What are dryer gears and pinions, and why do you need to know about them? They play a critical role in the proper operation of your industrial dryer. This article introduces you to everything you need to know about dryer gears and pinions -- from types to wear to alignment to maintenance tips -- and how to keep them in tip-top shape so your dryer runs smoothly.
Helical gears are preferred over spur gears for large equipment because they require a smaller face width for the same horsepower rating.
On a spur gear, only one tooth is in contact with the surface at one time. In the case of a properly designed helical gear, overlapping occurs, and there is always a portion of tooth contact at the pitch line. In other words, before the engaged tooth loses contact, the next tooth is engaged. A term for this factor is the face contact ratio, which must be greater than one.
A helical gear also is smaller in face width, with less weight and less manufacturing cost than a spur gear when design conditions warrant its use. Another factor to consider is the thrust load applied to the pinion pillow blocks due to the fact that the teeth are cut at an angle (helix angle).
Many processors do not choose to employ helical gears because they consider them less forgiving and have to be kept in alignment more often. This is not really the case. A spur gear is more applicable on lower horsepower drives because, in order to maintain the proper contact ratio, the helix angle gets too large, increasing the gear cutting cost and thrust load.