[ausev] VW FOX CONVERSION, GEAR RATIO QUESTION

Thu Jun 12 10:59:15 GMT 2008

Not sure what a taperlock connector is.  If you take a couple of pieces of 
cardboard, and set the tranny down and draw an outline, then do the same on 
the electric motor, and then mark the holes "precisely", they can make a 
template.  The trick is to make the center of the electric motor and the 
center of the transmission shaft align perfectly.   When you get to that 
stage, we can get together and work out a way to get the template to the 
waterjet place.

John Penry

----- Original Message ----- 
From: "loopcat" <loopcat at yahoo.com>
To: "AustinEV News Announcements and General Discussion" 
<ausev at austinev.org>
Sent: Thursday, June 12, 2008 1:46 AM
Subject: Re: [ausev] VW FOX CONVERSION, GEAR RATIO QUESTION

> My bad. There are 4 brushes, 10 separators between each brush. So around 
> 350 volts sounds right. The motor is equiped with interpoles. To my 
> understanding, it will not arc, and doesn't need the brushes moved.
>
> Finally got the garage free today. Tomorrow we're roll the fox back there. 
> The car is now on the front street, While it's outside, I will drain the 
> oil and coolant, hose down the engine compartment and exterior. My 
> neighbors must love me!)
>
> Our goal is to pull the engine and transmission out this week. I'd like to 
> get an adapter plate made soon. John Penry suggested a local shop 
> interested in doing the job.
>
> Do you know where I could find taperlock connectors for the motor and 
> transmission? Maybe the machine shop could fabercate them.
>
> All the Best, Stuart..
>
> --- On Wed, 6/11/08, 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: Wednesday, June 11, 2008, 10:53 PM
>> loopcat wrote:
>> >  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?
>>
>> Between adjacent brushes?  Or around the entire commutator?
>>  If you
>> actually count 45 separators between brushes (don't
>> count the ones under
>> the brushes, just the ones that are exposed), then I'm
>> going to guess my
>> rule of thumb doesn't apply and that this is a
>> commutator that's built
>> differently from what we normally see. With so many comm
>> bars and
>> separators, these are most likely thinner separators or
>> you'd have
>> insufficient copper-to-brush contact to carry enough
>> current. This means
>> each separator would individually withstand a lower voltage
>> difference,
>> but they should still add up to a reasonable total.
>>
>>
>> While the motor is powered, each brush is at the opposite
>> voltage from
>> the brushes to either side. The copper bars form a partial
>> "bridge"
>> between the brushes, with the separators preventing a short
>> between
>> them. If voltage applied to the motor gets too high, the
>> sum of the
>> separators' dielectric strength is exceeded and you
>> have a "flashover"
>> which can result in partial or total destruction of the
>> commutator,
>> brushes and brush holder.
>>
>> Makes for cool post-mortem pictures  :o)
>>
>>    --chris
>>
>>
>>
>>
>> > 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..
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>>
>> >> _______________________________________________
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