Forensic Engineering - Imperial War Museum North
8th May 2018
To some Matilda is the name of a Roald Dahl book. To others a film and if you’re lucky, a stage play.
To the Engineering Department at Chester, Matilda is a tank. A World War II tank weighing 25 tons that the Imperial War Museum North, in Manchester, wanted to position in the main exhibition area as part of the permanent exhibits in the museum space. Next door, if you visit the museum, is the 9/11 structure exhibit that was also designed at Chester.
Straightforward you may say, just drive the tank in. Problem one, someone has taken the engine out meaning it will have to be towed into the building up an inclined access ramp which doesn’t help, and the access ramp is a cellular structure, not solid. Problem two, there is already a Russian T34 tank already in the space designated for the Matilda. The plan was to get this out and get the Matilda in using military specification towing equipment, which alone weighs in at 28 tonnes.
This is a case of forensic engineering. Forensic engineering is a deductive process using basic principles to determine a likely course of events. Often, we have only limited information and we must use engineering judgement to give a subjective answer.
In this case for the original build of the ramp, the scheme drawings only gave dimensions and stated the concrete was reinforced, but not the actual steel size or spacing, which is normally shown on as-built drawings. Therefore, invasive investigations were instigated to break out the existing structure in a controlled manner to determine the steel content. Then by back calculating and using typical wheel loads from BS5400 we assessed the ramp access strength in order to use it to get the tanks in and out.
A video of Matilda being moved into the Imperial War Museum can be viewed on the IWM North Twitter account. https://twitter.com/IWMNorth/status/989540288426401792.