Product category:
Tooling and tools
News Release from: Norbar Torque Tools | Subject: Torque reaction plate solutions
Edited by the Engineeringtalk Editorial
Team on 10 October 2000
How reaction plates absorb forces in
tools
Torque reaction plates or arms are essential to absorb the reaction forces of powered and manually operated torque multipliers, and Norbar Torque Tools can offer a range of torque reaction solutions
Torque reaction plates or arms are essential to absorb the reaction forces of powered and manually operated torque multipliers Getting the right reaction plate for the job is vital, and Norbar Torque Tools can offer a range of torque reaction solutions to suit all applications
This article was originally published on Engineeringtalk on 7 Jul 2008 at 8.00am (UK)
Related stories
Easy ultrasonic measurement provides load details
The USM-3 can provide a 0-10V analogue output to precisely shut off torque tools when a predetermined bolt stretch or load has been attained.
Torque multiplier works deep under the sea
The gear unit has been designed as an adapter for torque tools used on subsea Christmas trees - the assemblies of control valves, gauges and chokes that control oil and gas flow at a well head.
"For every action there is an equal and opposite reaction" is, as every school child should know, Newton's Third Law of Motion.
When applied to torque tools it means that when a tool applies a torque to a fastener or other application there will be a (more or less) equal and opposite reaction torque that has be absorbed.
When using impact or impulse tools the applied torque is absorbed by the inertia of the tool and the operator, but Norbar does not make these types of tool, which can cause the operator health problems if vibration or noise levels are excessive.
Instead Norbar power torque tools and multipliers are rotate continuously with no pulsing or impact, and so rely on a reaction arm or plate to absorb the reaction torque.
With some tools applying torques of up to 100,000 Nm the design, construction and use of the reaction plate can be critical.
Further reading
Torque wrenches reduce health risks
Impact wrench users reach their daily exposure action value (EAV) in eight minutes during a test, while Pneutorque operators could perform the same task for over 24 hours without breaching the EAV.
Tougher torque wrench holds calibration for longer
The new TruTorque wrench uses an improved mechanism that still retains some of the best elements from Norbar's original tried and tested design.
Torque tool cuts vibration health risks
Low-vibration tools greatly reduce the risks of VWF, but purchasers of power tools often face a lack of reliable data on the actual vibration levels produced by various tools in use.
The standard reaction plate for a Handtorque, which uses a gearbox to multiply the torque applied by the operator by factors of 5, 25 or 125, is a low alloy solid steel bar.
This is located by the operator to rest on an adjacent solid structure, such as another bolt on the flange, where it is able to absorb the reaction torque.
Problems can arise however where there is no convenient point for the reaction plate.
If for example a fastener being tightened is recessed or in a difficult location the operator may be tempted to bend or extend the reaction plate.
This may cause the plate, tool or socket being used to twist, bend or break, with potentially disastrous consequences for the equipment or operator.
Options include reaction plates that are curved or have sliding feet to make contact with a suitable reaction point, and tubular steel plates that are lighter and more manageable for jobs where torque tools have to be frequently manhandled.
Norbar is also working on an aluminium reaction plate offering greater strength for its weight than steel, but there are drawbacks with aluminium.
One of these is that the metal tends to flake under pressure, as it is where the end of a reaction arm meets the reaction point, and this can produce dangerous splinters.
The solution Norbar is working on involves a steel sheath to protect the aluminium at the point of contact.
Where access to hard-to-reach fasteners is needed Norbar can supply nose extensions for hand or power tools.
These also have the advantage of including a bearing where the extension fits onto the tool which absorbs the torque reaction rather than passing it onto the tool.
There are also other factors to take into account when using standard reaction plates.
Extending a torque plate beyond its design length by welding on extra material for example may cause the plate to break.
Even though the torque remains the same and the force applied to the end of the longer plate is reduced, the bending moment on the plate close to the tool is increased.
If reaction is taken at distance L1 then the reaction force, F1 can be calculated.
This generates a bending moment of (F1 x a) at section xx.
If the reaction plate is extended and reaction is taken at L2, then the reaction force is reduced and becomes F2.
In this case the bending moment becomes (F2 x b) which will always be greater than (F1 x a), therefore the bending stress at section xx will be greater.
In the second instance the reaction plate may fail.
Where flat reaction plates with radiused ends are used to react with a surface that is not perpendicular to the axis of the reaction plate itself the force applied to the end of plate may increase dramatically.
In the case of the curved end of a flat reaction plate the line of action of the reaction force passes through the centre of the curve.
The further round the curve that reaction is taken the smaller will be the perpendicular distance, L, and in consequence the greater the reaction force, F.
Torque reaction tools are a safe and ergonomic solution to any high torque turning requirement.
Following the guidelines above will improve tool life and ensure their safe and efficient use. Request a free brochure from Norbar Torque Tools ...
• Norbar Torque Tools: contact details and other news
• Email this article to a colleague
• Register for the free Engineeringtalk email newsletter
• Engineeringtalk Home Page
Search the Pro-Talk network of sites
