JustFuya
626 posts
Oct 28, 2014
5:07 PM
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I promised this to @STME on a lost thread. Reed profile dimensions are too busy to add to dwg but are available in the CAD file (ACAD 2004 or ?). I did my best without blade mics or comparator.
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STME58
1144 posts
Oct 29, 2014
8:16 AM
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I have been having trouble accessing MBH lately. I can't access it from home. I am typing this from McDonald's!
I clicked on the image and it took me to PhotoBucket but I did not see a CAD file. I can imput from the dimension but if you already have it in CAD that would be faster. Is there a way I can access your CAD file?
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JustFuya
628 posts
Oct 29, 2014
2:29 PM
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@STME - This is my first dropbox experience. I did not set up a 'shared' folder so this is my [temporary] login & pw.
https://www.dropbox.com/home
Again, this is the best measurement I could do with personal tools but they are close. The rounded feature on the weighted end represents tuning grind marks so you can ignore it and run with the side profile.
EDIT: Removed login & PW
Last Edited by JustFuya on Oct 29, 2014 6:35 PM
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STME58
1146 posts
Oct 29, 2014
6:32 PM
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I got the .dwg file. I will loade this into my modeler and see what pitch this reed come out at and what the higher modes look like.
-Steve
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STME58
1147 posts
Oct 30, 2014
8:50 PM
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Here are the first 5 resonant modes of the geometry you gave me, shich looks to be between a C and C# reed. If I added some tuning scratchs in the tip it would come up to C#.
It looks like on the short reed mod3 3 is side to side and mode 4 is torsional. On the longer D seydel I have modeled (1st mode frequency of 1111) mode 3 is torsional and mode 4 is side to side;
Last Edited by STME58 on Oct 30, 2014 8:56 PM
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JustFuya
629 posts
Oct 31, 2014
9:38 AM
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Excellent work on your part.
It's the 1 draw on a key of D (E?) so my measurements are off somewhere. I did miss a radius (.002) on the corners of the reed tip that correspond to radii in the slot. And while the rivet pad has a ~45 degree chamfer, the transition to the narrow moving aspect is similar to that of the tip but with a large off center radius.
Does it make a difference where the reed is anchored in relation to the slot?
I used a mic and a cut/ground piece of drill shank to fit inside the slot to measure reed thickness. Not very scientific but the best I could do without ruining the new harp.
Earlier, I pooh-poohed coining as a possibility and I take that back.
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nacoran
8080 posts
Oct 31, 2014
1:26 PM
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Very cool!
STME, would your software accommodate testing stacked reeds? I was playing around with some pieces of brass. They are 5 or 6 inches long- I got them because I thought they would be a good way to demonstrate reed stuff, but playing around one of the interesting things was if you plucked them when they were stacked on top of each other tightly you got a lower pitch (presumably an octave lower with 2 of them but I didn't check it for accuracy). Could your software show was would happen with two reeds vibrating like that?
Also, maybe you could answer the age old aerophone question- is it the reed sounding or is it the interruption of the airflow by the opening and shutting of the airspace? Or some combination?
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Nate
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First Post- May 8, 2009
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STME58
1149 posts
Nov 04, 2014
3:00 PM
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MBH no longer allows me to log in from home, even when I VPN into my work site. I don't have much time at work to read and post.
To try and answer JustFuya's qestion about the anchor point, yes it is critical. I made the assumption that the wide tab is clamped firmly to the reed plate and that the edge of the wide part lines up with the top of the reed slot. In the analysis what I did to model this is to cause the entire bottom surface of the pad to be fixed in position.
I will think about Nate's question and respond later.
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