David, and others, the most fragile part, of a series DC motor, is the commutator. And that is, because the copper segments are glued to an insulating core. When the current is flowing, the segments heat up and soften the glue, then they are subjecting to "lifting," away from that insulating core, and causing problems with the brushes, resulting a need for an extensive repair. But, with no (or very low) current, the glue maintains its strength, and the motor can be spun to a higher RPM, without damage.
PS. added a new "You Tube" Link (Below) Dennis Lee Miles (*evprofes...@evprofessor.com <evprofes...@evprofessor.com>)* * Founder: **EV Tech. Institute Inc.* *Phone #* *(863) 944-9913 (12 noon to 12 midnight Eastern US Time)* *Educating yourself, does not mean you were **stupid; it means, you are intelligent enough, **to know, that there is plenty left to learn!* * You Tube Video link: http://youtu.be/T-FVjMRVLss <http://youtu.be/T-FVjMRVLss> * * NEW You Tube Video link: *http://youtu. be/Pz9-TZtySh8 <http://youtu.%20be/Pz9-TZtySh8> On Tue, Aug 5, 2014 at 5:25 AM, EVDL Administrator via EV <ev@lists.evdl.org > wrote: > On 4 Aug 2014 at 18:14, Ben Goren via EV wrote: > > > He says it's okay to spin the motors faster than 8000 RPM so long as > > it's not the controller that's sending the current to the motors that's > > doing the spinning. > > I wonder why this would be. > > David Roden - Akron, Ohio, USA > EVDL Administrator > > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > EVDL Information: http://www.evdl.org/help/ > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > Note: mail sent to "evpost" and "etpost" addresses will not > reach me. To send a private message, please obtain my > email address from the webpage http://www.evdl.org/help/ . > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140805/05c618f3/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
