JACKS

Jacks are used to raise or lower work and heavy loads short distances. Some jacks are used for pushing and pulling operations. Others are used for spreading and clamping operations. In this lesson, you will learn about different types of jacks and their uses. You will also learn how to select the right jack for the job, use various types of jacks, and provide the proper care of jacks to keep them in good working condition.

When you have completed this chapter, you will be able to do the following:

• Identify the different types of jacks.
• Determine the proper uses of jacks.
• Recognize the safety precautions that apply to jacks.
• Determine the proper care of jacks.

JACKS

Types and Uses

 Screw Jacks

 Vertical screw jacks come in several capacities and different lowered and raised heights. The screw moves up or down, depending on the direction the handle is turned. These jacks are used for many different purposes.

Screw jacks can be used to lift vehicles. They can also be used to raise heavy crates, small buildings, or other items too heavy to be raised by prying with wrecking bars.

 
Vertical bell base screw jack.

The vertical bell base screw jack is operated by hand using a steel bar handle which is inserted in the holes of the top housing or head.

Vertical screw jack with collapsible handle

The vertical screw jack with collapsible handle is operated by hand using the collapsible handle which is inserted into a socket.

Outrigger jack

Another type of screw jack is called an outrigger jack. The outrigger jack is equipped with end fittings which permit pulling parts together or pushing them apart.

Ratchet Lever Jacks

Vertical ratchet lever jack

A vertical ratchet lever jack has a rack bar that is raised or lowered through a ratchet lever. Some vertical ratchet lever jacks are equipped with a double socket. One of the sockets is used to lower the jack, while the other is used to raise the jack. Other vertical ratchet lever jacks are built with one socket and an automatic lowering feature.

An outrigger ratchet jack is ratchet-operated and has an extra reverse ratchet handle and a base plate.

Hydraulic Jacks

Hydraulic jack

Hydraulic jacks operate by applying pressure to one side of a hydraulic cylinder which in turn moves the jack head. Hydraulic jacks are lowered automatically by releasing the pressure on the cylinder. Vertical hydraulic jacks come in a variety of types, in capacities from 3 to 100 tons, and have different extended heights.

Porta power jack

A push-pull hydraulic jack, also referred to as a porta power jack, consists of a pump and ram connected by a hydraulic or oil hose. These jacks are rated at 3-, 7-, 20-, 30-, and 100-ton capacities and have many different applications.

The push-pull hydraulic jacks are furnished with an assortment of attachments that enable pushing, pulling, lifting, pressing, bending, spreading, and clamping operations. The pump is hand operated. The control valve on the side of the pump is simply turned clockwise, while the hand lever is stroked up and down to extend the ram. The flexible hydraulic or oil hose allows the user to operate the ram from a safe distance and in any desired position.

The ram retracts automatically by turning the control valve counterclockwise. The attachments can be threaded to the end of the plunger to the ram body or into the ram base.

Airframe (tripod) jack

Airframe jacks are used for lifting an entire aircraft off the ground or deck. Airframe jacks are commonly called tripod jacks. The jacks may also be called wing, nose, fuselage, and tail jacks. These names come from the jack placement on the aircraft.

There are two different types of tripod jacks�fixed height and variable height. Both are mobile, self-contained, hydraulically operated units. They consist of three basic assemblies; the hydraulic cylinder, the tubular steel wheel tripod leg structure, and the hydraulic pump.

Service or shop jack

Service or shop jacks (Figure 8) are used for lifting heavy vehicles for maintenance or repairs. Each jack is rated for different loads ranging from 2 to 20 tons. The long handle is used to pump the hydraulic cylinder to lift the lifting arm and saddle. Wheels and casters allow the jack to move to compensate for the lifting arc.

Using a Vertical Screw Jack

The following steps describe how to use a vertical screw jack properly:

1. Identify the lifting location on the item.
2. Place the jack on a solid surface.
3. Insert the handle (Figure 1) in the appropriate location and turn the handle to raise the jack (Figure 2). Typically, the handle is turned clockwise to raise the jack and counterclockwise to lower.
4. The jack will raise the load with every degree of hand turn.

5. Insert blocks or jack stands to support the load to remove the jack.
6. Screw the jack all the way down in the lower housing and withdraw the handle or bar for storage upon completion of the job.

Using a Hydraulic Jack

The following steps describe how to use a hydraulic jack properly:

1. The operator should become familiar with the jack, its capabilities, and its operations.
2. Identify the lifting location on the item and position the jack (Figure 3).
3. Place the jack on a solid surface.
4. To raise a load, pump the handle of the jack (Figure 4) using smooth, full strokes.

5. Insert blocks or jack stands to support the load to remove the jack.
6. to lower a load, slowly turn the handle counterclockwise to lower the load to the ground.

Care of Jacks

Use the following guidelines when working with jacks:

• Keep fingers away from all moving parts.
• Be aware of the capabilities of the jack, especially its load capacity.
• Overloading can be hazardous to the jack, the operating personnel, and the load in event of jack failure.
• Inspect all jacks prior to use.
• Coat all surfaces with a thin film of light oil when not in use. When storing for long periods, apply a rust-preventive compound and store in a dry place.
• Make certain that hydraulic jacks are filled with oil and that there are no visible oil leaks before use.
• Periodically check the hydraulic fluid level in hydraulic jacks. Make sure the ram is in the retracted position when checking the level of oil and when filling.
• Ratchet lever jacks should be well greased. A thin coat applied by hand or a brush is sufficient for all movable parts except the bushings. The bushings should be filled with grease in the small hole provided for greasing purposes. Keep rack sides and front greased, but do not grease the rack teeth.
• When jacking up vehicles, make certain no one is under the vehicle to be raised. Set the hand brake firmly and block the front wheels if a rear wheel is being changed. Block the rear wheels if a front wheel is being changed. Place blocking or other supports under the vehicle when it is raised to the desired height to prevent it from dropping if the jack fails.

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REVIEW QUESTIONS

1. The screw jack can be used to raise heavy crates, small buildings, or other items too heavy to be raised by what means?

A. Hoisting with a crane

B. Hoisting with slings

C. Lifting with a forklift

D. Prying with wrecking bars

2. Which of the following jacks is another type of screw jack?

A. Inboard

B. Outrigger

C. Push-pull

D. Porta power

3. What type of jack operates through pressure applied to one side of a cylinder?

A. Bell base

B. Hydraulic

C. Ratchet

D. Screw

4. A push-pull hydraulic jack is also referred to as what name?

A. Inboard

B. Outrigger

C. Push-pull

D. Porta power

5. On a push-pull hydraulic jack, the pump is operated by what means?

A. Electric motor

B. Hand

C. Hydraulic motor

D. Pneumatic motor

6. Tripod jacks are used to lift what item off the ground?

A. Aircraft

B. High-lift truck

C. Ship

D. Tank

7. Before using a jack, what is the first step the operator should accomplish?

A. Become familiar with the jack, capabilities, and operation

B. Clean the lifting point

C. Grease the jack wheels

D. Paint the lifting point

8. When selecting the proper jack, what capability should the operator consider?

A. Lifting height

B. Lifting speed

C. Load capacity

D. Load stability

9. Before using a jack, the operator should perform what action first?

A. Apply oil to the surface

B. Clean the wheels

C. Inspect the jack

D. Paint the rusty areas

10. Coat all jack surfaces with a thin film of what substance when not in use?

A. Grease

B. Light oil

C. Soap

D. Wax

11.At what interval should the hydraulic jack fluid level be checked?

A. Before each shift

B. Periodically

C. Quarterly

D. Annually

12.When checking the fluid level in a hydraulic jack, the ram should be in what position?

A. Quarter retracted

B. Half extended

C. Extended

D. Retracted

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