Page 34 - Goodyear2011PTMaintenanceManual

Synchronous Belts
INSTALLATION GUIDE
34
FLANGED SPROCKETS
Use fanges to keep the belt in the sprocket and prevent “rideoff.”
As each belt has its own tracking characteristics, even belts with
perfect drive alignment can have a tracking problem. Synchronous
belts will have an inherent side thrust while in motion and can be
controlled with fanged sprockets. If side thrust is severe, check the
drive for sprocket alignment, parallel shafts, and shaft defection.
For a Two-Sprocket Drive:
A minimum requirement should be two fanges on one sprocket.
For economical reasons, the smaller sprocket is usually fanged.
When the center distance of the drive exceeds eight times the
diameter of the smaller sprocket, it is suggested that fanges be
included on both sides of each sprocket.
On vertical shaft drives, one sprocket should be fanged both sides
and one sprocket fanged bottom side only.
For a Multiple Sprocket Drive:
Two fanges are required on every other sprocket or a single fange
on every sprocket, altering sides.
MULTIPLE SPROCKET DRIVES
Multiple sprocket drives typically have one DriveR and two or more
DriveN sprockets. In these cases, it is acceptable to size the drive
based on the most severely loaded shaft. This is usually the DriveR
shaft since the load of all the DriveN shafts must be transmitted
through one DriveR shaft. Sprockets with a low belt wrap angle,
less than 60 degrees, and/or a low number of teeth in mesh, less
than six teeth, will not transmit full rated load and service life of the
belt will be reduced. The number of Teeth in Mesh, TIM, is equal to
(Belt Wrap in mm)/(Pitch in mm). Backside idlers can be used to
increase belt wrap (see Using Idlers in this section). For detailed
multiple sprocket drive design, contact a drive design specialist at
Veyance Technologies, Inc.
BEARING LOADS
On many drives, bearing life is a concern. Reducing the bearing
load will increase bearing life. Bearing loads can be reduced in
the following ways:
Calculate the belt tension instead of using the belt tensioning
tables. The tables are general and may specify higher belt
tension than is necessary on some drives. Contact your local
Goodyear Engineered Products Authorized Distributor to
assist in calculating actual belt tension requirements for your
drive.
Larger diameter sprockets will require less belt tension on any
given drive.
Always position the sprockets close to the bearings. This
positioning will reduce the effect of the “overhung” bearing load.
Be sure not to install a belt at less than the recommended
tension. A belt that is under-tensioned will have a reduced
service life.
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