# of coils from # of pounds of wire

[fieldwrangler]

Folks -

Do any of you have a good estimate on how many typical (5000 turns or so) 'bucker coils you get from a pound of 43 ga. poly?

Bob P

[mr fab]

the average resistance for a paf bobbin wound 5000 turns with awg43 is 4600 ohms

the nominal resistance of 43 wire is 7.011 ohms per meter

therefore we have 4600/7.011 = 656 metres of wire

43 wire has a weight of 22.5 grams per 1000m

so one bobbin will use 22.5*656/1000 = 14.76 grams

one pound = 454 grams

therefore you will get approx. 454/14.76 = 30 bobbins or thereabouts...

obviously this will vary depending on tension, TPL, scatter etc etc

but I reckon its a good estimate

[fieldwrangler]

I must say I really like your way of going about this.

Realizing that I didn't have a quick answer for this was yet another indicator that I need to keep better records!

Bob P

[mr fab]

thanks bob

I would check my calcs by measuring the weight of an empty bobbin and then reweighing after winding, the difference between the two will tell you weight of wire per bobbin.

at the end of the day, I always compare my calcs against the real world

fab

[fieldwrangler]

I consider myself a die-hard empiricist, both in "the lab" and also in the philosophical sense.

So, for me, the comparisons, if any, happen in the beginning, middle & end of the day.

Bob p

[mr fab]

yeah I know what you mean...

[salvarsan]

. . .
43 wire has a weight of 22.5 grams per 1000m . . .

Teensy clarification: insulated wire, not bare copper.

The NEMA specs for fine wire diameter translate to +/- 5% in bulk resistance. Add that to scatter and stretch during winding. Without knowing more about tension control, any computational analysis of pickup windings is limited to being a +/-10% estimate. Hardly useless, but you need to keep the limitations in mind.

[mr fab]

Teensy clarification: insulated wire, not bare copper.

The NEMA specs for fine wire diameter translate to +/- 5% in bulk resistance. Add that to scatter and stretch during winding. Without knowing more about tension control, any computational analysis of pickup windings is limited to being a +/-10% estimate. Hardly useless, but you need to keep the limitations in mind.

\

as I said.... the results will vary depending on tension, scatter, tpl etc

[salvarsan]

The difference between craft and engineering is an explicit error margin.

[EmaEm1]

the average resistance for a paf bobbin wound 5000 turns with awg43 is 4600 ohms

the nominal resistance of 43 wire is 7.011 ohms per meter

therefore we have 4600/7.011 = 656 metres of wire

43 wire has a weight of 22.5 grams per 1000m

so one bobbin will use 22.5*656/1000 = 14.76 grams

one pound = 454 grams

therefore you will get approx. 454/14.76 = 30 bobbins or thereabouts...

obviously this will vary depending on tension, TPL, scatter etc etc

but I reckon its a good estimate

Sorry, how would this look like with 44 awg (0.05mm)?
I only need information for meters, as I am buying wire in meters?

[salvarsan]

Sorry, how would this look like with 44 awg (0.05mm)?
I only need information for meters, as I am buying wire in meters?

Rdc awg44 = 2593 ohms/1000 ft = 2.593 ohms/ft

50mm paf bobbin: 5000 turns @ awg44 ~= 5500 ohms


feet per PAF bobbin = 5500 ohms / 2.593 ohms/ft = 2121 ft = 646.5 meters per bobbin


A 1 pound spool of single build awg44 is 80060 feet long = 24400 meters


bobbins per 1# spool = 80060 / 2121 = 37.75, about 3 dozen, give or take 10%
bobbins per 1kg spool = (above) / .454 = 83.14


The average coil size was estimated computationally and assumes that PAFs have a tight machine wind with a fill factor ~90%.
Data for insulated magnet wire was found at MWSwire using their Magnet Wire Tool and assumes a generic single build P155 polyurethane.