free carriages have a rectangular frame from which vertical axis guide rollers are cantilevered so as to engage the sides of the rail the top portion of the frames have a vertical opening which is surrounded by the frame and the driven and free rolling wheels which ride on the top of the rail are loosely fitted into these openings on the respective driven and free rolling carriages application_number US 95585092 A description referring to fig1 and 2 a conveying tramcar 1 is supported by a guide rail 2 for travel thereon the tramcar 1 has a driven carriage 3 a freely rolling carriage 4 and front and rear auxiliary trolleys 7 and 8 are respectively connected by connecting rods 5 and 6 to the carriages 3 and 4 the trolleys are connected to a base supporting an article 9 to be conveyed the front and rear ends of the article 9 are respectively supported by the driven carriage 3 and the freely rolling carriage 4 the driven carriage 3 and the freely rolling carriage 4 are each connected to a respective main body 10a and 10b of carriages 3 and 4 respectively both of said main bodies being identical to each other as to their structure and size as shown in fig3 5 and 8 the main bodies 10a.