In terms of the tooth thickness, should we use the formulation with
respect to normal or transverse coordinate system? When normalizing
this thickness in order to normalize the backlash (backlash parameter),
we should divide by the circular pitch. Thus, when normalizing, should
this circular pitch be defined in the normal or traverse coordinate
system, depending on which formulation has been used? Is the backlash
parameter always defined with respect to the tangential plane or
normal plane for helical gears?
This paper outlines the comparison of
efficiencies for worm gearboxes with
a center distance ranging from 28 -
150 mm that have single reduction from
5 to 100:1. Efficiencies are calculated using several standards (AGMA, ISO, DIN, BS) or by methods defined in other bibliographic references. It also deals with the measurement of torque and temperature on a test rig — required for the calibration of an analytical model
to predict worm gearbox efficiency
and temperature. And finally, there are examples of experimental activity (wear and friction measurements on a blockon- ring tribometer and the measurements of dynamic viscosity) regarding the effort of improving the efficiency for worm gear drivers by adding nanoparticles of fullerene shape to standard PEG lubricant
A best practice in gear design is to limit the amount of backlash to a minimum value needed to accommodate
manufacturing tolerances, misalignments, and deflections, in order to prevent the non-driving side of the teeth to make contact and rattle. Industry standards, such as ANSI/AGMA 2002 and DIN3967, provide reference values of minimum backlash to be used in the gear design. However, increased customers' expectations in vehicle noise eduction have pushed backlash and allowable manufacturing tolerances to even lower limits. This is especially true in the truck market, where engines are quieter because they run at lower speeds to improve fuel economy, but they quite often run
at high torsional vibration levels. Furthermore, gear and shaft arrangements in truck transmissions have become more complex due to increased number of speeds and to improve efficiency. Determining the minimum amount of backlash is quite a challenge. This paper presents an investigation of minimum backlash values of helical gear teeth applied to a light-duty pickup truck transmission. An analytical model was developed to calculate backlash limits of each gear pair when not transmitting load, and thus susceptible to generate rattle noise, through different transmission power paths.
A statistical approach (Monte Carlo) was used since a significant number of factors affect backlash, such as tooth
thickness variation; center distance variation; lead; runout and pitch variations; bearing clearances; spline clearances; and shaft deflections and misalignments. Analytical results identified the critical gear pair, and power path, which was confirmed experimentally on a transmission. The approach presented in this paper can be useful to design gear pairs
with a minimum amount of backlash, to prevent double flank contact and to help reduce rattle noise to lowest levels.
I would appreciate if you could assist with a gear failure (occurring)
after just seven weeks in service, post installation. This driving gear
wheel has been installed in a medium-speed engine with backlash
present at four different positions; with additional backlash checked on
the mating surfaces. All backlash was found within (OEM)-recommended values. Please note included photos - it seems that the crack has started at the root fillet. Any comments would be appreciated.
Here is some history that bears repeating - or at least re-reading. So take a few minutes to give it up for a long-gone Brit named Henry Maudslay
(August 22, 1771 - February 14, 1831) - also known as "A Founding Father of Machine Tool Technology." You might
also consider him an early leader in inspection, as he also invented the first bench micrometer capable of measuring to one ten-thousandth of an inch.