3D printed former for 3DSS coil intended for Minipulse

[6666]

the distance between the deepest points of the inner and outer slots should be 1/4" or 6mm

Just measured the original Russian former printed on paper at 100%, and the distance between the bottoms of the slots is about 5-6mm.
and dont forget to move forward one slot after the initial winds.

[LukeJ]

You may have read my recommendation in the Chance PI Coil thread that the distance between the deepest points of the inner and outer slots should be 1/4" or 6mm. Also widening out the coil form spreads the coil cross section and is likely to diminish the self shielding effectiveness of the 3DSS coil. I try to keep the coil cross section circular to keep shielding uniform and effective.
Regards,
Dan

To be honest, I haven't read all of the Chance PI Coil thread. I didn't really land on the part where you discussed the depth of the slots, I just remembered one portion where you were saying that a roughly 3/4" wide former seemed to work well. Or something to that effect. Anyways, Thanks.

I wound the Russian version first and in that process I discovered some things. Once I 'drew' one in the CAD system, then I was able to start playing with the individual dimensions. There is probably a hundred ways to get to a similar result. As long as you are happy with the result, you did it right....

Here is a drawing I made to hopefully better explain what I was trying to say with regards to the ratio of slot depth to OD and ID. One also has to take into account the diameter of the wire being used so there is enough depth to accommodate the layers of wire. In this particular coil, I estimated that I would have 25 turns. Which means there would be five layers of wire in each slot. I needed to have slots that were deep enough and also formed the 'straight line' I was referring to. The OD is 11.75" and the ID is 10". I was able to get the slot depths adjusted to achieve what I was looking for. This coil is the one with 41 slots instead of 37. If I had left 37 slots, the distance between the slots would have increased which would have required slots with less depth and then the five layers wouldn't fit. Like I said, once you wind one or two, you can sit and look at it and really start to understand what is going on there. This is the template I used to make the 12" coil pictured previously. I just glue it to the plastic and cut along the lines...



I'm probably not the first to make these 'discoveries'. Not trying to take any credit for anything. Hopefully I can explain well enough to pass the idea on to the next guy...

Thanks,
Luke

[baum7154]

3DSS COILS

Thanks Luke,

I would recommend that you do read the Chance PI Coil thread as there has been a lot of development over the past 4 years. Like you have done I have been thinking of going to more prime number slots in order to gain an advantage in the wire angles on different sizes and shapes of forms. For a coil of 325uh to 335uh I like the form to be about 1.050" with the slots innermost points .25" apart. This forms the sensitive hot inner core of the coil with the outside layers acceptably dense to provide the shield effect.

I agree that the hand tool method of cutting these forms using a glued on pattern is the best way for most builders to construct these coils. It is certainly accurate enough and though it does take a bit more time, results in a fast, sensitive, durable, shielded high performance 'all metals' detection coil without all the effort of adding a separate graphite shield. That said, in extreme cases a graphite shield can still be added.

Welcome to the forum, I look forward to seeing more of your work.

Regards,

Dan