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Re: [EVDL] Gizmo EV "gearing"

Since the motor is SepEx, it will have a hard max RPM limit
which depends on voltage.
You can easily use a larger gear ratio to reduce the torque
(and thus amps) that the motor needs to sustain, but the
drawback is that you have to increase the voltage to reach
the same max speed, or accept that your max may drop well below
40, likely even below 35.
This can also be solved by rewinding the motor and keeping
the same pack voltage - the choice is yours.

Success,

Cor van de Water
Systems Architect
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David D. Nelson
Sent: Monday, August 27, 2007 3:08 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Gizmo EV "gearing"

Thank you for all the ideas coming in on this.

I just sent Mark Murphy an email so I report back what I hear from him. I have thought for a while that I needed to figure out a way to do some forced cooling.
I am pushing this motor to its max when I climb. The brushes showed evidence of arcing from the brush holder to the sides of the brush. I don't know if this happens only when the motor is hot (higher resistance) or at any time. The armature current routinely goes over 300amps during my hill climb.

David

--- keith vansickle <[email protected]>
wrote:

> david
> have you emailed Mark Murphy at Blue sky design he is in creswell
> oregon and originally built these veh kEVs
>
> --- Jeff Major <[email protected]>
wrote:
>
> >
> > Hi David,
> >
> > You might want to consider forced ventilation on
> the
> > motor. Sounds like your performance is O.K. Just that your duty
> > cycle is too hard.
> >
> > Increasing the gear ratio will lower the load on
> the
> > motor and slow down the top speed of the vehicle.
> > That would likely make the motor run cooler, but take you longer to
> > get where you're going. I'd try keeping the same ratio and blowing
> > a lot of clean air thru the motor.
> >
> > Regarding the larger motor, you'd probably have to retune the
> > controller.
> >
> > Jeff M
> >
> >
> >
> >
> > --- "David D. Nelson" <[email protected]>
wrote:
> >
> > > Hi all,
> > >
> > > I have a Gizmo EV (www.nevco-ev.com) which has a
> > 48V
> > > pack and a 6.7" D&D Separately Excited Motor. I
> > have
> > > run it for a year but the hill climbing I have
> to
> > do
> > > has started to burn up the motor. Jim H has it
> > right
> > > now to rebuild/repair. We had been considering installing a 7.5"
> > > motor to see if it would
> handle
> > > the
> > > workout I give it a little better.
> > >
> > > I decided to do some calculations to see what
> rpm
> > > the
> > > motor was spinning and here is what I found:
> > >
> > > Speed : tire rpm : motor rpm
> > > 10 : 171 : 514
> > > 20 : 343 : 1029
> > > 30 : 514 : 1543
> > > 40 : 686 : 2057
> > > 50 : 857 : 2572
> > >
> > > What I am wondering is if I can change the
> gearing
> > > to
> > > get a better than a 3:1 ratio maybe a 6:1 ratio
> > will
> > > I
> > > still have the same top speed? Right now my top speed on the level
> > > is about 44mph. Jim, and I think he said Tim, thought that maybe
> > > the existing motor would handle my needs if the motor spun at a
> > > much
> > higher
> > > rpm.
> > >
> > > My next question is, does any one have any suggestion as to where
> > > I might find some replacement gear/pulleys? This is a belt driven
> > > vehicle
> which
> > > has
> > > the "teeth" in a V shape like this:
> > >
> > > \\\\\\
> > > //////
> > >
> > > including the gap in the middle. The belt is a GoodYear Eagle
> > > W-1280. I also need to know what
> > the
> > > smallest drive gear I can safely use. The
> current
> > > one
> > > is 30 teeth. The one on the drive wheel is 90
> > Teeth.
> > >
> > > I have attached 3 pictures. (I hope this doesn't violate list
> > > rules.) It appears that there are
> two
> > > sets of bolts which bolt the gear/pulley on the wheel.
> > > One set bolts to the wheel hub, then there is an aluminum adapter
> > > which then bolts to the gear it self.
> > > There isn't much room to go larger with the
> > wheel's
> > > gear since the belt would interfere with a
> > support.
> > > I
> > > think I could go to a 115 tooth at the wheel so
> if
> > I
> > > could go as small as a 20 tooth drive it would
> be
> > at
> > > a
> > > 5.75:1 ratio.
> > >


David D. Nelson
[email protected]



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