Answer : when there are more than 2 and then they become a block and tackle.
A single pulley is seldom used on its own, generally several of them are used in the commonly known ‘block and tackle’ systems, an individual pulley being a block and, in an assembly of more than one block with rope or cable threaded through, they are termed tackle.
Just about everyone has seen a crane working at a building site, but have you noticed its attached mechanisms? (Its block tackle & pulley systems ) If you look carefully you’ll notice there’s a block and tackle, an indispensable piece of equipment which can be seen in numerous places and for numerous uses.
A block and tackle is a system where several pulleys, or blocks, are joined together with ropes, belts or chains to raise or move heavy weights, the word ‘pulley’ has become synonymous with the word ‘block’.
Different block and tackle systems are used according to the weight they are required to lift, working out the tackle needed requires some degree of mathematical ability but in simple terms, for those who dislike maths, it’s all to do with what is termed ‘mechanical advantage’.
If we imagine someone drawing water from a well the mechanical advantage is the ratio of the force produced, i.e. the power to lift a full bucket of water, to the force applied to it, i.e. the effort put into the lifting which, without the pulley, would only have been enough for half a bucketful.
For more the various tackles with their mechanical advantages please visit us.
Blocks are simple devices that consist of a grooved wheel through which a rope or cable can run and change the direction of the force needed to lift a load thus increasing the mechanical advantage.
Blocks are also known as pulleys, the differences between them are blurred in that they are often constructed from similar parts and materials and would seem to have the same purpose. However, although both redirect the force required to lift a load, they are called blocks when constructed with one or more sheaves between each side plate and are capable of handling shock loads, for example should a heavy log fall from a tree being felled, a block would be capable of holding the load until it was brought under control, whereas pulleys, more likely to be running on ball bearings, are used to simply improve mechanical advantage. They are not designed to handle shock loading, they are lighter and smaller than blocks and are usually designed to work with soft ropes rather than cables or wire ropes.
Where blocks are used
Hoisting Yacht Sails
Blocks are used wherever there is a need to lift or move a heavy load. The uses are numerous and include lifting gear in the construction industry; vehicle breakdown gear; leisure activities such as mountain chairlifts and hoisting yacht sails; bed hoists for the infirm and disabled; safety lifting gear; mountain or water rescue gear; suspension bridges; industrial safety equipment.
Typical industry sectors
Blocks and Tackle in Construction
Blocks and Tackle in Manufacturing
Blocks and Tackle in Marine
Mainly because of the mechanical advantage feature, i.e. the ratio of the force produced by a device that acts on a load to the applied effort needed to lift or move the load, blocks and tackle are an indispensable piece of equipment and used in almost all sectors of industry – agriculture, commercial, construction, manufacturing, logging, oil drilling and marine.
Depends on which mounting option you have gone for, but there are a few tips that should be followed when mounting any outrigger. Firstly all mounts should be through bolted, preferably with stainless steel and additional backing plates. Secondly you need to carefully consider placement, to make sure that you have adequate access to the outrigger components as needed. Thirdly, do not use poles that are disproportionately heavy for their intended usage – pick the lightest possible for your boat and desired set up.
When setting up your outrigger you need to ensure that the end where the line attaches is at the right height. If set too high or two low you can run into problems. The ends of the poles should be about four to five meters above sea level for optimum usage. That is, an angle of around 30-40 degrees from the horizontal marker. It is important to remember however that the further the lines run, the more the tow angle is reduced. A reduced angle doesn’t help the lure’s action but can be improved by lifting the tow point by running it from the outrigger out to sea.
Make sure you have the right components, and someone to help you, and setting up your outrigger should be pretty simple or if in doubt your local fishing shop or your boat supplier should be able to recommend themost appropriate set up.
Ronstan provide a range of specialist fittings which can be used for some of the key elements of outriggers. This includes our blocks and shackles.
Ronstan offers its wealth of knowledge and expertise in the many applications of cable systems. Our services include; design engineering, project management, and installation
Cables give balustrades and railings a sense of elegance, space and style. With careful planning and design, they have the ability to totally transform the look. Their clean and simple lines create a sleek and modern aesthetic, while offering uninterrupted views. They’re contemporary, low-maintenance and surprisingly easy and fast to install.
Ronstan has been setting the standard for cable applications in balustrades and railings since 1988.
Making it easier for you
Our new balustrade and railing was designed to make life simpler for you. The process of researching and selecting the right system has been streamlined. We have five new complete cable systems, each one with an individual part number. This means no more time-wasting and frustration selecting individual components. All the information you need is logically laid out, with clearly displayed diagrams and details. It’s the definitive resource for balustrade and railing cables.
The definition of catenary is “a curve formed by a wire, rope, or chain hanging freely from 2 points that are not in the same vertical line.” And can be used in a commercial and a domestic environment and the design ideas are endless.
Ronstan Tensile Architecture is a leader in the field of Catenary lighting. Have a look through at just some of the projects. We recently completed a catenary lighting supply job for the Ithaca Commons in Ithaca New York where we supplied a combination to Hanes Supply for the lighting installation.
The redesign of the Commons was intended to improve the retail environment and create a community gathering space in the vibrant college town.
For the design of this lighting system, the structural cables are arranged with upper and lower cables approximately 3 to 4 feet apart. The upper cable supports the weight of the 30-pound lights. The lower cable is there to provide stability to the light and to minimize swaying caused by winds.
Cable for lighting
There are additional vertical cable connections made with adjustable swage toggles, between the upper and lower cables to provide the tension required for the suspended system.
Ronstan design, General Hardware. The challenge of producing top-end, innovative hardware to meet the extreme demands of sailing has led to many technical breakthroughs for our products.
Smartphone Wind Meter – Vaavud™ 2 – VAV-2G (Sleipnir)
A Vaavud™ wind meter will enable your smartphone to be used as a high-tech meteorological tool. It enables you to take accurate wind readings and works on the most popular smart phones when using the free Vaavud App. There are currently two models with slightly different characteristics available: Mjolnir and Sleipnir.
The design of the Vaavud™ Sleipnir wind meter is inspired partly by professional cup anemometers, and partly by a Danish developed wind turbine with vertical blades. An asymmetrical rotor accelerates slightly when the largest surface is hit by the wind.
The built-in sensor makes 40.000 measurements per second allowing the app to detect even the slightest variations in wind speed. This high frequency signal can be used to derive both wind speed and direction.