Dynamo troubles.

[berger]

just a thought some carbons are no good and even only fit for the bin even before they have been fitted,

[raindodger]

Checked the carbons, 0 ohms from pigtail loop to rubbing face.
I think I'll take it back to Drags and find out how they get 28 volts.
Regards.
Tim.

[limeyrob]

0 Ohms is good.

[raindodger]

Hello, Groily and Swarfy.
Thanks for the comrehensive advise.  I'm going to bite the bullet and take my test leads,
meter, drill and the dynamo to Drags next week.  This has gone on long enough.
Watch this space.

Regards.
Tim.

[chaterlea25]

Hi Tim,
No real way to identify the field winding ends when the coil is fitted, the way it works is correct
I think that 12 ohms is high resistance value for the field coil??
Does anyone have a 12v dynamo apart to check the value?
I'm not sure if I have one???? Must look

John

[groily]

I think that 12 ohms is high resistance value for the field coil??
Does anyone have a 12v dynamo apart to check the value?
John

Yup.
Just measured three new unused 12v ones, UK-made and all are 12 ohms +/-   . . .which is what I expect to see with them.
6v ones at a tad under 3 ohms typically, also as expected  . . . and per Lucas at 2.8 /2.9 ohms (iirc).

[trevinoz]

My 12V field coils are about 11 Ohms. I used to wind them to 5.6 Ohms, and they were fine, but with the higher resistance the I squared R losses are much reduced resulting in less heat generated.

[CheeserBeezer]

Hi. I'm happy to check it out f.o.c. Just send it to me and I'll tell you how it performs on my tester. 10 ohms is correct (or thereabouts) for a 12v field coil.

[raindodger]

Dear all.
           I'm an idiot!!  I was not spinning it fast enough, that's all.
Increased the speed and all was well.
Thanks for all the advice, it's all sorted now.  Hooray!!

Regards to all.
Tim.

[groily]

Thought you told us you were spinning it 'at 3000rpm anti-clock'? Was there a 0 missing!?
Anyway, glad it works.

[raindodger]

Yes, Idid say that but I was mistaken. 
The drill is very old and makes the same noise no matter what gear is selected.
However, all is well!!

Regards.
Tim.

[groily]