A magnetic record/playback apparatus for continuously recording at least two tracks of data conforming to a digital recording format applied to a first magnetic tape having a first tape width onto one track formed on a second magnetic tape having a second tape width larger than the first tape width, and for reproducing the data from the second magnetic tape. This apparatus includes a fixed drum and a rotating drum adapted to be rotated relative to the fixed drum. The rotating drum has a record/playback head for recording and/or reproducing the data with respect to the second magnetic tape and an erase head for erasing the data recorded on the second magnetic tape. A plurality of grooves extending in a direction of rotation of the rotating drum are formed on the outer circumference of the rotating drum, and each of the grooves has a width of 0.21 mm.+-.0.02 mm. Further, the head width of the erase head as measured in a direction perpendicular to the direction of rotation of the rotating drum is larger than that of the record/playback head.
A guide plate is provided along the respective outer periphery of rotary and fixed drums on the upstream side relative to an inlet portion where a magnetic tape starts making contact with a magnetic head on the rotary drum, an airflow attendant on the rotation of the rotary drum is stripped by a wedge-shaped edge on the guide plate and is released to the outer periphery side by a guide surface of the guide plate, and the airflow flowing in the axial direction into the space between the tape and the rotary drum is restrained by an extended portion of the guide plate. In a rotary head drum device for a magnetic recording/reproducing apparatus, formation of an excess air film near an inlet portion of the tape is restrained, and stable recording and reproducing can be achieved without raising the tape tension, thereby enhancing the life of the tape.
To lower the coefficient of static friction of the circumferential surface of the guide or drum constituting the magnetic tape apparatus. A flat portion is formed between peak portions. The peak portions and flat portion are formed so that the relationship: a'<a is satisfied, where "a" represents a distance between the ridges of the peak portions, i.e., pitch of the peak portions, and "a'" represents a bottom width of the peak portions. When this relationship is satisfied between the peak portions and the flat portion, the total area of the meniscuses formed between the magnetic tape and the peak portions can be reduced, thus making it possible to lower the coefficient of static friction.
A magnetic recording apparatus has a rotating drum which rotates magnetic heads at a constant speed. The magnetic heads scan a magnetic tape. On a magnetic tape, an area written by each scan always includes a lateral portion of an area written by the previous scan. In this portion, old data is overwritten by new data, and writing continues. An area excluding the overwritten portion is a recording track. The running speed of the magnetic tape is changed by a system controller, and hence the recording track width can be changed.
