Help Ressurecting an Odyssey - geometry and effective mass?

[missan]

no, the effective length (BC) is fixed (I had this idea too - imagine the nightmare...)

best regards

Seb

I see what You mean, it is then a increasing mounting distance that will give narrower null points?
BR/missan
edit: changed to increase

[AndrewL]

Hi Seb,

I also get this same answer my first attempt, while possibly valid, is very very very much less likely...

-- Andrew

[Seb]

no, the effective length (BC) is fixed (I had this idea too - imagine the nightmare...)

best regards

Seb

I see what You mean, it is then a decreasing mounting distance that will give narrower null points?
BR/missan

the mounting distance is constant too over the record surface since the mounting distance is equal to the distance between the platter spindle (this one is not moving) and point B of my drawing (this one is not moving too)

now, the null points the manufacturer is obtaining are rather strange. It's not the first time a manufacturer is giving null points incompatible with the mounting distance, overhang and angular offset stated.

best regards

Seb

[Seb]

Hi Seb,

I also get this same answer my first attempt, while possibly valid, is very very very much less likely...

-- Andrew

in that case, or the 60° is not good, or the effective length is not good (or the guy who worked with the arrow did a very strange (bad...) job.

what is you distance between the center of the small dome and the stylus tip ?

best regards

Seb

[odaey]

Guys,

I did some actual measurments and 240 coincides with the distance from the center of the small dome to the tip of the cartridge mounting area of the armwand and not the stylus tip of the mounted cart.

odaey

[Seb]

I made a mistake...

the 60° apply to the angle formed by the arm tube and the line passing through the center of the two domes.... the angle between the line passing through the center of the two domes and the line between teh center of the small dome and the stylus tip is superior...

need to think more about that...

best regards

Seb

[AndrewL]

I checked aagin, on the angle, there's a pretty good enginnering drawing in the back of the Odyssey Brochure. No dimensions but its pretty close to full scale.

http://www.vinylengine.com/library/sour ... ange.shtml - page 21.

I am definitely using pivot to spindle of 213mm, but I'm not so sure the overhang is as much as 17mm, at least not the way I have it set up. With a possible variation of +/- 4mm there's quite a lot of scope to use different overhangs.

-- Andrew

[AndrewL]

OK, I got chance to measure between the center of small dome to stylus tip (AC) and I get in the region of 239mm. I only have a ruler so this is not 100% accurate.

-- Andrew

[Seb]

well I checked the drawing of the brochure, the 60° is good (and as indicated before, I didn't use that 60° correctly).

now, the 23.5° angular offset seems to be impossible with the drawing. A 21.5° angular offset is more plausible.

need to work on the various small dome / spindle center distances to see if there is something to do with that...

I don't know if there is a real possibility to understand the geometry of this tonearm since at least two data are wrong : the angular offset and the null points. (but drawing a 12" tonearm is possible )

if the stylus point is not aligned with the axe of the tube, a screw og the headshell seems to be aligned. could you confirm ?

best regards

Seb

[AndrewL]

well I checked the drawing of the brochure, the 60° is good (and as indicated before, I didn't use that 60° correctly).

Well it seemed OK to me, but perhaps you have got to another level of understanding the geometry of the arm.

if the stylus point is not aligned with the axe of the tube, a screw og the headshell seems to be aligned. could you confirm ?

Yes, the screw in question, is aligned with the axis of the tube.

thanks,

-- Andrew

[Seb]

well I checked the drawing of the brochure, the 60° is good (and as indicated before, I didn't use that 60° correctly).

Well it seemed OK to me, but perhaps you have got to another level of understanding the geometry of the arm.

if the stylus point is not aligned with the axe of the tube, a screw og the headshell seems to be aligned. could you confirm ?

Yes, the screw in question, is aligned with the axis of the tube.

thanks,

-- Andrew

I used the 60° wrongly because the stylus tip (dot C on my drawing) is not where I put it, the real stylus tip is a little on the left. The fact that the screw is right in the middle of the tube (on the 60° line) could help since the distance between the two screws is known : 12.7 mm and that the distance between the stylus tip and middle the line passing through the two screws is not known (not a standard) but said to be 9mm (it's only a proxy, it depends of the cartridge you're using)

well let's think again...

best regards

Seb

[AndrewL]

Hi Seb,

Yes, I see, and agree, on your point about the tip being to one side of where you drew it when you consider the tip in relation to the arm tube.

However, the tip will still be somewhere on that 230mm radius (effective length) so we just need to obtain the correct rotation of the tip and arm tube with respect to each other and then we can derive the length of the tube etc, I hope.

Good progress...

-- Andrew

[AndrewL]

I forgot to mention, the distance between the center of the small dome (root of the arm wand) and the on axis mounting hole is 233mm. I will double check this as I was tired last night.

The front face of the headshell, from the drawing, seems to be a 60 deg with respect to the tube axis (in other words parallel to the angle between two domes) so another right-angle triangle.

-- Andrew

[Seb]

what is the diameter of the arm tube ?

best regards

Seb