Skeletal vs Plinth style turntables

Halcro
Let's say, just for fun, we replaced one of your very nicely designed arm pods with a block of foam rubber and we mounted the arm on it.
The foam is just stiff enough to carry the weight of the arm.

On your TT...
This set up will play music
It will pass the timeline test.
Are you saying that this pod will not move?😊

Cheers

Audiogon log - Feb 11 - about 9:30 am EST. Time has clearly moved I have been transported to the next day - but its the same cold dreary looking winter day. As I sit down with my morning JAVA instead of logging onto to Banks lifeline to see if money still exists to pay the pile of bills that are in front of me, I am compelled to log on here to see if time really has moved on. There, a phenomena has occurred - I have been transported back in time to the Copernican thread.

I am feeling like Bill Murray in Ground Hog day

But wait. It is a little different this time. Some of the people are still the same,; but some are different. And there is a difference this time. Yes, its there. A sense of humor among the players. There is hope.

Base on this glimmer of hope instead of stepping away and going about by business I am compelled to add more to the madness.

*******************************************************************************************

Halcro/Richard et al

Well everything is indeed moving around me yet I am grounded to the earth, and even though It appears to be still, giving me a sense of calm, there are signs of movement all around. Sun position in the sky and its physical effect on my body temp. So this is real indeed.

Back to the fascinating turntable which we must now break into its main parts to make my point. Firstly I don't own a Timeline and never will because its information is only measuring one aspect of record play - some info on the table speed itself. It is not providing data on how the stylus is moving/vibratiing. It is not providing data on tonearm movement (up and down, left and right as it tracks the record) Am I wrong ?

Now Richard that was an interesting post you made.

Way back in high school we were tasked with this question..
What happens when you throw a snooker ball such that it hits the front of an oncoming train. The answer is that the train slows, and with relative weights and speeds, we were able to calculated how much.

Looks like you are comparing linear speed versus rotational speed of a record player.

Based on this formula linear versus rotational speed calculator lifted from the internet, are you able to do your calculation and tell us what the movement really is ? I was always terrible at formula in school.

Here is a crazy thought...

could this movement you are referring to, be temporary (out of shape movement) like when vinyl heats up when played, and they it cools down and goes back to form ? Hmmmm..... What do you think ? How else to explain that an armpod after extended time and play still rests on the same spot ?

back to those bills soon.

Just one more question. I will ask Richard but welcome comments from everyone.

The record for sake of argument spins at constant speed 33.3 - 45 rpm. this means its outside speeds are faster, with bigger grooves to track. The inside ones, slower speeds, smaller tighter grooves, more difficult to track. My pivot arms have all made this clear to me - audibly.

A CD solves this by varying its speed as it plays. The music starts on the inside groove and goes out. on the inside a CD can spin 200 rpm and as quick as 500 rpm as the laser beam approaches the outside edge. I can't measure this and take the experts word on it.

Getting to the question.

Richard, back more than two years ago now, your friend Dover presented what he called a POSER on the ET2 thread.
I ask you how measurable is this movement you allude to; and can its effect on the music be considered the same as what follows.

Maybe ....the human ear can't detect it - which would mean for this "audio hobby" it is irrelevant ?

Help, my Pivot Arm is Running too Fast

08-13-12: Dover
Ct0517 - I would not run an ET downhill, but I get the overhang argument.

NOW HERE IS ANOTHER POSER to ponder :

With a pivoted arm we have an overhang. The pivot arm/stylus tip moves in an arc, which means that for every 1.8 seconds ( 1 rotation ) the stylus tip has actually moved slightly forward with each rotation.
Put another way if you put the stylus tip in the first groove, and draw a tangent to the spindle centre, then with each rotation the stylus tip will move further ahead from that tangent.

This means that to achieve the correct playback speed, with a pivoted arm, then the TT needs to speed up with each rotation.

This means that the only playback system that is accurate in terms of speed is in fact a linear tracker.

Now...thoughts...
Dover (Threads | Answers | This Thread)

OPINIONS welcome ?

Simple argument. However minimal the force or friction in a cartridge we can and do have stylus drag. That being the case a pod not fixed will be pulled with the drag in the absence of an equal and opposite force. Whatever the theories I am not a pod fan due to the fact they seem mechanically clumsy. They can be knocked inadvertently and appear to be a bit of a pain to locate. Shoot me down if you disagree but I don't like the idea of a moving part not being fixed down in any way.

I want to stay out of this discussion, because it's all been said before, but I wanted to point out, with respect to the argument regarding whether the arm pod moves due to stylus drag, that the mass of the arm pod, no matter how great, is not the major determinant of its being moved by stylus drag. Rather, the major determinant is the coefficient of friction between the base of the arm pod and the shelf. (Think, if the shelf were made of ice and the arm pod was of the mass of a curling stone [38 to 44lbs, according to Wiki], the pod would move easily.) I am not pointing this out in order to take sides in the discussion. I really don't care whether the arm pod moves or not, because I don't use an arm pod.

Second, I must agree with Richard, the Timeline says nothing about whether the arm pod moves. It only says that IF the arm pod moves, the mechanics of the tt (motor/servo/mass of the platter) are such that the Timeline read-out is unaffected. For all we know based only on the Timeline, the arm pod could be swinging around the whole circumference of the platter as if tethered to the platter, and the Timeline won't tell us this is happening unless the motor/servo/platter is not up to overcoming the resulting drag (call it "arm pod drag"). This is as obvious to me as is the opposite view to Halcro.

I must be dreaming.......