Practical Problems
There were a number of problems to be overcome with this system. The high tape/head speed could lead to rapid wear of both the tape and the head, so both need to be highly polished, and the head made of a hard, wear resistant material. Most systems operate with an air bearing separating the heads from the surface of the tape. Supplying signals to a rotating head is also problematic: This is usually accomplished by coupling the signal(s) inductively through a rotary transformer. The transport mechanism is also much more complex than a fixed head system, since during loading, the tape must be pulled around a rotating drum containing the head(s). In a VCR for example, the tape must be pulled out of the cassette case and threaded around the drum, and between the capstan and pinch roller. This leads to complex and potentially unreliable mechanics.
Read more about this topic: Helical Scan
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