| Q. |
Why use a worm gear reducer? |
| A. |
A worm gear reducer is a right angle gear
solution that allows the maximum speed reduction in the smallest
package. |
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| Q. |
Why use a bevel gearbox? |
| A. |
A bevel gearbox is yet another right angle
gear solution but its efficiency is much higher than the worm
gear. If you need a right angle solution with a low ratio the
bevel gear is the right choice. |
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| Q. |
Why use helical gear reducer? |
| A. |
Helical gears are more efficient and capable
of handling higher OHLs. In-Line reducers are less expensive
than the more traditional parallel shaft but the parallel shaft
has more flexibility with more options. |
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| Q. |
When do you use a helical gear reducer versus
a worm gear reducer? |
| A. |
Worm gear reducers are used in low to moderate
horsepower applications. They offer low initial cost, high
ratios, and high output torque in a small package. They have
a much higher tolerance for shock loading then helical gear
reducers. Helical reducers are used in higher horsepower applications
where long-term operational efficiency is more important than
initial cost. |
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| Q. |
How is the ratio determined for a helical
gear set? A bevel gear set? A worm gear set? |
| A. |
The ratio of a helical or bevel gear set
is simply the number of teeth in the larger gear divided by
the number of teeth in the smaller gear. For example, a gear
set with 36 teeth in the larger gear and 12 teeth in the smaller
gear has 3:1 ratio.
The ratio of a worm gear set is the ratio of the number of
teeth in the gear to the number of threads (starts or leads)
on the worm. For example, a worm with two threads and a mating
gear with 60 teeth has a ratio of 30:1. |
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| Q. |
What is meant by the hand of drive? |
| A. |
The location of the output shaft of a reducer
relative to it's input shaft is called the configuration's
hand. It is generally referred to as right handed (J), left
handed (G) or left and right handed (H) if the output shaft
is double extended. |
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| Q. |
What are some of the advantages of ground
gears? |
| A. |
Some of the advantages of hardened and ground
gears are:
• less noise
• maximized efficiency
• higher load capacity
• correction of profile … longer life |
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| Q. |
What are two major reasons for premature
gear reducer failure? |
| A. |
Some of the most common causes for premature
failure of a reducer include improper selection for the application,
changing the motor horsepower or speed, incorrect alignment
of couplings, improper or insufficient lubrication, and lack
of regular maintenance. |
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| Q. |
How can you minimize the size of a major
drive component such as a motor and its reducer while maximizing
output torque capacity? |
| A. |
Introduce mechanical advantage or ratios
where possible.
Example: An application requires 700 in-lbs of torque at
90 RPM utilizing a 1HP 1750 RPM motor (36 in-lbs. of torque
generated from 1HP motor SCI)
Option 1 - 20:1 reducer with 720 in-lbs of output torque
capacity. 36 in-lbs X 20:1 ratio = 720 in-lbs capacity less
efficiency loss through reducer.
Option 2 - 10:1 gear reducer. 36 in-lbs X 10:1 ratio = 360
in-lbs capacity less efficiency loss through reducer plus
a 2:1 chain drive from reducer to drive shaft
Option 2 would be most economical because we are reducing
the gearbox size requirements (capacity needed) by half and
still mainating the application torque requirements at the
drive shaft with the use of the chain drive.
Note: The more HP or torque that the application needs to
transmit, the more money that can be saved by multiplying
torque through reducers and auxiliary drive components. |
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| Q. |
In what gearbox application would it be
advantageous to use a synthetic lubrication? |
| A. |
Most synthetic lubricants have lower pour
points, high oscillation resistance, and accept additives better
than their conventional petroleum equivalents. Therefore, a
gearbox in one of the following conditions would benefit from
the use of synthetic lubricants: hot or cold ambient temperatures;
heavy loads; continuous duty; or limited PM. |
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| Q. |
How to Balance Shock Load vs. Running Load? |
| A. |
It depends on the load demands and duty
cycle of your application. Is your load primarily frictional,
inertial, or a combination? Frictional loads tend to require
a small torque spike to start motion and a smaller relatively
constant torque to maintain it. Inertial loads typically require
high starting torques but low running torques. |
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| Q. |
What is backlash? |
| A. |
Backlash is the free-play between input
and output and is typically caused by movement of gear teeth
back and forth within tooth spaces, and results in lost motion
or error. |
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| Q. |
Are worm gear reducers "self-locking"? |
| A. |
A worm gear set is said to be self-locking,
or irreversible when the gear cannot drive the worm. This condition
is obtained, if the lead angle of the worm is less than the
friction angle, and as a consequence the efficiency for reversed
driving is zero. The friction angle for static conditions will
vary with such factors as surface finish and lubrication. Based
upon the generally accepted value of static coefficient of
friction equal to 0.15, the friction angle would be approximately
8°. However, the friction angle decreases rapidly with
the start of motion, also, vibrations from nearby sources quite
often upset the static condition of a locked set of gearing
a sufficient amount to reduce the friction angle to a point
where motion occurs, this is sometime called "stiction".
These unpredictable factors make it advisable to resort to
a brake rather than relying on the self-locking characteristics
of the worm gearing. |
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| Q. |
How hot does a speed reducer operate? |
| A. |
Under SCI conditions it is common for the
internal temperature to rise 100F above ambient. |
