▁locomot ive ▁configurations ▁had ▁to ▁be ▁found . ▁ ▁Therefore , ▁the ▁S BB ▁ordered ▁several ▁prototype ▁locomot ives . ▁In ▁addition ▁to ▁the ▁Be ▁ 3 / 5 ▁ 1 2 2 0 1 , ▁Be ▁ 4 / 6 ▁ 1 2 3 0 1 , ▁Be ▁ 4 / 6 ▁ 1 2 3 0 2 ▁and ▁Ce ▁ 6 / 8 I ▁ 1 4 2 0 1 ▁with ▁coupling ▁ro ds , ▁the ▁S BB ▁proc ured ▁the ▁Be ▁ 2 / 5 ▁prototype ▁locomot ive ▁with ▁fully ▁spring - loaded ▁drives . ▁When ▁tested ▁in ▁the ▁oper ational ▁environment , ▁this ▁locomot ive ▁turned ▁out ▁to ▁be ▁too ▁weak ▁and ▁too ▁slow . ▁As ▁early ▁as ▁ 1 9 1 9 ▁the ▁S BB ▁ordered ▁a ▁second ▁prototype ▁locomot ive ▁from ▁S LM ▁and ▁BBC ; ▁as ▁with ▁the ▁Be ▁ 4 / 6 ▁this ▁prototype ▁locomot ive ▁would ▁have ▁four ▁drive ▁ax les . ▁The ▁specified ▁requirements ▁correspond ed ▁to ▁those ▁of ▁the ▁Be ▁ 4 / 6 ; ▁ ▁however , ▁for ▁the ▁operation ▁of ▁express ▁trains , ▁a ▁maximum ▁speed ▁of ▁ ▁was ▁required . ▁ ▁Layout ▁ ▁Mechan ical ▁layout ▁▁ ▁The ▁Be ▁ 4 / 6 ▁util ized ▁the ▁maximum ▁ax le ▁load ▁of ▁ ▁fully . ▁The ▁mot ors ▁for ▁the ▁A e ▁ 4 / 8 ▁were ▁heav ier ▁than ▁those ▁of ▁the ▁Be ▁ 4 / 6 , ▁therefore ▁the ▁A e ▁ 4 / 8 ▁was ▁planned ▁with