Mechanical Design of Machine Elements by Graphical Methods

Frontmatter

Chapter 1. Torque

Abstract

Estimating torque is necessary during design of rotating elements such as gears, pulleys, shafts, etc. In this chapter, we introduce a graphical method for easy estimation of torque.

Majid Yaghoubi, Hamed Tavakoli

Chapter 2. Hertzian Contact Stress

Abstract

When two elements with curved surfaces make contact with each other and are pressed together, contact stresses (also called Hertzian contact stresses) are developed within the contact areas. Theoretically, the contact is either a point (when at least one of the elements is a sphere) or a line (when at least one of the elements is a cylinder). High contact stresses may lead to failures such as cracks, pits and flaking in the surface material. In this chapter, we only consider the line contact as it is more common and present graphs to simplfy designing of it.

Majid Yaghoubi, Hamed Tavakoli

Chapter 3. Press-Connect Joints

Abstract

Joining elements through press-connect creates durable and permanent connections that can transmit large and abruptly applied loads or fluctuating forces. Since this kind of joining does not require any connecting parts such as keys and consequently any keyways or grooves in which the stress concentration occours, it has a high design strength (operational strength). In this chapter, we present graphs that simplify the press-joint design.

Majid Yaghoubi, Hamed Tavakoli

Chapter 4. Welded Joints

Abstract

Welded joints are one of the most common types of permanent joints. Main welded joint designs are butt, lap, T-, edge and corner joints. Basically, there are two types of weld seams; butt welds, which are used to connect elements within a plane and fillet welds, which are used to join components in different planes. The calculations of welded joints are typically very time-consuming. However, in this chapter we provide diagrams that facilitate the calculations. Here, we only focus on fillet welded joints.

Majid Yaghoubi, Hamed Tavakoli

Chapter 5. Bolts

Abstract

A bolt is a threaded fastener that is a type of detachable joints. They are fundamental machine components as they facilitate manufacturing, assembly, disassembly, replacement and maintenance of different machine elements. One of the most time-consuming calculations in designing machine elements is related to bolts. In this chapter, we try to simplify the calculations regarding design of bolt by applying a graphical method.

Majid Yaghoubi, Hamed Tavakoli

Chapter 6. Power Screws

Abstract

Power screws are elements used for converting rotary motion to linear motion in machines. There are three forms of power screw threads: the square thread, the Acme thread, and the buttress thread. Power screws may also be either single-thread or double-thread or triple-thread. In this chapter, we only consider power screws with the Acme threads and provide unique graphical methods for designing them.

Majid Yaghoubi, Hamed Tavakoli

Chapter 7. Shafts

Abstract

A shaft is an important machine element that transmits rotational power and/or motion. Components such as gears, pulleys, flywheels, cranks, sprockets and couplings, are mounted on or attached to the shaft in order to perform the transmissions. Shaft design involves specifying suitable dimensions for the shaft that ensure its satisfactory and safe operation. The design process must consider the design of the mounted elements simultaneously. Because the elements are interdependent. Therefore, as a first step in the process of designing the shaft system, a rough estimate of the shaft is done. Then, after designing the mounted elements, a precise design of the shaft can be performed. This chapter presents graphical methods for the shaft design.

Majid Yaghoubi, Hamed Tavakoli

Chapter 8. Rectangular Keys

Abstract

A key is a detachable component used to connect a shaft and the hub of a power-transmitting element, which enables transmission of torque and power between them. Rectangular keys, also called flat keys, are usually used for large shafts and are also recommended for small shafts where the shorter key height can be tolerated. Designing the key includes determining its dimensions (height, width and length) according to the transmitted torque and the shaft diameter. In this chapter, three methods are presented for designing rectangular keys.

Majid Yaghoubi, Hamed Tavakoli

Chapter 9. Splines

Abstract

Splines are a series of keys machined on outside of a shaft, with corresponding grooves machined on inside of hub of a power transmitting element. The same as keys, splines are used to provide a joint connection between the hub and the shaft for torque and power transmission. However, they are typically used in applications in which a high torque needs to be transmitted. Crushing on the working surface is the potential failure mode for a spline. Therefore, the design is usually based on the bearing strength of spline. In this chapter, we propose a graphical method for designing splines.

Majid Yaghoubi, Hamed Tavakoli

Chapter 10. Conical Joints

Abstract

Conical joint refers to a connection in which the shaft and hub are conical (in fact conical frustum) at the joint interface. The connected elements are pressed together by means of a bolt so that the torque and power can be transmitted by friction. This chapter deals with estimating the maximum torque that can be transmitted solely by a conical joint. In addition, the suitable bolt size for fastening the hub and shaft is determined.

Majid Yaghoubi, Hamed Tavakoli

Chapter 11. Couplings

Abstract

Couplings are components used to connect two shafts at their ends, in order to transmit power and torque between two separate devices. The driving shaft usually transfers rotary motion from a power-generating device such as a motor or engine. While, the driven shaft is commonly the input of a transmission or a driven machine. In the industry, different couplings are used. The aim of this chapter is to partially compare the transmission of torque by the couplings using a graphical method.

Majid Yaghoubi, Hamed Tavakoli

Chapter 12. Flanged Couplings

Abstract

Flanged couplings are kind of rigid connections that are used to mate rotating shafts and transmit torque and power between them. They are applied when no relative motion should occur between the driving and driven shafts and an accurate shaft alignment is required. In the coupling, the flanges are connected to the ends of the shafts usually by keys and are attached together using a series of bolts on a bolt circle. In this chapter, a graphical method is proposed for designing flanged couplings in a facilitated manner.

Majid Yaghoubi, Hamed Tavakoli

Chapter 13. Universal Joints

Abstract

Universal joints (U-joints), also known as Cardan joints, are flexible couplings used to mate shafts, which are misaligned (at angles greater than 3º). This chapter presents a graphical method for designing U-joints.

Majid Yaghoubi, Hamed Tavakoli

Chapter 14. Pin Joints

Abstract

Pins are simple and inexpensive components used to join and fasten machine elements together. They are usually employed when low to medium torques are to be transmitted. Different types of pins with different functions are available. However, in this chapter we only discuss shear pins, Clevis pins and Dowel pins. Pins are generally subjected to bending, crushing, and shearing stresses. All these stresses must be taken into account for their design. This chapter deals with designing pin joints using our proposed graphs.

Majid Yaghoubi, Hamed Tavakoli

Chapter 15. Shafts and Their Associated Elements All Together

Abstract

The common method for designing a machine, is that each component is designed separately, and then they are assembled. Especially for the power transmitting elements, which are associated with each other, this is a very time consuming process. In this chapter, we propose a method to design and calculate shafts and their attached components all together. The method is on the basis that if the shaft diameter is known, some of the associated elements such as welding, splines, keys, joints, couplings etc. can be designed accordingly.

Majid Yaghoubi, Hamed Tavakoli

Chapter 16. V-Belts

Abstract

V-belts are flexible elements that are used to transmit power and motion between shafts, which have a relatively long distance from each other. There are several types of V-belts, however, in this chapter we only discuss the normal (or standard) and narrow-section V-belts. This chapter deals with introducing our proposed graphical method for designing V-belts.

Majid Yaghoubi, Hamed Tavakoli

Chapter 17. Timing Belts

Abstract

Timing belts perform power and motion transmissions by means of teeth that are on the underside of the belt. Timing belts with different tooth profile shapes are available. In this chapter, we only discuss design of trapezoid and High Torque Drive (HTD) types. Design of timing belts includes determining the size of tooth pitch (in other words the belt type) and belt width. In this chapter, for simplicity, rather than using equations, we propose a graphical method for the design.

Majid Yaghoubi, Hamed Tavakoli

Chapter 18. Chain Drives

Abstract

A chain drive is a common type of flexible drives. It is used for power transmission between shafts that are relatively far from each other. A chain drive includes a driving sprocket, a driven sprocket and a chain loop. Chain drives are typically employed for low to moderate speeds, high torque transmission, and applications in which precise speed ratios must be maintained. The design of chain drives usually includes determining size of chain (pitch), the chain type, number of strands, and the teeth number of sprockets. In this chapter, we propose a graphical method for designing chain drives.

Majid Yaghoubi, Hamed Tavakoli

Chapter 19. Spur and Helical Gear Drives

Abstract

Gears are toothed wheels that are widely used for power and motion transmission between rotating shafts. Based on the relative position of the shafts, gear drives can be fell into three principal categories, namely parallel-shaft gear drives, intersecting-shaft gear drives, and crossed gear drives. Parallel-shaft gear drives are the most common type of drives, because they are simples. Among them, spur gears and helical gears are more popular. This chapter deals with designing spur and helical gear drives. Gearings design requires using complex diagrams and many trials and errors. However, in this chapter, we propose methods that give very good approximations and easy calculations for the design.

Majid Yaghoubi, Hamed Tavakoli

Chapter 20. Bevel Gear Drives

Abstract

Bevel gear drives are used to transmit or transfer power or motion between intersecting shafts. The teeth of bevel gears are machined on conical surfaces. There are two primary types for the teeth of bevel gears, namely, straight and spiral. In this chapter, we propose methods for designing straight and spiral bevel gears in a simple way.

Majid Yaghoubi, Hamed Tavakoli

Chapter 21. Wormgear Drives

Abstract

Wormgear drives are used to transmit power and motion between shafts whose axes are neither parallel nor intersecting. A worm gearset is composed of a worm that resembles a power screw, in mesh with a wormgear having a similar appearance as a helical gear. Worm gearing are often used for applications in which the speed ratios are quite high (up to 360). In this chapter, we introduce graphical methods for easy design of worm gear drives.

Majid Yaghoubi, Hamed Tavakoli

Chapter 22. Rolling Contact Bearings

Abstract

Rolling contact bearings are machine elements that are most commonly designed to support rotating shafts. One of the most important characteristics of rolling bearings to be specified is their bearing life. To determine the variable, the forces applied to the bearings should be calculated. This needs a good knowledge of statics and referring to manufacturers’ catalogs, which is a time-consuming process. Instead, in this chapter we propose graphical methods for easy estimation of the bearing life and subsequently the tolerance.

Majid Yaghoubi, Hamed Tavakoli

Chapter 23. Hydraulic Systems

Abstract

In some machines, hydraulic systems are used to transfer power and move some parts. In the hydraulic systems, a pump pressurizes a hydraulic fluid and sends it through hydraulic tubes to actuators (hydraulic motors and cylinders). There, the fluid’s pressure is applied to move the parts or hold them in their position. Then, the fluid is moved through a filter, back to the pump, where it is pressurized again. The main advantage of hydraulic systems lies in their compactness and high efficiency. In this chapter, we only discuss simple hydraulic systems that have hydraulic cylinders.

Majid Yaghoubi, Hamed Tavakoli