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The Dennis N-Type is a model of commercial vehicle introduced by Dennis Brothers of Guildford (later Dennis Specialist Vehicles) in around 1905. It was the basis for their early fire engines and trucks.
The "N-Type" chassis was constructed from rolled steel channel; riveted and braced at appropriate points. It incorporated a sub frame on which the engine and gearbox were mounted.
As for later Dennis fire engines, the water pump was a centrifugal pump, rather than the piston pumps used by other makers. This was more complex to build than the long-established piston pumps, but had advantages in operation. Where water was supplied under pressure from a hydrant, rather than by suction from a pond, this additional pressure was boosted through the centrifugal pump, whereas a piston pump would have throttled it. Piston pumps also gave a pulsating outlet pressure which required an air-filled receiver to even this out. A drawback of the usual centrifugal design was the considerable axial force generated by the pump impeller, requiring a thrust bearing. Dennis avoided this by using a doubled-sided impeller which balanced the overall force. [1]
The majority of Dennis commercial vehicles were built on this type of chassis until further chassis designs were introduced. The last vehicles based on this design were produced in the late 1920s.
The chassis was generally fitted with engines by White and Poppe of Coventry. White and Poppe were bought by Dennis Brothers in 1919.
An engine or motor is a machine designed to convert one form of energy into mechanical energy. Heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a heat engine, in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion.
A pump is a device that moves fluids, or sometimes slurries, by mechanical action, typically converted from electrical energy into Hydraulic energy. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps.
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force is transformed, by a connecting rod and flywheel, into rotational force for work. The term "steam engine" is generally applied only to reciprocating engines as just described, not to the steam turbine.
A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. The purpose of a turbopump is to produce a high-pressure fluid for feeding a combustion chamber or other use.
A centrifugal supercharger is a specialized type of supercharger that makes use of centrifugal force in order to increase the manifold air pressure, MAP. An increased MAP allows the engine to burn more fuel, which results in an increased power output. Centrifugal superchargers are generally attached to the front of the engine via a belt-drive or gear-drive from the engine's crankshaft.
An air compressor is a pneumatic device that converts power into potential energy stored in pressurized air. By one of several methods, an air compressor forces more and more air into a storage tank, increasing the pressure. When the tank's pressure reaches its engineered upper limit, the air compressor shuts off. The compressed air, then, is held in the tank until called into use. The energy contained in the compressed air can be used for a variety of applications, utilizing the kinetic energy of the air as it is released and the tank depressurizes. When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. An air Compressor must be differentiated from a pump because it works for any gas/air, while pumps work on a liquid.
Centrifugal compressors, sometimes called radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.
A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.
Dennis Specialist Vehicles was an English manufacturer of commercial vehicles based in Guildford, building buses, fire engines, lorries (trucks) and municipal vehicles such as dustcarts. All vehicles were made to order to the customer's requirements and more strongly built than mass production equivalents. For most of the 20th century the Dennis company was Guildford's main employer.
A dynamometer or "dyno" for short, is a device for simultaneously measuring the torque and rotational speed (RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated, and usually displayed by the dynamometer itself as kW or bhp.
Steam power developed slowly over a period of several hundred years, progressing through expensive and fairly limited devices in the early 17th century, to useful pumps for mining in 1700, and then to Watt's improved steam engine designs in the late 18th century. It is these later designs, introduced just when the need for practical power was growing due to the Industrial Revolution, that truly made steam power commonplace.
An impeller or impellor is a rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.
Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic axisymmetric work-absorbing turbomachinery. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from which it exits.
A hydraulic brake is an arrangement of braking mechanism which uses brake fluid, typically containing glycol ethers or diethylene glycol, to transfer pressure from the controlling mechanism to the braking mechanism.
White and Poppe Limited owned a Coventry proprietary engine building and gearbox manufacturing business established in 1899. Many early motor vehicle manufacturers making only a small number of vehicles bought in their major components and White and Poppe soon had a large customer base and by 1914 a staff of around 350 people. By then the number of these customers, once as high as 15 or more, had fallen away though not the production volume leaving Dennis Brothers, always an important customer, taking much of their output.
A fan is a powered machine used to create a flow of air. A fan consists of a rotating arrangement of vanes or blades, which act on the air. The rotating assembly of blades and hub is known as an impeller, rotor, or runner. Usually, it is contained within some form of housing, or case. This may direct the airflow, or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors, handcranks, and internal combustion engines.
A rotodynamic pump is a kinetic machine in which energy is continuously imparted to the pumped fluid by means of a rotating impeller, propeller, or rotor, in contrast to a positive displacement pump in which a fluid is moved by trapping a fixed amount of fluid and forcing the trapped volume into the pump's discharge. Examples of rotodynamic pumps include adding kinetic energy to a fluid such as by using a centrifugal pump to increase fluid velocity or pressure.
Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine.
The Rotax 185 is a 9 hp (7 kW), single cylinder, two-stroke, direct drive, industrial engine, built by Rotax of Austria for use in fire fighting water pumps that has also been adapted as an aircraft engine for use in ultralight aircraft.
An internal combustion engine (ICE) is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is applied typically to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, transforming chemical energy into useful work. This replaced the external combustion engine for applications where weight or size of the engine is important.