[ausev] High torque or High RPM?

[Josh Handel]

by "20 mile commute" I mean 1 way.. sorry 40+ roundtrip + traffic if you add
everything in :-P... (if it was just 10 each way, I would just cycle to work
:-P

Josh


On 12/5/07, Josh Handel <jhandel at ktomics.net> wrote:
>
> Constraints.. (these I have a few, not many) of.
>
> 1) Range - 60+ mile Highway range (I have a 20 mile commute all hill
> country).
> 2) Performance -
>      A) Acceloration - sub 6 sec 0 - 60?
>      B) Top Speed - 70+ (anything more and I'll just get a ticket
> anyways).
> 3) Budget - Undefined (I want to scope "ideal" then work backwards from
> there :-P)
>
> You mentioned a single speed transmission, and I had that thought.. If I
> understand correctly Electric motors have 100% torque at 0 RPM. Too me, that
> meant I should use a single gear that is a blance between not bogging down
> my motor off the line and reaching my ideal topspeed when the motor reached
> its max RPM. I talked it over with a friend and he seemed to think that
> electric motors were more efficent at higher RPM so your better off using a
> full blown transmission. He also seemd to think that the larger magnets of a
> high Torque electric motor were performance prohibative over a higher RPM
> motor that can run with smaller magnets. From a NON EV perspective that
> makes since, but I don't know if those costs are real applicable to design
> when you are talking about something that is already 1000lbs + in size...
>
> So all that leads back to my first question. Which Electric motors are
> more efficient, High RPM low torque or Lower RPM high torque?
>
> Thanks
> Josh
>
>  On 12/5/07, Ian Ward <ian.ward at gmail.com> wrote:
> >
> > Josh,
> >
> > You're going to get sick of hearing "it depends", but it is totally
> > true.
> >
> > Define your expectations for performance in terms of:
> > - top speed
> > - range
> > - acceleration
> >
> > Then put a cap on the price you're willing to spend (on just the drive
> > components).
> >
> > Lastly, throw in any must-haves.  For me, this included regenerative
> > braking and single-speed transmission.  Neither of these has a huge
> > influence on the other constraints that I had for the vehicle, but they do
> > constrain your choices of components.
> >
> > Weight will certainly play a major role in configuring your 7, but if
> > you're willing to throw down some coin, there are some screaming batteries
> > that you can put in it that will give you great weight, performance and
> > life.
> >
> > At this point, there are no design constraints to make any decisions
> > upon.
> >
> > - ian
> >
> >  On Dec 5, 2007 1:24 PM, Josh Handel <jhandel at ktomics.net > wrote:
> >
> > >  Howdy all,
> > >    So I've been piecing togeather my "master plan" and I came to a
> > > perverbial "fork" in the road.   The vehical I am building will be based on
> > > a Lotus 7 Clone and is extremely light; so light that many builders of these
> > > cars use Motorcycle engines & Transmissions in them AND still have a heck of
> > > a fun car to drive.   This brings up a few questions.
> > >
> > > 1) Motorcycle transmissions are designed for higher RPM & Lower
> > > torque. Given that I have the freedom to choose my transmission for my
> > > roadster, is there any EV advantage to going with a transmission designed
> > > for RPM or a traditional RWD Standard car transmission..
> > >
> > > 2) How much "extra" weight should I account for in an EV based car
> > > (yes its all dependent on battery but a ball park).. Lotus 7's can be built
> > > ICE and weight in at under 1200 pounds.. I am sure I get 2 ~ 300 of that
> > > "back" for loosing the Gas engine, but how much MORE do I loose to
> > > batteries, controllers, etc?
> > >
> > > Thanks
> > > Josh
> > >
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> > >
> > >
> >
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> >
>
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