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I thank those here who took the time to answer my questions.
You gave me a much better idea of what to expect.
With all the aero upgrades mentioned, I’m now thinking it
is possible to have a .33-.34 Cd, frontal area of about 14.9
feet square, brake/steering/suspension drag coefficient of
0035, rolling resistance coefficient of about .0085 with
the minimum width tires I will allow for my handling goal,
curb weight including myself as driver between 2,400 and
2,500 pounds, energy consumption at 60 MPH of about 190
wh/mile, easy 45 miles usable highway range to 80% DoD at 60
MPH, 0-60 acceleration < 7 seconds, and a top speed in
excess of 110 MPH. I plan for a 47/53 weight distribution(Or
better). It would look killer with an almost black BRG
paintjob. I even have a few names I might give such a
conversion when I build it, either “Greenpeace”, “The
Green Meanie”, or perhaps “The Green Eyed Monster”.
Here’s a tally of the parts I intend to use in the
conversion and the price/weight of each:
-1x WarP 9'' series DC motor, $1,395, 160 lbs
-20x Exide Orbital ORB-DC-36 battery, $1,900, 820 lbs
-1x Godzilla Controller(72-300V DC, 1,000 amp max), $2,495,
23 lbs
-1x PFC 20 Charger, $1500, 15.5 lbs
-4x Vicor DC-DC converter, $400, 8 lbs
-Steel for battery racks, $100, 50 lbs
-Battery Cable, $100, 20 lbs
-x2 EV200AAANA contactors, $150, 5 lbs
-x2 Feraz Shawmut A50QS600-4 fuse, $220, 1 lb
-x1 Curtis Potbox, $75, < one ounce each
-x1 E-Meter, $235, 1 lb
-x1 Solid-State Ceramic Heater Core, $75, 1 lb
-Adaptor Platex1, $1000(I will be machining myself, so
don't count cost), 40 lbs
-Miscallaneous components(Heat shrink tubing, ect.), $800,
100 lbs
-Triumph TR6 Transmission + Rear Axel, $1000 from Ebay,
+50 pounds from original
-Leaf springs, $300
Along with that, I figure it is possible to shave about
100-150 pounds from the interior and from other unneeded
parts within the car.
In addition to the parts cost, the restoration plus
conversion, of which I will be doing my own work, will put
the price of the entire conversion at about $15k. Not at all
bad.
David Dymaxion wrote:
>The Insight and the Coconni's Honda covered the rear
>wheel wells.
Yes. And that alone could reduce drag 6-8%, since wheel
wells alone contribute to between 18% and 24% of a car's Cd.
I won't necessarily go the covered rear wheel well route
unless needed, as I want to keep my car looking like a
fetish object for speed freaks. Ever see Picton Sportscar's
ultimate spec Spitfire?
http://www.picton-sportscars.co.uk/p1a.html
An EV with looks like that would be sure to grab attention
to the car, and at gas stations with the hood propped open,
tempt people to take a look at what’s in there, causing
some to promptly scream: "What the f*** is that!?" I hear
EVs get a lot of attention in scenarios like this. Imagine
taking it to get 'emissions checked'.
>When Porsche put a cover under the rear part of the
>944 (a bellypan
>behind the rear wheels), it was reported it reduced
>aero drag by 10%.
Wow. I never figured results would be that extreme, from
what I gathered looking at old SAE books on car
aerodynamics. But I do plan a full belly pan all over the
underside of the car. Underbody contributes between 12 and
15% of a car's Cd, so I figure I could reduce it by about 4%
from that area.
>In addition to cutting down your windshield, you
>might be able to
>rake it back further, too. Safety would dictate
>putting in a roll bar
>if you do this (and it is a good idea in a
>convertible anyway).
Roll bar and a hard top is certainly planned. Take a look at
the ADU 4B LeMans Spitfire for an indication of how I want
to do a hard top:
http://www.triumphspitfire.com/images/race/adu4B.jpg
http://www.triumphspitfire.com/images/race/adu4Brear.jpg
http://www.triumphspitfire.com/images/race/adu4Bnose.jpg
Imagine that profile and bonnet with the racing green paint
job of the Ultimate Spec Spitfire. The fastback style is
also generally good on drag.
I've been looking at various custom hardtops done on the
Spitfire, and the fastbacks in this link all look great:
http://amicale.com/spitfire/hardtop1.htm
I'm especially fond of the Fibrepair top. I might have to
fabricate me a replica of it, either that top, or the one
that was on the LeMans Spitfire...
>You could check out what the Land Speed racers do.
>Here are some
>common tricks:
>
>Smooth hubcaps (be careful brakes won't overheat)
>Lowering the car
>Taping up seams
>Narrow tires
>Air dam and side skirts
>Chop top
>Remove right side rearview mirror
>Make left side mirror small
>Shave the door handles
>Shave off the rain gutters
>Remove radio antenna
>Shorten bumpers if they stick out past the sides
Thanks for the list. Victor Tikhonov uses smooth wheel
covers, which would have a similar affect to smooth hubcaps,
negligible at best. I'd rather have the snazzy look of
either wire wheels(although difficult to maintain them!) or
aluminum-alloy LeMans style wheels. Lowering the car will
definitely be done, by at least an inch. The lower the car,
the worse your visibility, the worse your blind spot, and
the more prone you are to feeling every tiny bump, the
better, in my opinion! Why worry about behemoth road
brontosauruses when you can always accelerate out of the way
and flip them the bird if the said suburban utility vehicles
try to cut you off!?(Just half kidding) Taping up seams
would certainly be done wherever possible. Narrow tires
would only be used insofar as they didn't negatively affect
handling too much, although I'd like to achieve a skidpad
rating of at least .85 using thetires the car would have for
daily driving, .90+ preferred. Lower center of gravity by
sinking the 820 pounds of lead into the floor will certainly
help this. Air dam and side skirts may be done, as long as
the car's looks weren't interfered with too much. I'll
certainly have a low top, to keep frontal area down. Both
mirrors will stay, although I will hunt down smaller and
more aerodynamic ones. Door handles will be shaved, as will
the rain gutters. Radio antenna would be kept, but moved
onto the center of where the proposed roof would be, much
like the Audi TT or Opel Speedster does. Bumpers? BUMPERS?
We don't NEED no stinkin' bumpers! I figure doing all the
things I now have planned within the above list you gave
would give a 2-3% reduction in drag.
A stock Spitfire also has a height of about 50 inches. I’d
like to get that height down to 46-47 inches, like the
LeMans Spitfire did. I’d like lower, but not many
available/affordable cars can do that, without going the kit
car route.
Raymond Knight wrote:
>To reduce weight and drag, the first two places I
>would look are the rear
>and side glass panels. If the vehicle is older there
>might be over a 100
>pounds just there.
>I wouldn't touch the windshield though. It is
>against the
>laws in some places, and is just plain inconvenient.
I kind of figured I could remove about 30 pounds in this
manner, but 100? I'll have to investigate. Thanks for the
idea. I do intend to use lightweight replacements for all
glass parts, provided I can still meet the requirements to
get the car registered. As for the windshield, I live in the
redneck state of Missoura', so chances are state law might
allow me to mess with it. I'll just have to check first. :)
>Covering in the grill will have a huge impact on
>drag efficiency.
I figure 2-3%. A worthwhile endeavor, and wouldn't at all
interfere with the car's looks.
>Building a
>belly pan will help a lot as well. But for safety
>concerns I would make sure
>you are creating a low pressure (vacuum) when you do
>so. In other words make
>the sides closer to the road than the middle. If you
>make it smooth and
>even, you run the risk of turning yourself into an
>airplane wing. By
>creating suction underneath, you will force the car
>to hug the road. Rear
>wings can help a lot with drag, as they can clean up
>the air as it exists
>off your car.
I'll be doing a belly pan. That should give me a 4%
reduction or so, maybe even better if I can optimize the
underside of the car's rear.
As to that vacuum you mentioned, Colon Chapman demonstrated
that principle known as ground effect in his Lotus Type 78.
You basically leave little area for air to go at the front
of the car, and leave a large open volume at the rear of the
car, with the amount of space under the car that air can go
gradually shifting from very low in the front, to a lot in
the rear. This created a vacuum helping hold the car to the
ground, without negatively affecting the drag coefficient,
eliminating the need for a large wing to add downforce. I'm
certainly going to keep this in mind when building an
underbelly.
A rear wing will only be used if needed for high speed
stability(I intend to take this thing over 110 mph on
occasion, don’t ask, don’t tell), or if it would
actually reduce the Cd. Usually, it marginally adds to it,
but provides great downforce.
>If you have removed 500lbs of ICE and tranny, and
>are only replacing it with
>a 100lbs of electric motor, you can look at
>lightning the front end
>components. Replacing them with alloy aluminum or
>chrome moly parts.
>Plexiglass headlight covers can make a big
>difference as well, believe it or
>not. Basically anything that smoothes out the front
>of your car. I am going
>back a lot of years, but I think I remember this
>accurately. A Firebird had
>a 10% difference in efficiency between having its
>headlights up or down.
Thanks for the ideas. I'm not removing the tranny. In fact,
I'll be replacing it with a considered 'bulletproof' tranny
from a Triumph TR6. That will add some weight. Glider weight
with stock tranny of the heaviest Spitfire made is 1,380
pounds. I figure with heavier tranny and differential from a
TR6 as well to handle the 300+ lb-ft of a WarP 9 at 1,000
motor amps, about 50 pounds weight will be added from the
heavier transmission and axel.
I'm definately going to have a smooth front end. Look at the
LeMans bonnet I want to use.
http://www.jigsawracingservices.co.uk/body.htm
That should be good for a 3-5% reduction in drag if done
right.
Jerry Dycus wrote:
>While you can lower the Cd to that and maybe even
>lower, I doubt you would get that kind of range from
>Orbitals.
Yeah. Calculations are all theoretical. But at least 40
miles range 60-65 mph shouldn't at all be out of the
question, which would be all I need, really. Given Otmar can
take the orange terror of Palo Alto 20-25 miles at 60-65 mph
to 80% DoD with the battery pack I want to use, without
having been too concerned on drag, and with a highly
innefficient motor setup, along with what appears to be
optimistic computer smilulation results, it has got to be
doable. Less than 200 wh/mile at 60 MPH means a lot less
powerplant emissions, and a lot less solar panels I'll have
to save money for after finishing the car.
>Ah, a Triumph Spitfire! Now we can have a starting
>point.
>Just building or modifing an aero hard top for it
>like that on 914's would lower your CD to .35 if you
>make the leading edge blend in with the windshield
>and
>have a clean cutoff in the rear.
>Add an air dam in front for another 2% or so and
>side dams for another 1%. Remove and body strips,
>bumps, more aero mirrors, flush the turn signals,
>block the air intake, sheet the bottom, cover the
>rear
>wheel well outside and as close under as possible,
>remove any wheel flares, Syn tranny, diff oil, ect.
>These should get you to about .30cd if done right.
>Follow the Insight for tips on how to make a car
>aero.
I think .35 with just putting on a roof alone seems a bit
optimistic(I think that .42 number in the source I provided
is with top on), but it would certainly help. I won't cover
the rear wheel wells if I can achieve my goals without doing
so, although if need be, I may suck it up and do it. The
Insight is an excellent piece of work when it comes to
aerodynamics, although I do find it somewhat ugly. Thanks
for the suggestions.
I figure with what I have planned, .33-.34 Cd and 14.9
square foot frontal area would not at all be out of the
question. That would be an overall Cd comparable to a Honda
Insight, without even having covered up the rear wheel well.
With the rear wheel well covered, efficiency would be
exceptional, but looks would suffer a bit.
>It took John yrs to get to that point. It's hunting
>down all drag you can find and lower it as far as
>possible.
I'm curious to see what results he's achieved. Improving
your car along with finding out how the manufacturer of the
car did things wrong just makes things that much more fun.
The idea of doing this brings to mind Greenpeace's remake of
the Renault Twingo. They had proven an affordable 80+ mpg
car with better acceleration and more passenger room than
the original could be done with off the shelf technology and
no compromises on the things consumers expect in a car. :)
>Tires is a point that you may need to get 2 sets
>if you need range and want handling, drag racing.
>You could increase range by having a good charger
>on board. With getting 100wthrs/mile as you should if
>you work at it, you can charge at a 15 mph rate from
>an 120vac outlet.
If I got a mere 100 wh/mile consumption, and had
requirements of 11-13 amp draw at the speed that efficiency
is achieved, I'd have about 80-90 miles range to 80% DoD...
That would be awesome, but sounds way too optimistic for 60
MPH on a pack of Orbitals. That sounds more like what I
might get at 35-40 MPH. At 60 MPH, with all the proper
aerodynamic drag hunted down and tackled, I might be able to
do 60 MPH using 40 amps or so which would give me 40-45
miles to 80% DoD, 55+ miles maximum. Consumption would be
about 190 wh/mile. 100 wh/mile wouldn’t be realistic at
highway speeds, given GM’s EV1 with its .19 Cd, no
transmission, and AC drive consumed a mere 140wh/mile.
I won't get 2 tire sets if I can help it. I prefer the idea
of the car being able to perform as is, to where using the
tires it uses each and every day, it would be able to
out-perform most anything else. If aerodynamic improvements
on their own merit can allow a decent amount of efficiency
improvements, enough to keep me happy, I probably won't be
using low rollers, although I will still consider trying a
set. If they still allow decent handling in the case they
are tried, they will be keepers. Acceleration? Low 15s in
the 1/4 and faster is my goal, preferably somewhere in the
14s, like simulation results keep showing. If a $15k-ish
restoration + conversion can compete with a $30,000+ car
like a Porsche Boxter, Audi TT, or Nissan 350Z, it will
certainly turn heads. Later will be the upgrade to a Zilla
2k.
As for charge time? I'm planning on using a PFC 20. Charge
time won't even be an issue.
>Yes, it's a good way to go. Most of the kit cars
>are as bad aero wise as most regular cars, just
>lighter.
>OT- Spitfires make a great biodiesel car getting
>about 80 mpg with a 17hp Kabota diesel!
>Your project sounds cool and should change some
>minds on EV's being slow!
Kit cars also have problems such as leaking in the rain,
rattling, and poor reliability(Not that a Spitfire is much
better, nor are these things I personally care much about.).
I’ve considered biodiesel, but the 17 hp you suggested
wouldn’t be enough for me, unless that was for the trailer
acting as a generator for a bank of batteries to turn the
car into a hybrid for long trips. If I did a pure B100
Spitfire, I’d want at least 120 horsepower from a
turbodiesel. I’m practically drooling over the thought of
a VW Jetta turbodiesel in an 1,800 pound Spit. 0-60 < 6
seconds, 50+ MPGs, no petroleum, and top speed > 130 would
be a reality….
Thanks for your reply. I figure if the common American is
going to get interested in EVs, they need to be shown an EV
that has few compromises. Something that looks great, is
practical for 95% of driving, is affordable, fast, powerful,
and above all, fun. Myself, on the other hand, I just want
something that is ecologically sustainable, very energy
efficient(well to wheels > 45 mpg), fast when compared to
most cars on the road, and above all, a toy. Try combining
those things to a reasonable degree and you will see what I
am aiming for.
John Bryan wrote:
>That's right, it did take time to find and correct
>the sources
>of drag and reduce or elliminate them. I posted a
>big detailed list
>of all the items I did and even a fairly extensive
>driving guide
>years ago.
I’ll be looking around the archives for that list then. :)
>Adjusting the driving is certainly the easiest item
>to change and can have dramatic results.
With this, I agree, but I prefer the no compromises attitude
on driving the car I have planned. That’s how Wayland
approached his Blue Meanie. In careful driving, I have no
doubts I could get exceptional results with what I have
planned.
>Skinny tires pumped up hard -(yes Dave, as hard a
>Teak wood)-
>has the side benefit of being the ultimate tranny
>saving clutch. My
>actual clutch is getting to be pretty much shot, the
>mighty XP1227
>just pumps out way more torque than it can handle.
>Time for a
>"vill not schlipp" clutch.
I wish I could get an XP1227, as they offered the kind of
torque I’d like to have with significantly less
amps(700-800 needed, as opposed to 1,000), but they are
discontinued. I like the low price of the WarP9, and it’s
virtually the next best thing. A racing clutch will be a
must with my project. 300+ lb-ft and 1,000 motor amps will
slip like crazy. If skinny tires can give me the minimum
handling I want, they might be used.
>Removed the bumpers and gave them to a friend who
>runs a big
>VW boneyard. (Bill Dube' said that they were worth
>big bux!)
>I installed little nerf bars in their place and a
>bra, so it doesn't look
>bad at all.
I intend to have no bumpers, and add the necessary bars and
covers the LeMans Spitfire race cars used. This will really
help, just as long as I don't get into an accident.
>Designed the rear battery tray to make a decent
>belly pan
>extension of the car's floor pan - which is a pretty
>good belly pan
>to begin with.
I'll have to keep this in mind.
>Redline MTL in the transmission made a huge
>difference, especially
>in the winter, where I hadn't needed brakes to stop
>with the standard
>gear oil in there.
This gear oil. Is it good enough to handle large amounts of
torque on a regular basis without killing the transmission?
>Also, the motor I'm using is amazing. I believe that
>the XP-1227 puts
>out more torque per amp than any other ADC motor.
I wish I could still get a hold of one. Been checking the EV
trading post though...
>The combination of traits has me occasionally
>looking at the analog
>ammeter thinking "Oh no, my controller is stuck
>slightly on! - I can feel it!"
>just to find that the current draw is zero and that
>the car just coasts
>extremely well.
Quite a shame regen is so hard to do with DC motors at such
a high voltage. Having 30% more range in city driving would
be nice. But that's the tradeoff. This trait of being able
to coast well shows that your car is quite efficient.
Any idea what its wh/mile consumption at 60 MPH is in normal
weather conditions, such as a 7.5 mph or so wind speed,
normal air pressure, ect.? On austinev.org, you list your
range as 60 miles, but is that cycle range to 100% DoD, or
city range to 80% DoD, or is that highway range to 80%, and
if then, at what speed?
>My Ghia's Optimas unceremoniously started into their
>9th year the
>other day. I've been driving it quite a bit lately
>and am so pleased with
>the performance and longevity of these batteries,
>and EVs in general,
>as it's been the only thing in my entire life that
>I've been able to depend
>on. The trusty little feller always works perfectly
>and has never needed
>a repair since being placed into service. It still
>performs absolutely great,
>very peppy!! Driving yesterday I was noting how even
>with the way the
>voltage sags more than when the pack was new, I can
>still match the
>acceleration performance of the average ICE driver
>on a touch less than
>100 battery amps. It's plugged in right now, to the
>plug and forget modular
>charging system that's holding each battery at 13.8
>Volts. If a charger were
>to ever fail, I would know it right away since I
>always glance at the
>LED indicators when I plug it in, and again before I
>unplug it. Someday
>though, I'll make a circuit that checks all the
>chargers for me and reports
>to a single indicator, mounted next to the power
>inlet socket. (the same
>circuit that will then someday operate the series
>charger for me providing
>bulk and equalization charging services
>automatically that I now must do
>manually).
I'm glad to hear your car is so reliable. It's a shame the
major automakers are so persistent in refusing to offer them
and keep claiming that consumers wouldn't want them.
How many miles have you put on those Optimas and to what DoD
did you typically take them? I'd love getting an idea of how
long my planned Orbital pack would last. I'm aiming for
10,000-15,000 miles, better if I can manage it. I'm quite
impressed. I always though shelf life of PbA batteries was
awful, but 9 years? Hot damn! How about the capacity you
have now versus what you had new? Is your maximum usable
range still consistent with what you normally had? If I
could have a pack of Orbitals last more than 20,000 miles,
my overall cost of operation of a powerful EV sports car
would be cheaper than an anemic economy gas car for certain!
I’m shying away from Optimas, however, since they moved
their production to China. I heard that their quality may be
a bit lacking now.
The Deka Intimidators Wayland mentioned look interesting,
and I await the day the Madman gets to test them out. They
just might be better in range and/or performance than the
Orbitals.
>I've been thinking about how I could easily add 8
>more batteries to
>the car without losing any valuable space (stacking
>them on top of the
>4 in the motor area and the 4 under the package
>tray), rotate the torsion
>bars to level it back out, get a Z1K running at 288
>Volts, and then see
>what kind of range I get! Acceleration? Let's just
>say that I'd better have
>that VNS clutch in place by then.
288V and a Zilla 1k at a 2,800 pound curb weight would be
wicked fast. Better than most $40,000+ sports cars you can
buy off the lot. And to think, not one drop of crude used to
power the car(Although the amount used in production of its
components cannot be forgotten, it is small in the long
term). Range? If you’re getting 60 miles per charge now,
maybe 80-85 miles with that battery pack upgrade? That more
than covers most needs.
I myself intend to upgrade to a Zilla 2k after my initial
building. The Z1k would be just something to learn off of,
get an idea of what my transmission and motor combo might
handle, and a way to save some cash initially building the
car. The idea of having a Corvette killer is rather
appealing to me. Even more so, is by the time I get out of
college, I will know how to start experimenting with Li
Ions, and might even try to whip up a management system to
turn my conversion into an EV capable of interstate travel.
150+ miles usable range would give that potential.
Thanks for the advice. I’ll do what you did, and keep
hunting down sources of drag until they’re gone once I get
my initial conversion going.
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