Load calculation

[Nigel Thomas]

How do you calculate the sizes of square section EN8 mild steel bar to be used to pick up a load, if I know the weight of the load and the length of the bar. I need to lift a 1 ton injection moulding tool with a bar of 400mm length. The bar is bolted to the top of the tool at both ends and an eye bolt is secured to the middle of the bar. Both eye bolt and fixing bolts are 16mm. I know I have to build in a safety factor of about 4 to 1 so I really need this bar to lift 4 ton.
Any thoughts would be appreciated.

[wildwestpat]

Hi Nigel

You need to be compliant with the UK HSE regs if this work is in the UK. The regulation is known as LOLER:- http://www.hse.gov.uk/pubns/indg290.pdf

You will note that the certification as safe to lift has to be done by a competent person. As with much of the HSE regulation that has been interpreted by the courts and will probably mean a qualified member of one of the recognised engineering institutes with a specialism in stress calculation.

Calculation formulae can be found in 'Roark's Formulas for Stress and Strain' and in the Machinery's Handbook.

Stay safe

Regards

Pat