Are linear tracking arms better than pivoted arms?

I dug out the old article (High Performance Review, Vol. 4 No. 2, by Ted Simmons/David Tarumoto). Here is what it says: "...normal pivoted arms must confront this same dynamic alignment issue. To look into this motion we mounted an Orsonic Side Force Checker SG-1 in ET2 and SAEC WE 407/23 (double knife-edge pivoted) arms. The SG-1 is a cartridge complete with cantilever and stylus that has an indicator pointer attached to the cantilever to show the relative motion of the stylus. It's a very handy device to check the amount of side force correction to dial in with pivoted arms. Here we're using it to measure more dynamic changes.

"In this case, we used it to see the relative side-to-side motion when tracking sample LPs. Normal LPs, plus those with obviously off-center holes and those with definite warps were tried.

"Surprisingly, SAEC's WE 407/23 showed a much wider side-to-side movement of the pointer than the ET2 on all of the sample LPs that we used. This happened when playing both test records (produced very precisely) and typical mass market pressings."

Interesting, but only one data point, and not able to be easily verified.

Following a near 3 decade hiatus from records, I acquired via AudiogoN a VPI HW-19 MKIV with an ET-2/Benz Glider combo...I've been mesmerized by tangential arms since I first saw the beautiful Rabco ST-7, as a teenage nascent audio-enthusiast, in magazine adverts and the beguiling B&O 4002, in person...I favored the Transcriptor Vestigial for radial arms. I suppose I'm examining it from a different angle :-)

Enjoy!
Sam

Atmasphere is absolutely correct.

"The idea that a pivoted arm of correct effective mass is going to induce greater side-to-side excursion than an air-bearing straight-tracking arm strains credulity."

I would even say it neglects fundamental aspects of mechanic and physic.
But nothing in physics can be obvious enough not to be questioned if it doesn't fit the preference of an audiophile. Must have been a test of true insight and scientific brilliance.
Oh my.

02-27-10: Dertonarm
I would even say it neglects fundamental aspects of mechanic and physic. But nothing in physics can be obvious enough not to be questioned if it doesn't fit the preference of an audiophile. Must have been a test of true insight and scientific brilliance.
Oh my.

Main Entry: snarky
Pronunciation: \ˈsnär-kē\
Function: adjective
Etymology: dial. snark to annoy, perhaps alteration of nark to irritate
Date: 1906

1 : crotchety, snappish
2 : sarcastic, impertinent, or irreverent in tone or manner

— snark·i·ly \-kə-lē\ adverb

I have been doing some research on the issue of stylus pressure that a pivot arm vs a linear arm exerts as the record progresses from the outer edge to the inner grooves. There is some pretty good information on the airtangent and Kuzma airline arms concerning this issue. In fact i found one reference where a reviewer compared the Airtangent to an SME arm on a VPI table. In addition, I had several discussions with some pretty good engineers who helped me understand the issue a little better. After going over it several times, I recognize now what Dertonarm, Raul, Atmasphere, and others were trying to relate. The easiest way to say it is that for two tonearms of equivalent mass, the pivot arm will result in less pressure applied to the stylus and suspension system of a cartridge as the stylus moves across the record. If you state the issue as forces applied and represent the forces as vectors in the xy horizontal plane. (assume x axis is the path of the linear arm), the linear arm forces are entirely represented by the x vector. As the pivot arm actually strikes an arc across the record, the distance the stylus moves is further and part of the forces is represented in the x axis and part of the forces are in the y axis. In addition, the pivot point also reduces the net force needed to move the arm. It is a similar to why a lever can lift a 100 pound weight with less than 100 lb downward force. Having said this, the better linear arms attack this issue by having less total mass that a typical pivot arm. The airtangent site clearly indicates this issue and explains how they attach this issue by using the spindle as a fixed part and using a bearing sleeve as the moving part as well as using a carbonfiber armwand to decrease weight without giving up stiffness. In addition, the manufacturing tolerences of the arm is pretty small to minimize the "Slop" that Dertonarm indicated was an issue with these types of arm. Similar comments are also on the Kuzma site outlining their approach to the problem. I ended up addressing this issue (by accident) as I modified the maplenoll arms by eliminating the aluminum wand and heavy, cumbersome vta adjustment bracket with a carbonfiber arm, spindle and wood headshell. My arm on my apollo is a very short ceramic armwand and very lightweight spindle. I have not compared the total weight to my modified arm on my ariadne signature but i believe it is lighther due to the very small length. Obviously, without the vacuum platter, this short length would be an issue. I appreciate the various contributors to this string as it opened my eyes to some more opportunities to continue to improve the system i have. I have invested pretty heavily into some top notch cartridges and understanding this issue better will help me protect that investment. Having said this, I do like my modified arm and look forward to trying to develop a smaller mass arm for my apollo.