conical versus ellipticals

[Ldg]

Thanks, Pivot. The concept is courtesy of Thomas_A, so credit there.

[missan]

Nice work ld. I have tested and what I can see the calculations works fine. I have only one comment regarding moment of inertia, it is for many platters more complicated to calculate, but for Rega platters and such it should be good enough.
missan

[Thomas_A]

Thanks ld,

I got ≈175 s for platter spinning and 75 s with stylus on r ca 12 cm, VTF 1.4 gram, Shure/JICOSAS.

Now the moment of inertia of the Linn Axis platter is more difficult. Around 2-3 kg ?, but with an inner platter and an outer "rim" which is more heavy. This would affect the results.

2 kg would give 0.00045 Nm for bearings (3 kg-platter > 0.000675)
0.00105 for stylus (3 kg-> 0.001575)

T(F)=0.0006Nm (3 kg 0.0009)

F=T(F)/r->0.0006/0.12=0.005 Nm(3 kg 0.0075)

I got a time ratio of 2.3 (stylus off/on)

You got a time ratio of 1.9 (off/on)

Suggests similar frictional force, although you used 2.0 g VTF.

T

[Ldg]

Good stuff, Thomas_A.

If the platter weight is uniform, say made from a solid cylinder, then I =(m*r^2)/2. If the weight is entirely around the rim then I = (m*r^2), i.e a factor of 2 bigger. So perhaps a reasonable approach to estimate moment of inertia with the Linn Axis platter is to estimate how much weight is on the rim and choose a factor between those limits, in proportion ? And hopefully someone out there knows how much a Linn Axis platter actually weighs ? Just that it is necessary to know, unfortunately.

Those absolute friction numbers you measure (0.005N - 0.0075N are lower than those I measured (0.0089N - 0.0093N). Your figures equate to c 0.5gf - 0.75gf for a VTF of 1.4gf, whereas my figures equate to c 0.9gf for VTF = 2.0gf . However, as you say, the friction co-efficients seem about the same, though yours is probably a bit lower. The stylus profiles are very different, of course. But much depends on being confident of a true estimate of the moment of inertia of the Linn Axis platter. My platter is a solid uniform cylinder, so moment of inertia is pretty well determined.

Still, accords with Yosh's range of coefficients though, which says something for the method.

Must get a better bearing !!!

[Thomas_A]

Just measured the mass of the Axis (significantly lighter than the LP12 platter, seen values of 3.75 and 4.1 kg)

Inner platter is 0.5 kg
Outer platter is 1.05 kg

I would suspect a factor of 1.7 instead of 2, to compensate for the outer rim mass.

I=0.0205

T(b)= 0.0205*3.5/175=0.00041

T(F)=0.0205*3.5/75-0.00041=0.00055

F=0.00055/0.12=0.0046

I.e. about half the value of your case.

T

[Ldg]

F=0.00055/0.12=0.0046

I.e. about half the value of your case.

Great, Thomas_A, it seems quite reasonable to expect a lower friction coefficient from your stylus compared with the OM5E on my test deck. Your friction coefficient is within the low part of the range of Yosh's quoted figures, then. Friction coefficient is approx 0.33, and friction force at 1.4g VTF = c 0.46gf . I think.

Then AS is also predicted to be quite low.

[Thomas_A]

F=0.00055/0.12=0.0046

I.e. about half the value of your case.

Great, Thomas_A, it seems quite reasonable to expect a lower friction coefficient from your stylus compared with the OM5E on my test deck. Your friction coefficient is within the low part of the range of Yosh's quoted figures, then. Friction coefficient is approx 0.33, and friction force at 1.4g VTF = c 0.46gf . I think.

Then AS is also predicted to be quite low.

Yes, it appears to be around 0.33. In your case, around 0.45.

Now, I thought I had even lower µ, but no. I need to reinvestigate some things. I will redo my setup first and measure crosstalk for optimum value and then lateral tracking alignment, and finally SRA.

Then redo the antiskate measurements.

A lot to do...

T

[missan]

Good work guys.

I have a little higher VTF, so let´s say I have a stylus drag of about 0,6gf.

That would mean tan23deg*0,6gf= about 0,25gf in Skating Force.

I do not know how these AS-mechanisms are calibrated, if these figures are the ones one is adjusting, but I think that it could make sense if it is so. That is about the figure I am normally using, or maybe a tiny bit higher.

missan

[flavio81]

I have reviewed ld's vinyl temp rise calculations and got an even lower value. Please follow at:

http://www.vinylengine.com/phpBB2/viewt ... 414#162414

[analogous]

Ok, now a fact sheet so some forum members here can GET IN TOUCH WITH REALITY for a change...

1. The best cantilevers are made of a material that is STIFF and LIGHT, the manufacturers currently prefer BORON as the best in stiffness & lightness. You need a cantilever that is RIGID, not flexible like cactus thorns. A flexible cantilever would at the very least roll off the high frequencies.

Haruo Takeda uses aluminum. Art Dudley consider his Miyabe 47 the best cart he has ever heard. Dudley is not in touch with reality?

Boron cantilevers. Lucite turntables. Carbon fibre tonearms. Whatever is the flavor of the month.

[flavio81]

Ok, now a fact sheet so some forum members here can GET IN TOUCH WITH REALITY for a change...

1. The best cantilevers are made of a material that is STIFF and LIGHT, the manufacturers currently prefer BORON as the best in stiffness & lightness. You need a cantilever that is RIGID, not flexible like cactus thorns. A flexible cantilever would at the very least roll off the high frequencies.

Haruo Takeda uses aluminum. Art Dudley consider his Miyabe 47 the best cart he has ever heard. Dudley is not in touch with reality?

Did i write that aluminium-cantilevered cartridges are bad?

[1200y3]

Aluminum has its merits, but purity is getting expensive. I don't think tapered cantilievers will be affordable for very much longer. There is alot of waste product in the manufacturing of quality cantilevers and diamond tips, and there is an unpredictable amount of excellent alternatives and options.

(Thorns are pre-taperd, and I have no trouble with them in the treble, but to get the correct amount of bass they have to have some mass. They break too. Actually, they are way more rigid.)

[Ldg]

For those seeking empirical evidence of lack of heating of groove walls during play, or for those simply seeking sensation, you might find ice pressing interesting........in fact friction coeffs would be very different, but interesting anyway.

http://www.dangerousminds.net/index.php ... e_records/