for polymer composite gear design

A new design method for polymer composite gear has been proposed in the current paper. This design method is based on the link between polymer gear wear rate and its surface temperature. It has been found from the tests that the polymer (acetal) gear wear rate will be increased dramatically when the load reaches a critical value for a specific geometry. The gear surface will wear slowly with a low specific wear rate if the gear is loaded below the critical one. The possible reason of the sudden increase in wear rate is due to the gear operating temperature reaching the material melting point under the critical load condition. Gear surface temperature has been then investigated in detail through three components: ambient, bulk and flash temperatures. Through extensive experimental investigations and modelling on gear surface temperature variations, a general relation has been built up between gear surface temperature and gear load capacity. The method has been related to test results under different operating ambient temperature and gear geometries. Good agreement has been achieved between the proposed method predictions and experimental test results. Experimental investigation on polymer composite (glass fibre reinforced nylon with PTFE as internal lubricant) gears have also been carried out and two forms of failure have been found, root and pitch fractures.

Acetal gear wear and performance prediction under unlubricated running condition

Tests have shown that the acetal gear wear rate will be increased dramatically when the load reaches a critical value for a specific geometry. The gear surface will wear slowly with a low specific wear rate if the gear is loaded below the critical condition. The sudden increase in wear rate may be due to the gear operating temperature reaching the material melting point under the critical load condition. Gear surface temperature has been investigated in detail by studying three components: ambient, bulk and flash temperatures. Through extensive experimental investigations and modelling on gear surface temperature variations, a general relation has been built up between gear surface temperature and gear load capacity. A new design method for acetal gear has been proposed based on the link between polymer gear wear rate and its surface temperature. The method has been related to test results under different operating ambient temperature and gear geometries. Good agreements have been achieved between the proposed method predictions and experimental test results. The maximum torque the acetal gears can transmit is 9 Nm for both the driver and driven with a 2 mm module, 30 teeth and 17 mm face width. Copyright © 2006 John Wiley & Sons, Ltd.

内接円筒面の面圧負荷能力

A pair of gears with the contact of concave and convex tooth surfaces, such as internal gears has a higher load capacity in comparison, with the contact of convex and convex tooth surfaces, because of its, smaller Hertz contact stress. But the experimental explanation of this problem has not yet been clarified. Surface durability of contact of concave and convex surfaces has been tested by the tworollers testing machine which is simulated for the contact of internal gear tooth profiles. The experimental results indicate that the surface durability of concave and convex rollers can be assessed by the Hertz contact stress on the whole, and so the internal gears have higher surface durability than those of external gears. Furthermore the surface hardening by the heat treatment and the accurate finishing of surface roughness have a great effect to improve the load capacity of gears with the contact of concave and convex tooth surfaces.

A Rating Formula for Fine Pitch Boundary Lubricated Gears

For the Instrument Engineer involved in the design of mechanisms that transmit power under boundary lubricated conditions, little information is available on which to base fine pitch gear load capacity and life. This paper discusses a gear test program and the development of a rating formula for the surface loading of these gears, and in particular those made from stainless steel and aluminum and stocked by precision gear manufacturers.