E3L Dynamo conversion to 12volt failed

[RichardL]

Roger,

I can't speak to the issue of turns on the dynamo armature, but I can offer you a quiet welcome to the forum.

 ROGER,

 WELCOME TO THE ONE AND ONLY BSA A7/A10 FORUM!!!

[trevinoz]

Roger,
             There are indeed 18 turns per coil in an E3N armature.
As long as you are not using too large a conductor, they fit easily.
I quite often wind them with20 turns per coil with no issues.

  Trev.

[fump]

Thanks you two gentlemen for the welcome and reply..........Trev thanks for that, I will persevere with the rewind then, it's just that there seems hardly enough room for 36 wires in that small channel! I guess I will have think hard about how to lay them. The old wire appears to be about 0.75 mm.

Regards

Roger

[trevinoz]

Roger,
                Without going to the shed to confirm, 0.7mm is the conductor size.
As you wind, keep it tight and push the conductors into the slots with a piece of insulating board or a piece of Laminex, which is what I use.

  Trev.

[fump]

Thanks Trev............I can only get 0.8mm here or 0.65 mm for some reason, so have gone for the 0.8mm. Have done 6 windings tonight as am awaiting more wire! It's a tight fit. I wonder if 0.65mm would be too small to carry the current safely? It would be a better fit....

[trevinoz]

Steve,
            Use a piece of insulation or whatever which is a snug fit in the slot between the insulation and tap down with a small hammer, I use an 8oz ball pein.
The windings should compact OK.
I just went to the shed and had a look in the scrap bag for original windings and found that the old cotton covered conductors are 0.024" and the enamelled are 0.028".
The 0.65mm should be alright.

  Trev.

[fump]

Trev
Thanks very much for that. I am using the 0.8mm presently and have done six coils and am now awaiting another batch of wire from local supplier as they only had one unit in stock. I modified a plastic paint stirrer and that is doing a good job geting the windings in place. Though it is pretty tight in there, but tests out okay with the meter.
I guess I am not very confident as I have put an AD in the local club mag for a E3N !
Cheers

Roger

[fump]

Well I have done the re-wind but...................... I am geting only 150 mv out of the B....y thing when driven with my electric drill (at about 800 rpm I think). It motors well with 12Volts on it and in the correct direction too. But will not drive a 6volt 21watt lamp, which is no surprise with 150mv out.
The Field coil reads 3 ohms, armature is infinite to earth and all adjacent com segments are connected and the highest reading between furthest segments is about 0.6 ohm. I would appreciate any informed comments please!

[trevinoz]

Roger,
                    800 rpm is a bit slow to test, I use a drill which runs around 2500 rpm.
But, the question is, have you connected the coils to the correct segments?
Connecting just one out will cause very low output. [Don't ask how I know.]
Testing resistance between segments is not much use.
I find that "drop testing" between segments is best as I don't own a growler.
Another problem can be a reversed coil, i.e. one that is connected wrong way round. This will be picked up with a drop test but not with a resistance test.

  Trev.

[fump]

Trev thanks for your reply. I think I under estimated the revs on my drill. I have got it going now there was an intermittant earth fault on one coil. So I had to rewind four coils to clear it! It will light the 21 Watt bulb now and gives 7.8 volts on load.Wonderful!