Influenced by the architect Thorvald Bindesbøll, Engelhardt understood that successful production depended on both an industrial and a graphical approach.
While still at the Academy, he designed new tramcars for Copenhagen Tramways (Københavns Sporvogne), replacing the usual rectangular profiles with rounded contours both inside and out so as to provide a more human look for passengers.
[3][4] Recognized for his typographical talents, in 1923, Engelhardt was invited to design street signs for the Copenhagen suburb of Gentofte.
They can be clearly identified as Engelhardt's as, in lieu of a signature, he replaced the dot on the J (present on most signs as vej means road) with a little heart.
He practiced in many other fields including architecture (with a house innovatively designed at Højen near Skagen), oven manufacture (for H. Rasmussen, Odense), and the development of functional lines for Bindesbøll.