 The wheel has an overall diameter of 35 metres ( 115 ft ) and consists of two opposing arms extending 15 metres beyond the central axle and taking the shape of a Celtic @-@ inspired , double @-@ headed axe . Two sets of these axe @-@ shaped arms are connected to a 3 @.@ 8 @-@ metre ( 12 ft ) diameter central axle of length 28 metres ( 92 ft ) . Two diametrically opposed water @-@ filled caissons , each with a capacity of 250 @,@ 000 litres ( 55 @,@ 000 imp gal ; 66 @,@ 000 US gal ) , are fitted between the ends of the arms . 
