test dynamo

[Tumbleweed]

hi everybody  .  I am trying to make a good dynamo out of two old ones .  when I spin it with a drill A/Clockwise I only get2-3 volts set on  20 position on my  meter joining F and D together  to  neg   and pos  to + it wont light a bulb just a faint glimmer, but it motors quite fast.        any ideas TW  how fast does it have to turn befor it works with the dynamo off the bike

[bsa-bill]

oining F and D together  to  neg 

Dynamo body would be neg or pos depending on polarity usually positive earth on these bikes

[Tumbleweed]

 yes Bill its off my a10 and its +earth  , 

[JulianS]

Lots of interesting stuff on electrics on Matchless Clueless site;

https://matchlessclueless.com/

[bsa-bill]

a week or so ago I got similar results before changing polarity back to positive earth (long story)  , turned out I had painted the dynamo not thinking about it's need to earth, had to rub of the paint (under the strap) and put a piece of copper between the strap and the dynamo, magic upto 20 volts at times

[trevinoz]

That is usually indicative of an armature with open circuits.

[Tumbleweed]

thanks for your help chaps ,  the matchless site was useful as well     TW

[Tumbleweed]

hi, everybody ,  I have just run a test with a electric drill and at 2000 rpm    I get  14 v charge from it I am hoping this will do for my a10 ?    TW

[Rex]

a week or so ago I got similar results before changing polarity back to positive earth (long story)  , turned out I had painted the dynamo not thinking about it's need to earth, had to rub of the paint (under the strap) and put a piece of copper between the strap and the dynamo, magic upto 20 volts at times

It should earth just fine through the ally end plate to the engine.

[bsa-bill]

It should earth just fine through the ally end plate to the engine.

Really , I find on mine the cork gasket makes a good insulator 

[Rex]

Mine must be a different design then, as the cork gasket only touches in the middle section and the outer portion is well and truly butted up to the crankcase.

[bsa-bill]

possible the cork has compressed, if the alloy touches first then the cork is doing nothing.
The reason mine did not earth was I had stupidly painted the body ( a bit too well)

[trevinoz]

TW, if you are getting 14V the generator is fine.

[coater87]

 After some of the hassle I had with mine after rebuild, I would power up a bulb with it before I buckled it up. 14V is nice, but I would make sure it will run a load first.

 Lee

[Tumbleweed]

hi folks ,   well I fitted  it to the bike and I don't even get 1 volt direct from dynamo      also I  flashed the F terminal for polarity ,  the D terminal flashes as well  is this normal ?   TW