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Suspension systems
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
In the study of mechanics a parallel motion mechanism is an arrangement for constraining a point to move in a straight line. Two such mechanisms are known as the Watt and the Scott-Russell linkages, so-named after James Watt and F. Scott-Russell, who invented them in the 18th and 19th centuries respectively for use on steam engines. Our interest in these historic mechanisms is concerned with their application to live and dead axle rear suspension systems, and their ability to provide accurate sideways control of vehicle body and axle motions.
Applications of mechanical systems and technology
Published in Alan Darbyshire, Charles Gibson, Mechanical Engineering, 2023
Alan Darbyshire, Charles Gibson
Two of the most common mechanisms are the slider-crank and the four-bar chain and we have given these some consideration in Chapter 2. Closely related to these are the slotted link and Whitworth quick-return motion and Watt’s parallel motion. When a mechanism is required to transmit power, the various links and joints have to be designed, with an appropriate factor of safety, to carry the forces to which they will be subjected. The mechanism, or a series of linked mechanisms, is then classed as a machine.
A ‘revolver’ evolving: the careers of a Boulton & Watt rotative steam engine at the Whitbread Brewery, London and the Powerhouse Museum, Sydney, 1784–2020
Published in The International Journal for the History of Engineering & Technology, 2020
David Philip Miller, Debbie Rudder
So what were the key features of the design? All their rotative engines had the separate condenser, of course. Many, including the Whitbread engine, had the sun-and-planet system for producing rotary motion. The governor was not featured on the initial version of the Whitbread engine but was added not long after the device was developed in 1788. Watt’s system of ‘parallel motion’ was not on the June 1784 drawings, but was included on the revised ones issued in November that year. It replaced the original arch head and chain arrangement to transfer motion between piston rod and beam, and also to move the plug rod. The parallel motion was not really needed until engines were made double-acting, with steam injected alternately above and below the piston. But Watt considered it a beautiful piece of mechanism – one of his greatest achievements – and seems to have decided to incorporate it in the Whitbread engine even though it was not strictly necessary, except perhaps to ‘future-proof’ the machine.16
Normal contact stiffness identification-based force compensation for a hardware-in-the-loop docking simulator
Published in Advanced Robotics, 2018
Qian Wang, Chenkun Qi, Feng Gao, Xianchao Zhao, Anye Ren, Yan Hu
Serial robots are widely used in many space tasks, their main advantage is the large workspace. They also have a big drawback, where the stiffness is weak and varies with different poses. This can cause a series of issues, such as weak end-effector position accuracy, light payload and small bandwidth which is of great importance for the HIL simulation. Therefore, a parallel motion simulator is built for the docking HIL simulation in the research. The 6-DOF parallel motion simulator adopts 6 prismatic-spherical-universal (6-PSU) Stewart platform format, it consists of four parts: the moving platform, 6 PSU chain, the translational driving units and the base. The six chains can be divided into two groups, three horizontal placed chains, and three vertical placed chains. This design ensures a better isotropy for the dynamic parameters (stiffness, inertia, etc.) of the 6-DOF motion simulator.
The attempted introduction of steam-pumping technology at the Buarcos coal mine, Portugal, in the early 19th century
Published in The International Journal for the History of Engineering & Technology, 2022
José Manuel Brandão, Robert W. Vernon, Pedro Miguel Callapez, José Manuel Soares Pinto
The specification was for an engine with a 44 inches diameter cylinder and an 8 feet stroke. It incorporated all of Watt’s patented improvements. The latest parallel motion replaced the curved beam-ends and chains, which ensured that the piston rod was always vertical relative to the up-down motion of the beam. The beam consisted of two oak logs of the appropriate length. The engine was also double-acting with an external condenser. The boiler, also supplied by the company, was horizontal, without fire tubes. The specification also included 45 fathoms of 12 inches diameter pumps (two pump lifts of 22.5 fathoms), which would have been installed in the shaft.