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Seems like a good idea, do you install an endpin bushing on violins as well? 

 

Hi Daryl -  since looking at Michael's picture and finding it most pleasing, I think that I will make it a standard detail on all my future instruments.

 

The trouble with a new idea is that it begats children.

 

In previous posts there has been discussion of inserting a spline into the front edge of the neck to improve the compressive properties of the heel of the neck.

 

Expanding on Michael's end-pin dowel, I'm mulling over the idea of inserting a 10 - 12mm thick maple strip into the neck block so that the neck mortise is a maple/maple joint. The thinking being that if the grain runs vertically one has reduced movement due to compression at the front of the neck almost to zero. (the ratio stress-with to stress-across the grain being roughly 7:1).

 

Might reduce movement.

 

cheers edi

 

Dimwit!

 

Inserting a 4 - 6mm thick piece of maple (vertically running grain) into the the front face of the heel would achieve the same thing. Make it 6mm narrower than the width of the heel and it becomes completely invisible.

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He did not say "static friction". He said it's not a "frictionless pulley". It is a common mistake to believe friction needs a ramped force to get things going. I don't think confusing them would work in any engineering and Langragian mechanics needs a PhD for the later. It's incredibly difficult to describe "Sticktion", mathematically while it's trivial for friction even in non-linear cases.

 

I believe catnip is correct.   The tail cord tension (Tp) on the end pin is much less than the total string tension (Ts) due to friction between the cord and the saddle.

 

The same effect is used for mooring boats where a rope is wrapped around a cylindrical post a several times or when tree surgeons hold up a cut off branch by wrapping a rope around the tree trunk a few times.  Rock climbers sometimes wrap their ropes around their forearms or to improve their grip or around their body to hold their weight. 

 

The reduction of string tension is dependent upon the static coefficient of friction (u) and the angular radian number (a) of wraps around the cylinder:

 

Ts = Tpeua

 

where e is the base of the natural logarithm and is about 2.17

 

This equation is called the "Capstan Equation" and Wikipedia has a good write up on it.  A Google search will show lots of examples.

 

 

In our case the saddle shape is similar to a cylindrical surface with a contact angle of about 80 degrees.  There are 2pi radians in 360 degrees so the tail cord is making contact in about 1.4 radians.  The coefficient of friction u between the tail cord and the ebony saddle is probably about 0.4.

 

Catnip said the total violin string load Ts was around 50 lbs so:

 

50 = Tp (2.17)(0.4)(1.4)

 

This equation can be solved to find the total tension on the end pin is only about 29 pounds.

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Marty wrote above...

 

Rock climbers sometimes wrap their ropes around their forearms or to improve their grip or around their body to hold their weight. 

 


Hi Marty - in my youth I used to spend my weekends rock-climbing. What you have described is correct - but - it's what the leader does when he is safeguarding the next guy coming up the pitch.

 

The leader doesn't have that luxury - someone has to get the safety rope to the top of the pitch. Toward the end I did a couple of solo climbs - thoroughly enjoyed not having the constant drag of my "tail" spoiling my fun.

 

post-98-0-31706900-1471978963_thumb.jpg

 

My climbing days ended when I had my third leader-fall. I was lay-backing up a crack when the right-hand handhold let go. Can't say how far I fell - back somersaulted, straightened out and looked down to see where I was going. Noted that I was going to land on a clean bit of ledge and thought "Good - won't break an ankle". Landed - couldn't absorb the shock - still remember how my knees whistled up past my ears and then I flipped off and back into space. Then the rope caught up with me and I yo-yoed a couple of times before dragging myself up onto a ledge.

 

Looking up to my No 2 I could only laugh - his eyes were as big a saucers. He asked if I was OK - I sobered up and replied "Yes - thank you"

 

The shock of hitting the end of the rope moved my L3 vertebra out of position and I couldn't feel anything in my legs for about three days.

 

That injury has plagued me for the last 52 years - the only regret is that as I whistled down past my No2, I didn't think of waving

"goodbye".

 

A few years back I met a guy who'd climbed El Capitan - took him 3 days or something. Impressed me no end and made my local climbs seem rather simple. However somewhere in the conversation I related leading a 100' pitch in a thunderstorm, up a watercourse, normally dry but which now had 40mm of freezing cold water running downwards. The only blessing was that all the hand and footholds were at least clean of sand. He asked how many slings I'd placed for protection and looked absolutely stunned and unbelieving when I told him that I'd climbed the full pitch absolutely clean i.e. no safety aids at all. He thought I was crazy and admitted that none of his friends would ever dream of leading a full pitch unprotected.

 

I had to think about which one of us had more impressed the other. How could I tell him that way-back-then one climbed only with one sling and carabiner - and that was because one might have to abseil to get down off the face - not for safety while climbing. (That beret that I'm wearing was actually an accessory for abseiling. One rolled it up and placed it under your shirt on your left shoulder - it helped to reduce the pain of the rope running over the shoulder.)

 

Later when "mechanical" pitches began appearing one was either a "purist" or not. Me? I couldn't afford the extra "jewelry" so played the "purist" card while all the time wishing...

 

cheers edi


 

 

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I overlooked an obvious example of how the string tension is reduced by friction and wrap angle:  The string end at the peg.  The string's tension where the string goes into the peg's hole is miniscule because of all the string wraps around the peg.

 

 

It also follows that the string's tension between the peg and the nut is about 25 to 50% higher than the string's tension between the nut and the bridge due to friction at the nut grooves.

 

Does anybody lubricate the nut grooves to make tuning easier?

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I use a 2B pencil too but I wonder if that is the best (lowest static coefficient of friction) lubricant available.

 

Wax is a very good lubricant under high pressure, so I've been experimenting with melting in a small amount of wax-based slipping compound into the grooves (and wiping off the excess) and then using the graphite. 

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I use a 2B pencil too but I wonder if that is the best (lowest static coefficient of friction) lubricant available.

 

So the question is:    2B or not 2B?

 

 I use 6B pencil, the feeling is more "greasy" and work just fine.

 I really do not know if there is significant difference in reducing friction compared to 2B, but seems to stick better to the wood and stay in place for longer.

Just my impression, never done a real test.

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 I use 6B pencil, the feeling is more "greasy" and work just fine.

 I really do not know if there is significant difference in reducing friction compared to 2B, but seems to stick better to the wood and stay in place for longer.

Just my impression, never done a real test.

Thanks Davide,

 

I'll ask at my local art shop what they would recommend for lubricating my nuts.

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Marty wrote above...

 

Rock climbers sometimes wrap their ropes around their forearms or to improve their grip or around their body to hold their weight. 

 

Hi Marty - in my youth I used to spend my weekends rock-climbing. What you have described is correct - but - it's what the leader does when he is safeguarding the next guy coming up the pitch.

 

The leader doesn't have that luxury - someone has to get the safety rope to the top of the pitch. Toward the end I did a couple of solo climbs - thoroughly enjoyed not having the constant drag of my "tail" spoiling my fun.

 

attachicon.gifedionrock.jpg

 

My climbing days ended when I had my third leader-fall. I was lay-backing up a crack when the right-hand handhold let go. Can't say how far I fell - back somersaulted, straightened out and looked down to see where I was going. Noted that I was going to land on a clean bit of ledge and thought "Good - won't break an ankle". Landed - couldn't absorb the shock - still remember how my knees whistled up past my ears and then I flipped off and back into space. Then the rope caught up with me and I yo-yoed a couple of times before dragging myself up onto a ledge.

 

Looking up to my No 2 I could only laugh - his eyes were as big a saucers. He asked if I was OK - I sobered up and replied "Yes - thank you"

 

The shock of hitting the end of the rope moved my L3 vertebra out of position and I couldn't feel anything in my legs for about three days.

 

That injury has plagued me for the last 52 years - the only regret is that as I whistled down past my No2, I didn't think of waving

"goodbye".

 

A few years back I met a guy who'd climbed El Capitan - took him 3 days or something. Impressed me no end and made my local climbs seem rather simple. However somewhere in the conversation I related leading a 100' pitch in a thunderstorm, up a watercourse, normally dry but which now had 40mm of freezing cold water running downwards. The only blessing was that all the hand and footholds were at least clean of sand. He asked how many slings I'd placed for protection and looked absolutely stunned and unbelieving when I told him that I'd climbed the full pitch absolutely clean i.e. no safety aids at all. He thought I was crazy and admitted that none of his friends would ever dream of leading a full pitch unprotected.

 

I had to think about which one of us had more impressed the other. How could I tell him that way-back-then one climbed only with one sling and carabiner - and that was because one might have to abseil to get down off the face - not for safety while climbing. (That beret that I'm wearing was actually an accessory for abseiling. One rolled it up and placed it under your shirt on your left shoulder - it helped to reduce the pain of the rope running over the shoulder.)

 

Later when "mechanical" pitches began appearing one was either a "purist" or not. Me? I couldn't afford the extra "jewelry" so played the "purist" card while all the time wishing...

 

cheers edi

 

 

 

 

Nice story Edi, of course apart from L3 vertebra injurie, although often with such an approach to climbing many may not even be here to tell......

It is much safer to be "purists" in violin-making than on the rock. :)

post-70417-0-11829200-1472077284_thumb.jpg

(Me in a much safer situation than Edi, with many safeguarding bolt and carabiner around)

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Nice story Edi, of course apart from L3 vertebra injurie, although often with such an approach to climbing many may not even be here to tell......

It is much safer to be "purists" in violin-making than on the rock. :)

attachicon.gifetoile noire 2000.jpg

(Me in a much safer situation than Edi, with many safeguarding bolt and carabiner around)

 

Hello Davide - oh to be that flexible again - an impressive stride. Those were fun days.

 

cheers edi

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I believe catnip is correct.   The tail cord tension (Tp) on the end pin is much less than the total string tension (Ts) due to friction between the cord and the saddle.

 

The same effect is used for mooring boats where a rope is wrapped around a cylindrical post a several times or when tree surgeons hold up a cut off branch by wrapping a rope around the tree trunk a few times.  Rock climbers sometimes wrap their ropes around their forearms or to improve their grip or around their body to hold their weight. 

 

The reduction of string tension is dependent upon the static coefficient of friction (u) and the angular radian number (a) of wraps around the cylinder:

 

Ts = Tpeua

 

where e is the base of the natural logarithm and is about 2.17

 

This equation is called the "Capstan Equation" and Wikipedia has a good write up on it.  A Google search will show lots of examples.

 

 

In our case the saddle shape is similar to a cylindrical surface with a contact angle of about 80 degrees.  There are 2pi radians in 360 degrees so the tail cord is making contact in about 1.4 radians.  The coefficient of friction u between the tail cord and the ebony saddle is probably about 0.4.

 

Catnip said the total violin string load Ts was around 50 lbs so:

 

50 = Tp (2.17)(0.4)(1.4)

 

This equation can be solved to find the total tension on the end pin is only about 29 pounds.

Gosh I get all dreamy eyed when you talk like that :lol:

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