▁story ▁told ▁about ▁Johann sen ▁around ▁this ▁period ▁is ▁that ▁he ▁once ▁broke ▁an ▁ax le ▁when ▁far ▁from ▁assistance ▁and ▁managed ▁to ▁fix ▁it ▁well ▁enough ▁to ▁get ▁back ▁to ▁town ▁using ▁a ▁mul ga ▁tree ▁and ▁a ▁kn ife . ▁ ▁Over ▁the ▁following ▁years ▁Johann sen ▁had ▁many ▁roles ▁and ▁was ▁involved ▁in ▁many ▁explo its ▁before , ▁in ▁ 1 9 3 6 , ▁starting ▁on ▁his ▁most ▁remembered ▁innov ation , ▁the ▁' B itzer ' ▁Mul ga ▁Express ▁which ▁was ▁designed ▁to ▁be ▁able ▁to ▁ha ul ▁more ▁as ▁well ▁as ▁handle ▁the ▁bad ▁roads ▁around ▁Central ▁Australia ; ▁and , ▁in ▁the ▁early ▁years , ▁was ▁quite ▁an ▁unexpected ▁sight . ▁Over ▁the ▁following ▁years ▁the ▁' B itzer ' ▁Mul ga ▁Express ▁was ▁followed ▁by ▁the ▁' B itzer ' ▁Mul ga ▁Express ▁II ▁and ▁III , ▁the ▁' B itzer ' ▁Mul ga ▁Express ▁III ▁was ▁able ▁to ▁ha ul ▁an ▁un he ard ▁of ▁ 2 2 ▁t onnes . ▁ ▁Between ▁mail ▁runs ▁and ▁driving ▁his ▁tr uck ▁Johann sen ▁pros pected ▁extens ively ▁and ▁was ▁also ▁involved ▁in ▁various ▁tour ism ▁vent ures ▁with ▁Australian ▁Ex ped itions ▁( with ▁Mont y ▁Em bury ) ▁and ▁Bond ' s ▁T ours . ▁During ▁World ▁War ▁II ▁Johann sen ▁moved ▁to ▁T enn ant ▁Creek ▁and ▁opened ▁a ▁gar age ▁where ▁he ▁created ▁a ▁wood - gas ▁producer ▁that ▁converted ▁wood ▁into ▁gas ▁to ▁run ▁the ▁motor ; ▁it ▁consum ed ▁about