Can you under-sling a DROPS rack?
I have been asked to look into designing a system that would allow a lorry loaded with supplies to pull up under a crane, and have all its stores unloaded in a single lift. This could range from a full load of rebar, to a single machine, weighing up to 15t.
The purpose is to speed up unloading so that the crane can get on with construction, and to remove the lorry from site sooner, as logistics and unloading spaces are tight.
Does anyone know if you can under-sling a DROPS rack? I am relatively sure that the APFB comes on a DROPS rack, and clearly that can be under slung, but I am not sure of the maximum load that rack could carry like this (ignoring the limitation of the hook, the crane is perfectly capable of the loads required.)
I have trawled through the BA Battlebox logistic pamphlets but with no luck. I know that the DROPS can carry 15t and has a self weight of 1.5t, but I do not know if this capacity would reduce if lifted by a crane and not loaded onto a lorry.
Any suggestions?
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I think that you’d have to make sure a lifting beam or something was used to reduce the span between lifting points. At least to equal the 8 lifting nodes shown in the picture of the chinook.
I’m also not sure if the rack is U/S or in need of an inspection after a helo lift.
Dan,
Good point about the lifting beam, I have done more research which backs up your point.
I have now found a civilian equivalent (flat rack containers) and the vast majority of them are lifted with a lifting beam. They have a capacity of roughly double what I need, so I will try to do some analysis of how much to reduce this capacity by if a lifting beam is not used. Hopefully a reduction of 50% will be enough!
The horizontal component between lifting points in the rack might be the bastard – could be quite high without a beam.
Hi Laurie,
Not certain, but pretty sure that the main components of the APFB come on a trailer. Not sure if a Chinook would have the ability to lift a full rack!? I did a 5 bay MGOB bridge build on a 3 Bde exercise and we used a chinook to lift in the frame (main skeleton minus deck panels) complete and then the panels were lifted in separately. But not on a full rack.
Isn’t that a drops rack in the image you’ve posted? Looks like some general supplies and probably not near the loads you will need to lift on site.
Would a spreader bar be a more efficient way of lifting a rack?
Al,
It is a DROPS rack in the image yes, but like you say, I have no idea of the load that it is carrying, and like Dan said, if the rack can be repeatedly used like this or if it becomes U/S afterwards. Thanks for the points about the APFB on trailers, I was just going to find the weight of an APFB and use that as a known load that has been carried.
Yes, spreader bars or a lifting frame would make this much easier, but they are specifically excluded in the design brief. I have suggested that the first vehicle in a delivery packet could come with the frame, it is used to unload the packet, then the last vehicle could take it away, but the client does not want this. They are very specific that the rack is to be lifted from a single point, with a single hook, that the rack must have a fully open top and that nothing other than the rack (and the lifting chains) are to remain on site afterwards.
Taking on both your and Dan’s points I will look at developing / finding something that will serve this purpose. Worst case would be a flat rack with relatively large beams running along the sides to resist the lifting forces.
I will update with the final design.
James,
Thank you for your comments, you are right that ISO containers have already been discarded, this is because the brief specifically omits them.
The client is a sub-contractor who are planning on developing a system that they can use on a wide variety of sites, but it must be suitable for the extremely tight logistics of central London. The brief is that there is only enough room for one lorry to park at a time, then all stores need to be unloaded and stored within a tower footprint before the lorry can leave. ISO containers do not work as it is specified that the item must have a fully open top, so that they can accommodate bulky items. This also allows future unloading with the crane when time permits.
The client’s ambition is to be able to win bids based on reduction in program, freeing up crane time through more streamlined logistics is one of many avenues that they are exploring.
I have now found an off the shelf product that fits their purpose, a platform container. When lifted using a lifting beam these can support up to 40t. I am now waiting on some information from the manufacturer to check what this reduces to when a lifting beam is not used. As I only need to lift 15t it may be suitable already. If not, additional beams will be added to increase the capacity as required.
Laurie, just to add some more onto your point ” ISO containers do not work as it is specified that the item must have a fully open top, so that they can accommodate bulky items. This also allows future unloading with the crane when time permits”. ISO containers with an open top do exist, they can be either full or half height. We use them offshore all the time for as you said, you can load out of gauge items that wouldn’t normally fit.