A modular support frame assembly for attachment to a railway vehicle body is provided. The modular support frame assembly generally includes a support frame comprising a plurality of tubular frame members and a plurality of connecting brackets connecting the tubular frame members to form a three-dimensional structure. The connecting brackets comprise flange elements to accept respective ends of the tubular frame members to form the three-dimensional structure. The ends of the tubular frame members are swaged to the flange elements of the connecting brackets. A mechanical device is supported by the tubular frame members, such as an air compressor driven by a driving motor.