When the record was first cut the cutting stylus was moved across the record on a rail. Some record players use this system for playback. It is called tangential tracking (See B&O Beogram7000 below which shows a tangential arm i.e. it doesn't pivot as a normal arm but tracks across the record on a rail at the rear.) This tangential system means that the stylus is always seated squarely in the record groove at a tangent to the groove at any point on the playing surface, just as the original cutter did, where it inflicts minium wear on the record groove sides. The fact that most arms pivot rather than track tangentially means that there is therefore a compromise in which gramophone manufacturers develop tonearm shapes in order to try and match the original track as closely as possible. However as the tonearm pivots, the soundbox and therefore needle in the groove, deviate from this ideal path, the needle skews in the groove with additional wear on the record being the result. Any deviation from the 90 degree angle is called tracking error. (See photo panel below)
Some tracking examples.
In attempts to overcome error in tracking gramophone designers created an offset between the pivot point of the tonearm and the angle of the soundbox. It's easier just to look at the diagram I have created in the above panel, through which all should become clearer. Much has been written about tracking and Eric Reiss in his book "The Compleat Talking Machine" explains it in more detail with more information on the relation of offsets to tonearm length but its value is academic. The importance of tracking for collectors lies purely in assessing the tracking error of a gramophone so that we are aware when we play a record of the degree to which we are subjecting our records to wear.
I have put a link (above right) to a PDF file that shows a simple tracking error assessment tool. I have used it in the photographs below that show some sample shots of the tracking on several of my gramophones. Note in particular that tracking error changes as the arm moves across the record so it's necessary to take 3 readings beginning, middle and end). In his book “The Compleat Talking Machine” Eric Reiss states the increased record wear starts at a 2 degree tracking error with damage occuring at 17 degrees and above. If you want to assess the tracking error further I have also included a download for a Tracking Protractor that can be used with the Tracking Assessor tool. Instructions are on the downloadable PDF. The photo bottom right shows the tool in action on my HMV 163. The 2 degree and 17 degree angles mentioned are shown on the protractor.
The only other couple of things further to mention is that the soundbox, looking end on, should be at 90 degrees to the playing surface and the angle of the needle to the playing surface when looking from the front of the sound box should be 60 degrees. (See diagram below). With bayonet fitting boxes this latter item is automatically catered for. However with non bayonet fitting ones it is something that needs to be adjusted manually.
Finally please, oh please don't go overboard ( as if I haven't!). As collectors of these lovely pieces of history be aware that their design can have detrimental effects upon our record collection and that knowledge helps us make an informed choice regarding what we play on them. First and foremost gramophones and records are there to be enjoyed so go on and enjoy them!
See text for information on these downloads
in use on an HMV 163
All the images below can be enlarged by clicking on them