Coil need opinion

[Reno]

Hello, it has been a while. My motor conversion is still flying going on a couple of years.

Any way I took on making a dual rotor but have been working at it slowly, all by hand and hand tools. I have finished my 9 coils and after comparison I would like comments on whether I need to tighten up on the sizes.

The coils are made of #14 wire and wound 80 turns (suppose to be)

After they were done I weighed then in grams and got as high as 367g and low as 274g this works out to be 15ft more wire on the largest to the smallest (1ft wire = 5.9 grams). 7 of the 9 coils are within 4 ft total length of each other.

The question, is this difference in length acceptable and if so, how would I orient the coils to cancel out any possible vibration caused by the different lengths?

Next time I think I will slightly over wind each coil and then remove the proportionate amount of wire from each.

[Flux]

If the things all have 80 turns then it will make no difference. If the differences in weight come from differing number of turns then then again it will not make much difference but ideally you might try to  keep the phases similar. If you have 3 very heavy coils then put one in each phase rather than all 3 in the same phase.

In real life as long as the things will go in place it really doesn't matter. There have been designs that deliberately unbalance the phase windings to get nearer to the cube characteristic but whatever you do it will be a glorious compromise. Slight unbalance between phases doesn't matter much. The vibration will be small on light load and as the load comes on the phases will share current well enough. The things behave rather as current sources and a little voltage unbalance gets lost.

Sometimes with these machines the ones built with most care and the highest precision don't always perform better so I wouldn't worry.

Flux

[Reno]

Thanks

[veewee77]

Here is a test. . . mount each coil, one at a time to something and spin the rotor with the coil close. Spin at the same RPM for each coil. Same distance from coil, etc. . .

Get as uniform as possible between each one.

Measure Voltage from each coil.

Mark them somehow. . . if they are all the same or real close, no worries. . .If you have some that are high and some low, balance them out in sets. . . no worries.

Get each set (phase) as close to each other as possible but it really shouldn't matter that much. . .

DS