How does a hand winch work?
A hand winch is a tool for moving a load both horizontally and vertically. The load is connected to the hand winch by a steel cable or a synthetic rope. A winch consists of a crank, a transmission, a drum, a cable, a brake and the housing. We will discuss all the parts in more detail in this blog.
The crank
Winches can be driven by, for example, an electro – hydraulic motor or by hand. With a hand winch, muscle power must be used to get the drum into a circular motion using a crank (read more about the difference between a hand winch and an electric winch here). Muscle power has a limiting factor, some people are stronger than others but there is a maximum. The average force a person can deliver for a few minutes without becoming severely exhausted is between 10 – 15 kg. In addition, a person can turn about 25 revolutions per minute without becoming severely exhausted. Therefore, all of Gebuwin’s hand winches have a maximum pendulum force of 15 kg. The average is 12 kg (at maximum load). This means that with our WW7500 hand winch, you can hoist 7.5 Fiat Pandas with only 15 kg of muscle power.
You can achieve more revolutions per minute if you adjust the crank at a shorter distance since less distance needs to be covered (watch the video how to do that here: https://youtu.be/MzqL8sBbUcY?t=53).
The transmission, speed and force
A difference exists between the force of a person and the desired lifting or pulling capacity of the hand winch. Therefore, a transmission must be used between the person (crank) and the drum. In some cases, no transmission is needed since a lever effect can convert enough force. Take for example our gear winch TL150, which has no transmission. This means that the crank is in direct contact with the drum.
The lever effect
The physical formula for this is force x arm = moment. The formula does not apply when there is no pivot point. In the picture on the right, see the different parts. In this example, the crank is the arm of the hand winch.
The force we apply to the pendulum is 100 Newton (+/- 10 kg). The maximum length of the pendulum is 0.325 meters. The moment realized by the force on the pendulum is 32.5Nm.
If you make the pendulum longer while maintaining the force then the moment increases. This is important to remember.
Is everything clear so far?
Now we know the moment that can be realized by applying muscle force on the pendulum. But we are not there yet, we are going to use the formula again since we want to know the force of the cable on the drum. In the example on the right, the blue circle is the drum of the hand winch.
Force –> the cable pulling on the drum (black line)
Arm –> the distance between the cable and the center of the drum (red line). The new arm is the radius (half the diameter) of the drum, which for the TL150 hand winch is 0.0175 m
The pivot point –> the center of the drum (yellow curved arrow)
What is the force now?
The formula can be used again, however the other way around since we already know the force released on the drum (32.5 Nm).
–> moment / arm = force
–> 32.5 Nm / 0.0175 m = 1857 Newton (+/- 185 kg).
The winch consists of about 20 parts, this means that there is also some play in this, which causes loss of force. So the TL150 can lift 150 kg with power loss (185 kg – power loss – 150 kg).
So the maximum lifting capacity which can be achieved with 10 kg of muscle power and a crank length of 325 mm is 150 kg of lifting capacity. Of course, the crank can be extended, but this in turn makes the hand winch less practical. Gebuwin therefore uses a transmission on hand winches that require a higher lifting capacity.
The speed – without gearing
The rotation speed of a winch without gearing is 1 to 1, since the crank is directly attached to the drum, as in our gear winch TL150. This means that one rotation of the crank produces one rotation of the drum. The speed involved is equal to the circumference of the drum. The circumference of the drum on the TL150 is 12 cm. A person can turn the pendulum an average of 25 times per minute, so this means a speed of about 3 m/min.
The speed on a hand winch with transmission is considerably lower, why this is so you will read further below.
The transmission
There are several different gears to use. Gebuwin uses with a hand winch, a gear and a worm gear transmission. Read more about the difference between a gear and worm gear winch here.
In this example, we are using a gear transmission. By engaging two gears of different diameters, a greater torque can be obtained at a lower rotation speed, or vice versa. With a small gear first and then a large gear, a higher moment can be obtained, vice versa a higher speed.
Since a person has a limited force and the standardization for hand winches prescribes a maximum force, we choose to use a smaller gear first to achieve a higher torque, however, this comes at the expense of speed. Depending on the size of the wheels, number of teeth and number of gears, a desired result can be obtained.
The speed of a winch with a transmission is lower since a transformation takes place. Suppose we use a gear ratio on the TL150 of 1 to 10. This means that 10 crank revolutions are required to achieve 1 drum revolution. This results in a speed of 0.30 m/min (the speed without gearing was 3 m/min). But this also means that the force a person provides on the pendulum a 10 kg can convert 10 times as much force. This means that a person can then lift a load of 1500 kg (note: this is a theoretical value, which does not take friction and thus force loss into account).
So the speed of the winch and the desired lifting capacity always affect each other. It is not possible to achieve both high speed and high lifting capacity on a hand winch. If this is desired, you need an electric winch. Read more about the difference between a hand winch and an electric winch here. A person can pull a heavier load with the same muscle power since there is no/less gravitational force. Read more about the difference between hoisting and pulling here.
The drum
The drum is a tube or shaft with a flange on each side. On the drum, the cable is secured with a clamp. The drum is positioned in the winch with a shaft that is fixed in the frame (housing) of the winch. The drum is connected to the large sprocket and this is connected to the small sprocket and then this in turn has a connection to the crank. The cable is wound up or down on the drum of the winch with a circular motion, causing the load to move horizontally or vertically, depending on the direction of the cable. When the crank is turned clockwise the load is lifted, counterclockwise it is lowered again.
The drum ensures that the cable is stored neatly. The amount of cable that can be stored on the drum depends on the height of the flanges, the length and diameter of the drum and the diameter of the cable used. We can of course adjust these dimensions so that the desired number of meters of cable can always be used.
The rope
Either steel cable or synthetic rope can be used on a hand winch. The cable or rope is an essential part of the winch as it allows the load to be connected to the winch. Watch a video on how the cable can be mounted on the drum here: https://youtu.be/MzqL8sBbUcY?t=7
The thickness of the cable is determined by the maximum lifting capacity of the winch. After all, the cable must be strong enough to hold the load. Cables used on winches must always have a safety factor (VF) of 3 (According to the EN13157 standard). This means that when a load of 500 kg needs to be lifted, the cable should only break at 1500 kg. This is called the minimum breaking load (MBL). When we do the MBL divided by the VF we get the safe working load or the working load limit (WLL) called (WLL = MBL / VF).
There is a difference between the length of the cable and the length that the load must be moved. In the example below, blue shows the length of the cable and yellow the length that the load must be lifted. Only the length that the load is to be lifted is wound on the drum. In extreme cases, this can also be as little as 1 meter while the length of the cable is 100 meters.
The lifting/pulling force of the winch decreases as more cable is wound onto the drum.
The brake
One of the most important components of the hand winch is the brake. Heavy loads are moved with hand winches. The brake ensures that when the crank is released the load remains stationary. When you want to lower the load again, you push the crank counterclockwise, actually pushing through the brake. Gebuwin hand winches use a load pressure brake. As the name implies, the load activates the brake mechanism. Therefore, without a load, there is no brake. Therefore, for a hand winch, it is important to always have a load of at least 20 kg hanging from the winch. This article goes into further detail about the brake mechanism of the winch.
The housing
The housing refers to a metal structure that is placed around all the components. In addition to holding all the components together, the housing also protects these components from weather conditions and use by people. The housing is constructed to withstand all forces released during lifting or pulling. To test the housing, we perform so-called breaking tests. We put a winch on a test rig and proceed as far as possible until the winch breaks. We analyze the results and adjust the house if necessary. A hand winch should always have a safety factor of 4. This means that if a hand winch is suitable for lifting a load of 500 kg, it will only break down at 2000 kg.
Of course, there are different finishes possible for hand winches, such as multiple coats of paint, galvanization or in full stainless steel. However, the winch must be well protected from weather conditions such as salt water. Read more about the possibilities here.
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