Spiral bevel gearboxes are often
selected for continuous running applications due to their high efficiency
ratings up to 96%. However, in low ratio configurations, the input and
output shafts will be running at higher speeds resulting in greater heat
generation. A properly sized gearbox will be able to dissipate the heat
effectively and the temperature will stabilize to an acceptable level.
While there are several factors
that impact the gearbox temperature, two important considerations are the input
running speed and mounting orientation. These two criteria will help to
determine if minor adjustments can be made to the gearbox during assembly to aid
heat dissipation. Adjustments can be made to the backlash, bearing
pre-loads, lubrication (volume/viscosity), and a vent filter or oil cooling
system may ultimately be required. Spiral bevel gearboxes that cannot be
adjusted may not be suitable for continuous running applications.
The chart above graphs the
housing temperature of a V-Series gearbox (blue-dash) and a competitive spiral
bevel gearbox (red-dotted) of comparable size. Both gearboxes were 1:1
ratios and tested at a continuous input speed of 1,800 RPM for 2 hours.
Because the V-Series gearbox (blue-dash) was sized and assembled for the
continuous application, it was able to dissipate the heat properly allowing the
temperature to stabilize to an acceptable value of approximately 80°C.
The competitive spiral bevel gearbox (red-dotted) could not dissipate the heat
and the gearbox temperature continued to rise to 140°C before the test was
terminated to avoid eventual failure.
To help prevent a spiral bevel
gearbox from failing due to overheating, it is important to specify the duty
cycle, input running speed, and mounting orientation. Those criteria are
specified in GAM's V-Series type code to help ensure the gearbox is ordered and
assembled to best suit each application.
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