Garrard Super Motor. Reinventing the wheel............
Posted: Thu Oct 15, 2015 6:22 pm
Throughout history, people, events, designs and articles become forgotten for many different reasons. One such reason for knowledge to die out has to do with competitive corporate secrets. Many of the finer points of the manufacture of gramophone records have gone to the grave with their inventors and producers and, similarly, important details of the operation of Garrard Super Motors have been lost.
I admire these beautifully made spring-driven power sources but have encountered a few problems over the years, particularly in relation to exactly what oil to use, what quantity and what material to employ for the oil pump washer.
It is fortunate that we have amongst our fraternity on this forum someone who winds his motors for many hours a day resulting in a usage which is probably equal to the total amount in a lifetime for less enthusiastic gramophiles. It has thus been possible to make a good assessment of operational requirements and longevity of components.
What oil ?
In the past, and being unable until recently to find contemporary specifications, I have used 20/50 motor car oil which, although excellent for prohibiting mechanical wear, has proved too heavy for the delicate mechanism of a gramophone motor and, in particular, the governor. One of the problems encountered has been a variation or wobble of pitch and it is fortunate that, whilst browsing the ‘net, I was lucky enough to come across the following link---see page 7 :
http://www.radio-workshop.co.uk/service ... ble%20.pdf
The use of sewing machine oil has transformed the performance and reliability of the Super Motor.
What oil quantity ?
Finding the original recommended amount has, so far, proved impossible. We do have a picture of the bottle containing the correct amount but, not having the scale, it is rather meaningless—see photos. Some years ago I made a guess at 100 ml but have now learned that this is too much in view of the fact that, with so much liquid floating around the system, the grease in the spring barrels is eventually leached out to form a combined glutenous heavy sticky fluid which tends to gum-up the mechanism and can exacerbate pitch flutter. I am now experimenting with just 30 ml which, to date, seems to work well.
What pump washer material ?
The Super Motor is said to be an oil-bath motor. The whole mechanism is enclosed within a 99% oil-tight case---a small aperture is built in for the purpose of breathing. An ingenious pump is situated in the lower section drawing oil from a shallow sump which is then circulated up into a gallery at the top of the casing from where it is directed to all parts requiring lubrication. Motive force is generated every time winding takes place---a simple but clever reliable arrangement.
The small washer screwed to the front end of the pump plunger is usually cracked, worn away or partially destroyed when it is time to service the motor. There seem to have been several different materials used which are not easy to identify. Leather certainly seems to have been one and does work well for a while. Recently, I have discovered that extensive use causes the leather to wear and break down, allowing particles to be distributed throughout the motor casing and onto shafts, bearings etc. This has almost certainly been responsible for some of the pitch flutter.
To get over this difficulty, new washers have been manufactured from a nitrile rubber, the definition of which is as follows :
DMR NBR is a black Nitrile Butadiene Rubber, commonly referred to as NBR, Nitrile or Buna. Good physical properties and chemical resistance to the most common hydraulic fluids makes NBR an excellent sealing material. NBR materials are one of the most commonly used elastomers in sealing applications.
The shape, as shown in the photos, is partly conical (45 degrees) which ensures that outward washer pressure is increased in line with oil pressure in the cylinder. The diameter of the plunger is 0.500” and the nitrile cone outside diameter varies 1/16” either side of this measurement.
I now have a good stock of these washers if anyone should be in need. They work well and should greatly increase longevity.
I admire these beautifully made spring-driven power sources but have encountered a few problems over the years, particularly in relation to exactly what oil to use, what quantity and what material to employ for the oil pump washer.
It is fortunate that we have amongst our fraternity on this forum someone who winds his motors for many hours a day resulting in a usage which is probably equal to the total amount in a lifetime for less enthusiastic gramophiles. It has thus been possible to make a good assessment of operational requirements and longevity of components.
What oil ?
In the past, and being unable until recently to find contemporary specifications, I have used 20/50 motor car oil which, although excellent for prohibiting mechanical wear, has proved too heavy for the delicate mechanism of a gramophone motor and, in particular, the governor. One of the problems encountered has been a variation or wobble of pitch and it is fortunate that, whilst browsing the ‘net, I was lucky enough to come across the following link---see page 7 :
http://www.radio-workshop.co.uk/service ... ble%20.pdf
The use of sewing machine oil has transformed the performance and reliability of the Super Motor.
What oil quantity ?
Finding the original recommended amount has, so far, proved impossible. We do have a picture of the bottle containing the correct amount but, not having the scale, it is rather meaningless—see photos. Some years ago I made a guess at 100 ml but have now learned that this is too much in view of the fact that, with so much liquid floating around the system, the grease in the spring barrels is eventually leached out to form a combined glutenous heavy sticky fluid which tends to gum-up the mechanism and can exacerbate pitch flutter. I am now experimenting with just 30 ml which, to date, seems to work well.
What pump washer material ?
The Super Motor is said to be an oil-bath motor. The whole mechanism is enclosed within a 99% oil-tight case---a small aperture is built in for the purpose of breathing. An ingenious pump is situated in the lower section drawing oil from a shallow sump which is then circulated up into a gallery at the top of the casing from where it is directed to all parts requiring lubrication. Motive force is generated every time winding takes place---a simple but clever reliable arrangement.
The small washer screwed to the front end of the pump plunger is usually cracked, worn away or partially destroyed when it is time to service the motor. There seem to have been several different materials used which are not easy to identify. Leather certainly seems to have been one and does work well for a while. Recently, I have discovered that extensive use causes the leather to wear and break down, allowing particles to be distributed throughout the motor casing and onto shafts, bearings etc. This has almost certainly been responsible for some of the pitch flutter.
To get over this difficulty, new washers have been manufactured from a nitrile rubber, the definition of which is as follows :
DMR NBR is a black Nitrile Butadiene Rubber, commonly referred to as NBR, Nitrile or Buna. Good physical properties and chemical resistance to the most common hydraulic fluids makes NBR an excellent sealing material. NBR materials are one of the most commonly used elastomers in sealing applications.
The shape, as shown in the photos, is partly conical (45 degrees) which ensures that outward washer pressure is increased in line with oil pressure in the cylinder. The diameter of the plunger is 0.500” and the nitrile cone outside diameter varies 1/16” either side of this measurement.
I now have a good stock of these washers if anyone should be in need. They work well and should greatly increase longevity.