Quote, Warren! exactly my present portrait.
consolation prize/secret hope -
even if it couldn't use the SD, still remains the SF as for all the other LTAs: but now with a 15 cm favorable lever to turn on the pivot not the opposite to slide on the rail
Doug. it would be nice if it were the joining link between PLT and LTA -- if it works..
Alighiszem #4976 - don't know if you're right or wrong, We need to know where is the virtual pivot, and probably it's not where i naively think, because the rhombus is not rigid. (the Ray string test with the wooden mockups shows little sensitivity)
It would take a real mechanical modeling program, not our toys
consolation prize/secret hope -
even if it couldn't use the SD, still remains the SF as for all the other LTAs: but now with a 15 cm favorable lever to turn on the pivot not the opposite to slide on the rail
Doug. it would be nice if it were the joining link between PLT and LTA -- if it works..
Alighiszem #4976 - don't know if you're right or wrong, We need to know where is the virtual pivot, and probably it's not where i naively think, because the rhombus is not rigid. (the Ray string test with the wooden mockups shows little sensitivity)
It would take a real mechanical modeling program, not our toys
Just a little knowledge of vector decomposition (trigonometry) would suffice. #4893
If things were simple (i.e. if the rhombus were rigid), my little knowledge would be more than sufficient, and you would simply be wrong.
As I (and others) had already explained in the post #4957 (I repost that graph with further clarification).
Things instead are not simple: I redid the string tests of the Peaucellier type A (the best known) and type B (more suitable for our needs). Previously I had built just a type A mock up, thinking the B behavior was the same
Instead:
- if the rhombus is rigid - string test 1 - both behave exactly as expected, i.e. left - null - right skating
But when the Peaucellier is free to move - string test 2 - we notice (to my surprise) that
- Offset skating is much less than on string test 1
- In type A we have left - null - right skating as previewed
- in type B -- surprise - we have the opposite right - null - left skating (maybe because is an "inversed" A type?)
This is what I can observe on these rough mockups.
So, more than simple lessons, I need someone able to define and calculate in details this complex mechanism
carlo
If things were simple (i.e. if the rhombus were rigid), my little knowledge would be more than sufficient, and you would simply be wrong.
As I (and others) had already explained in the post #4957 (I repost that graph with further clarification).
Things instead are not simple: I redid the string tests of the Peaucellier type A (the best known) and type B (more suitable for our needs). Previously I had built just a type A mock up, thinking the B behavior was the same
Instead:
- if the rhombus is rigid - string test 1 - both behave exactly as expected, i.e. left - null - right skating
But when the Peaucellier is free to move - string test 2 - we notice (to my surprise) that
- Offset skating is much less than on string test 1
- In type A we have left - null - right skating as previewed
- in type B -- surprise - we have the opposite right - null - left skating (maybe because is an "inversed" A type?)
This is what I can observe on these rough mockups.
So, more than simple lessons, I need someone able to define and calculate in details this complex mechanism
carlo
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I think that this variant needs to be redesigned in such a way as to use the force of the lever for the tone arm tube in all units. Too thin and too flimsy cantilever of the head with the needle to drag and most importantly to bend all units of the mechanism.Always remember about poor cantilever when we create such steam locomotives
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And I would also add, all the nodes and all the axes of this design will work on the fracture, since the top will press the tube, head and weights of the tonearm.
And this means that the friction of the bushings and axes will increase several times.
By the way, it is also true for all wheeled tonearms, where bushings and axles also work on the fracture.
.And I would also add, all the nodes and all the axes of this design will work on the fracture, since the top will press the tube, head and weights of the tonearm.
And this means that the friction of the bushings and axes will increase several times.
By the way, it is also true for all wheeled tonearms, where bushings and axles also work on the fracture.
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You can't move something which can move only along a straight line with a perpendicular force.
The underlying mechanism is indifferent. It can be a rail, a Peaucellier linkage, my mechanism or anything else.
You don't have to believe me. Ask a mechanical engineer or a physics teacher you trust.
I'm an EE, by the way, I had my mech studies completed.
The underlying mechanism is indifferent. It can be a rail, a Peaucellier linkage, my mechanism or anything else.
You don't have to believe me. Ask a mechanical engineer or a physics teacher you trust.
I'm an EE, by the way, I had my mech studies completed.
Pull the DJ arm without an offset angle. To see what is going to happen. If the DJ arm doesn't move sideways, the arm doesn't skate by Ray's string test. Ray's string test is based on offset angle only. In the string test, geometry is not a factor at all and so is the friction between the stylus and the groove. But in reality, the existence of skating has a lot to do with geometry and friction.
Here is the only correct definition of skating. It can be tested in reality and it makes sense theoretically.
A tonearm doesn't skate as long as the line between the needle point of a cartridge and the pivot or the virtual pivot (for tangential pivot arms) is tangential to the groove.
In the definition above, the word, tangential means a lot. It involves friction and geometry.
By the definition, Carlo's model skates. Just as Warrjon correctly pointed out. It doesn't skate only at one point.
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The Theta angle is what counts, not the offset angle. (Angle between groove tangent and effective length axis).
"Ray's string test is based on offset angle only".
Not true, it is based on the same Theta angle.
Illustration taken from Tejinder Singh Randhawa's article in Wireless World (March 1978).
"Ray's string test is based on offset angle only".
Not true, it is based on the same Theta angle.
Illustration taken from Tejinder Singh Randhawa's article in Wireless World (March 1978).
Even Ray himself wanted to come up with a String Test version 2, do you want to come up with a version 3?
'A tonearm doesn't skate as long as the line between the needle point of a cartridge and the pivot or the virtual pivot (for tangential pivot arms) is tangential to the groove.
In the definition above, the word, tangential means a lot. It involves friction and geometry.
By the definition, Carlo's model skates.'
The definition is near to true, but you can only see where the pivot point is by the naked eye only in the most simple cases. For example, you are talking about a virtual pivot point for tangential pivot tonearms, even though they have a completely real pivot point at the centre of the Thales circle.
By the definition, where would you put Carlo's model's pivot or virtual pivot? Since when has a point describing a straight line a pivot?
There is a simpler way to decide if a tonearm skates, may it be as complicated as a Peaucellier linkage: if the groove tangent and the tangent to the path of the stylus are not perpendicular, it will skate.
And the underlying mechanism does not count.
In the definition above, the word, tangential means a lot. It involves friction and geometry.
By the definition, Carlo's model skates.'
The definition is near to true, but you can only see where the pivot point is by the naked eye only in the most simple cases. For example, you are talking about a virtual pivot point for tangential pivot tonearms, even though they have a completely real pivot point at the centre of the Thales circle.
By the definition, where would you put Carlo's model's pivot or virtual pivot? Since when has a point describing a straight line a pivot?
There is a simpler way to decide if a tonearm skates, may it be as complicated as a Peaucellier linkage: if the groove tangent and the tangent to the path of the stylus are not perpendicular, it will skate.
And the underlying mechanism does not count.
Carlo's model is not a tangential pivot arm. It is basically a linear arm with a different driving mechanism. There is no virtual pivot. Some of the comments I posted about the models you posted can be applied to his model as well.
I don't know what you are talking about. This is Birch style tonearm. In the diagram, 01 is the center of the Thales circle. P3 is what I called a virtual pivot. There is no physical pivot at P3, but an imaginary one.
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....mayday
Dear friends, would anyone like to apply his vast and consolidated knowledge to the new challenge of a "simple" vector breakdown of a Peaucellier mechanism?
As said, to design this working TA it would be necessary to know the distribution of the tracking forces - SD /SF - at the 6 joints level, in correspondence with the outer and middle groove positioning.
I made a simulation by forcing the angle and sizing to highlight as much as possible what happens during rotation
thanks in advance - carlo
funny - no one has asked me yet how the headshell will not rotate, like in SIM ONE. (the point draws a line, but does rotate too) and instead stay parallel as on SIM TWO; Without that...
Maybe i've already got a solution but I'm interested in knowing yours, probably much better.
Dear friends, would anyone like to apply his vast and consolidated knowledge to the new challenge of a "simple" vector breakdown of a Peaucellier mechanism?
As said, to design this working TA it would be necessary to know the distribution of the tracking forces - SD /SF - at the 6 joints level, in correspondence with the outer and middle groove positioning.
I made a simulation by forcing the angle and sizing to highlight as much as possible what happens during rotation
thanks in advance - carlo
funny - no one has asked me yet how the headshell will not rotate, like in SIM ONE. (the point draws a line, but does rotate too) and instead stay parallel as on SIM TWO; Without that...
Maybe i've already got a solution but I'm interested in knowing yours, probably much better.