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Unfortunately, I have somehow misplaced my Lowell Downbearing gauge which I have had for quite some time.

Wondering if anyone has experience with both the Lowell gauge (about $90.) and the gauge sold by Schaff (#3138 page 63) which is $45. Any preference and reasons why?

I'm not a rebuilder, but I'd like something in the toolcase for accurate diagnostics in the field.

Any thoughts appreciated...

I have used the Schaff gage. Lowell wrote in PT Journal articles about why such devices are not reliable.

Your only reliable ways to determine bearing is with a wire/thread or a Lowell-type gage. The dial and "rocker" gages can lie.

This is what I use. A digital angle gauge.

I greatly prefer it to the lowell gauge...easy to use, precise to .2 deg, available for $39 in any woodworking catalog. Make foot cradle out of scrap...works great for setting very picking downbearing in my shop

can't get the image to work...how?

Jim Ialeggio

Jim, I believe you are probably referring to one of the Wixey model digital inclinometers.

There are two basic design types of digital inclinometers. One uses accelerometers and software to deduce the angle, much like the cell phones do with an inclinometer app. This type, although accurate if held very stable, is very susceptable to vibration and you will see them flicker on the reading. A passing vehicle near the home or even a furnace running will send enough vibration through them to skew the reading/accuracy. Trying to hold these motionless by hand on the strings is near impossible.

The Wixey type use capacitive measuring technology which is similar to how digital calipers work. There is a circuit board on a rotating counterweight that has a repeating pattern etched on it. These are more stable and get more useable reading when held on something by hand.

Bear in mind there are a number of cheap models on Ebay ect.. that show a resolution of .1 degrees on the specs. This is neither repeatability nor accuracy, it is simply a number they decided to resolve the readout at. I have a really nice one I use in machining that is accurate to .05 degrees but it costs 5 times as much as the $40 Wixey and is overkill for a downbearing application.

Jim,

Here's video explaining how to put images on a forum.

https://www.youtube.com/watch?v=jehxvujkalM

I have thought these things over, and I am still not certain what one would look for with a downbearing gauge. There are a number of variables that might be considered, and what they should be depends on other variables. What do you look for when measuring downbearing?

don't have time to mess with the photo upload right now...gotta work...I'll do it tonight

Jim Ialeggio

Jim, although it says "Full Member" under your "handle", I have got to break it to you that anyone who hasn't yet learned how to jump through the hoops to upload a picture to the forum is a PW Noob.

Being able to post a picture here separates the wheat from the chaff, the men from the boys and the Pros from the DIYers, the tooners from the tunas [...he says, strutting around, extending his suspenders out to arm's length in front of himself...]


The instructional video shows how you can upload using Photobucket, but uploading can also be done directly from your computer to the PW site. But everyone has to figure that out for themselves... it's part of the orientation process.... hint: search for "upload images" in the box at top left.

WARNING: Rant ahead...
Seeing that this question of how to upload images comes up fairly frequently, it really should be explained in the FAQ Forum. However, it seems that forum is closed and no one can post there anymore. Although the question of uploading images does come up again and again (i.e. frequently), maybe the powers that be don't consider it a real FAQ? Compare with: "Seiler Grand vs. Irmler Grand" or "Mehlin Regulating Dimensions and Hammers" and similar things everyone is simply dying to know which make up the bulk of the FAQ Forum. end of rant...

Posting pictures is in the FAQs of the Piano Forum.

Well, first of all you look for . . .
Downbearing!!

Downbearing = good
Negative bearing = bad

(I'm speaking of genuine bearing off the front of the bridge -- such as can be determined by the various means mentioned that either assess the angle of the string segments or use a wire/thread.)

Beyond that, it's a little more vague and the actual numbers depends on your mode of measurement -- thread will give you a different number than the Lowell-type for the same amount of absolute bearing. But since the general thought is that you want more or less even displacement throughout the scale (or perhaps not if you are a design maven) then you will have lower readings on the longer strings since there is a longer distance over which to achieve the displacement.

But if you are evaluating a piano or doing your first rebuilding jobs, you'll be fine with avoiding negative bearing. "Some" will be quite good.

Those of us who do soundboards/bridges can take this discussion into the stratosphere . . . but you won't go wrong with these basics.

Alright you guys...this is be nice to Luddites week...didn't you know.

Pics are up on the original post. Uhh...I was typing the URL without realizing it was case sensitive

Emmery, I agree about being careful about what to expect in resolution on these gauges. Though they say it has a .2 deg resolution, the display reads in .1 deg which is foo-foo. In theory .2 means +/- .2 deg which is .4 deg, but since its being used in the same orientation throughout most of the measuring, I have found them to give me repeatable numbers, quickly. I feel they are well within the tolerances required for this measurement, especially for just checking for downbearing on site.

BDB, depending on how you set up the feet, they can measure component or composite downbearing. I personally, in all my shop work, don't bother at all with component downbearing, but there are some that do. I just want to know what downbearing forces I'm generating at each string and get that by simply by taking the sine of the composite angle*tension.

And Jurgen...well foo on you (how do you like all those fancy icons)...pretty fancy footwork for a Luddite, No?

Well, I am not entirely certain that downbearing necessarily has to show with a gauge, because downbearing should be the distance that the bridge is above the line of the string if the bridge were not there, and if the string did not bear down on it. In theory, the pressure of the string could flatten the soundboard assembly enough so the bridge is at the level of that line, although that is probably not enough, just because the adjacent strings will hold the bridge down as a played string moves.

Now you could measure the deflection angle from the plain of the top of the bridge. You would need enough so the string does not lift off the bridge with a heavy blow. That would probably be an increasing amount on the speaking length side as one goes down the range of the piano, and very little on the back side of the bridge.

Jim, I realize you are reading the front and backside of the bridge for a composite angle, can I assume then that you don't zero out the gage and use the factory default setting? If this is the case then it would be difficult to ascertain if the two sides are unequal because of structural issues or a colapse in the soundboard in some areas....assuming you have no way of knowing that the soundboard rim is level with the gages default. I'm pretty sure your using it in the field for the same reasons I use mine but on occasion I've come across a few pianos where there was very minimal downbearing and the majority falls on one side of the bridge, on the other side the string wants to lift off or comes out in line with the top of the bridge at neutral...a leaning bridge is another way to look at it.

I'm trying to figure out how to compensate for an uneven floor, or uneven soundboard installation, or even the crown of the board (if there is any), when reading with the digital angle gauge?

I'm trying to figure out how to compensate for an uneven floor, or uneven soundboard installation, or even the crown of the board (if there is any), when reading with the digital angle gauge?

Emmery,

I use the gauge as a relative reference, not an absolute reference. I know you know that, but I mention it because many people have trouble understanding the difference between an absolute measurement(the amount off from level) and a relative measurement(the angle created by two intersecting planes)

As a relative reference, I usually just read the angle and directional arrow on the speaking length, put the gauge on the backscale, read the new angle and arrow and mentally do the math. If one doesn't like doing mental math, you could just place it on the speaking side, zero it out, then place the gauge on the backscale and read the composite angle reading directly off the screen. Pay attention though to the arrows which indicate bearing or negative bearing.

Either way, for this application, because I want to know the composite angle, which is the angular relationship of the speaking length to the backscale, I use it as a relative reference.

You are describing the "component" portion of the Lowell gauge's name. That is, trying to ascertain whether and how much the bearing the string portion on the speaking length and the backscale has independent of each other but relative to the bridge top. As I said in an earlier post, I don't take a composite measurement because the information it contains is not something I'm interested in...it seems like a lot of effort to acquire confusing and inconclusive data...but whatever...

If I were to use it as a component gauge, the idea would be to use the bridge top as your reference. Rather than look for some index at the rim or whatever, I would construct a "foot" cradle that only spanned the bridge top, ie the reference, between the pins. This way,rather than use the wider feet I show in the above pics, you zero it out on the bridge top, then see what the difference from zero each side exhibited.

Jim Ialeggio

Luddite? You, Jim? Nahhhh - you have proved you are no Noob no more by successfully posting pictures (great ones, I might add) to the PW site. Congratulations. Now you are a true "Full Member"!


[I could never really figure out what that one means, but I kinda like it.....showing my own noobish side, I guess...]

Nice idea. But it looks like it is too long to work in the highest treble section?

Jim, thanks for the elaboration. I basically use it the same way as you do yourself. Its nice and handy for the table saw set up and other things also.

Hi Jim,, this is the best tool that we have seen lately, the availeability of those digital jauges is excellent !

THen, one can also ascertain how the bore angle of hammers need to be in regard of the huge slant we will find in the high treble...

I also use it to measure hammer bore angles, laying the head on its side (assuming it have not been sanded) the gauge on the shank gives a precise measure)

P.S 132.7 degrees is way too much downbearing, be careful not anyone is a professional rebuilder here


Due to the slant that is sometimes large on the bridge top, the angles are not giving all informations, unless related to speaking and backside lenght. then mm can be used too +

I mean : all measuring methods have their flaws and limits