You might consider changing the gear ratio. I am using a BMW diff that has a 4.44 to 1 ratio which is a little low also but I am using 2 9" motors in series that will make things better. If I don't like it I am going to use a Ford thunderbird diff which can be loaded with 5.13 to 1 gears.
Mark Grasser -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of forrest.whitmore via EV Sent: Wednesday, December 04, 2019 3:50 PM To: ev@lists.evdl.org Cc: forrest.whitmore Subject: Re: [EVDL] Rear Diff IRS | Direct Drive Electric Vehicle Discussion List mailing list wrote > > Finally, there is the efficiency advantage of operating at the motor's > peak > of the rpm-vs-efficiency curve, which also means less of the energy wasted > as heat. > > I think you probably want to gear your drive so that your motor is > operating > at its peak efficiency rpm when you're at your typical cruising speed, and > so that the top speed you want doesn't exceed the motor's red line. But > that's not usually the gearing you get with an ICEV factory differential. > That's why most single-ratio conversions I know of have either locked the > stock transmission in a lower gear, or used a custom gearbox. > > I expect that a 3.27 final drive with no other reduction would call for > either absurdly small wheels or a large, heavy, low-rpm motor. Maybe > both. > > What vehicle are you converting? Are any other final drive ratios > available > for it? Maybe there's a transaxle from a FWD car you could somehow > shoehorn > in? Thanks for the response David and direction. I worked out the rpm-vs-efficiency and gearing out in a spreadsheet. A 3.27 diff with no reduction doesn't work out well at all. I'm going to develop a custom single-speed gearbox coupled to the rear diff to get the final drive that works best. Although there's a transaxle for my vehicle, I'd rather optimize the use of space and gearing in the vehicle. Forrest Walker Whitmore -- Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com/ _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
