July 2019 59
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Lift ing Beam
14000Young’s Modulus For Woods
120001000080006000400020000
0.1 0.2 0.3 0.4 0.5
Specific gravityYoung’s Modulus, N/mm20.6 0.7 0.8 0.9Designing a Lift ing Beam
Introduction
Aft er I moved house, I lost my old workshop which was in a
wooden shed but the new house had a double garage which
would house my new workshop. The fl at roof consisted of wooden
joists, spanning the full width of the double garage, covered with
corrugated steel sheeting. As the roof was steel, condensation was
a problem, and the garage was always damp during cold weather.
It needed insulating, but I did think about fi tting a lift ing beam at
a later date. In order to do this, I measured the defl ection of one of
the beams with a known load (me) hanging from it in the centre of
the beam, before insulating the roof space and lining it with sheets
of plywood. Once insulated and split into two halves – one for the
car and one for the workshop – I left the lift ing beam as a ‘future
development’. Subsequently I decided to buy a milling machine
which would be delivered on a pallet brought into the garage on
a hand truck and left for me to unload it. This provided the spur I
needed to design and install the lift ing beam, photo 1. Whilst there
are many equations in this article, it is not particularly diffi cult to
follow the design by substituting your own values in the equations.
If you are put off by the mathematics, then just have a slow read
through and you should be able to follow what is going on.
Disclaimer!
All the information in this article is given in good faith, but reliance
placed upon the contents of this magazine is at the reader’s own
risk. You must use your own judgement as to whether you are
competent to undertake any design work, if not, then consult a
qualifi ed structural engineer.
Roofi ng joist properties
Prior to insulating and lining the garage roof, I inspected each beam
that could be used to support the lift ing beam looking for knots,
splits and cracks in the beams. All the beams seemed to be in good
R. Finch designed a lift ing beam to be installed in his garage and gives a
detailed method for anyone to design and fi t their own lift ing beam.
1
Fig.1
condition without any signifi cant fl aws, so I
insulated and lined the roof and continued
building the workshop. When the time to
purchase of a milling machine came, I set
out to design the lift ing beam, knowing that
the wooden roof beams did not have any
imperfections which would restrict the use
of the beams despite their now being hidden
from view.
As the roofi ng beams were wood, they
would not have ‘standard’ properties listed
in text books, as do steel beams, which could
be used for calculations. I did look up values
of Young’s Modulus (also known as the
Modulus of Elasticity) in a handbook, ref. 1,
which gave values of Young’s Modulus for
soft wood of between 4400 N/sq.mm and
13000 N/sq.mm, depending on the species
of wood and its specifi c gravity, as shown in
fi g. 1. Unfortunately, all the data are based
on American native soft woods, so some
degree of interpretation would be required
for timber used in the UK, as this may be
British timber or European, depending on
the purchaser of the original wood. Also,
the correlation between specifi c gravity
and Young’s Modulus is too poor to permitThe installed beam