Battery not charging

[Chris Sealy]

The brushes appear to be connected correctly, in the pictures.
The 2.5 ohm reading means that the field coils are probably ok.
The other measurement should be very low. Depending on how good your meter is; it may read 0 ohm.
If you are getting an open circuit it probably means that one, or both, of the brushes is not making contact with the commutator.
You will need to lift the spring with a small screwdriver or bent wire, then pull carefully on the wire attached to the carbon brush.
When they are both out, clean the brushes, the inside of the brush holder; cotton buds are useful here; and the commutator. You can clean between each of the copper segments of the commutator with a a sharpened matchstick or toothpick; do not use a metal tool, to avoid damage.
Oil can soak into the surface of the carbon brush. Usually it is enough to wrap some very fine sandpaper around a finger to remove the surface layer at the end in contact with the commutator.
When its back together, put the drive sprocket on, and turn it a few times then measure the resistance whilst turning, or at least measure at several positions, if you cannot measure and turn at the same time. Again it depends on the meter you are using, but the reading will vary slightly as you turn, and should stay below 1 ohm.
Good luck, Cheers, Chris.

[BruceWatts]

Hi Chris
This is why I became a mechanical engineer !!
If I put one lead of the multimeter directly on to commutator, I get 0,3 ohms.
If I put the lead on the alloy body, and ensure a good contact, I can get up to 19 ohms !! It seems to vary. Is this because the resistance measurement has to go thru roller brearings etc? Does it "go that way "if the brushes are oily?
I did re install the dyno into the bike and run it. It did not show any voltage on the ammeter or on my multimeter.
I will indeed clean the carbon brushes well or just buy new ones. I did not do that before. I will also give the commutator a "surgical" clean.
I have a old Hornby model railway and the trains suffer from bad performance due to oily brushes etc. The solution there is to heat them up with a soldering iron until the oil burns off. Don't think I can do that here. I will soak them in rubbing alcohol or similar, then give them a sandpaper.
I need 6 volts and the power of the force !!
Bruce

[will_curry]

Bruce,

Once the dynamo has been apart it may well need 'flashing' to get it to start
generating again. Did you try motoring the dynamo when if was disconnected
from the timing chain?

[nevhunter]

Current should NEVER go through the Ball Bearings. There should be no Path to earth in the armature. Usually ONE of the brushes is earthed to the frame. Brushes must be free to Move in the Holders and the commutator should run true and be undercut carefully. Left, they can lose residual Magnetism or after being pulled apart. It's essential that the wiring around the brushes is as it should be and the dynamo is running in the correct direction. Nev

[BruceWatts]

Thks for the help guys.
I have purchased new brushes and will check the earthing again.
I will also attempt to motor the dyno and flash it.
Chrs
Bruce

[Chris Sealy]

Hi Bruce. I would recommend that you dismantle your dynamo and replace the oil seal. The leakage will only get worse.
Also the rear bearing probably still has its original 1958 grease in it. Oil seals, and bearings, are available from Draganfly.
Cheers, Chris.

[BruceWatts]

Hi All,
Well the dyno is now producing a good voltage, but the ammeter does not go into the +ve.
I now suspect the ammeter itself. The wiring seems to be OK.
How can you check it? Can I somehow put a 6v power supply to it, to see if the needle moves as it should?
If it were not seeing a charging voltage, would its red light not shine? I assume that is the purpose of the light.
Chrs
Bruce

[Mick D]

Hi

Assuming the battery has some life in it, with the engine off, turn on the headlight, the ammeter should deflect to the negative side, about -6 amps, turn off the lights, it should return to about zero or a little negative. Start the engine, it should read positive, how much will depend on the charge of your battery, turn on the lights and rev the engine a little, it should remain a little positive.

Do the above and let us know what you see.

Regards Mick

[BruceWatts]

HI Mick,
The negative side of things seem to be as per what you say.
I just cannot seem to get the needle into the positive.
I have installed a new battery, so maybe a big deflection to the right is not going to happen. I did read that if the lights brighten when the engine is revved, then all is well.
Anyway, I will play again tommorrow and let you know.
Chrs
Bruce

[Simon.Gardiner]

Will it balance (no discharge) with the lights on and the engine running?
(From what you're saying it seems that the lights brighten when the engine is revved which suggests that it does balance)

SG