The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: nigeldtr on 20.09. 2009 21:51

Title: Dynamo output
Post by: nigeldtr on 20.09. 2009 21:51
On my plunger A10, I find the dynamo kicks in when I get above tick over and matches the demands of the lights etc when I get to about 50 mph in 4th (around 45W at 6V). Below this speed or around town, nearly always in the discharge zone. Is this normal. On my M21 she belts out loads of power and has no problems matching the demands of the lights even at low engine speed ????

Title: Re: Dynamo output
Post by: trevinoz on 20.09. 2009 22:57
          First, what type of dynamo are you running? If you have the long E3L, it nominally delivers 60W at probably around 60 MPH. It is proportionally lower at lower speeds.
If you have the short E3H, it has 45W output.
The generator gearing also comes into the equation. The E3L has a 11 tooth sprocket and E3H 13. It is not unknown for the sprockets to get mixed up.
What wattage head light are you using? You should have a 30/24W if traditional incandescent. Over that loads the generator beyond capacity at low speeds.
The short dynamo requires a 24/24W lamp.
Title: Re: Dynamo output
Post by: nigeldtr on 21.09. 2009 08:44
Hi Trev,

I have the long E3L. I had put a 36/36 Halogen bulb in but it is too much for the dynamo. I shall put this in the M21 which bangs out loads or current and from much lower revs! I will take a look at the sprocket when I have the timing cover off next, I seem to remember it being very small.

Thanks for the tips and the 60 mph seems to tie up with what I have experienced.

Title: Re: Dynamo output
Post by: Dynamo Regulators Mike on 22.09. 2009 19:16
Nigel, the lucas dynamos should give their rated power output at about 2,000 rpm. My regulator test figures concur with the makers specification; 8 amps at 7.2 V (60W) at 2050 dynamo rpm. This equates to less than 40 mph on a Flash. Something is not performing on your bike if only getting 45W at 50 mph.
Title: Re: Dynamo output
Post by: nigeldtr on 22.09. 2009 20:53
Hmmm, I will have to take some more measurements and see what is happening.