Since my first instructable on the dan moi jew harp, I grow up from the technical point of view,
I had some troubles with making those dan moi really working properly. It was not highly satisfying I admit.
But now I am very very proud!
Still some aspects to deal with. In particular the tone, I did very low tone making those jew harps entering the category of the "bass" jew harp.
So I came up with a crazy idea first: doing a spiral - dan moi. How to do that?
It is how I came up with the electro chemical machining (electrolytic cutting of a metal).
Why spiral? Because nobody did it!
In fact, some reasons are there explaining that, and I did prepared a spiral dan moi... which was not working...
Then I made maybe 10 differents trials to understand where it was necessary to go.
I imagined and designed those dan mois with the aid of very complex folding technics and living hinges.
And finally I imagined those novel designs that are unique.
I wanted a jew harp that like a dan moi are made from a single piece.
But a bit more complicated because I wanted to make profit of my living hinge idea.
And you got that jew harp: Froggan Moi --- No, I was kidding ... I can t find a decent name ...
Not like for the kalim beer here:
If you have a suggestion that took in account the idea of folding... It will be be very kind of you.
So I hope you will enjoy this instructable
Just a mention on the contents of this instructable-->attribution non commercial sharealike. You can re-use my texts and my pictures, modify or whatever, if you do so please cite the author, my work or even better put a link to this instructable. I would appreciate your cooperation :) In addition if you have any comment or improvement that you would like to share with me please do it. Last but not least, Share with me the metal homemade danmoi you made. I will probably add a gallery for your danmoi later on.
important notice/ safety issue
Step 1: Again Some Information
This music instrument is called a lamellated jew harp as explained by
Robert Vandre www(dot)rvandre(dot)de/ (as opposition to the bow shaped jew harp).
The lamellate jew harp is structured in several subcomponents:
the tail or pluck where the energy input is given (by hitting/plucking it), the intermediary frame part, which acts as a spring, the tongue/prong or reed responsible of the sound formation by entering the wished vibration motion, the frame which is rigid (and must act as the energy storage but this is a guess only), and the frame´s end or hold location.
The player must place his/her lips on the frame - rigid part so that the end of the tongue can vibrate freely “in” the mouth of the player. See the playing modus operandi.
Step 2: Inventory and Notification About Electrical Hazards
As It will be necessary to use electrical current for cutting through metal sheet... This is not without to say, be cautious it is DANGEROUS! but effective yes But really Dangerous! Do not put your fingers if you do not know, ask someone who does! otherwise do not carry out this experiment!
This point sharedwe can go forth
-a tin can ( old candy box or a metallic box for gifts... magnets sticks to them? yes then this must be what you are looking for)
for the preparation prior to the electrochemical bath
-a DC 12V or 9V with 0.5 to 1 A ( an old mobile phone charger do the jobs - I got mine from a recycling station - you do not imagine all what people can throw away or maybe you do... ;))
-some aligator clips
-a stainless steel wire or sheet
(I wrote an instructables on two DIY stuffs from left stainless steel curtain wires - this could be the third Hijacks;))
-sea salt, a plastic cup (deep enough to immerge the whole metal sheet in it), and water (concentration salts vs water in weight 1 to 10)
-a flat screwdriver / or a strong needle (must be very thin and precise, but strong at the same time)
and as allways: you need time...
Step 3: Prepare the Metal Sheet Part 1
just cut out of the tin can a flat sheet of metal 5 cm x 10 cm must be more than enough
Step 4: Prepare the Metal Sheet Part 2
apply two layers of nail vernish over the inner side of the tin can metal sheet
(the one without colours / writings / drawing)
A) Let one corner free of nail vernish (for a direct contact for the current)
B) Work in a free air space - or at least with a window open (vernish contains VOC that can make you feel bad)
this one is either the nude tin can metal (in fact it is a sandwich metal materials go to a wiki to know more)
or with a protective layer (to avoid direct contact of the metal with the food)
On the outer side, apply a layer of tape so that extra tape can protect the edges as well.
Step 5: Prepare the Metal Sheet Part 3
draw the shown pattern on the nail polish side.
The design is as follow:
a ! (inverse i) in the center of a U wich is found in a Y the tail of the Y is the effective reed. This part will be in motion and generate the sound!
The ! is the inner prong subpart the U is the middle prong subpart the Y is the outter prong subpart.
Understand that you need to get a size for your prong which effectively works.
I mean by that if you do a 5 cm long prong you will not get vibration as expected. it will not last long enough.
To get different tones/pitch, you will need to act on the width of your prong.
So once you decided of your own design, you need to scratch the surface with the screwdriver (use a ruler or a credit card to help you for the straight parts)
Do not harm yourself when attacking the metal surface... this may hurt...
Do maximum two attacks on the same spots.
If you made mistakes, I did, you can allways apply a correcting nail vernish layer on the desired spots
On the very left down you can see two other designs that did not work but from those I understood what to do next.
Step 6: A Small Scheme of the Whole Process for Comprehension
basically it summarized the whole process:
the set up of the metal sheet, the electrochemical bath and the electrical hazard.
One point to understand is: if the stainless steel wire is plugged on the wrong place, you will see bubbles on the sheet of metal (H2)
So you need to exchange the position of both eletrodes (there the stainless steel wire and the sheet of metal)
Step 7: Electro Chemical Machining Stage
Set everything as shown on the picture, the whole metal sheet is not immerged in the salty water but at least the whole scratched part!
Do not make contact between the two electrodes! Do not put your finger on water when power is ON!
Do not make anything stupid, this is current dude! The contact made from the cables with the electrodes is done outside water! DO NOT IMMERGED THEM!
Plug the power source and wait, the metal sheet will start to corrode at the location of the scratches. The vernish allow a quite selective corrosion.
The water will turns green or orange-red. Use a plastic rod to agitate the water time to time and remove aggregates from the metal sheet surface with it (Do not put your finger in water, only this platic rod)
After 30min make power OFF. Check the advancement of the corrosion. It is not necessary that the corrosion went through metal on the whole pattern. You will see by transparency that the half was corrodIfed.
If yes: Good enough, go next.
If no: back into the bath for 20 more mins, and do that as long as at least the half of the scratches are fully corroded.
Step 8: Extra Mechanical Machining
You need here to finish the work undone by the current. The reason you do not wait until the end is to avoid a too intense corrosion at some location, it could be very unpleasant.
So you need to scratch again with the screwdriver, but this is done quite fast and with little effort, eletrical fairy did a good´but unfinished work.
You will be then able to separate each prong subpart.
Sand off the edges of each subpart with the aid of the file.
I also cut a bit of the side of the outer prong subpart.
You can already notice the difference by eye. This operation turns the prong to be weaker near to the base, to get a larger amplitude when it will vibrate. But as a near effect it will be at lower frequencies.
Step 9: Final Stage: Folding the Dan Moi
You need to fold the metal sheet at different locations with the aid of a pliers:
on the base (upper part), you need to fold 90° (but after the "cut" location, so that those stay together)
This fold allow then to fold the middle prong subpart as follow:
the middle prong subpart is fold at 180° from the outter prong subpart.
The inner prong subpart is fold at 180° from the middle subpart.
Middle and inner prong subpart are forming the plug of the dan moi!
the outter prong subpart the tongue!
(you can use a flat surface to help you to get 180°)
Fold the side of the frame of the dan moi at 90° or little more. But avoid any hinderance of the vibration of the main prong part: the reed.
Do not fold the whole side, let 1/third of space from the base (this is the spring frame part! the folded part will be the rigid frame part of the dan moi!)
Try to keep the frame part straight with the reed during that operation!
So then this is a serie of trials and errors to place the central reed/prong to vibrate freely without touching the frame. Once you get there, you will enjoy your new dan moi with a modern living hinge design!
That s all folks!