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Double Bass Total pull at tail piece?

#61
David Potts said:
Doesn't ANYONE have a tension gauge?

DP
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They're expensive and not an essential tool even for most people who've invested in them. They tend to tell experienced riggers and wheel builders what they already knew and eventually end up gathering dust. That said you live in a coastal city, call around to the yacht riggers. In a city of four million one of the better rigging lofts will have a set. They might even gauge your bass for free just for the novelty factor...or to shake the dust off the thing.

A spoke tension gauge that many bicycle wheel builders have would probably work as well as anything. They're small and would fit better between bridge and tailpiece than a lot of rod or wire rope gauges.
 
#62
I've got these but I;m not sure how to get them between the tailpiece and the endpin collar. :D
 

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#64
iiipopes said:
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)
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Of course it does, d'oh... but that just makes the proportional change smaller, so I was still right that it doesn't matter.
 
#65
Eric Hochberg said:
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.
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Mine too... it does make a big difference, removing that big spring controlling the end of the tailpiece and replacing it with something flexible.

Synthetics tend to be too stretchy, wire rope seems to be the best compromise between flexibility and stretch.
 
#66
JoeyNaeger said:
The simplest way I can explain this is that you have one single rope holding the weight of the tailpiece. The fact that it wraps around the endpin changes nothing. It is one single single rope bearing the full tension of the strings. ..
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Joey, if I understand your premise properly, you need to read about block & tackle systems. If the wire goes from the tailpiece around the endpin and back to the tailpiece, its tension is half the combined string tension. The tailpiece is in equilibrium, the total forces on it are equal. Furthermore, the tension is the same at every point along the length of the cable, including the halfway point in the bend.

Yes, if you cut either 'half' of the rope the total thing fails, but that's also true for a 10:1 block & tackle. It doesn't mean the tension isn't reduced.

As for overbuilding.. in most cases the market does not want overbuilt products. They're heavy and expensive. Cars, motorcycles, bicycles, air/spacecraft, skis, shoes.. these things would not be at the development level they are at if they were naively designed with 5~10 times the necessary material.

Unfortunately the ragged edge does bite us in a few cases, but it's far more common that we allow ourselves to be bitten by cheap products that are either marginally built or underengineered to drive costs down. Lawn mowers, shovels, BBQ grills, we have rewarded companies who produce complete junk by buying their products. The parking lots at Walmart and Harbor Freight are always packed.
 
#67
AntonLargiader said:
Joey, if I understand your premise properly, you need to read about block & tackle systems. If the wire goes from the tailpiece around the endpin and back to the tailpiece, its tension is half the combined string tension. The tailpiece is in equilibrium, the total forces on it are equal. Furthermore, the tension is the same at every point along the length of the cable, including the halfway point in the bend.
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I get what you're saying here (sort of). However, it still seems to me that, as you say, the tension on both sides of the tailpiece must be equal. For that reason it seems that the one cable is withstanding the complete force that is being applied from the north side of the tailpiece.

Looking from another direction (and thinking back to the above mentioned buckets), are you saying that I can take a rope with a breaking strength of 500# and a) hang it straight from a point and load it to 499# without failure; and I could take that same 500# rope and b) run it over a sheave and hang 499.5# on each end and it will not fail? I think I'm going to have to try this in the back yard, it just does not seem logical to me.
 
#68
I suppose I could be wrong, but I did look up how to calculate rope tension in such a system and feel satisfied with my intuition. My understanding of block and tackle systems is they can reduce the amount of force needed to lift something, but I still don't see that affecting the actual tension of the rope. Based on my experience, I have seen several tailguts failing on basses and would absolutely not trust using a tailgut that was rated to hold only half the tension of the strings. There are several options available that are low mass, flexible, and have a large safety margin so I don't really see the point of this discussion...
 
#70
JoeyNaeger said:
My understanding of block and tackle systems is they can reduce the amount of force needed to lift something, but I still don't see that affecting the actual tension of the rope.
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That's just self-contradictory. The reduced force is applied to the rope, ergo the rope has less force applied to it. That means less tension. It's that simple.

If you, as a 160 pound person, use a 10:1 block & tackle to lift a 1500 pound object using 150 pounds of your weight (we'll leave you ten pounds just so you don't float around) the rope tension is 150 pounds.

The rope tension will not be 1500 pounds. You would never be able to exert that.
 
#71
AntonLargiader said:
That's just self-contradictory. The reduced force is applied to the rope, ergo the rope has less force applied to it. That means less tension. It's that simple.

If you, as a 160 pound person, use a 10:1 block & tackle to lift a 1500 pound object using 150 pounds of your weight (we'll leave you ten pounds just so you don't float around) the rope tension is 150 pounds.

The rope tension will not be 1500 pounds. You would never be able to exert that.
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I'm confused. What does compound block and tackle rigging have to do with rigging a tailpiece on a double bass?

As for synthetics stretching more than wire rope Amsteel has less than 1% stretch loaded at 30% of breaking strength which you'd never come close to on a DB tailpiece. Breaking strength on 1/8" Amsteel is 2500lbs. Your real stretch would be less than .5%. Even Tech 12 which has a little more give but is a little more durable would stretch less than 1% on a DB tailpiece. These hollow braids are a lot easier and cleaner to splice than wire too. Other than already being tooled up to use wire rope I can't think of a good reason not to use Tech 12 instead.
 
#72
And how does all that mechanical advantage change the fact that your rope is supporting a hypothetical 1,500 pounds? Surely you wouldn't use a dinky little rope to hold all that weight. I challenge anyone to do a real test or show some real math. Until then, I've said enough...
 
#73
JoeyNaeger said:
And how does all that mechanical advantage change the fact that your rope is supporting a hypothetical 1,500 pounds? Surely you wouldn't use a dinky little rope to hold all that weight. I challenge anyone to do a real test or show some real math. Until then, I've said enough...
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This stuff is common knowledge. Any sailor knows it.

Tell me, though, when you pull on that 10:1 block & tackle I described, how many pounds of tension do you think you are putting in the rope that you are pulling?
 
#74
JoeyNaeger said:
And how does all that mechanical advantage change the fact that your rope is supporting a hypothetical 1,500 pounds? Surely you wouldn't use a dinky little rope to hold all that weight. I challenge anyone to do a real test or show some real math. Until then, I've said enough...
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Look, go to the library and check out Stage Rigging Handbook by Jay Glerum. In it he simply and clearly explains compound rope rigging by using diagrams that will help you visualize the problems and solutions. A compound system actually reduces the lifting load on the anchor point because you need to apply less force to move the load than on a 1 to 1 single pulley. The trade off is the load moves more slowly.

And compound pulley systems still have nothing to do with rigging a tailpiece on a double bass.
 
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#75
JoeyNaeger said:
...I have seen several tailguts failing on basses and would absolutely not trust using a tailgut that was rated to hold only half the tension of the strings.
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I hope no one is advocating that; it would be a terrible design decision. One consequence would be that when Joe Bass Player accidentally cranks his D string when he's trying to raise his E string, he'll break the tailgut. Bad design. You have to design for certain expected but abnormal conditions.

A reasonable decision might be to size the tailgut breaking strength to the breaking strength of the strings. So if your typical working string was 65 pounds and had a breaking strength of 140 pounds (I'm making that number up) then four of those strings would be 560 pounds. That would get offset by two tailgut wires, each of which 'should' (by that criterion) hold at least 280 pounds. The fact that they are actually the same piece of wire doesn't matter, but that is a separate issue.

Of course something else on the bass might have failed before you reached 560 pounds, which could be worse overall. That's the tricky thing about design. Maybe you want the tailgut to break first.
 
#78
I think people are confusing tension with force. I understand how pulley systems work to reduce the necesary force to lift something. I did take physics... That does not however change the fact that your rope is supporting the full weight of the load.
 
#79
JoeyNaeger said:
I think people are confusing tension with force. I understand how pulley systems work to reduce the necesary force to lift something. I did take physics... That does not however change the fact that your rope is supporting the full weight of the load.
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Did anyone say it wasn't?
Whatever point you're making isn't at all clear and I deal with this stuff daily in situations where getting it wrong means time loss, property damage and human injury.
 

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