dynamo

aobp11 · Post by **aobp11** » Thu Jan 01, 2009 10:12 pm

The dyno keeps rotating in the same direction when the battery leads are interchanged. But only when the battery plus is connected to the dyno housing the polarization is OK (for positive earth). The other way around, though showing the proper rotation, produces the wrong polarization. Right? Your statement suggests that one *only* has to look at the direction of rotation and that the wrong direction results in wrong polarization, and correct direction in proper polarization. It probably is just a matter of words while we want to say the same.
Albert

56G80S · Post by **56G80S** » Tue Jan 06, 2009 1:17 pm

I had a dynamo which ran as a motor but produced very little output as a dynamo. When I checked the segments against each other I found there were failures (thanks, Don). A search would show up this thread from a year or more ago.

With a replacement armature it was fine; although of course my pocket wasn't

Johnny B

peterallen · Post by **peterallen** » Thu Feb 05, 2009 4:36 pm

Hi,

I have a dynamo with a similar problem, I have cleaned the armature with a fibreglass pen, tested the armature on adjacent contacts with the correct readings, segment gaps cleaned, brushes good and well shaped and under tension, field windings tested reading as book, contcat windings tested as book - ok. Run dynamo in vice with electric drill at 1000rpm only 0.2v output. Connect battery to dynamo and it motors in the direction it would normally be driven by the pulley. Any ideas? How did you resolve yours?

Regards
Pete

SPRIDDLER · Post by **SPRIDDLER** » Thu Feb 05, 2009 5:09 pm

Pete
Although it seems that all is in order the fact that the dynamo 'motors' doesn't mean much in terms of its performance as a dynamo.
A low reading of up to 0.5v normally indicates a field winding problem, whereas 1.5 to 2.0v would indicate an armature problem. It is necessary to use a 'Growler' to detect if the armature coil is shorted to itself.
BTW a test speed of 2000 rpm is better than 1000 but even at 1000rpm you should get better that 0.2v
I check my E3H (short dynamo rated at 40W) at 2000 rpm with a 6v 40 watt load (2 x 20W lamps in series). They are bright and the voltage holds at 6 - 6.4v
The E3L (longer than E3H) is rated at 60W and has two screws holding the field coil pole shoe (the E3H has only one).Edited by - SPRIDDLER on 05 Feb 2009 5:10:36 PM

Don Madden · Post by **Don Madden** » Thu Feb 05, 2009 5:58 pm

1000rpm is insufficient. The books say to run the engine at a fast idle, (1500rpm?), at which 10v should be measured. The dyno drive system runs it at 2 to 2-1/2 times engine speed, depending on the sprockets on singles or gears on twins.

Cheers, Don.

One pot · Post by **One pot** » Mon Feb 23, 2009 8:55 pm

Sorry to add another question, perhaps it should be a new thread, but should keep it together with similar info.

My E3NL dynamo was not working on the bike so I have now removed it and given it a thorough check.
Resistance across each opposite commutator pair is equal (about 1 Ohm Measured through the disconnected brushes) The Field resistance is about 3.2 Ohm. All connections have been removed and cleaned.
Brushes look healthy and slide well in their pockets under reasonable spring load.

However:
at 1300 rev/min (on the bench under a strobe)I get about 5.5V under no load, (between linked D&F and case). However under load (21W 6V bulb) the voltage struggles to achieve 1V.

I know from the previous posts I should spin it a bit quicker, but I need to find a better way of doing it.

I have polarised the unit and it will motor (albeit a little sluggish - how fast should it go?)

Sprocket on the engine is 20 teeth, Dynamo sprocket is 16 teeth (1.25 speed increase)

Any ideas would be appreciated.

Thanks

One Pot