Lucchi meter

[Ferrara]

Is there anyone on this forum that actually owns and uses the Lucchi meter?

[MarkHoffman]

What is a Lucci meter?

[Oded Kishony]

It's a tool that measures the speed of sound through any material. It's mostly used by bow makers to test pernambuco. It's not considered a particularly useful indicator of tonewood quality.

Oded

[Regis]

A year or 2 ago I tried to find out something about Lucchi meters and read a lot of 3rd hand information. And disagreements about consistancy and availability.

In that process, I learned of a technique of measuring stiffness by placing weight (2lb) on the center of bow and measuring movement. I can confirm that better bows($$'s) fall into the low 300's mm bend which means stiffer. Cheap bows fall into the 400+mm. I like this because there appears to be some lower quality pernumbuco bows that are not as good as some higher quality Brazilwood bows for approximately the same weight.

Please bare in mind that I don't have access to $10,000 bows. I'm trying to develop enough data to supprt/help me with playability/quality measurement of bows in the < $2500 bow range which I encounter.

There are other folks doing this that have a lot more experience and data. Perhaps some on this board.

Regis

[David Tseng]

Some thing strange with the number "300's mm" bend?

[Froggie]

The bowmakers I know use a 1-pound weight for deflection for violin, viola and cello. They use a 2-pound weight for bass bows. I think that is pretty standard. Deflections are usually reported in inches, (thousandths of an inch). The pound/inch system leads me to believe deflection measurements may be more prevalent in USA, as all other bow measurements (except balance point) are usually given in millimeters. You could use a 2-lb. weight on violin bows, but you cannot easily compare the results to tests with one-pound weights.

If you have access to VSA journals, "Grading Methods for Pernambuco" by Joseph Regh in Vol. XIX, No. 1, from the November 2002 meeting. Mr. Regh goes into a complete discussion on grading using his hands, eyes and a "bounce test". The bounce test is good, but don't bounce blanks on the head end or you are liable to break it off. Boards can usually be safely bounced, but I would not bounce one that has checks in it. The article goes into detail comparing Lucchi to grading by hand, eye, bounce, etc. You should be able to find the article in larger librarys.

I don't own a Lucchi meter, but I have borrowed one. My good wood does tend to have higher Lucchi than the ones that don't ring when bounced. Most bowmakers like to bend the stick in their hands, but that only works for me if all the sticks are cut to the same dimensions. A small change in thikness will make a big change in the feel of stiffness.

I would not use the Lucchi as the only tool in grading wood, but I do think if used properly, it can be helpful. Lucchi has a newer version of his meter coming out this year.

I don't think very many people are measuring Lucchi readings on finished bows. They are normally tested by playing them.

[GMM22]

It is not difficult to correlate stiffness values obtained by using either a one or two lb mass. According to Hooke's law, deflection is directly proportional to applied force. Let's say a given bow will deflect by .350" under 2 lbs. of force. If you half the mass or rather applied force, the deflection will be half or .175". Hookes law is valid for elastic materials. Innacuracies may manifest in the deflection of simple beams (such as a bow) when applied forces differ greatly with respect to each other. In other words it will be less accurate if you were to compare stiffness results of a given bow using a 1/4 lb mass as compared to a 3 lb mass. Hookes law is easily demonstrated by ordinary spring scales. Double the force and you double the spring length.

I investigated the Luuchi meter some time ago. I have a copy of the instruction manual. To say it is poorly written would be a compliment. It is rife with errors and is sorely lacking in all regard. Some of its contents is downright bizarre. The manual hardly instills any confidence in the machine. Anyone producing such a device should be able to provide a clear and error free technical manual.

I am curious about the values you have regarding the range of deflection of good bows. Can you provide them?

[Froggie]

Go to http://www.giannaviolins.com/Information/HowBows.html

To me, these seem to be in thousandths of an inch using a two pound weight. You should check with Gianna if you want to do a comparison.

You can also go to

http://members.aol.com/bowedstrings/violin-bow-review.html

where you can find a spreadsheet with bow data

http://members.aol.com/bowedstrings/ I have not reviewed this data enough to make a comment on it.

I do have drawings by bowmakers that show deflection. I don't have permission to distribute the drawings, but for one Sartory, the one pound deflection is 0.141 inches. That would be rather stiff.

[Screpach]

Good evening,

It's already passed 12 year since last message in this thread, and some links are not useful anymore, like those hosted by AOL.

And I have one question more, if there are any studies about good bows stiffnes?

 

[NickIsWorking]

If you are on Facebook there is a group called Les Archet.  There was discussion between several great bowmakers about target deflection goals in bowmaking.  Evan Orman and Jean Grunberger, and others, contributed some data.

[bengreen]

A word from a nerd....

Before you give up on an old URL, it's always worth running it through the Wayback Machine.

https://archive.org/

They've been crawling public web sites for a bit over 20 years and saving copies of what they find. I have a luthier friend who had previously been an artist. We were able to find her old web site, which she had thought long lost, complete with photos of all her sculptures. It's an incredible resource. And free, though donations are welcome.

I ran  Froggie's three links above. They all had multiple copy dates available, including the spreadsheet.

The only limitation I've found is that the crawler only follows links it encounters to a certain depth. So even if a web page is archived, you can only follow the links so far before they dead end. And some pages are incomplete, though if that happens try clicking on another date.

But thank you for refreshing this subject. I'm very happy to have those resources.