My dates may be off a wee bit. But the S12 and the S6 were both discontinued a few years before the Dymotec 6. It was the last high quality sidewall dynamo standing for a few years. The S6 and S12 both used some sort of negative feedback to cancel out most of the drag from the power generation, leaving just the mechanical drag of the roller rolling against the tire's sidewall. With the S6, if my memory serves me well (that's a laugh) and if carefully aligned, drag was only slightly higher than with the SON28. But you still had the problem of the roller slipping in the rain, and having to listen to the roller spinning on the tire.
On Thu, Dec 4, 2025 at 7:00 PM Corwin Zechar <[email protected]> wrote: > Hi Peter - > > I'm really confused here. If Dymotech was "state of the art" 25 years > ago... how is it the drag was about twice the drag of the SON dynamo hub, > and the S6 and S12 hubs were somehow better? > > Regards, > > Corwin > Berkeley, California > On Friday, November 14, 2025 at 5:23:59 AM UTC-8 [email protected] wrote: > >> The Dymotec 6 was state of the art 25 years ago. If I remember correctly, >> the drag (if correctly aligned) was about twice the drag of the SON dynamo >> hub, which is extremely low. There was a higher spec version, the S6, which >> had even lower drag by somehow introducing negative feedback. The S6 was a >> fair bit more expensive. Then there was the S12, a 12 volt version which >> powered 12 volt lights. >> >> Alignment is critical. If it's off by just a bit, the rubber roller will >> melt from the friction. So when aligning it, be sure that the axis of the >> dynamo intersects the axis of the hub. >> >> PJW >> >> On Thu, Nov 13, 2025 at 8:45 PM 'Eric Norris' via RBW Owners Bunch < >> [email protected]> wrote: >> >>> I know there’s been some interest on this list for this item in the >>> past, so … >>> >>> Going through some of my bike paraphernalia a few days ago, and found a >>> new-in-box B&M Dymotec 6 bottle generator. This is a classic, “bottle”-type >>> generator that mounts to the frame and runs on the side of the tire to >>> generate 6 volt/3 watt power. >>> >>> Peter White used to sell them—here is his archived page about the >>> Dymotec 6: >>> >>> [image: B&MDymotec6.jpg] >>> >>> peterwhitecycles.com <https://www.peterwhitecycles.com/dymotec.php> >>> <https://www.peterwhitecycles.com/dymotec.php> >>> >>> Per Peter (and my experience), this will power modern 6-volt lights, >>> with or without a taillight (max of 3 watts of power draw).[image: >>> IMG_0325.jpeg][image: IMG_0326.jpeg][image: IMG_0327.jpeg] >>> >>> The one I have is for mounting on the left side of the bike (it won’t >>> work on the right side). The box has just the generator; you will need to >>> supply the mounting hardware. >>> >>> How about $45 shipped in the USA? >>> >>> Let me know if you have any questions! >>> >>> --Eric Norris >>> [email protected] >>> Insta: @CampyOnlyGuy >>> YouTube: YouTube.com/CampyOnlyGuy >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "RBW Owners Bunch" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To view this discussion visit >>> https://groups.google.com/d/msgid/rbw-owners-bunch/40AB4F73-5F7C-495F-95FA-BFB99C4D19C5%40me.com >>> <https://groups.google.com/d/msgid/rbw-owners-bunch/40AB4F73-5F7C-495F-95FA-BFB99C4D19C5%40me.com?utm_medium=email&utm_source=footer> >>> . >>> >> >> >> -- >> Peter White >> > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/rbw-owners-bunch/bc12c035-f7c6-4219-b728-028c0a3237d7n%40googlegroups.com > <https://groups.google.com/d/msgid/rbw-owners-bunch/bc12c035-f7c6-4219-b728-028c0a3237d7n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- Peter White -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/CA%2BD%3DXm-PewC-d7_FxtDaaYYr2Ar636gzLsBQHtF5B0jf5xkSSw%40mail.gmail.com.
