[ausev] VW FOX CONVERSION, GEAR RATIO QUESTION

[loopcat]

 Hey Chris,
 I counted 45 saparators. So about 1575 volts! WOW I could only imagine that kind of power! What would be the max current?
All the Best, Stuart..


--- On Tue, 6/10/08, Chris Robison <chris at chrisrobison.org> wrote:

> From: Chris Robison <chris at chrisrobison.org>
> Subject: Re: [ausev] VW FOX CONVERSION, GEAR RATIO QUESTION
> To: "AustinEV News Announcements and General Discussion" <ausev at austinev.org>
> Date: Tuesday, June 10, 2008, 9:14 PM
> Good advice. To get an empirical estimate for your motor
> voltage limit, 
> count the minimum number of comm bar separators (the black
> part between 
> the copper bars) visible from one brush to either of its
> immediate 
> neighbors. It's a really rough estimate, but each one
> of these is 
> typically worth about 35V of separation. Add them together
> to get the 
> total number of volts that's safe to put across the
> motor. Otherwise, 
> 150V is a good number to go with.
> 
>    --chris
> 
> 
> 
> 
> loopcat wrote:
> > FYI, this is the reply from Otmar at Zilla...
> > 
> > "Hello John,
> > The motor looks like a good one to me.
> > I would make sure you have a good clutch in the setup
> so it does not slip.
> > 
> > A safe motor voltage limit is usually 150V. I've
> heard that some GE 
> > motors can take much more than that, but it's a
> good starting point. 
> > Current limit is going to limit the torque and
> therefore protect your 
> > clutch and transaxle. I would start off at 400 to 600
> amps on the 
> > motor and see how that feels.
> > 
> > You don't mention your batteries. If they are
> flooded lead acid then 
> > you may want to protect them with a 350 amps battery
> current limit to 
> > start and a low voltage limit of about 9V per 12V
> block. High current 
> > AGMs won't need a reduced battery current limit
> but still you should 
> > limit the voltage.
> > 
> > Once you have it running well, you can contemplate the
> risks to the 
> > batteries, motor and drivetrain of turning up the
> power.
> > 
> > -Otmar"
> > 
> > 
> > 
> > --- On Sun, 6/8/08, Chris Robison
> <chris at chrisrobison.org> wrote:
> > 
> >> From: Chris Robison <chris at chrisrobison.org>
> >> Subject: Re: [ausev] VW FOX CONVERSION, GEAR RATIO
> QUESTION
> >> To: "AustinEV News Announcements and General
> Discussion" <ausev at austinev.org>
> >> Date: Sunday, June 8, 2008, 9:52 PM
> >> Did you plug in these gear ratio numbers directly,
> or did
> >> you multiply 
> >> them by the final drive ratio (the gearing at the
> >> differential) first? 
> >> Uve's calculator does not provide a separate
> spot for
> >> the final drive 
> >> ratio, so you have to do the math yourself as you
> input
> >> each number. A 
> >> quick google search reveals that the Fox 4-speed
> >> transmission had a 3.89 
> >> final drive ratio, and the 5-speed was 4.11. 
> Multiply 3.89
> >> by each of 
> >> your gear ratios to get the full ratio for each
> gear in
> >> Uve's 
> >> calculator. Remember that your redline with this
> big motor
> >> is going to 
> >> be somewhere in the neighborhood of 5000rpm.
> >>
> >> Beyond that, I'll just say this -- given your
> design
> >> goals as you've 
> >> stated in the past, you haven't solved your
> primary
> >> issue. You still 
> >> have *way* too much motor for your car. Although
> it may
> >> physically fit 
> >> within the Fox's engine bay, you've
> actually made
> >> this fundamental 
> >> problem worse in that the Fox was not intended
> even as a
> >> diminutive 
> >> sportscar like the NX was. In gasoline terms,
> you're
> >> effectively 
> >> cramming a 350 small block into an economy car,
> which
> >> generally 
> >> speaking, is something people do if they're
> aiming to
> >> race. What comes 
> >> along with that intent are the modifications to
> the
> >> driveline -- bigger 
> >> transmission, custom hardened gears, multi-disk
> racing
> >> clutch, enlarged 
> >> axles and CV joints, wider and softer tires etc,
> that are
> >> necessary for 
> >> a small car to withstand the input from a big
> powerplant.
> >> Without these 
> >> modifications, your car is going to be undergoing
> regular
> >> repair.  With 
> >> the stock transmission, don't be surprised if
> you end
> >> up needing a 
> >> rebuild every 5 or 6 months. The stock clutch will
> slip
> >> under the torque 
> >> and will definitely need upgrading and the
> performance
> >> aftermarket for 
> >> Foxes may be limited (I don't know).
> >>
> >> Operating the motor at lower RPMs is actually
> something to
> >> avoid, as 
> >> torque will be higher placing higher mechanical
> stresses on
> >> your 
> >> transmission, current draw will be higher, cooling
> less
> >> effective, and 
> >> generally the motor will run hotter and a bit less
> >> efficiently.
> >>
> >> The way to make this motor work and not tear up
> your car
> >> would be to 
> >> keep RPMs high, drive gently and limit the motor
> current
> >> from your 
> >> controller, to limit the motor's output
> torque. Doing
> >> so will render 
> >> unusable all the extra power the motor is capable
> of, which
> >> means you're 
> >> carrying around a lot of extra mass that you
> won't be
> >> using. Worse yet, 
> >> much of this will be rotating mass, which reduces
> >> efficiency during 
> >> acceleration.
> >>
> >> This motor really belongs in a full-size pickup,
> van or
> >> SUV, in a 
> >> direct-drive configuration in a light truck or RWD
> >> sportscar, or in a 
> >> small vehicle if high performance is desired (and
> planned
> >> for). It will 
> >> work in your application, but I think it is far
> from ideal.
> >>
> >>    --chris
> >>
> >>
> >>
> >>
> >>
> >> loopcat wrote:
> >>> Hello All,
> >>>  After my 1st failed attemped at converting a
> '91
> >> Nissan NX (motor too big for car) We had to make a
> >> decision, keep the motor or keep the car. So we
> decided on
> >> another donor car, a 1993 vw fox. 
> >>> Putting the cart before the horse, last year I
> >> purchased a rather large GE DC motor. The
> demensions/weight
> >> are very similar to the famed Warp-11. The motor
> tag states
> >> 16hp at 70v, 214amps, 1822rpm, ~210lbs. From what
> I have
> >> heard, The motor was designed for an
> air-craft-tug. So it
> >> should have a ton of torque. By most accounts the
> motor
> >> will function well in an EV.
> >>> The major reason for buying the vw fox was
> that the
> >> engine is latitudinally mounted so my GE-11"
> motor
> >> will fit into the car. 
> >>> After buying the fox, I did a bit of research
> and
> >> found some interesting facts on the transmission.
> The gear
> >> ratios are very low numerically speaking.
> 1st-3.450,
> >> 2nd-1.790, 3rd-1.130, 4th-0.830 R+P-4.110. So I
> was curious
> >> how this would perform with the motor. So I went
> to
> >> Uve's EV Calculator and added these
> transmission ratios
> >> to a vw rabbitt, zilla lv, and trojan t-105. The
> closest
> >> motor on the list was a Kostov. I then lowered the
> volts
> >> (120 t-105) and the motor rpm's (3600)  The
> results are
> >> interesting, the motor rpm's were low, but the
> >> speed/distance was very repectable, 1st gear was
> the best
> >> with a range of 30 miles between 40-60mph. Top
> speed
> >> ~70mph. At first, I thought the ratio info was
> bad. Most of
> >> the cars on the list have a 2nd gear ratio of
> about 8.0. But
> >> then I saw that the Fiat Palio also had lower gear
> ratios.
> >> So for kicks-and grins, I lowered the volts to
> 96v. In 2nd
> >> gear the rpm's were below 1700 at 50-60mph. 
> >>> And this leads me to my question. I have
> sometimes
> >> heard that these old GE-11" spin too slow at
> lower
> >> volts, "tons of torque, but no top-end
> speed".
> >> But if the transmission has lower gear ratios then
> it
> >> should produce the mph's, right? Any insights
> would be
> >> appeciated.
> >>> Thanks, John Stuart in San Antonio tx..
> >>>
> >>>
> >>>       
> >>>
> _______________________________________________
> >>> AusEV mailing list
> >>> AusEV at austinev.org
> >>> http://www.austinev.org/mailman/listinfo/ausev
> >> _______________________________________________
> >> AusEV mailing list
> >> AusEV at austinev.org
> >> http://www.austinev.org/mailman/listinfo/ausev
> > 
> > 
> >       
> > _______________________________________________
> > AusEV mailing list
> > AusEV at austinev.org
> > http://www.austinev.org/mailman/listinfo/ausev
> 
> _______________________________________________
> AusEV mailing list
> AusEV at austinev.org
> http://www.austinev.org/mailman/listinfo/ausev