Physics
Lab 1.16 Torque Wrenches
In this Lab we use a crude
torque wrench to tighten and loosen a nut.
Getting
Started
Carry out the experiment using the method illustrated in
the video presentation. See also the instructions below.
Record the data from the experiment in the table provided
and perform the calculations needed to complete the table.
Experiment
1.16.1 Torque Wrench
The purpose of this
experiment is to illustrate the operation of a torque
wrench in tightening and loosening nuts and bolts.
Materials and Equipment
- Nut that can be
tightened and loosened. A wheel nut on a car may
be suitable.
- Wrench
- Pipe that fits over
the wrench to extend its length.
- Wire to attach a
spring balance to the pipe
- Spring balance –
2000g
Procedure
- Loosen the nut to be
used in the experiment
- Remember
to tighten the nut correctly after the experiment.
- Attach the wrench and
place the pipe on the wrench to extend its length
- Fix a piece of wire
to the pipe to connect the spring balance to the
pipe.
- Measure the distance
from the center of the nut to the point at which
the spring balance is connected to the pipe.
- If the stud or bolt
that the nut is attached to is in a horizontal
position, measure the force needed to support the
pipe and wrench without applying any torque to
the nut.
- Subtract this from
the spring balance reading obtained in Step 7
below before calculating the torque.
- Use the spring
balance to pull the pipe in a clockwise direction
until a predetermined reading is obtained on the
spring balance.
- Calculate the torque
as outlined below.
- Move the wrench to
the opposite side of the nut and repeat the
procedure to determine the torque needed to
loosen the nut. Remember to account for the
weight of the wrench and pipe if necessary.
- Repeat the experiment
by attaching the spring balance to a different
point on the pipe – or use a longer or
shorter pipe.
- Record the results in
the table below and calculate the torque values
needed.
Calculations
For each spring balance
reading recorded, subtract the weight of the pipe and
wrench if necessary and calculate the torque by
multiplying the force applied by the distance to the
center of rotation.
Results
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Description of action on
nut
(Tightening
or loosening)
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Distance from center of
nut to spring balance
(m)
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Weight of pipe and
wrench
(with
no torque)
(N)
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Spring balance reading
(N)
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Torque applied
(N-m)
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| 1 |
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| 2 |
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| 3 |
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| 4 |
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| 5 |
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| 6 |
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Discussion
When a nut is tightened,
friction holds it in place. Static and dynamic friction
come into play
Once a nut starts to move,
it takes less torque to keep it moving for a very short
time. Tightening the nut increases the force between the
surfaces and so the torque increases as the nut is
tightened.
The torque also changes
because the surfaces between the threads are not perfect.
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