KiwiEVs next project fast EV

[Hillhater]

....The drag of a Beetle as it comes from the factory is 0.38. After I got done, it's something less than 0.30. A little better maybe than the Jetta"....[/ quote]
So how do they measure, quantify, and compare these Cd figures ?.

 

[liveforphysics]

....The drag of a Beetle as it comes from the factory is 0.38. After I got done, it's something less than 0.30. A little better maybe than the Jetta"....[/ quote]
So how do they measure, quantify, and compare these Cd figures ?.

In practice, OEM's tend to just make up whatever number marketing thinks sounds nice for Cd figures.

https://www.tesla.com/sites/default/files/blog_attachments/the-slipperiest-car-on-the-road.pdf

As an example, Honda claims insight is 0.25 Cd, it measures at 0.30-0.31.

Mercedes claims CLA 250 is 0.23 Cd, it measured 0.30

EV1 was claimed 0.19 Cd, from a handful of rare tests it was at least >0.25 Cd.


Tesla Model S claims 0.24 Cd, which isn't a very impressive claim, but unlike all the other OEM's, they actually measure in a wind-tunnel at 0.24Cd, making it more slippery than pretty much everything else.

The odds your beetle will duck under 0.35 Cd measured is extremely unlikely, as stock its likely >0.40-0.45 (I realize this is more than VW claimed, but they lied about all drag co-efficients by large margins on every vehicle, along with most other MFG's).

 

[kiwiev]

I guess the proof in the pudding does Cd make a big difference on battery drain and is Cd constant for all speeds???


Cheers Kiwi

 

[The Toecutter]

Hey Toecutter

with the Hilux ute I am thinking of getting a fibreglass hard cover do you think some sort of rear spoiler would help ????

Thanks Kiwi

A pickup truck is a different shape and has different requirements for drag reduction. Check the following article out and feast your eye's on Phil Knox's aeromodded Toyota pickup for inspiration:

http://evworld.com/article.cfm?storyid=870

From the article:

Phil Knox's streamlined 1994 Toyota Tacoma pickup saw its fuel economy go from 25 mpg to 32 mpg at 70 mph just by improving its aerodynamics, reducing its Cd from 0.44 to 0.25, the same as the Honda Insight gasoline-electric hybrid.

Phil Knox also posts on the ecomodder forums as "aerohead" if you have any questions to ask him. About 9 years ago, the aeroshell was destroyed by a herd of goats, FYI.

In practice, OEM's tend to just make up whatever number marketing thinks sounds nice for Cd figures.

https://www.tesla.com/sites/default/files/blog_attachments/the-slipperiest-car-on-the-road.pdf

As an example, Honda claims insight is 0.25 Cd, it measures at 0.30-0.31.

Mercedes claims CLA 250 is 0.23 Cd, it measured 0.30

EV1 was claimed 0.19 Cd, from a handful of rare tests it was at least >0.25 Cd.


Tesla Model S claims 0.24 Cd, which isn't a very impressive claim, but unlike all the other OEM's, they actually measure in a wind-tunnel at 0.24Cd, making it more slippery than pretty much everything else.

There's also the issue of wind tunnel calibration. The Society of Automotive Engineers had to revise the standard by which drag coefficient is measured because of inconsistent test results from wind tunnel to wind tunnel.

I once did some calculations to estimate the Wh/mi of the EV1 at 60 mph and was off of GM's published figure by 30 Wh/mi. My estimate was lower than the figure GM came up with. The published 0.19 figure being false would certainly explain that...

With that being said, in 1979 Volkswagen put a 1921 Rumpler Tropfenwagen in a wind tunnel and it came out to a 0.27-0.28 depending on test. Not bad for an open-wheeled design... it exemplifies that fuel economy really hasn't ever been much of a concern in automotive design, which is a shame.

http://www.treehugger.com/cars/its-...are-not-as-aerodynamic-as-a-1921-rumpler.html

With proper attention to detail, we could potentially have had 150-200 mile range EVs using flooded lead acid golf cart batteries 30+ years ago(think of a car with a Cd in the sub 0.2 range and a ton of batteries).

The odds your beetle will duck under 0.35 Cd measured is extremely unlikely,

That all depends on what he does to it. I'm confident that one could get an old Beetle into the upper 0.2 range if they knew what they were doing. Full undertray, rear diffuser, rear roof extension/spoiler, rear wheel skirts, Bonneville salt flats style hubcaps, removal of front/rear bumpers, side skirts, front air dam, vortex generators, wheel spats, and a bunch of other pieces could be made to manage the airflow around the car and keep it laminar. It won't look anything like it does stock though...

I suspect that most of its turbulence is generated in the rear, so cleaning that up as much as possible would yield the most gains. The rear angle of the roof of a stock Beetle is roughly such that it will generate the most possible drag. I don't have a copy of "The Aerodyanmics of Road Vehicles" by Wolf-Heinrich Hucho handy to reference its tables, but I remember referencing a table for rear roof angle versus Cd value, and both the Beetle and my Triumph GT6 were at the worst possible angles.

 

[Hillhater]

The Cd is a coeficient figure, so theoretically its a constant....but in practice areo effects change with speed, so its only accurate for a limited range of speeds.
Cd will directly affect battery usage, but only at speeds where aero drag becomes significant,..IE above 25-30 mph.
Since most DIY EVs have limited range and tend to be for urban use, the amount of time spent at speeds where aero becomes important,..is minimal for most.
Weight is a much more important factor if you are looking to improve range.

 

[Cowardlyduck]

Hey Conrad,

If you wanted to keep working on and testing the electric skidoo through the summer, you could always put wheels on it like this.

[youtube]TdQOu24HHJI[/youtube]

Cheers

 

[kiwiev]

Yeah I seen that CD only problem is the track will melt without snow.

Cheers Kiwi

 

[kiwiev]

Sad day today drove the Sonic around for a couple of hours got the pack down to 45% then low pack alarm came on. I stripped out the controllers and motor. Then started on battery removal the first group of 6 cells voltage was all over the shot 3.3 to 3 and 1 cell was 0.7 volt I am trickle charging this up now so the bloody BMS didn't do much

The rest of the cells were 3.299 to 3.300 volts so all good
So do you think that one cell would effect perfrom or just range

Cheers Kiwi

 

[Cowardlyduck]

So do you think that one cell would effect perfrom or just range

Both.
I've had lots of experience with the LiFe cells in my Stealth Fighter pack dying like this. If they trip the BMS they will kill range early, but once a cell is bad like that they will also cause much larger voltage sag due to higher internal resistance which will also reduce performance.

If you've only got the one bad cell, I would just turf it, replace it or just accept a slightly lower voltage from removing it.

Cheers

 

[kiwiev]

So do you think that one cell would effect perfrom or just range

Both.
I've had lots of experience with the LiFe cells in my Stealth Fighter pack dying like this. If they trip the BMS they will kill range early, but once a cell is bad like that they will also cause much larger voltage sag due to higher internal resistance which will also reduce performance.

If you've only got the one bad cell, I would just turf it, replace it or just accept a slightly lower voltage from removing it.

Cheers

Yeah its a bugger you know how much use the car has done, I think that may have been the problem last time I took you for ride.

Cheers Kiwi

 

[kiwiev]

A Wee bit of progress on the 66 VW Bug

AC-50 mounted complete with flywheel clutch and controller mount.

Cheers Kiwi

 

[kiwiev]

batteries turned up today for the bug

36 x 180 Ah LiFe batteries to give 20.7 Kwh of cruising juice.

plan is to put 24 on the back parcel shelf and 12 up front where the fuel tank was.

Cheers Kiwi

 

[kiwiev]

Big day today De-Iced the Hilux what a PITA job it really turns me off ICE motors oil and crap every where

The ICE motor weights over 160 Kg and then the radiator, exhaust, fuel tank water and fuel which should be another 60-70 Kg so hoping not to go over 100 Kg from original weight of 1240 Kg

Cheers Kiwi

 

[kiwiev]

thinking of painted motor and adapter orange and place the two controllers on top at an angle sort of like a V6 look :lol:


Cheers Kiwi

 

[The Toecutter]

That bug is a thing of beauty. I can't wait for you to do burnouts with it.

The Hilux would look great in camouflage with a gun rack, confederate flag, and a set of truck nuts. :lol:

 

[kiwiev]

Thanks Toecutter that means alot mate

Really please with how the bug is turning out.
My daughter agrees the ute needs nuts

Removed gas tank today looks like I can fit 15 cells where the tank was and 15 cells where the muffler was, then 18 at the rear where the spare wheel was.

Next job is to remove the auto gearbox mount the cllutch brake pedal assembly for the manual gearbox, and work out front motor mounts.

Cheers Kiwi

 

[kiwiev]

made some progress today

Fabricated rear battery box cross member and also painted up motor and adapter.

Cheers Kiwi

 

[Cowardlyduck]

Nice progress mate. Like the orange motor colour.

I reckon your bug might even rival this beauty once your done.
[youtube]fXsQGWWz3Is[/youtube]

Cheers

 

[kiwiev]

Yes I will be happy with 0 to 100 in 8 seconds.

Waiting on aluminum battery boxes to be cut and folded up for both projects.
Cheers Kiwi

 

[The Toecutter]

Thanks Toecutter that means alot mate

Really please with how the bug is turning out.

The bug looks really good. I would paint it in a dark green, almost black gloss, so that it resembled a dung beetle. It would look even better like that...

 

[kiwiev]

A wee bit more work got the following done:

-clutch master cleaned out and installed
-manual pedal box in for clutch and smaller brake pedal
- gearbox in and hole cut for shifter not too much bigger
-mounts for power steering pump.
-and clutch flywheel and adapter plate mounted up.

Cheers Kiwi

 

[kiwiev]

The motor was a real bitch to slide on to gearbox I had placed the motor up side down to hide terminal phase mounts and they were catching on the steering arm

Then the motor would slide on so far, and stop even used a few bolts to pull it in no luck, so I pulled it out and gave the gearbox input shaft a good grease. Still no go then I turned the motor shaft from the front and on she went.

Now have to make up motor adapter to ICE motor mounts and a mount for the controllers and contactor box.

Cheers Kiwi

 

[kiwiev]

My shed is feeling like a EV conversion shop today

Got the controller chiller, battery charger and motor side covers mounted today.

Drilled a couple of hole for gland nuts to come out by transmission tunnel linkage inspection cover, I will slide in 2 conducts from the front to connect the front and rear pack.

Also started fabricating a bullet proof mount for the front of motor in the ute aka ELECTRO-UTED :lol:

Cheers Kiwi

 

[Cowardlyduck]

Looking great mate, and very professionally done. Very neat and clean looking install...you totally could run an EV conversion shop!

Also started fabricating a bullet proof mount for the front of motor in the ute aka ELECTRO-UTED :lol:

Nice :lol:
I guess that makes the VW a Bug-E. :lol:

Cheers

 

[kiwiev]

Looking great mate, and very professionally done. Very neat and clean looking install...you totally could run an EV conversion shop!

Also started fabricating a bullet proof mount for the front of motor in the ute aka ELECTRO-UTED :lol:

Nice :lol:
I guess that makes the VW a Bug-E. :lol:

Cheers

Nice also have a line of LG pouch cells coming online good for 700Amps 40 AH


Cheers Kiwi