How to deal with collapse-o-matic bridges

[carfish7]

Not a Gibby, but a similar design with similar results. '70's Yamaha SG2000 is unplayable due to radius of the bridge changing over time. Replacement is available but expensive and quite shiny. Can these be rehabbed somehow? Pressed back into shape? Re-radius the saddles? 

What say you HFC brethren?

[gorch]

Just wondering how the bridge radius can change over time on a stable construction like this. I'd suspect a different problem here. Are you sure you have spotted the real reason of the problem?

Have more details?

[murkat]

that is not too bad.

see what it is made of.

whatever you do, trying to re shape it back straight, will damage the tinsel strength more than what is now.

reslot to  radius or purchase a replacement.

[crunchee]

3 hours ago, gorch said:

Just wondering how the bridge radius can change over time on a stable construction like this. I'd suspect a different problem here. Are you sure you have spotted the real reason of the problem?

Have more details?

+1 on what Murkat said...Tune-o-matic style bridges are generally made from a zinc alloy called Zamak, or a variation of it (dunno what Yamaha used back in the '70's)...it's often called 'pot metal'.  String tension/pressure can eventually cause the bridge body to bow like this, whether one likes it or not.

https://en.wikipedia.org/wiki/Zamak

 

[hamerhead]

You could reshape it, then put some kind of support under it. You'd have to get the height just right, but it should help hold it's form. Never tried it, but it sounds plausible..... in theory.

Listen to Jay.

[PaGator]

I'd probably just get a replacement. You might be able to find a used one if you prefer or certainly a new one.

[carfish7]

Thanks for the replies guys. I suspect this may be a solid brass bit which makes me wonder if the same tensile strength loss issue comes into play as prominently? That is some soft stuff, but I do recall working with it back in the day and see how it might not dig being worked much back into shape. 

The size is of course unique to Yamaha so their bridge is the only replacement option. My advice to the owner was to buy the genuine replacement while he still can since these are, IMHO, very good guitars and worth being made functional again. He is broke so that isn't happening. I guess I will investigate replacement saddles (or make some) and see about making up for the collapse there.

edited to add; bridge and TP are NOT brass, but cheap pot metal per usual. The bridge sits atop a solid brass bar that is inset into the top. For some reason.

[murkat]

A TOM should be really close to that oem height screw spread. if not, a slight bore out to the TOM should work in a pinch. fwiw.

[Sugartune]

I had that on a used Gibby. Just replaced it with a Callaham. I don't suspect it will happen again. Crazy that it happens though. 

 

[gtone]

44 minutes ago, Sugartune said:

I had that on a used Gibby. Just replaced it with a Callaham. I don't suspect it will happen again. Crazy that it happens though. 

 

Yep - pretty much guarantee those Callahams WILL NOT bow like that for say, a century or two anyhow.

[Hamer Dave]

On ‎6‎/‎21‎/‎2016 at 10:10 AM, murkat said:

that is not too bad.

see what it is made of.

whatever you do, trying to re shape it back straight, will damage the tinsel strength more than what is now.

reslot to  radius or purchase a replacement.

Yep. I've heard the term 'banana bridge syndrome'. I've certainly seen it as well.

[Hamersaur]

On ‎6‎/‎21‎/‎2016 at 8:10 AM, murkat said:

whatever you do, trying to re shape it back straight, will damage the tinsel strength more than what is now.

Metals can become brittle over time. I would not try to reshape it as you may run the risk of snapping it in half (or more). As far as the the movement  metals have elastic properties to them and are not completely solid. Years ago I worked at a steel fab and machine shop and we had a 15" thick steel plate ( around 12' wide x 30' long) stored in our yard for about 2 weeks. Due to the fact the dunnage was not spaced properly underneath, it moved/sagged about half an inch under it's own weight. We had to machine the whole thing down to 13-1/2" thick so we were still able to use it.

[triodecr]

On 6/21/2016 at 11:04 AM, gorch said:

Just wondering how the bridge radius can change over time on a stable construction like this. I'd suspect a different problem here. Are you sure you have spotted the real reason of the problem?

Have more details?

It's bent due to years of string pressure.  Look at the top edge of the bridge from left to right - it's concave.

[triodecr]

On 6/22/2016 at 10:24 AM, carfish7 said:

... The bridge sits atop a solid brass bar that is inset into the top. For some reason.

It's for sustain/tone.  Alembic has done / does the same thing and it is quite literally called a sustain block.