FEATURE SPRINGS & SHOCK ABSORBERS
Anti-vibration solutions for safer machine designs
Vibration can be a real challenge for all types of machinery, but specifying anti-vibration components can help you to design safer products and machines, as Jet Press explains
M
achinery of all types can be affected by vibration and movement, therefore keeping
these to a minimum is essential. After all, not only can damage occur but it can result in, for example, the fasteners that hold the components together working loose and eventually falling out. This problem can be overcome by using anti-vibration Lock Nuts and Locking Washers, enabling you to design safer products. Palnut Regular Lock Nuts, which are
available from Jet Press, are one example. These are low in cost and easy to use – simply turn the Lock Nut to finger-tight then use a spanner to tighten them a further third to half a turn. They work by pushing the teeth of the thread form down the thread helix, which results in the ends of the teeth biting into the root of the thread on the bolt. The hex nut becomes slightly concave when tightened correctly. Of benefit to many applications, Palnut Regular Lock Nuts can be specified with a Hot Dip Galvanised finish that offers corrosion resistance up to 1,000 hours of salt spray. An alternative can be found with Nord-Lock
Quarter Turn Fasteners
Washers, which use tension rather than friction. These come as a pair and are used with a conventional bolt. With these, the outer surface has serrations that dig in to the lower surface of the bolt and the mating surface, which features cams. As the angle of the cam is greater than the helix angle of the thread of the bolt, a wedge effect is created when the bolt is tightened. To suit application demands, these have a high level of corrosion resistance. As a result of the features and benefits they
offer, Lock Nuts and Locking Washers can be used in a wide range of industries and applications. In one of the more unusual applications, these have been use in the assembly of electricity pylons, where safety is imperative.
PREVENTING DAMAGE If a nut or bolt becomes loose and falls out, not only can it cause damage but it could potentially injure someone. To help, many designers and machine builders specify Bi-Fix Quarter Turn Fasteners which are designed so
22 APRIL 2020 | DESIGN SOLUTIONS
they won’t fall out of the panel. There are a number of types available –
Quarter Turn Dome Head Studs, Quarter Turn Wing Head Studs and Quarter Turn Knurled Head Studs – so called as they only need a quarter turn to open or close them. Wing Head Stud and Knurled Head Studs can be released by hand; and the Knurled Head Stud and the Dome Head Stud are slotted so you can open them with a flat blade screwdriver. These are used in a
wide range of applications – from heavy industry to campervans. These are
useful in applications that require panels or doors to be opened or removed
regularly for maintenance. Bi-Fix Quarter Turn Fasteners are made
of three parts. The Spring Clip is installed permanently in the framework and the spring ejects the stud which stays captive in the panel which is being removed by a washer. The washer also reduces vibration when everything is in the assembled or closed position. Push Nut Bolt Retainers can be used to prevent
a bolt falling out of the application during the assembly process. These slide down the thread and hold firmly at any point. When you install the panel or component they stay in place
and the teeth fold flat, meaning little extra thickness is added to the final assembly.
GAS STRUTS In vehicles, hoses are used to carry flammable fuel, brake fluid or hydraulic fluid. But with vibration present, these essential cables and hoses can become dislodged or be subject to chaffing. Cable or Pipe Clips with flared edges can be used to reduce the chance of damage. As well as preventing damage, designing
in the right component can help to prevent accidents. For applications where personnel need to lift a cover to maintain equipment, gas struts can be used to make the job easier. However, an additional safety rod is required in case the Gas Strut fails. As well as providing lift assistance, Econoloc
Gas Struts have an automatically engaging locking shroud so the operative cannot forget to use the safety rod. When the strut is fully extended the spring-loaded shroud moves into place, preventing the gas spring from compressing. Econoloc Gas struts can be combined with a Swift and Sure Gas Strut for a more cost-effective solution. With quality control so important, JET PRESS
supplies a range of parts in varying colours to help with error prevention and detection - from yellow zinc plated T-Nuts in furniture to coloured Hose Bands in vehicles.
Jet Press
www.jetpress.com
CALCULATE TORSIONAL VIBRATION
Occurring naturally as part of the operation of a diesel engine, torsional vibration is induced by torque pulses from the combustion process. It can vary depending on the number of cylinders, the firing order and the speed of the engine. Driven components such as piston compressors, plunger pumps and propellers can also induce torque pulses in a torsional system. If left unchecked, the resulting torsional vibration can lead to significant failure of one or more parts of the drive train. To avoid this, all parties must perform torsional vibration calculations and, where required, torsional vibration analysis, based upon the engine, alternator and the coupling proposed for the application. Torsional vibration calculations, and more detailed torsional vibration analysis of the proposed
application, are offered by Reich – the choice will be determined largely by the complexity of the application. The standard torsional vibration calculation, for a 2-mass system, has been developed in-house by Reich and conforms to DIN 740 Part 2. The relevant coupling values used in this calculation include: nominal torque, maximum torque, fatigue torque and torsional stiffness. For more complex applications, and in instances where information other than coupling loads is required, Reich uses the more comprehensive n-mass system, which is widely recognised by industry bodies.
Reich Drive Systems UK
www.reich-uk.com
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