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Double Bass Total pull at tail piece?

#21
robobass said:
So, what strength rope would you guys recommend?

I really think it's true that the tension in the rope will be half the total string pull, and unless you have some very unusual way of going around the socket, it should be pretty even across the two lengths. My number is kind of a theoretical minimum, but I bet it would work.

Besides, I bet those nylon hangers you see on many student basses wouldn't hold much more than 150 lbs., and they only rarely break.
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I use 1/16" SS cable for my tailpiece wires and its plenty strong for the job, as Joey says. I used 3/64" for a time but I always worried about it, so I went up a size. I can't hear a difference between 3/64" and 1/16" anyway; they are both very flexible. ;)
 
#23
JoeyNaeger said:
The tension is not being divided by the two halves of the tailgut. It's one rope and is holding all the tension by itself. Focus on the tailgut where it passes behind the endpin, not the two halves coming out of the tailpiece. There is force being diverted into the top, but the tension of the strings will constant throughout. I think most sets of strings are around 250 pounds, so I would want something with a safe holding strength of around 500 pounds as a measure of safety. I use some thin 1/16" stainless cable that has a safe holding strength of 480 pounds. I have also used the Pecanic tailgut which I don't have specs for, but it works well.
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So you're saying that if you doubled it around again and had four strands going over the saddle that each strand would still have the same tension as if there were only a single strand holding the TP? Is there any number of wrap-arounds where the break strength of the system might be increased without increasing wire gauge? I love this.

The tension is not being divided by the two halves of the tailgut. No. It's being shared:hyper:
 
#25
JoeyNaeger said:
The tension is not being divided by the two halves of the tailgut. It's one rope and is holding all the tension by itself. Focus on the tailgut where it passes behind the endpin, not the two halves coming out of the tailpiece.
Click to expand...
+1. Precisely.
robobass said:
So you're saying that if you doubled it around again and had four strands going over the saddle that each strand would still have the same tension as if there were only a single strand holding the TP?
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No, that's a different situation. Again, think of what would be passing behind the endpin collar. It would be a double thickness, essentially the same as if you wrapped them together to create one "rope."
 
#26
Eric Hochberg said:
Yes, give it a try. You can always go back...doubt that anyone does.
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Thanks, Eric. You're right. But I'm still not clear on exactly what changes I can expect? Except for slight deviations because of temp and humidity, my bass stays pretty well in tune. The force on the tail piece will be the same unless I also change strings, so that's not a problem. However the weight of the wire versus the cable will probably differ, but to what extent?
If some one were to perform a blind test, changing or not changing the wire/cable would I even notice? :hmm:
 
#27
gerry grable said:
Thanks, Eric. You're right. But I'm still not clear on exactly what changes I can expect? Except for slight deviations because of temp and humidity, my bass stays pretty well in tune. The force on the tail piece will be the same unless I also change strings, so that's not a problem. However the weight of the wire versus the cable will probably differ, but to what extent?
If some one were to perform a blind test, changing or not changing the wire/cable would I even notice? :hmm:
Click to expand...

Flexibility of the whole chain. It will probably change the feel for the better and possibly volume and tone. It's something you'll have to experience on your bass. When I did mine 30 years ago it was a significant improvement. My bass played better.
 
#28
drurb said:
+1. Precisely.

No, that's a different situation. Again, think of what would be passing behind the endpin collar. It would be a double thickness, essentially the same as if you wrapped them together to create one "rope."
Click to expand...

Why does it matter if it's a single strand wrapped around a pulley (or endpin socket in this case), or two separately anchored strands? Are you saying that the tension will be different in these two cases? How would the cable tension in either case compare with a fixture with only a single rope connecting the TP to the socket? Inquiring minds want to know:hyper:
 
#29
. When I did mine 30 years ago it was a significant improvement. My bass played better.[/QUOTE]

Okay. You've convinced me.
It's like when I told a friend of mine that I finally got the bass I that I now play restored after its having been stored in my barn for twenty years:

"Got it fixed, eh? After twenty blanking years?
But then you don't want to rush these things."
 
#30
Andrew McGregor said:
It's actually a simple bit of physics... the tension is what determines the pitch at a particular scale length. If your bass has that scale length, that is what the tension on the strings will be, and therefore just add them up to get the tension on the tailpiece.

If your scale length is a little different, the tension will change in inverse proportion, so 1% longer scale length gives 1% less tension. But given the range of numbers we're talking about, that's insignificant. Also stiction in the bridge slots will make a small difference as the tensions on either side don't have to be strictly balanced... but it has to be fairly small, or else the bass is hard to tune and the bridge eventually falls over.

Certainly adding the string tensions up then doubling it will be adequate for sizing a tailwire... but most people would look at the result and say 'That can't possibly be enough' and double the strength again.
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NO!!! Tension varies as the square of the scale length. So a 1% longer scale length will have 1.01^2 more than the rated tension.
http://liutaiomottola.com/formulae/tension.htm
(By the way...note the picture of the "Pandora's Box" Renaissance lute which is the inspiration for modern fanned fret instruments, including my electric bass and electric guitar)
 
#31
gerry grable said:
Thanks, Eric. You're right. But I'm still not clear on exactly what changes I can expect? Except for slight deviations because of temp and humidity, my bass stays pretty well in tune. The force on the tail piece will be the same unless I also change strings, so that's not a problem. However the weight of the wire versus the cable will probably differ, but to what extent?
If some one were to perform a blind test, changing or not changing the wire/cable would I even notice? :hmm:
Click to expand...

Its not a subtle difference Gerry, its adding a whole lot to your tone. The entire tailpiece 'assembly' from bridge to saddle will be free to vibrate and add nuance and air and bottom and complexity to your tone.

Nobody's ever asked me to switch their DB back! ;)
 
#32
robobass said:
Why does it matter if it's a single strand wrapped around a pulley (or endpin socket in this case), or two separately anchored strands? ....
Click to expand...

Let’s try this. Imagine you have a bucket on the floor and a pulley on the ceiling. You attach a length of rope to the bucket, thread it through the pulley and raise the bucket by pulling down. Now the tension in the rope is equal to the weight of the bucket, but the weight on the pulley is double that, since each side of the rope is pulling the bucket’s weight downward. Now tie the end you were holding to a second bucket of equal weight and let go. No change. You’ve simply exchanged one weight for another. Now replace the two buckets for one bucket twice as heavy, tying both ends to the new bucket. Again no change. The the weight on the pulley is equal to the weight of the new bucket, and the tension in the rope is half that. On your bass, the strung tailpiece is that bigger bucket, the endpin socket is the pulley, and the the rope is your tailpiece gut.
 
#34
robobass said:
Let’s try this. Imagine you have a bucket on the floor and a pulley on the ceiling. You attach a length of rope to the bucket, thread it through the pulley and raise the bucket by pulling down. Now the tension in the rope is equal to the weight of the bucket, but the weight on the pulley is double that, since each side of the rope is pulling the bucket’s weight downward. Now tie the end you were holding to a second bucket of equal weight and let go. No change. You’ve simply exchanged one weight for another. Now replace the two buckets for one bucket twice as heavy, tying both ends to the new bucket. Again no change. The the weight on the pulley is equal to the weight of the new bucket, and the tension in the rope is half that. On your bass, the strung tailpiece is that bigger bucket, the endpin socket is the pulley, and the the rope is your tailpiece gut.
Click to expand...

Nope, the tension is equal to the weight of two buckets from the very beginning. I suppose it would be possible to wrap a really long tail gut in such a way that the tension is spread, but at that point you would effectively be using two tailguts.
 
#35
robobass said:
Let’s try this. Imagine you have a bucket on the floor and a pulley on the ceiling. You attach a length of rope to the bucket, thread it through the pulley and raise the bucket by pulling down. Now the tension in the rope is equal to the weight of the bucket, but the weight on the pulley is double that, since each side of the rope is pulling the bucket’s weight downward. Now tie the end you were holding to a second bucket of equal weight and let go. No change. You’ve simply exchanged one weight for another. Now replace the two buckets for one bucket twice as heavy, tying both ends to the new bucket. Again no change. The the weight on the pulley is equal to the weight of the new bucket, and the tension in the rope is half that. On your bass, the strung tailpiece is that bigger bucket, the endpin socket is the pulley, and the the rope is your tailpiece gut.
Click to expand...

Find the center line of the radius where the rope breaks over the sheave (or socket groove). While each side of the rope is loaded with X lbs, the center point where both sides meets experiences the pull from both sides and bears the full load (X + X). In a 1:1 system the entire length of the rope is considered to carry the full load.
 
#36
bssist said:
Find the center line of the radius where the rope breaks over the sheave (or socket groove). While each side of the rope is loaded with X lbs, the center point where both sides meets experiences the pull from both sides and bears the full load (X + X). In a 1:1 system the entire length of the rope is considered to carry the full load.
Click to expand...

So, I guess statics has changed since I was in school, or I learned it completely wrong. Answer me one question though and I'll shut up:

Take my first bucket which you are holding off the ground by pulling down on the rope on the other side of the pulley. Remove the rope from the pulley and tie it to a hook on the ceiling. Is the tension in the rope the same or different now?
 
#37
robobass said:
So, I guess statics has changed since I was in school, or I learned it completely wrong. Answer me one question though and I'll shut up:

Take my first bucket which you are holding off the ground by pulling down on the rope on the other side of the pulley. Remove the rope from the pulley and tie it to a hook on the ceiling. Is the tension in the rope the same or different now?
Click to expand...

I have completely missed the point of tying your rope to a hook. If you are using another section of the rope to compress a single point and divert the force of the load you are changing the system entirely. My understanding is that in a 1:1 system the rope bears the complete load.

Please send me a link to whatever info I am missing or not understanding, I would love to increase my knowledge. But I'm not comfortable with the idea of taking a rope rated to carry 1000 lbs, laying it over a sheave and expecting it to carry 1000 lbs at each end. Maybe I fell asleep in that class ;)
 
#39
bssist said:
I have completely missed the point of tying your rope to a hook. If you are using another section of the rope to compress a single point and divert the force of the load you are changing the system entirely. My understanding is that in a 1:1 system the rope bears the complete load.

Please send me a link to whatever info I am missing or not understanding, I would love to increase my knowledge. But I'm not comfortable with the idea of taking a rope rated to carry 1000 lbs, laying it over a sheave and expecting it to carry 1000 lbs at each end. ;)
Click to expand...

Maybe I fell asleep in that class
Well one of us did at least. Note: If you could try to argue your point without large doses of confusing jargon (as I have attempted to do) then we might resolve this disagreement more quickly and clearly, and include a broader base of readers, including me!
 

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