Re: e-tek speed ratings

[Douglas Hartley <douglas.hartley@sympatico.ca>]

The 3200 RPM minimum rating should be what you can expect (or slightly
better) at a specific torque load (160 LBin) and at the rated voltage
(50V)  The speed is adjusted by the controller effectively presenting
the motor with a lower voltage and the motor acts like the inductor in a
buck regulator.  If you run the motor on 12V directly, for example, it
will run at a lower speed, such as 900 RPM.

Doug

Roger Stockton wrote:
> 
> On Tuesday, January 29, 2002 10:12 PM, Dylan Pfeifer
> [SMTP:dcpfeifer@earthlink.net] wrote:
> > While the E-tek motor is in on the table, I was wondering if I
> could
> > drop in a question that maybe other buyers have...
> >
> > Suppose I've got an 810 rev/mile tire, and I'm designing it to
> > cruise at 60mph with the E-tek.  Single gear trans.
> >
> > Well, the E-tek says "min nonload speed"=3,200rpm, and "max nonload
> > speed"=3,600rpm.  Not knowing any better, suppose I think this
> means
> > "can't run slower than 3,200 rpm and can't run faster than 3,600
> > rpm."
> 
> Just a guess, but I think what this means is that the no-load speed
> is spec'ed to be in the range of 3200-3600RPM.  Put another way, they
> are stating that the RPM/volt constant of the motor is in the range
> 67-75RPM/volt (assuming a 48V pack).
> 
> > So say I gear the E-tek with chain and sproket 0.23:1 ( 60mph with
> > 810rpm @ tire and 3,500rpm @ motor).
> >
> > Well, but if I go 30 mph.  Then the E-tek is going 3,500 * 0.5 rpm,
> > below it's minimum speed rating.
> >
> > So what happens... does the motor overheat... blow up.. what.
>   What
> > happens also if you exceed 3,600 rpm, say going downhill.
> 
> You are fine going slower, although if you go too slow, the motor may
> have insufficient cooling and overheat.  If you exceed 3600RPM, the
> motor will fail, though possibly not until 4000RPM or so.
> 
> Gearing for a top speed of 60MPH with a motor that can only sustain
> about 8HP for any length of time seems a bit ambitious; but the real
> problem may end up being at the lower speeds.  Because of the tall
> gearing you will need a fair bit of torque to accelerate or climb
> hills, but the motor cannot take very high current, and not for very
> long.  The vehicle will need to be very light and aerodynamic.