end of side distortion

[Qwin]

Richard - Does ESD play a part in Linear trackers?

Not heard of that.

This is the Arm I am going for (It will fit on an SL-1200 variant).

http://www.trans-fi.com/terminatortonearm.htm

I may well draw up a protractor myself its a piece of pish but I don't have access to a CAD package, might be possible in Corel Draw but a challange.
Hardest part is doing the Maths, but that has allready been done. We know where the null points are and the overhang curve, angle etc. Suprised no one has done this Mmmnnn..... Am I missing something

[Qwin]

Hi Barry,
You have used IEC standard for inner groove radius for Stevensen values. If you use DIN values you get my results which are even closer.

I'm not being clever with the maths here, I am just reading off what Conrad Hoffmans program calculates, like I said, I'm no expert. Check the program out at the link I gave on post #3. Very usefull.

[Stratmangler]

The trouble with the plastic gauge is it depends on the arm "S" bend being bent EXACTLY right - have you ever tried bending tube to that level of accuracy?

Matsushita are a serious major player in Japan - they will have the bending issue nailed.
It ain't yer average tinpot engineering shop

[Qwin]

Ok I've drawn up a protractor for the standard Arm using the stated Technics values of:

Pivot to Spindle = 215
Effective Length = 230
Overhang therefore = 15
Offset angle = 22 Deg
Inner null point = 58.8
Outer null point = 113.5

I have saved this as a PDF document and it prints at 1:1 providing you have scaling set to NONE on the PDF printing window. I have added horizontal and vertical dimensions to check against.

I will check it works tomorrow on my deck. If every thing is Hunky Dory I will find a way of posting it so everyone can find it easily.

[The Grand Wazoo]

Good work if it works!
If you'd like to email it to Nick (Beechwoods), Barry or myself, we can get it uploaded into The Knowledge - the AoS Library.

[walpurgis]

Interesting. We have some clever people on AOS.

I would not have known how to do this offhand as I've never had to look into alignment protractor design.

[Qwin]

Chris - do you mean in a PM when you say e-mail?

like I said, I will check it out first, don't want to put something out there that doesn't work properly.

[The Grand Wazoo]

Yes, check that it works first & then PM one of us & we'll send you an email address for you to send it to.

[Barry]

Hi Barry,
You have used IEC standard for inner groove radius for Stevensen values. If you use DIN values you get my results which are even closer.

I'm not being clever with the maths here, I am just reading off what Conrad Hoffmans program calculates, like I said, I'm no expert. Check the program out at the link I gave on post #3. Very usefull.

Stevenson does not explicitly quote the inner and out groove radii. He does however quote the two null-points as being 60.325mm and 116.992mm. From these one can back-calculate the inner and outer groove radii to be 54.821mm and 145.263mm.

These are similar to, but not identical with, the DIN standard radii of 57.5mm and 146.05mm.

There is no a priori choice of the inner and outer groove radii for a 12" microgroove LP. Whilst the outer groove radius is generally agreed to be 146.05mm (= 5.75"), the inner groove radius is up for debate.

Stevenson chose his figures as the best compromise for 7", 10" and 12" records.

Once the inner and outer groove radii have been chosen, the null-points are automatically determined and vice versa. From these the overhang and offset angle are then determined and depend on which of the three prescriptions: Baerwald, Loefgren or Stevenson, is followed.

Baerwald provides equal distortion at the start, finish and at a mid point across the record playing surface for records of constant diameter.

Loefgren provides lowest distortion for all radii between the null-points, at the expense of increased distortion at the start and finish of records of a constant diameter.

Stevenson claims to provide optimal tracking for all records of 7" - 12" diameter, with zero distortion at the inner groove (60.325mm), and at 117mm, at the expense of increased distortion elsewhere.

"You pays your money ....."

[Qwin]

Yep, agree with everything you quoted Barry.

If you use the IEC Standard on Conrad Hoffmans program it calculates the null points you stated Stevensen used.

If you use the DIN standard the null points, overhang and offset are closer to what Technics used.

Now I must state, I am using data for the arm on the Technics from the vinylengine database, they quote the inner null point of 58.8 and outer of 113.5 do not know where these figures came from but these are what I am basing everything on. Can anyone confirm these and give a source?

Technics must have had a reason for the direction they took, so to simplify the whole thing I have drawn up a protractor using their (quoted) geometry.
I will be testing it today.