Being in the ground gear business, we are often asked by our customers about “quieter gears”.
The October 2014 issue of Power Transmission Engineering has a great article by Mark Findlay about the various effects that might cause “gear noise”. Interestingly, many of those reasons might NOT be gears.
Mark points to the preponderance of Electric Vehicles (EV) now being produced and on the road. EV’s are a type of vehicle that it is very easy to hear “gear noise” within, which really has brought this issue and challenge to the forefront.
Very often the first thing we think of when we have a noise problem is the gear sets. The next thing we do is to call the gear manufacturer, or gear engineering department, and tell them “we need to tighten the specs on those gears”, or “we need better ground gears”.
Not so fast, says Mark. “Old rules of thumb such as choosing overlap ratios, and different contact ratios, may be part of a movement away from these traditional approaches, again, thanks to the EV industry which has begun to take a much more “systems” approach to “quiet gears”.
On the way to taking a more “systems” approach to noise, the EV engineers, in addition to challenging some of the old accepted rules of thumb, like increasing helical gear helix angles, have actually discovered that the opposite direction may be the answer. In fact, there have been a number of designs that have actually gone back to the spur gear design and save money all along the value chain.
If you are interested in a little out of the “gearbox” thinking about gear noise, check out Mark’s article, entitled “Electric Vehicles Need Quieter Gears”.