The Talking Machine Forum — For All Antique Phonographs & Recordings

contessa wrote:

Daithi wrote:Sticktion is also an issue however the vibration generated by the sound itself tends to minimize that.

even encluding the slightest friction caused by the bearing in its base, the record wall should solely bear. Therefore, it is not a matter of distribution.

Please correct me if I am wrong...

I also addressed the issue of bearing drag with the following sentence. "Sticktion is also an issue however the vibration generated by the sound itself tends to minimize that."

contessa wrote:it is not a matter of distribution.

Please correct me if I am wrong...

Weight distribution is absolutely an issue.
Imagine just for illustration purposes a one pound weight sitting on the soundbox end of the tonearm versus a one pound weight sitting on the tonearm pivot.

Both will effect the needle weight on the record. However the one pound sitting on the pivot is largely supported by the pivot while some of its weight is transferred down the tonearm to the needle point. Conversely the one pound weight sitting on the tonearm end will be largely supported by the needle and only some of its weight is transferred up the tonearm to the pivot end.

So therefore weight distribution is absolutely an issue.
This is one of the reasons why many tonearms break in the middle so that only the soundbox end bears on the record and the pivot end is supported by the pivot. If you look at a close up picture of the needle in the groove the needle impinges on the groove walls and not on the groove bottom so the side walls also take the weight of the soundbox tonearm combined downward force as well as overcoming the inertia of the soundbox tonearm combined mass acting on the side to side motion of the needle. There is also the issue of leverage if you think of the tonearm as a lever since its easier for the record groove to move a weight at the pivot end of the lever versus moving the weight at the soundbox end of the lever.

Daithi wrote:

contessa wrote:it is not a matter of distribution.

Please correct me if I am wrong...

Weight distribution is absolutely an issue.
Imagine just for illustration purposes a one pound weight sitting on the soundbox end of the tonearm versus a one pound weight sitting on the tonearm pivot.

Both will effect the needle weight on the record. However the one pound sitting on the pivot is largely supported by the pivot while some of its weight is transferred down the tonearm to the needle point. Conversely the one pound weight sitting on the tonearm end will be largely supported by the needle and only some of its weight is transferred up the tonearm to the pivot end.

So therefore weight distribution is absolutely an issue.
This is one of the reasons why many tonearms break in the middle so that only the soundbox end bears on the record and the pivot end is supported by the pivot. If you look at a close up picture of the needle in the groove the needle impinges on the groove walls and not on the groove bottom so the side walls also take the weight of the soundbox tonearm combined downward force as well as overcoming the inertia of the soundbox tonearm combined mass acting on the side to side motion of the needle. There is also the issue of leverage if you think of the tonearm as a lever since its easier for the record groove to move a weight at the pivot end of the lever versus moving the weight at the soundbox end of the lever.

The two of you are talking about 2 different things. Contessa is asking about the lateral inertia of the arm/reproducer assembly, (where distribution would not be a factor), while Daithi is referring basically to needle pressure, (where distribution is a factor).

JerryVan wrote: The two of you are talking about 2 different things. Contessa is asking about the lateral inertia of the arm/reproducer assembly, (where distribution would not be a factor), while Daithi is referring basically to needle pressure, (where distribution is a factor).

Downward needle pressure also effects lateral movement.
And weight distribution is a factor in lateral inertia of the assembly as indicated in my comments above regarding leverage. Its easier for the groove to move a pound laterally at the pivot than it is to move the same pound at the soundbox.

Concerning wall wear, isn't the groove part of the wall? In the case of Edison phonographs, both cylinder and disc, the groove or wall is not what pilots the stylus through the groove. The Edison Diamond Disc machines and cylinder machines were tracked across the record by a gear that propelled the tonearm across the record. Also the recorded information was located at the bottom of the groove, not on the walls like lateral records.