Re: [CR]Help with generator (dynamo) lights

Example: Framebuilders:Brian Baylis

Date: Tue, 23 Dec 2008 09:12:48 -0800
From: Jerome & Elizabeth Moos <>
Subject: Re: [CR]Help with generator (dynamo) lights
To: M-gineering <>
In-Reply-To: <>

I checked the SON hub dynamo wiring instructions on Peter White's site.  For the SON one wires the headlight to the tailight, i.e. the lights are wi red in series.  But the SON has only one pair of male connectors on the hub.  The B&M Dymotec sidewall dynamo I am using has two pairs of male c onnectors, i.e. two "hot" connectors and two "ground" connectors.  I as sumed this meant the headlight could be connected to one pair (one hot and one ground) while the tailight could be connected to the other, that is tha t the lights could be connected in parallel, which is what I did.  Is thi s not correct?  Must the lights still be connected in series?  If so, w hat is the purpose of the two pairs of connectors on the dynamo?  Any one have a link to wiring instructions for a B&M Dymotec with B&M front and rear racks?

Another question. Peter states that if the dynamo is positioned behind the mounting point, the opposite "hand" version of the dynamo must be used.  That is, if you mount a dynamo behind the left fork, then you need a Right Hand dynamo, whereas if you mount it in front of the left fork, then you ne ed a Left Hand dynamo.  So what happens if you have the wrong "hand"?  The reason I ask is, although Peter says that the dynamo should be mounted in front of the fork to guard against a loose dynamo jamming the wheel, no less a frame builder than Ron Cooper built my new Bates with the dynamo bra zeon behind the left fork.  (This does have the advantage of the brake ca liper not interferring with the postioning of the dynamo).  Which means, according to Peter, I should have a Right Hand dynamo.  Now it's been sev eral yaers, but I built up the Caygill and Bates at the same time, and orde red dynamos and lights at the same time.  And being blissfully ignorant of the issue of behind or in front of the fork, I'm almost sure I would have ordered two identical Left Hand dynamos.  Yet the one on the Bates w orks behing the fork, driving a front light only, and the one on the Caygil l works in front of the fork, at least until I try to connect the tailight.   Can the "wrong hand" dynamo actually work, or did I get the correct dyn amos just by sheer dumb luck?  Lacking the original box, is there any mar king on the dynamo itself that will indicate whether it is RH or LH.

I would never have thought that something so seemingly simple as bicycle li ghting could be this complicated.


Jerry Moos
Big Spring, Texas, USA

--- On Tue, 12/23/08, M-gineering wrote:

From: M-gineering <> Subject: Re: [CR]Help with generator (dynamo) lights To: Cc: Date: Tuesday, December 23, 2008, 12:59 AM

R.C. (Dick) Felton wrote:
> BEST place for wiring instructions for SON is Peter White Cycle and "IF" all
> fails call him.Here is direct link to wiring instructions for rear lights
> Hope it helps
> Regards
> Dick
> Richard C (Dick) Felton
> 519-464-6134
> Sarnia, Ontario, Canada
> -----Original Message-----
> From:
> []On Behalf Of Jerome &
> Elizabeth Moos
> Sent: Monday, December 22, 2008 8:50 PM
> To:
> Subject: [CR]Help with generator (dynamo) lights
> This weekend I dug out of storage two custom touring bikes that had been bo
> xed for three years since I moved to Big Spring. One is a Ron Cooper bui
> lt new Bates, the other a Richard Kent built Arthur Caygill Artisan. The
> se are the only two bikes I have on which I have dynamo lights that I've ac
> tually tried to operate, although I have a 60's LeJeune tandem with what lo
> oks to be an original dynamo which probably doesn't work.
> I had never installed the lighting on the Caygill, athough I had bought i t
> when I built up the frame several years ago. Finally installed the dynam
> o and front light yesterday, but struggled much of today to install the rea
> r, as I had to go to Radio Shack for some wiring terminals.
> After finally connecting the rear light, not only did it not work, but th e
> front did not either, although it did previously. When I disconnect the
> rear light, the front works again. ,The whole system is 6 volt Busch and
> Muller, all bought together 5 or 6 years ago. The lights ahave the "Stan
> dlight" feature. Is it possible the dynamo will simple not drive both th
> e font and rear light? Or is there probably a defect in the rear light o
> r its wiring?
> Regards,
> Jerry Moos
> Big Spring, Texas, USA

most obvious mistake with these symptoms is that you swapped the leads for the rearlight. If you connect the phase wire to ground you will have no lights. With B&M lights you will need a torch and reading glasses to find the marks which define which terminal is which. Cycle lights will also connect to ground if bolted to clean metal.

If this doesn't work: as you have a standlight: if the front light has a bad bulb (wrong wattage, or worn) system voltage will be limited and it might take a long time before the rearlight powers on, as it has to charge the capacitor first or something

-- mvg

Marten Gerritsen
Kiel Windeweer