Free Gear Research Articles

ДОСЛІДЖЕННЯ ПЕРЕДАТНИХ ВІДНОШЕНЬ ПЛАНЕТАРНИХ ПЕРЕДАЧ ПІДЙОМНО-ТРАНСПОРТНИХ МАШИН

Lifting and transporting machines (PTM) are one of the important equipment for the mechanization of work in various spheres of the national economy. In addition to the multi-rescue system, the cargo lifting mechanism also includes a winch. Winches with one drum, which have standard parameters - traction force from 3.2 to 125 KN at rope speed from 0.5 to 0.1 m/s, are most often used in PTM. Such winches include a two-stage gear reducer that connects the electric motor with the drum. Such a winch drive scheme is quite large and has considerable weight. One of the areas that will help reduce these indicators is the use of planetary gearboxes. They allow the use of winches in which the electric motor and gearbox are coaxial, and the planetary gearbox itself can be mounted in the drum. Such a drive scheme of the load lifting mechanism allows to reduce the dimensions and weight of the winch. The paper considers the calculation and compares the transmission ratios of planetary gears, which are used and can be used in lifting and transporting machines to reduce the dimensions and weight of cargo lifting mechanisms. Schemes of simple and closed planetary gears, as well as a scheme with three central gears, are given. The scheme of the planetary transmission with free gear wheels is considered. The presence of internal gears and several satellites makes planetary gears compact and light in weight. AII transmission with two internal gears and a free carrier allows to obtain significant transmission ratios with a small number of gears. Schemes of planetary gears with free gears allow you to change the angular speed of the output shaft.

Reducing discards without reducing profit: free gear choice in a Danish result-based management trial

The 2013 Common Fisheries Policy introduced a landing obligation on a range of species, bringing more focus on the full accountability of all catches. To investigate the potentials and challenges of these paradigm shifts, a 6-months ‘unrestricted gear’ trial was performed in Denmark in 2015. Twelve trawlers were challenged to test their own solutions to reduce unwanted bycatch and/or choke species, while maintaining profitable. The participating fishers tested different options depending on their fishery and the type of issues they faced individually, and adjusted their test fishery over time through incremental small steps. Nine vessels reduced discard ratio in the test fishery, one showed no difference between test and control fishery, while two vessels displayed an increase in discard ratio. Catch compositions also differed, with fewer “choke species” occurring in the test fisheries and a more valuable size composition. Ultimately, despite smaller landings in multiple vessels, no vessel showed reduction in value-per-unit-effort (VPUE) and one Baltic vessel significantly increased the VPUE. This trial showed that relaxing technical regulations combined with proper incentives has a potential to provide some flexibility to cope with the landing obligation, where unwanted catches could be reduced to some extent without negative effects on economic viability.

An investigation of cutting edge failure due to chip crush in carbide dry hobbing using the finite element method

The aim of this research is to investigate a type of failure of dry carbide hobbing that occurs when the generated chips are pinched and crushed between the hob cutting edge and the work gear tooth flank by utilizing the finite element method. This problem is of great importance because gear hobbing is extensively used in the manufacturing industry. Many machine tool manufacturers have so far developed dry hobbing techniques using carbide hobs as there is a growing acknowledgment that it is necessary to employ carbide hobbing for higher productivity and pollution free gear cutting. To meet the increasing needs of cost reduction and environmentally friendly methods, dry hobbing being employed for gear mass production has completely eliminated the need of tool cooling. However, carbide hobbing has not come into wide use due to the high cost of carbide hobs, and mainly due to the unexpected chipping of the brittle carbide material, making it difficult to control the tool service life. Dry hobbing often causes problems such as chipping of the carbide hob tooth and/or damage of the surface finishing when the generated chips are pinched and crushed between the hob cutting edge and the work gear tooth flank. A manufacturing case of helical gears is taken as a case study, and it was simulated using a coupled thermomechanical rigid viscoplastic FEM analysis. Simulations have successfully identified a chip crush between four adjacent generating positions and thus, a definite mechanism that cause chip crush is revealed. Furthermore, valuable insights during chip formation, i.e., stress, strain, strain rate, temperature gradients, etc., are also provided.

Carbon/chromium low friction surface coating for gears application

Purpose – Provide tribological information about the applicability of multi‐layer carbon‐chromium composite coatings to gears. Discuss the protection provided against scuffing failures, wear and the influence on gear power losses.Design/methodology/approach – Several screening tests, such as Rockwell indentations, ball cratering, pin‐on‐disc and reciprocating wear tests, were performed in order to evaluate the adhesion to the substrate and the tribological performance of the carbon/chromium composite coating. Afterwards, twin‐disc tests were performed at high contact pressure and high slide‐to‐roll ratios to confirm the good adhesive and tribological properties of the coating under operating conditions similar to those found in gears. Gear tests were performed in the FZG machine in order to evaluate the anti‐scuffing performance of the carbon/chromium coating using additive free gear oils. Finally, the carbon/chromium composite coating was also applied to the gearing in a gearbox and its influence on the ...

Vibratory Response in Helical Gear Cystem. 1st Report, Analysis of Mesh Exciting Force.

This paper presents analytical study of gear mesh exciting force that causes the vibrations of the helical gear systems and resulting gear noise. In equation of one degree of freedom for rotational vibration, displacement and tooth stiffness are separated into mean and fluctuating components. As the result, mesh exciting force is shown to be a composite of exciting force due to tooth stiffness variation and that due to tooth surface error. Then a simplified method to calculate mesh exciting force is proposed. This method uses tooth stiffness of error free gear in order to eliminate computational effortS. For validation, gears with modified tooth surface are run in the gearbox. The calculated mesh exciting force shows good correlation with the measured acceleration of the gearbox housing, and also shows good correlation with the mesh exciting force identified by shaking test.

Simplified sound reproducing device of random selecting type

A simplified sound reproducing device for randomly selecting recordings to be reproduced, having a free gear formed with one or more intermittent tooth portions with tooth crest in the direction of rotation longer than that of other normal teeth. The gear system which includes this intermittent tooth portion is constructed such that this portion can contact any one gear tooth among other normal teeth of the mating gear in the gear system including the free gear and a center gear disposed at the center of the record disc. When the swing arm approaches the end point of sound reproduction at the urging of pickup, the free gear can engage the center gear. A cam member is interposed between the record disc and sound transmitting member. The cam member has two cam pieces axially stacked one on another such that the total length of the cam member can be lengthened when the two pieces are twisted. One upper piece 7 is capable of engagement with the free gear. When the free gear abuts the crest of tooth of a gear tooth in the mating gear of the gear system in the device and stops rotation against the driving force imparted by the center gear upper cam piece also stops resulting in elongation of the cam member. Because the location of the intermittent tooth portion is unpredictable with regard to the phase of rotation of the record disc the timing for initiating twisting action in the cam member which releases the stylus force is also made random.