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Double Bass Total pull at tail piece?

#81
jeffbonny said:
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.
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You know me well enough to know that I'm willing to try different things. I've tried quite a few Kevlar type synthetic tail guts and found the sound to be too 'woolly' - bigger in the bottom perhaps, but with a noticeable loss of focus and immediacy.

Which is too bad, because I have hundreds of feet of cool rope, some of which I got from kite surfing shops in Hawaii! ;) So its 1/16" SS wire rope for me - it simply sounds the best.
 
#82
Jake deVilliers said:
You know me well enough to know that I'm willing to try different things. I've tried quite a few Kevlar type synthetic tail guts and found the sound to be too 'woolly' - bigger in the bottom perhaps, but with a noticeable loss of focus and immediacy.

Which is too bad, because I have hundreds of feet of cool rope, some of which I got from kite surfing shops in Hawaii! ;) So its 1/16" SS wire rope for me - it simply sounds the best.
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Thank you for this post. That was my first question when the discussion went back to kevlar.
 
#83
Jake deVilliers said:
You know me well enough to know that I'm willing to try different things. I've tried quite a few Kevlar type synthetic tail guts and found the sound to be too 'woolly' - bigger in the bottom perhaps, but with a noticeable loss of focus and immediacy.

Which is too bad, because I have hundreds of feet of cool rope, some of which I got from kite surfing shops in Hawaii! ;) So its 1/16" SS wire rope for me - it simply sounds the best.
Click to expand...

Ah, silly me not thinking about the sound when I spoke. In my mind's ear I can hear exactly what you're talking about.
 
#84
You nerdy fellows make me laugh; I've been watching this thread and holding back on comments.

I HAVE worked as a professional rigger and high ropes course builder, climbing guide and instructor, my education is in engineering and the sciences, and I string a lot of tailpieces every week. Funny thing is that I've been sitting in a graduate level classroom loaded with Phd physicis instructors and posed the same questions and could not get a straight, consistent answer from any one of them!!! It gets even more random when you start asking about different afterlengths.:hmm::hmm::hmm:

That said, my personal bass is strung with .080" (approx. 5/64") braided steel wire and my ears tell me that is the best choice so far having been through numerous styles and thicknesses of synthetic and steel wires.

j.
 
#86
Jake deVilliers said:
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! ;)
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Well, I did it! I had Jake send me a 1/16" SS cable and connector and I put it on yesterday.
It went fine-- except for the sound post rolling around and the ebony saddle falling off. Both minor distractions ;)
But what a difference! I noticed it immediately, even my wife said that it sounded louder. And the E string, which I thought always sounded okay really came to life. Now in the cold (hot!) light of (next) day, I'm still impressed.
Any body want to buy a slightly used threaded coat hanger wire with end nuts?
 
#94
There is one or two positions where you do NOT have twice the load capacity and this is on top and bottom of the lengthy loop. There you have the single load from two sides, which doubles the load, so there it might break there. If you put the ends of two ropes into a solid block or some stronger rope that winds around on top and bottom (like with the basket configuration at the bottom) it will work, but only if the load is perfectly balanced.

So my advice: the single rope should be able to hold the complete load.
Also remember that knots are the weakest points in a rope. Ask a sailor...
 
#95
I didn't mean to sound like I was adding to the controversy.
We use those slings at work and it seemed like a perfect example of the same principle.

But referring to the original question about tailpiece tension, I think something important
has been overlooked. The strings on the tailpiece side of the bridge are not unique in
angling downward. The strings on the neck side also angle downward. In fact the angles
are very nearly equal. Also I think it should be easy to see that the length of the strings,
neck side vs tailpiece side, shouldn't matter. Imagine that you are looking at 4" of string
length on either side of the bridge and can see no further. You might not even be able
to tell which side the neck is on! The direction of the forces on either side of the bridge
are almost perfectly symmetrical.
Now if the angle has any effect at all on the tension, it would have to have the same effect
on the afterlengths as it it does on the speaking length. In other words there would be no
difference in tension due to string angle. So if we know the tension on the neck side, and
we do (or can), we also know the tension on the tailpiece side.

There is some friction in the bridge string slots that will cause a certain amount of imbalance.
But this an additional effect, not the effect in question. Also the friction is not entirely limiting
on the tension balance. The bridge is not fixed; if the strings cannot slide through the slots,
the bridge will simply begin to tip, after overcoming the tension seating the feet against the top.
(we know what happens if we fail to keep an eye on the bridge when stringing up a bass)

Regarding the tailgut forces, I cannot explain why looping around the endpin bushing doubles
the capacity of the cord (compared to a simple straight cord). I know that it does, though.
The mechanics of it all have been around a while and are in fact not controversial. Yet, it
continues to trip up physicists and engineers. A puzzle very similar to the tailgut configuration
goes back at least 30 years. I've seen physicists get it wrong. And almost all need to think about
it a bit before getting it right.

I think the mistake is in thinking about the tension forces as if they were differential, that is, the
total force is the difference between the two opposing forces. So if you have a 10 lb weight pulling
on one end of a rope and another 10 lb weight pulling on the other end of the rope, the total tension
should be 20 lbs (the difference between plus 10 and minus 10).
The best way to see why this is wrong is to consider another example using the same reasoning.
Suppose you had a 10 lb pull on one end of a rope and a zero lb pull on the other end. What is the
tension in the rope? 10 lbs? By the same reasoning it should be, but zero force on one end means
there is no resistance to the 10 lb pull at the other end. Tension is zero! You see, it doesn't work.
 
#96
Sheesh!!!!

Tension IS force!

Roughly, 4 x 70 lbs in the strings is counteracted by 2 x 140 lbs in the two sides of the tail gut. Otherwise the bridge would accelerate toward the scroll or downward toward the floor, at the rate a = F/m where F is the unbalanced amount of force.

Because the strings angle down toward the table, the bridge exerts an upward force on the strings and an equal and opposite force downward on the table. Otherwise the bridge would accelerate into the table or away from it.

The string tension won't be exactly the same between the tail gut and the strings, because there is considerable friction between the top of the bridge and the strings.

By the way, I AM a mechanical engineer, and if someone wanted me to, I could play one on TV (except for that little unattractiveness problem).

Please open a copy of "Statics and Dynamics", by Beer and Johnston. This is the standard sophomore ME statics/dynamics text. For the statics part, no math more involved than basic trig is required.

Finally, of course you would not design a tail gut with 150# breaking strength for a string load of 140#!!! I would think you would want at least 2X factor of safety, and probably something more like 4X. Kinks, bends, local defects in material, accidental overtightening of a string, etc., etc., are all reasons why I would not want to take a chance on getting a string in the eye.
 
#97
turf3 said:
Sheesh!!!!


Please open a copy of "Statics and Dynamics", by Beer and Johnston. This is the standard sophomore ME statics/dynamics text. For the statics part, no math more involved than basic trig is required.
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I took a course like this. We used a different book, and had a really grouchy Korean Prof. I only got a "C", but think it was one of the most valuable courses I ever took. "Statics" is an incredibly useful thing to learn, even if you don't become an engineer. Whether you are an "evil genius" like me, or move refrigerators for a living, it just helps out in your daily life!
 

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