Engineer shares how to build an electric vehicle...

[bigmoose]

Might be fun for us to analyize, support or tear apart this gent's assumptions as this series progresses. This was in my EDN email today:

Engineer shares how to build an electric vehicle from the ground up -- Part 1: Design choices

http://www.edn.com/article/518720-E...php?cid=NL_Newsletter+-+Electronic+News+Today

The goal

While Santini's original goal was to build a plug-in hybrid vehicle, the fast-falling cost of lithium-ion (Li-ion) batteries spurred the decision toward the end of the project to postpone the engine/generator and to add some weight back in as additional lithium ion batteries. As a result, the current vehicle is all-electric, although the space remains to add an engine-generator in the future. Doing so will increase the cruising range of the vehicle well beyond the 90-mile range of the current system. The total vehicle weight, with batteries, is now 2,050 lbs.

AC motor

The AC motor from ABM is rated at 18.7 kW, almost as much power as the old GE motor Santini had in his Electric Corvette design back in 1975. It weighs only 165 lbs and with an 84V input, it will operate at constant torque up to around 3000 rpm and then constant horsepower (hp) up to 6000 rpm. The drive uses a single 62-mm wide gear belt with a single reduction of around 6.3:1. See Figure 3.

Engineer shares how to build an electric vehicle from the ground up -- Part 2: Specs, challenges, and future design

http://www.edn.com/article/518809-E...Part_2_Specs_challenges_and_future_design.php

 

[Arlo1]

Cool. Weird looking but cool. One thing about the induction motors and most electric motors in genaral is how they can produce WAY more power then they are rated for for a short length of time. I read as geaneral AC motors can produce 8-10 times there rating for a short time as a rule. And for this reason people need to look at comparing them in different ways to gas motors that are always rated by their peak HP!

 

[StudEbiker]

Unless he's got some mad hYdrauliCZ on that car, speed bumps are not going to be much fun.

 

[Hillhater]

I think i see a business opportunity making Large scale vacuum formed Polycarb body shells ( as used on RC cars) .. just for these DIY EV builds.
3/4 scale Replica Corvettes , Ferrari's , Mustangs, Jags, etc etc..
...should find a good market since it seems that few of these EV home builders have any sense of style, proportion , or taste ! :lol: :lol: :lol:

 

[bigmoose]

Here is what's under the fiberglass:

Those two tires on one wheel meeting motorcycle requirements has a lot of potential in my book. I never knew about that loophole before a week ago!

Engineers are known for lack of artistic/elegant design... here is the perfect example of function before form or an anti-Italian-design-studio project:

 

[Ypedal]

mega-fugly ... i hope it runs better than it looks!

 

[TylerDurden]

Don't get that too close to an Aptera, the universe will implode.

 

[Gödel]

~2200 lbs with driver
18.7 kW
at constant torque up to around 3000 rpm and then constant horsepower (hp) up to 6000 rpm.
a single reduction of around 6.3:1

Knowing the drive wheel radius (usually around 11"), drag coefficient, and a few simple physics formulas one should be able to predict initial acceleration, the 0 to 60 time and distance, 1/4 mile times and top speed.
This is best done on a spreadsheet, on a second by second basis.

 

[gor.]

nice weight distribution spreadsheet - nearly every nut count

guy is not automotive engineer - when he started, he had no idea of challenges involved to make car from scratch
- but he had an idea from his own perspective and made it happen - most kudos to him
HIS commuter car runs as he wanted to, looks - as he wanted to; in this world - there is a room for any weirdmobile

as to details - his fiberglass shell, skin can be easily changed, frame - reinforced, reconfigured, etc
good man

 

[Hillhater]

Here is what's under the fiberglass:

I hope his electrical skills are better than his mechanical / design skills !!
( that rear spring support defies belief ! )

.Those two tires on one wheel meeting motorcycle requirements has a lot of potential in my book. I never knew about that loophole before a week ago!,,,

Well,..actually he has 2 wheels on one (rigid) axle !..so just how wide could that rigid axle be, before the "loophole" closes and it simply becomes the same as any other rigid truck axle ??

 

[bigmoose]

Well,..actually he has 2 wheels on one (rigid) axle !..so just how wide could that rigid axle be, before the "loophole" closes and it simply becomes the same as any other rigid truck axle ??

Me too! I guess the tires/wheels must turn together, as in a solid axle with no differential action between the tires/wheels. If that is the case, there is a limit to the distance or you are scrubbing a tire in turns, with the end result of not wanting to turn well.

 

[Hillhater]

well if they are non driven wheels, then they could simply be free wheeling.
... It would be a strange law that required them to be "locked" together ?? :?

 

[pdf]

Well, this is what (usually) happens when an engineer designs a car. And as an engineer, I say this with pride.

I admire the ambition of anyone who conceives a plan to build something and executes it. However, I am not that impressed with yet another hand-built electric car. Also, the technology of building an electric car does not require formal training in engineering. It is pretty mature and available to anyone with a mechanical bent. If you want to see electric cars (although I think this is actually a motorcycle, by law) more common, the issue is not the availability. You can buy a darn nice electric car right now. The problem with most conventional designs (the Leaf, the Tesla) is the cost. With anything else, it is the public acceptance, utility (of, for example, a BugE or other low cost three wheelers), and safety. With the size, the utility is probably high, but I doubt he is going to win the public acceptance points. Also, it is undetermined how safe the vehicle is, but I think you have to give car companies credit for making cars increasingly safe. Of course, safer cars usually mean heavier cars and for electrics, reduced range.

One example of a potential electric vehicle that I do think is well-executed is the Lithium Hawk:
http://www.nappepin.com/LithiumHawk.htm

With two seats, the utility is higher than a one seater, although not as good as a five passenger vehicle (a la Leaf). If the safety is acceptable, I would imagine public acceptance would be better than average; it looks cool so people will want to drive it. The guy building it has given some thought to safety (he build a BugE) with a cage around the driver. However, crash testing would have to be done to quantify this.

I think as gasoline prices get much higher, you will see increased public acceptance of a wider variety of vehicles, some three-wheelers probably or other low weight vehicles. However, personally, I think the price of gas will have to more than double or possibly triple in the States before this will happen. Relatively speaking, gas is still too cheap to encourage innovation in this area.

 

[salty9]

Thanks, BigMoose,

I found a link to the article - http://www.edn.com/article/518720-E..._from_the_ground_up_Part_1_Design_choices.php

I found a couple of points of interest. It's heavy - over 2000 lbs and the body is fiberglass over foam.

 

[SHiFT]

That thing reminds me of a streamlined Hammerhead-i Eagle Thrust from Top Gear.