Weight when replacing strings?

[hogues]

Thought I'd get around to asking something that's been on my mind forever - years ago I was having a seam reglued in a little shop in Central PA, one thing led to another and we got to talking about how often he saw soundpost issues with students trying to change strings and letting the post fall over.

He recommended placing a weight on the bass near the g-string side of the body when doing any string work to simulate the tension of a tuned-up bass... I seem to recall he mentioned a few books as a rough idea of how much weight to apply. This struck me as an odd idea, maybe putting too much stress on the top. Haven't heard of it since then. Anyone want to chime in?

[relacey]

You'll need some weighty tomes! While it's different for every bass and string combination it's a matter of geometry. A full set of Spiro Mittels at concert pitch on a 42" string length will have a total tension of 274 lbs. If the angle over the bridge is 5 degrees then the resultant force on the top is about 24 lbs. (= sine(5) * 274). A larger angle will result in greater force on the top.

For string changing advice go to this sticky.

If I were changing strings using books to weight the soundpost, the first thing that would probably happen is that I'd knock the books off while I was fumbling around with the string. Unless there is a need, I change strings one at a time. It's a little more awkward working around the other strings but less risk of knocking the SP over and I have an easy reference to tune the new string close to pitch.

[hogues]

Originally Posted by relacey

If I were changing strings using books to weight the soundpost, the first thing that would probably happen is that I'd knock the books off while I was fumbling around with the string. Unless there is a need, I change strings one at a time. It's a little more awkward working around the other strings but less risk of knocking the SP over and I have an easy reference to tune the new string close to pitch.

Agreed - I always go the one-at-a-time route. I didn't like the idea of the thing, just never got around to asking if it was a worthwhile idea, or if it would work if you needed to remove your bridge for whatever reason for a few minutes. One of those things that sticks in your head... sort of like this article I'm reading on chocolate covered bacon. "...people try that?!"

[Jake deVilliers]

Originally Posted by hogues

Thought I'd get around to asking something that's been on my mind forever - years ago I was having a seam reglued in a little shop in Central PA, one thing led to another and we got to talking about how often he saw soundpost issues with students trying to change strings and letting the post fall over.

He recommended placing a weight on the bass near the g-string side of the body when doing any string work to simulate the tension of a tuned-up bass... I seem to recall he mentioned a few books as a rough idea of how much weight to apply. This struck me as an odd idea, maybe putting too much stress on the top. Haven't heard of it since then. Anyone want to chime in?

I use a weight on the top to keep the soundpost in place when removing all tension from the strings, usually when working on the bridge or endpin.
I use a 25 lb. bag of shot used for reloading shotgun shells - anywhere from size 7.5 to 12 works well.

Its also the best neck rest for re-fretting g***ars.

Good luck finding some in Japan!

Chocolate-covered bacon!?

[Eric Hochberg]

I used books when changing tailpieces and the post didn't fall. Could have been pretty snug anyway...

[arnoldschnitzer]

Originally Posted by relacey

A full set of Spiro Mittels at concert pitch on a 42" string length will have a total tension of 274 lbs. If the angle over the bridge is 5 degrees than the resultant force on the top is about 24 lbs. (= sine(5) * 274). A larger angle will result in greater force on the top.

The average angle over the bridge is 32-36 degrees. I'm curious what that computes to as far as downward pressure.

[Phil Rowan]

I just did some self-luthiery yesterday, changing the tailpiece wire length to bring the tailpiece back down to the saddle (I have a pecanic wire which, over time, stretched a little too much, resulting in too soft a feel for the already soft guts). I used a 10lb weight first just below the bridge, and with the bridge off I put it where the treble side foot would be. Got it done w/ no sound post slippage. I know this is different from just changing strings. For that I usually just lay the bass on its back and do one at a time...but, ya'll making me a little paranoid now.

ps - I did the original installation of the pecanic wire, and this time around, as I'm a little more hip to it, I used 3 square knots instead of 1.

[relacey]

Originally Posted by arnoldschnitzer

The average angle over the bridge is 32-36 degrees. I'm curious what that computes to as far as downward pressure.

Thanks Arnold, I was going to guess 30 degrees but thought that would sound like I was padding the numbers. 34 degrees would result in 153 lbs of force on the top using the Spiro Mittels. No wonder sound posts can push through the backs of some basses.

BTW - happy birthday!

[relacey]

Originally Posted by Jake deVilliers

Chocolate-covered bacon!?

Here you go Jake. Bon appetit!


And for those moments when you're craving something with bacon but don't want the chocolate --

[Jake deVilliers]

Wow, its a recipe!! Fellow foodies, we're in business.