Design And Analysis Of Screw Jack Pdf

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Design, Development and analysis of electrically operated toggle jack using power of car battery

Power Screws Power screws are used to convert rotary motion in to translational motion. It is also called translational screw. They find use in machines such as universal tensile testing machines, machine tools, automotive jacks, vises; aircraft flap extenders, trench braces, linear actuators, adjustable floor posts, micrometers, and C-clamps. There are two kinds of power screws, hydraulic and mechanical power screws. A special case is screw jack which raises or lowers the load by applying a small force in the horizontal plane.

A screw thread is formed by cutting a continuous helical groove around the cylinder. These grooves are cut either left hand or right hand. The majority of screws are tightened by clockwise rotation, which is termed a right-hand thread. Screws with left-hand threads are used in exceptional cases.

For example, anticlockwise forces are applied to the screw which would work to undo a right-hand thread , a left-hand-threaded screw would be an appropriate choice. Power screws are typically made from carbon steel, alloy steel, or stainless steel and they are usually used with bronze, plastic, or steel mating nuts. Bronze and plastic nuts are popular for higher duty applications and they provide low coefficients of friction for minimizing drive torques. There are important terms and figures that need to be understood before designing power screws:.

Pitch: is the distance from a point on one thread to the corresponding thread on the next adjacent thread, measured parallel to the axial plane. Lead: is the distance the screw would advance relative to the nut in one rotation. For single thread screw, lead is equal to pitch. Helix Angle: is related to the lead and the mean radius by the equation below;. There are 3 types of screw threads used in power screws: 1.

Square threads: a. Is used for power transmission in either direction b. Results in maximum efficiency and minimum c. It is employed in screw jacks and clamps 2. Acme threads: a. It is a modification of square thread b. Efficiency is lower than square threads c. The slope increases the area for shear d.

It is easily manufactured. Buttress Thread: a. It is used when large forces act along the screw axis in one direction only. It has higher efficiency like square threads and ease of cutting like acme threads c. It is the most strong thread of all d. It has limited use of power transmission.

Screw Jack Design Procedure 2. Design Tools 1. Books 2. Websites 3. Stationary 4. Calculator 5. Laptop 6. Printer 2. Problem Statement A mechanical power screw that can raise or lower 7 tons or Different parts of the assembly such as the screw, the nut and the handle will be designed in an efficient and cost effective manner. Design Considerations 1. Factor of safety for the assembly is taken 5 due to the nature of the design.

Actually the factor of safety is taken 1. A higher factor of safety is considered due to the consequences of the failure. Selection of Material for the screw and nut is of great importance. There are common materials used in the design of screw jacks like steel for the screw and cast iron, bronze or plastic for the nuts. Mild steel or hard steel is considered for different screw designs. In order to prevent friction cast iron or bronze is preferred for the design of the nut.

Cup and frame are made of Grey cast iron which is cheap and has good mach inability. Material is selected as following: a. Screw: Plane carbon steel 30C8 IS: is selected because screw is always under Torsional, bending and axial load.

Carbon steel is chosen due to the strength issues. This steel is also used for the handle of the screw jack. In order to reduce the friction resistance between the screw and nut a softer material is selected for the nut.

Phosphor Bronze Grade 1-IS: is a proper material for nut construction because it acts very well against wear resistance and reduces torque to overcome friction.

Screw Jack Handle: Plane carbon steel 30C8 IS: is selected for the handle of the jack because of the high strength it offers.

Frame: Grey cast iron is used which is cheap and has good mach inability. The effective lifting height is chosen to be 0. Average coefficient of friction between the material soft steel and cast iron is taken 0. But for this specific design, it is taken 0. Limiting values for bearing pressure between steel and cast iron is taken According to agronomists the force of the hand is about to N.

In this design we assume that is the handle is rotated by two hands which give N hand forces for the design of the handle. Calculations 3. Design of the screw Procedure i. Core diameter of the screw is determined using allowable stress and the given load ii.

Using the core diameter, the rest of the diameters and the pitch will be determined. Torque will be determined using the mean diameter, coefficient of friction and the pitch iv. Principle stresses due to the shear and compression stresses will be studied v. The next available diameter is 35 mm. Now, it is time to study principle stresses due to the combined stresses compression and Torsional and see if they are in limit for safe dimensions.

Procedure i. Number of threads in engagement is found ii. Height of the nut is determined iii. Shear stress produced at the threads of the screw at the core diameter and at threads of the nut at the major diameter is studied.

The nut threads are subjected to crushing and shear. From the above result, crushing is not expected because crushing stress is much smaller than the bronze yield stress at compression. The screws are safe against the shear produced by the axial loading. Design of the handle. Note: If the length of handle is too large, an alternative is to place the handle centrally and apply the force. Buckling is studied when the load is compressive and the unsupported length between the screw and the nut is long.

When it is short, then it is assumed a column and buckling issue doesnt rise. If the critical load is more than the load we have then our design is safe and there is no chance of buckling.

There is no chance of buckling because the critical load is much greater than the design load which is If the screw friction and collar is friction is neglected, the efficiency of the system is calculated as below:. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd?

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Design & Fabrication of Human Hoist with Screw Jack for Mechanic

Power Screws Power screws are used to convert rotary motion in to translational motion. It is also called translational screw. They find use in machines such as universal tensile testing machines, machine tools, automotive jacks, vises; aircraft flap extenders, trench braces, linear actuators, adjustable floor posts, micrometers, and C-clamps. There are two kinds of power screws, hydraulic and mechanical power screws. A special case is screw jack which raises or lowers the load by applying a small force in the horizontal plane. A screw thread is formed by cutting a continuous helical groove around the cylinder.


Note 1. For detailed analysis of screw jacks and their systems consult Power Jacks. 2. Safety factor of for column strength's used for normal industrial cargo‚Äč.


Thesis on screw jack+pdf for case for christ study guide pdf

Authors : K. Saravanan Kumar. Abstract: Control screws are utilized to change overturning the movement into translatory movement. A screw jack is a case of a power fasten which a little constrain connected on a flat plane is utilized to raise or lower a huge load.

Power Screws Power screws are used to convert rotary motion in to translational motion. It is also called translational screw. They find use in machines such as universal tensile testing machines, machine tools, automotive jacks, vises; aircraft flap extenders, trench braces, linear actuators, adjustable floor posts, micrometers, and C-clamps. There are two kinds of power screws, hydraulic and mechanical power screws.

Without his help we would not have been able to complete our project. A Screw jack is a portable device consisting of a screw mechanism used to raise or lower the load. Proper size, strength and stability are essential requirements for the design of the screw jack from safety consideration. Assuming that a force of N is applied by a person intermittently, therefore length of handle required.

Journal of Engineering and Applied Sciences

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Udgirkar and M.

This paper describes the novel approach of Human hoist using power screw. Generally Automobile mechanic have to work under the car chassis and it becomes very painful to work under such situations. Though there are many inventions and mechanism to help the car mechanic to work in such situations, they are very costly.

A jackscrew , or screw jack , is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderately heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable supports for heavy loads, such as the foundations of houses. A screw jack consists of a heavy-duty vertical screw with a load table mounted on its top, which screws into a threaded hole in a stationary support frame with a wide base resting on the ground. A rotating collar on the head of the screw has holes into which the handle, a metal bar, fits. When the handle is turned clockwise, the screw moves further out of the base, lifting the load resting on the load table. In order to support large load forces, the screw is usually formed with Acme threads. An advantage of jackscrews over some other types of jack is that they are self-locking , which means when the rotational force on the screw is removed, it will remain motionless where it was left and will not rotate backwards, regardless of how much load it is supporting.

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Without his help we would not have been able to complete our project. A Screw jack is a portable device consisting of a screw mechanism used to raise or lower the load. Proper size, strength and stability are essential requirements for the design of the screw jack from safety consideration. Assuming that a force of N is applied by a person intermittently, therefore length of handle required. Considering bending effect, the maximum bending moment on the handle,. Assuming that material of the handle is same as that of screw, therefore taking bending stress.

Without his help we would not have been able to complete our project. A Screw jack is a portable device consisting of a screw mechanism used to raise or lower the load. Proper size, strength and stability are essential requirements for the design of the screw jack from safety consideration. Assuming that a force of N is applied by a person intermittently, therefore length of handle required. Considering bending effect, the maximum bending moment on the handle,. Assuming that material of the handle is same as that of screw, therefore taking bending stress. Since critical load is more than the load at which screw is designed I.

Screw Jack Design

Without his help we would not have been able to complete our project. A Screw jack is a portable device consisting of a screw mechanism used to raise or lower the load. Proper size, strength and stability are essential requirements for the design of the screw jack from safety consideration. Assuming that a force of N is applied by a person intermittently, therefore length of handle required. Considering bending effect, the maximum bending moment on the handle,.

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