Linner Strømlinet Vogn II

[Sven7]

Ideas have been percolating.

A few questions.

-Generally, a large ICE running at low rpm uses more gas than a small ICE running in the BSFC sweet spot. Does this happen with electric motors as well? If I get a 25hp motor for the get-up-and-go, will it use more energy at a cruising speed than a, say, 15hp motor? I ask because perhaps the instant torque would allow the car to accelerate faster than a comparably powered ICE.

-I was planning on mounting an optional range extending single cylinder engine atop the rear wheel, behind the driver's head. This would allow it to drive for extended highway journeys (much like a Volt) instead of being limited by range. Let's say something like 150-200 mpg? A few days ago I learned about aptly named generator trailers. They haul the generator behind the vehicle, and while being better for packaging, they carry the obvious aero and RR penalty that will be hard to surmount in a car with such a small wake. Would the extra drag likely cancel out much of the vehicle's inherent efficiency?

[sheepdog 44]

Some generalizations, (because i've also asked this question before). You want an electric motor sized for your car. The 25 hp motor will be able to give the constant hp needed to cruise. It'll be rated 25hp max, and such and such for constant hp. Where the 15hp motor may have heat issues etc and be inefficient driving through the whole range of power needed for hills etc. The motor with the constant hp rating needed to cruise at 65mph is the best choice. Bigger or smaller hp motors are not more efficient than the other like an ICE.

Are you planning on making it an EV? Depending on how efficient the platform is maybe a small motorcycle engine will do. You could make it modular to drop in or take out of the car depending on the expected range you'll travel. But the total weight and space of the engine may not be that big (Unless you still want to abide by hypermiling principles) to warrant going through the trouble of making it modular.

You will not be getting 150-200mpg on gas in a serial hybrid. With all the losses of gas engine, generator, storage, motor. I don't know the scale of your car, but if it could do 100mpg on gas like the Edison2, it'll only do 44mpg running on gas in a serial hybrid form. Which is why a plug in Prius gets 50mpg on gas, and the volt does 35mpg or so on gas.

It would be better efficient wise to have the engine directly driving the car. And manually stop EV mode when you have 10miles left. Just use the remaining battery power to accelerate with (or without) the gas engine. Only assist the gas engine when accelerating, and you can get away with a more efficient small displacement gas engine.

[sheepdog 44]

Okay, I read back a few pages. What are you shooting for?

cda 1.5 square feet at cd 0.16 so about 10square feet frontal area.
How much range do you want?
What will be the total weight?
From how small your frontal area is, i imagine it'll be far less than 1,500lbs, 1,000lbs or less? At that weight you'll have great acceleration and a top speed past 90mph depending on how you gear it. With an EV you can have both speed and efficiency without compromise. It just depends on your battery pack.

At these numbers we're talking about less than 100wh/mile. So battery packs will be smaller, lighter, and CHEAPER!

[sheepdog 44]

I've gotten ok at crunching numbers for potential EV projects. I've thought about doing Allerts 125cc Innova in an electric drivetrain myself. That way you don't have to deal with finding the same exact efficient engine in the USA to replicate the efficiency, or emissions for that matter.

(Below i projected these numbers for your car, which is just the VLC with half frontal area.)

Using these batteries as just an example.
Electric Motorsport EV Parts
dimensions in mm: 116 x 46 x 181. 3.2volts 60ah $90 each.
144volt pack using 45 3.2volt 40ah batteries for 8.63kwh, 150lbs, $4,050. 90mile range at projected goal of 75wh/mi 80% total capacity use. 70 mile range at 100wh/mi (the worse end of the spectrum).

Thats a 35-45mile round trip range, which is good. For practical use 40miles total range would suffice 90% of the time. So you could go with a smaller battery and save a couple hundred $, but minimal use of a larger pack will increase the life of the battery.

For comparison a good motorcycle conversion can get 100wh/mi. They have a small frontal area but terrible aerodynamics. There is much room for improvement going from .5cd to 1.6cd, you'll end up using much more energy accelerating than a motorcycle though.

[sheepdog 44]

I believe i figured out how to convert your mpg to wh/mi in the aerodynamics tool!!!!!
Plug in all your numbers. Then take the watts (hp conversion) and divide by the mph in the same row.

(Again, these are projections for your car)

for one hour at 65mph, 3821watts / 65miles = 60.78wh/mi
(on the conservative side i'd think it would be higher in the real world.)

But this also tells us that to make your car a serial hybrid with an infinite range on gasoline. You'd need at minimum a 3.82 kwh generator. Say 4.5-5kw generator to be safe and account for losses.

This gives you an idea of you would need. It would basically be plug and play for a 120volt battery pack. Like carrying an electrical outlet with you everywhere you go!
http://www.electricgeneratorsdirect....tor/p6398.html
$1,859
389cc
Weight: 177 Lbs. (80.29 kilograms)
Dimensions: 26.8L x 22.8W x 22.6H
(68.07 x 57.91 x 57.40 cm)
6 gallons fuel tank.

So $4,050 80 miles battery pack + $1,859 generator = $5,909 for your gas "tank." 327lbs combined. But since it's portable, you can save 177lbs of weight and increase your cargo area when you don't need it.

It would get you the electric range of a Nissan Leaf, with the extended range of a Volt, at Prius mpg.

[Sven7]

I'm hoping the range extender, depending on efficiency, could be as small as a 5hp go-kart motor. Wired to turn off when the batteries are full. But it will be primarily, 90% of the time, a full EV (with no gas engine at all).

Originally Posted by sheepdog 44

Okay, I read back a few pages. What are you shooting for?

cda 1.5 square feet at cd 0.16 so about 10square feet frontal area.
How much range do you want?
What will be the total weight?
From how small your frontal area is, i imagine it'll be far less than 1,500lbs, 1,000lbs or less? At that weight you'll have great acceleration and a top speed past 90mph depending on how you gear it. With an EV you can have both speed and efficiency without compromise. It just depends on your battery pack.

At these numbers we're talking about less than 100wh/mile. So battery packs will be smaller, lighter, and CHEAPER!

I appreciate the detailed response! I covered the goals earlier but you're forgiven because these threads tend to ramble.

About 40 inches wide and tall... let's say 9 square feet? Cd target of 0.15. So CdA of 1.35 I guess. Still kinda up in the air.

100 miles electric range.
Weight 750lbs dry, 900 loaded
I want to do it with the good stuff- Li ion, etc. It's nice to hear the larger motor won't be a compromise. Used ones for a few hundred bucks. I'll see what the budget allows hp wise.

On gearing, how does that affect electric motors? Does running at low RPM and high "load" offer significant energy savings? Maybe there's a thread on this that someone could point me to.

100wh/mi? I'll try to keep that in mind. Again, I haven't even gotten the EV bible to look through.

[Sven7]

Originally Posted by sheepdog 44

I believe i figured out how to convert your mpg to wh/mi in the aerodynamics tool!!!!!
Plug in all your numbers. Then take the watts (hp conversion) and divide by the mph in the same row.

for one hour at 65mph, 3821watts / 65miles = 60.78wh/mi
(on the conservative side i'd think it would be higher in the real world.)

But this also tells us that to make your car a serial hybrid with an infinite range on gasoline. You'd need at minimum a 3.82 kwh generator. Say 4.5-5kw generator to be safe and account for losses.

This gives you an idea of you would need. It would basically be plug and play for a 120volt battery pack. Like carrying an electrical outlet with you everywhere you go!
Honda EG5000 Portable Generator - EG5000C - 4500 Watt Portable Generator
$1,859
389cc
Weight: 177 Lbs. (80.29 kilograms)
Dimensions: 26.8L x 22.8W x 22.6H
(68.07 x 57.91 x 57.40 cm)
6 gallons fuel tank.

So $2,700 80 miles battery pack + $1,859 generator = $4,659 for your gas "tank."

It would get you the electric range of a Nissan Leaf, with the extended range of a Volt, at Prius mpg.

I'm a little overwhelmed at all the numbers, but holy crap, batteries are expensive! The range extender isn't a thing I need to do, but it would be nice. For the money, probably not worth it vs. driving a normal ICE car for longer journeys. I'm a car guy; I have a few cars.

Is the $2700 battery pack... one single unit? Or could I order something a little larger to more easily accommodate my range requirement? Some research is in order.

Thanks again for all the help

[sheepdog 44]

The pack is made up of 3.2 volt cells that can be anywhere from 40-100ah. You just string 45 or more together. You can add more batteries, or get larger capacity batteries. It's all modular.

Edit: I got got the price of the pack wrong, i changed the numbers to reflect it. Sorry
This is just any old battery i picked to give you an idea, You could find cheaper ones or better performance ones.

$4,687 for a 10kwh battery. If you build as efficient a car as you plan too, You could get 100 miles out of it. $6k for 13kwh would be ideal. It'd give you more than 100miles easy, a long battery life, and when the range decreases as over time, you'd still get 100miles.

These are conservative numbers though so you don't fall short in range, or expect to pay more.

[sheepdog 44]

The primary motive for a PURE EV should be driving a futuristic vehicle, using zero foreign oil, and having zero emissions. Cause it won't save you a whole lot of money. With a 20 mile electric range and 60+mpg direct drive motorcycle engine, you could see the fuel cost equivalent to 200mpg or more, about $350 a year for 15,000 miles. Thats $7k for 20 years and 300,000 miles. Compared to $225 a year for 15,000miles for a Pure EV getting 100wh/mi (most EV's are 250+wh/mi) , you would only save $2,500 over 20 years. For one thing, The Pure EV battery pack would not last 20 years or 300,000miles, and you would save more by buying a smaller battery.

Less is more. The cheapest way to get greater than 100mpg equivalent fuel costs is the best answer. Because the difference in fuel costs for a 100mpg car vs a 1,000mpg car is not a whole lot, you save less and less comparatively. Which is why 60-100mile range EV's are not economically sound. You can accomplish the same goal with a quarter the battery size. The cheaper you make it to the same mpg goal, the more you save.

Most people don't know that buying a $30k Nissan leaf does not save money. Anyways, thats the end of my rant.

[mloveland78]

Sven7,
I may be able to help you out here if you are still interested in moving forward with this project. I have several years experience in composites building and automotive design on the mechanical side. I was in the FSAE program in college. If you have not heard of that one you can easily look it up.
I have been thinking of building a vehicle exactly like this one for years and have done a fair amount of research. I might be able to help you out with mechanical design and building technique. Also if you can create a 3d model of what you want, autodesk has a great new software out called 123d make that will print out sliced templates from a 3d model. The best part is the software is free. I think the sketches and model you have created look great and are worthy of pursuing to a drivable prototype.