Ever-Power Arrow manufactures hypoid gears with offsets, a far more common style produced by Arrow is the spiral bevel gear – an Arrow Gear specialty. Spiral bevel gears are used to transmit power between shafts that are typically at a 90-degree orientation to each other.
Ever-Power the spiral bevel gear is actually a hypoid gear, it is not always viewed as one because it does not have an offset between the shafts.
The teeth on spiral bevel gears are curved and have one concave and one convex side. They also have a spiral angle. The spiral angle of a spiral bevel gear is defined as the angle between the tooth trace and an element of the pitch cone, similar to the helix angle found in helical gear teeth. In general, the spiral angle of a spiral bevel gear is defined as the mean spiral angle.
Because spiral bevel gears do not have the offset, they have less sliding between the teeth and are more efficient than hypoids and produce less heat during operation. Also, one of the main advantages of spiral bevel gears is the relatively large amount of tooth surface that is in mesh during their rotation. For this reason, spiral bevel gears are an ideal option for high speed, high torque applications.
Spiral bevel gears, like other hypoid gears, are designed to be what is called either right or left handed. [Fig.1] A right hand spiral bevel gear is defined as having the outer half of a tooth curved in the clockwise direction at the midpoint of the tooth when it is viewed by looking at the face of the gear. For a left hand spiral bevel gear, the tooth curvature would be in a counterclockwise direction.
Ever-Power size range and capabilities for Spiral Bevel Gears are provided in the list below.
Maximum Pitch Diameter – 30”
Diametral Pitch – 1.5 – 48
Face Width – 5.0
Unground Tooth – AGMA Q9*
Ground Tooth – AGMA Q13