Adding weight to a base bridge

Posted by: Goof

Adding weight to a base bridge - 03/26/13 10:04 AM

Can somebody supply advice on how to add a weight to the base bridge of an upright piano? I have read, "here and there " in the forum, that this ia way to improve the "tone" of the first few strings on this bridge.
I have renewed the problematic 1956 strings, 6 bichords, and this has made a big difference.
Posted by: Ed McMorrow, RPT

Re: Adding weight to a base bridge - 03/26/13 10:39 AM

I assume by the "top" of the bass bridge you mean the highest pitched strings on the overstrung section. They often sound thin, nasal, can have a pulsing chime sound and/or twangy sound. Adding weight here would probably not help since the bass bridge is significantly heavier than the treble.

Adding weight is usually done to the bottom of the long bridge to help reduce the jumpiness of the end of the bridge. Techs call this the end of bridge effect. I have had some success with this.

If the top bass problem is a pulsing chiming sound it is probably due to the bridge rocking back and forth too much. This augments longitudinal modes. Devising the simplest, cleanest, most workman like way to stiffen the top end of the bridge against rocking motion is what I do.

The wound string specs can influence this as well. It is seldom a single thing acting here. Many small scales sound small because the bi-chord stringing has to be carried far too high in the scale-this reduces the normal trichord unison sound that we have come to expect from the piano.
Posted by: Ed McMorrow, RPT

Re: Adding weight to a base bridge - 03/26/13 11:03 AM

GOOF; would you please edit the title of your post to correct the spelling of "BASE" bridge. It just kind of bugs me. I make typos too-but let's fix the title.
Posted by: Gene Nelson

Re: Adding weight to a base bridge - 03/26/13 12:05 PM

If you are curious about weighting the bridge you should experiment.
About 50g to 200g is typical.
Finding the best location will take a bit of trial and error.
You can try a spring clamp or similar device on the bridge just to get a start with weight location and listening - weigh the clamp.
Once you have found the best location and optimal weight you will need to attach a permanent weight to the bridge from the back side in the same location.
Possibly there is a soundboard button that can be removed and your weight can be attached in place of it? This would be ideal.
You will find that upright support posts are great obsticles.
Posted by: Goof

Re: Adding weight to a base bridge - 03/26/13 01:50 PM

Bass vs Base.
Fascinating: one lives and learns.
I always thought that BASS was reserved for fish; a certain of wood; and some sort of sewing.
Strange that the obvious BASE as in the the "lowest" is not used for the lowest bridge.
So there you go Ed and thank you. I have yet to find how the usage in music of the BASS comes about- I'll return to Wiki and see what it has to offer.
Posted by: Goof

Re: Adding weight to a base bridge - 03/26/13 01:53 PM

Thanks - will do and report back !
Posted by: jim ialeggio

Re: Adding weight to a base bridge - 03/26/13 02:28 PM

I think you'll find adding weight to the high bass will muffle and deaden things more...but always worth a try, just to see what happens. I agree with Ed, that these weight additions work better at the end of the long bridge.

Ed, I have several short piano bass bridges that are darn near perpendicular to the strings. Do you by chance have any pics of how you achieved your "stabilizing"? I though about doing it on a recent belly job, but was afraind my structural solution would add too much mass to the bass bridge, which really wnats to be as light as practicable...at least in my experience.

Jim Ialeggio
Posted by: Supply

Re: Adding weight to a base bridge - 03/26/13 02:55 PM

The problem with things like bass vs base is that once they are allowed to stand, other readers begin to think that is the correct terminology and spelling.
Supermarket signs drive me crazy: "Banana's $0.49 per lb"
Posted by: Zeno Wood

Re: Adding weight to a base bridge - 03/26/13 03:06 PM

That's not bad at all. Banana's are selling for more than that around hear.
Posted by: Del

Re: Adding weight to a base bridge - 03/26/13 05:07 PM

Originally Posted By: Zeno Wood
That's not bad at all. Banana's are selling for more than that around hear.

Of course banana's are more expensive -- apostrophe's are expensive!

ddf
Posted by: Del

Re: Adding weight to a base bridge - 03/26/13 05:25 PM

Originally Posted By: Goof
Can somebody supply advice on how to add a weight to the base bridge of an upright piano? I have read, "here and there" in the forum, that this ia way to improve the "tone" of the first few strings on this bridge.

Sometimes adding weight to the bottom of a bass bridge will “improve the tone.” Other times you’ll not notice much of any change or improvement at all. What effect it will have on your particular piano depends on many variables. And on what you are trying to accomplish.

Adding mass to a bridge will increase its mechanical impedance. Adding mass makes it less willing to accept vibrating energy from the strings; particularly high-frequency energy or the energy in the higher partials. If this is what you are trying to accomplish—though I rarely find pianos in which this would be an improvement—that adding weight is the way to go.

More often at the upper end of the bass bridge we’re more concerned with controlling the rate of energy transfer at the fundamental pitch and lower partials. For this it is more effective to add a bit of stiffness to the system. This also alters the mechanical impedance of the system but its affect is more noticeable at lower frequencies. You might consider a short, auxiliary rib placed immediately under the end of the bridge body—or as close to the end as you can reasonably get. Some experimentation may be necessary to come up with the best balance between height, width and length.

ddf
Posted by: Grandpianoman

Re: Adding weight to a base bridge - 03/26/13 06:29 PM

I have read and tried 'loading the bridge' by using small vice grips...the smallest they make. You attach one to the bridge pin. Make sure you do not touch the string, otherwise you have buzzing. It does change the sound, depending on where you place the vice grip/s.
Posted by: Ed McMorrow, RPT

Re: Adding weight to a base bridge - 03/26/13 07:55 PM

Jim, I make quarter-sawn spruce plywood with nearly 1/16" plies. Ala Wurlitzer spinet low tenor bridge, if you know what I mean.
Posted by: Grandpianoman

Re: Adding weight to a base bridge - 03/26/13 08:40 PM

I might add that you can also use these vice grips in the other sections of the bridge. I have tried that, it does change the souund.
Posted by: Goof

Re: Adding weight to a base bridge - 03/27/13 05:08 AM

YES!! There is a button at the start of the BASS (as in fish and not as in base ball,) bridge, so some big washers there will be the place to start.
Then I'll buy some 30X30X3mm ALUMINIUM angle and fix that to the back of the bridge so that I can experiment with various weights and positions without moving screws in and out of the bridge.
Many thanks.
Posted by: kpembrook

Re: Adding weight to a base bridge - 03/27/13 08:35 PM

Originally Posted By: Del
Originally Posted By: Zeno Wood
That's not bad at all. Banana's are selling for more than that around hear.

Of course banana's are more expensive -- apostrophe's are expensive!

ddf


And then, in one customer's yard by a pile of scrap wood was the sign:
Would 4 Sail
Posted by: kpembrook

Re: Adding weight to a base bridge - 03/27/13 09:31 PM

Originally Posted By: Grandpianoman
I have read and tried 'loading the bridge' by using small vice grips...the smallest they make. You attach one to the bridge pin. Make sure you do not touch the string, otherwise you have buzzing. It does change the sound, depending on where you place the vice grip/s.


Yup, that's how I do it.
Posted by: Goof

Re: Adding weight to a base bridge - 04/02/13 08:47 AM

Originally Posted By: Goof
Can somebody supply advice on how to add a weight to the base bridge of an upright piano? I have read, "here and there " in the forum, that this ia way to improve the "tone" of the first few strings on this bridge.
I have renewed the problematic 1956 strings, 6 bichords, and this has made a big difference.

2nd April.
Well! Now on my BASS bridge I have added two sets of 32X2mm dia washers. There are three screws which secure the bridge to the soundboard and I have added about 90gm to the lowest screw, and 120gm to the middle screw.
Adding to the highest screw (i.e. near my problematic D3 to A2 bichords)made NO difference.
Overall I would say there is a purer tone to all the notes more especially the lower.
Those notes on the long bridge have always had a great deal more power.
I'm still trying to post photographs - difficult process!
Posted by: Nash. Piano Rescue

Re: Adding weight to a base bridge - 04/03/13 01:09 AM

I am thankful that writers have not resorted to the ever popular " text speak" language. Too many abbreviations and W's So reading Base as Bass while a writing faux paw isn't too bad.
Posted by: MacMacMac

Re: Adding weight to a base bridge - 04/03/13 07:39 AM

We've fixed bass ... and now we've broken faux pas.