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andy_b
05-11-2009, 08:47 AM
i think wind chimes were discussed here a while back. my mom bought this cool one made form 1.5" aluminum tubing. it is LOUD. :)
the problem is, even with the wind we had here yesterday (northeast PA, USA), the chimes were relatively unresponsive. and when they did chime, it was like hitting the tubes with a feather, very quiet.

i seem to recall that a larger paddle (or whatever the thing is called that hangs down under the chimes to capture the breeze is) would make the wind have more of an effect on the chimes. is this correct? is it supposed to be a larger and lighter paddle, or larger and heavier? should the length of string holding the paddle be shorter or longer to increase the effect? any good ideas for the material to make the paddle out of? the current one is some type of 1/4" thick wood.

any other tips or ideas are appreciated.

adny b.

A.K. Boomer
05-11-2009, 09:38 AM
I think you answered most of your own questions -- just experiment with it, larger paddle --- heavier -- longer string -- and you might add a cross section to the paddle so it catches it from all sides --- the distance between the unit that hits all the tubes is very critical also (needs to be very hard material and weight matters as well and shouldn't be too close or there will be no momentum)

SGW
05-11-2009, 09:43 AM
Yes, the place on the tube where it is hit will have an effect. The trouble is, it will be different for each length of tube, so it will take some experimentation to find the best average. I suppose you could vary the length of the tube supports to adjust where each tube gets hit.

Another thing that affects it is the point at which each tube is supported, but you probably can't change that.

Frank Ford
05-11-2009, 09:51 AM
Yep, that's exactly how it's done on this fine wind chime by Grace Notes:

http://www.gracenotes.com/windchimestore/images/2xxMedium.JPG

Each tube is supported at the ideal point by a rod cross piece inside to which the string is tied, and they are hung so the striker hits the right place.

andy_b
05-11-2009, 10:59 AM
I think you answered most of your own questions -- just experiment with it, larger paddle --- heavier -- longer string -- and you might add a cross section to the paddle so it catches it from all sides --- the distance between the unit that hits all the tubes is very critical also (needs to be very hard material and weight matters as well and shouldn't be too close or there will be no momentum)

i was hoping to avoid the "experiment" part and jump right to the "when i ran my experiments for three years this is what i found". :)

the chimes seem very well made and other than the fact that they are all hung near the same height, the design seems to be close to optimum. well, except for the wind-catching part. i guess i will inform my mom that i will be conducting several experiments. :)

andy b.

BigBoy1
05-11-2009, 12:51 PM
the chimes were relatively unresponsive. and when they did chime, it was like hitting the tubes with a feather, very quiet.

any good ideas for the material to make the paddle out of? the current one is some type of 1/4" thick wood.

any other tips or ideas are appreciated.

adny b.

Andy,

The wood paddle is way too heavy for the sail. I use stainless steel or aluminum sheet metal for the sail, 0.030" to 0.070" thick. My rule of thumb is the area of the sail in square inches is equal to 1.5 times the length of the longest pipe. For example, if the longest pipe is 36 inches, then the sail should have about 54 inches of area. (Make the sail rectanglar with the ratio of approximately 1 to 2 for the sides.) Our area needed is 54 square inches so I would cut the sheel metal sail 10.25 inches long and 5.25 inches wide. I also hang them by a corner so they will "spin" less on their own axis and have a more random movement in the wind. I bouble over the corner and use a re-enforcing gromet to provide extra strength in the corner. I hang the sail with a 360 degree fishing swivel to prevent the hanging cord from tangling.

If the sound of the pipes in not lound enough, make the striker of the metal. Plastic or wooden strikers have a deadening effect on the sound while metal on metal, makes a crisp, ringing sound.

The chimes pictures in a previous post with the uneven hanging are properly made as the hanging point has to be located where the standing vibration wave in the pipe has a node point. (This point is different in each lenth of pipe.) Also, maximum energy input occurs when the center of the tube is struck.

lugnut
05-11-2009, 01:10 PM
Andy, here is site that explains the workings of a good wind chime. There is a science to it. I like the "Striker" shown in this article and plan to change mine to one like it. http://home.fuse.net/engineering/Chimes.htm

Mel

BigBoy1
05-11-2009, 02:37 PM
Posted Twice -- Sorry!

ckelloug
05-11-2009, 02:56 PM
I do remember one of the masochists at school solving the PDE's of motion for the wind chimes. She then made 10 sets of the overengineered wind chimes for her manufacturing class individual project. . .

I don't have the report. I'm also very sorry I don't have the report on optimizing trebuchets.

Fasttrack
05-11-2009, 03:20 PM
I do remember one of the masochists at school solving the PDE's of motion for the wind chimes. She then made 10 sets of the overengineered wind chimes for her manufacturing class individual project. . .

I don't have the report. I'm also very sorry I don't have the report on optimizing trebuchets.


:D In seventh grade I built a two story trebuchet. It worked great until the homeowner's association told me it was dangerous and had to be taken down...

I worked through the math for a trebuchet, but I never treated a general case. There is, however, a great program online that will calculate ideal parameters based of your inputs. It's pretty neat.

saltmine
05-11-2009, 03:29 PM
Sounds familiar....In high school I was making intricate sand castings and various auto parts while all my classmates were making ashtrays and gearshift knobs.

In my senior year, the school sponsored a "Tricycle Race". With the help of one classmate, I designed a trike featuring an upside-down trike frame and low-slung seating to get better purchase on the pedals. We won the Tricycle race handily by more than half-a-lap....I still kick myself every time I see a "Big Wheel"...I designed it five years before anybody ever heard of it.

andy_b
05-11-2009, 04:41 PM
Andy,

The wood paddle is way too heavy for the sail. I use stainless steel or aluminum sheet metal for the sail, 0.030" to 0.070" thick. My rule of thumb is the area of the sail in square inches is equal to 1.5 times the length of the longest pipe. For example, if the longest pipe is 36 inches, then the sail should have about 54 inches of area. (Make the sail rectanglar with the ratio of approximately 1 to 2 for the sides.) Our area needed is 54 square inches so I would cut the sheel metal sail 10.25 inches long and 5.25 inches wide. I also hang them by a corner so they will "spin" less on their own axis and have a more random movement in the wind. I bouble over the corner and use a re-enforcing gromet to provide extra strength in the corner. I hang the sail with a 360 degree fishing swivel to prevent the hanging cord from tangling.



BigBoy,

THANKS!!! and the longest pipe is around 36", so i think i will try your sail numbers.

andy b.

ps - trebuchets are cool!

Your Old Dog
05-11-2009, 08:13 PM
I got big pipes too! Mine are 1 1/4" hardened aluminum (antenna stock). My striker is 3/4" thick plywood and about 4-5" in diameter. I radiused the peripheral with a router. It gives a nice pleasant soft/muted strike to the pipes.

The sail is two. I have a small one for windy days and a larger 11" x 11" for calm days. I used aluminum flashing. You'll find the sail will work better if it isn't dead flat. It needs a very subtle arch so it can't set neutral to the wind.

To size my tubes, I laid them out on the workbench with an imaginary tube between each one. I had the tops all lined up and then drew from the full length of one diagonally across all the tubes to the shortest. My shortest tube is about 1/2 of the longest and my chimes are 5 pipe.

I don't find much of a difference on where the gong is placed along the pipes as long as its near the middle of the shorter tube.

Are these tuned? No. But they sound great. Call it slop luck if you want but my neighbors liked them when I asked if they wanted me to mute them at night for sleeping with the windows open. They said no they liked them just the way they were. I don't think mine would work as well with dead soft aluminum like they do with the hardened antenna stuff.

I'd like to make a set of 3" diameter chimes for the corner of the property. I love the deep quiet bass notes from these gongs.

BigBoy1
05-12-2009, 07:00 PM
I'd like to make a set of 3" diameter chimes for the corner of the property. I love the deep quiet bass notes from these gongs.

I built a set with pipes that were in the 6 to 8 foot length. I used 2" diameter aluminum fence posts. They have a very deep rich mellow tone and sound like European cathedaral chimes. If you'd like, I can the use the computer program I wrote to caclulate the correct length for the desired frequency to tell you the length to cut the pipe.

Your Old Dog
05-12-2009, 08:43 PM
Bill, I'd appreciate that. I'd like a 5 pipe set in 2" pipe.