Robert Macy wrote in message
...
On Aug 19, 12:37 am, "N_Cook" wrote:
Is there an online calculator anywhere ? or failing that what sort of
"packing factor" for 0.08mm (+/- .005mm ) winding on a relay coil.
I have a good idea of the weight , subtracting an estimate of the plastic
former and this would give the length from the density of copper but
number
ot turns ?.
Impregnated coil so cannot count-off turns
Rectangular section to coil , on the inside anyway, 14x 16.4mm , 16.8mm
width, outer layer is curved at "corners" and bulging (from the winding
not
abuse) so more scatterwound than precise regular lay-up .
Outer dimensions of 21.4mm bulge / 20.3mm , or so, at outer edges one way
and 23.4/22.2mm , the other, a bit of geometry would give a good idea of
the
volume of this space but what ratio of that volume would be copper and
what
air+varnish, then what sort of weight would be contributed by the varnish?

I found that tables from wire suppliers are a great guideline. But,
nothing beats having to fight 'stacking factor' on your own.

I use 0.5 for wrapping 36 Awg enameled wire. I know I should be able
toget better than 0.7.

So take the winding area multiply by SF and divide by wire cross
section area and you'll get very close..

And, from experience, if there are a few layers, don't count on nice
neat, high density layering and stacking, doesn't work that way.

Oh, also watch out for stretching the wire, making it slightly thinner
and 'appear' to be able to put on more turns, you'vve actually reduced
the wire size instead.

++++

By stacking factor do you mean the ratio of copper volume to the volume
occupied by the copper ? ie the last layers always need squahsing into the
available (calculated) space between former and iron core etc.

I will try that , also calculation via derivation of a formula for such
situations , and also try cutting through the coil mass and counting
directly , hopefully . For future reference as to accuracy of each method
(in one instance anyway)