Posted By Phil Markham A project I have been asked to consider is the suspension of a display exhibit from a mobile crane for ca. 24 hrs. This would take place in October and wind issues have been considered. However if the display is set up during the day and anchored to prevent drift, would temperature gradient cause problems if the crane line cools significantly at night. Security of the crane is also well considered but is there anything else about a load being suspended for so long that we might need to take into account- Suggestions gratefully received.

Posted By Guderian Struggling to see the temperature gradient would make that much difference. This will depend upon the length of the crane cable - i.e. height the load is suspended. Also the expected change in temperature. Steel has a co-efficient of expansion of about 0.00016383mm/*F Assuming a reasonable day 18*C (64*F) dropping to 0*C (32*F) at night gives a temperature change of 32*F. Probably won't drop that much in October. Assume the load is suspended by a cable 10m long. This gives a change in cable length of 0.00016383 x 32 x 10 x 1000 = 52.42mm (2" in old money) I would be more worried about the weather conditions/wind speed etc

Posted By alex mccreadie Phil nothing to stop you leaving a load on a crane overnight, or an extended period. That is of course as long as a crane operator is in the operators seat. This is for obvious reasons like bad weather wind or any unforeseen incident. BS7121 Part 1 Page 34 Para 14.4 (This does state present but surely means in the seat) Done it loads of times and it is probably happening as we write and read this post. Regards Alex

Posted By Eddie Campbell Phil You may not experience much change in the length of wire rope due to the temperature differences at that time of year in the UK depending on the height of boom point. If this is a mobile lattice boom crane then the same logic applies. However if this is a mobile hydraulic telescopic crane then changes in temperature and other factors can produce significant changes to the boom tip height and thus the hook height due to expansion and contraction of the hydraulic oil in the cylinders. Not a good idea to leave this unattended over night for all of the reasons already given. Eddie

Posted By Guderian Phil, Thanks for your comments - not so sure many of our learned friends will quite get your joke. OC 2nd Pz Group I believe in the formentioned campaign. Also much success in May 1940 in another country closer to the UK.