Years ago, I tried to replicate a musical bell instrument my mother owned. My maker-eye said it was nothing more than aluminum bar stock and golf bag tubes, so I bought the pieces I spec'd and glued them together. Naturally, when I tapped it, I got a dull thud instead of a resonating tone. I chalked up the failure to my lack of musical knowledge and moved on to something else.
Years later, I found that if you want a bar to sound musical, you have to attach it at the right spot, whereas I just stuck tape at the ends and hoped for the best. The silver lining is that I learned the solution, but I didn't spend excessive time back then, because I didn't even know what question to ask. The place to attach a bar is approximately 2/9 (two-ninths) of the way from each end where the lateral vibration is the smallest due to nearby nodes.
I liked the idea of being able to cut an arbitrary length of steel or aluminum and find the sweet spot immediately. In practice, this is a thought experiment more than a productive project. The path I took exemplifies the natural procedure of starting with a sophisticated device and working it down to a simple and functional one.
The first idea was never fleshed out but should have been possible. In my mind, it would look like a compass/divider with four legs. The outer limbs would reach the ends of the bar in question, and through a series of linkages, the inner ones would always point at the 2/9ths point and the 7/9ths node.
My next idea was like the compass/divider, but it would use gears instead of levers. Rotation is more challenging to calculate, whereas gear proportions are straight-forward. The posts would attach at right angles to a rack-type cog, and those would ride on a two-tier gear with a ratio of 5:9.
At this point, I started experimenting with less mechanical means, and I realized that a piece of paper with projection lines at appropriate angles would allow me to place a segment of metal across the tracks. When the ends lined up with the outer borders, the inner markings would rest at the 2/9 point.
I developed this idea since it was simple to draft and print. As I thought about it more, I added a central line, like a spine, and perpendicular lines, like ribs. This solution was pretty simple, and I could quickly replicate it with a piece of paper, a ruler, and a pen.
My final solution was so simple that it made the first ideas seem laughable. I stretched a rubber band across a ruler and made black marks at 0" and 9" and then blue lines at the 2" and 7" points. So long as the rubber stretched uniformly, those marks would always be proportionally the same, and I had a way to test this with my printed line paper.
Here is yet another story about developing an idea until it cannot get any simpler. That's how you know it's done.
First time here?
Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
Disclaimer for http://24hourengineer.blogspot.com and 24HourEngineer.com
This disclaimer must be intact and whole. This disclaimer must be included if a project is distributed.
All information on this blog, or linked by this blog, is not to be taken as advice or solicitation. Anyone attempting to replicate, in whole or in part, is responsible for the outcome and procedure. Any loss of functionality, money, property, or similar, is the responsibility of those involved in the replication.
All digital communication regarding the email address 24hourengineer@gmail.com becomes the intellectual property of Brian McEvoy. Any information contained within these messages may be distributed or retained at the discretion of Brian McEvoy. Any email sent to this address, or any email account owned by Brian McEvoy, cannot be used to claim property or assets.
Comments to the blog may be utilized or erased at the discretion of the owner. No one posting may claim property or assets based on their post.
This blog, including pictures and text, is copyright to Brian McEvoy.
2020-01-14
My mom's bell instrument
Years later, I found that if you want a bar to sound musical, you have to attach it at the right spot, whereas I just stuck tape at the ends and hoped for the best. The silver lining is that I learned the solution, but I didn't spend excessive time back then, because I didn't even know what question to ask. The place to attach a bar is approximately 2/9 (two-ninths) of the way from each end where the lateral vibration is the smallest due to nearby nodes.
Steel strap vibrating mid-air
I liked the idea of being able to cut an arbitrary length of steel or aluminum and find the sweet spot immediately. In practice, this is a thought experiment more than a productive project. The path I took exemplifies the natural procedure of starting with a sophisticated device and working it down to a simple and functional one.
The first idea was never fleshed out but should have been possible. In my mind, it would look like a compass/divider with four legs. The outer limbs would reach the ends of the bar in question, and through a series of linkages, the inner ones would always point at the 2/9ths point and the 7/9ths node.
Specialized compass
My next idea was like the compass/divider, but it would use gears instead of levers. Rotation is more challenging to calculate, whereas gear proportions are straight-forward. The posts would attach at right angles to a rack-type cog, and those would ride on a two-tier gear with a ratio of 5:9.
Gear ratio with extending legs
At this point, I started experimenting with less mechanical means, and I realized that a piece of paper with projection lines at appropriate angles would allow me to place a segment of metal across the tracks. When the ends lined up with the outer borders, the inner markings would rest at the 2/9 point.
Paper scale sketch
I developed this idea since it was simple to draft and print. As I thought about it more, I added a central line, like a spine, and perpendicular lines, like ribs. This solution was pretty simple, and I could quickly replicate it with a piece of paper, a ruler, and a pen.
Drafted 2/9 lines
My final solution was so simple that it made the first ideas seem laughable. I stretched a rubber band across a ruler and made black marks at 0" and 9" and then blue lines at the 2" and 7" points. So long as the rubber stretched uniformly, those marks would always be proportionally the same, and I had a way to test this with my printed line paper.
Marked rubberband
Lines compared to paper
Stretched and still accurate
Here is yet another story about developing an idea until it cannot get any simpler. That's how you know it's done.
First time here?
Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
Disclaimer for http://24hourengineer.blogspot.com and 24HourEngineer.com
This disclaimer must be intact and whole. This disclaimer must be included if a project is distributed.
All information on this blog, or linked by this blog, is not to be taken as advice or solicitation. Anyone attempting to replicate, in whole or in part, is responsible for the outcome and procedure. Any loss of functionality, money, property, or similar, is the responsibility of those involved in the replication.
All digital communication regarding the email address 24hourengineer@gmail.com becomes the intellectual property of Brian McEvoy. Any information contained within these messages may be distributed or retained at the discretion of Brian McEvoy. Any email sent to this address, or any email account owned by Brian McEvoy, cannot be used to claim property or assets.
Comments to the blog may be utilized or erased at the discretion of the owner. No one posting may claim property or assets based on their post.
This blog, including pictures and text, is copyright to Brian McEvoy.
2020-01-14
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