Plug in hybrid project

[tomislavp4]

I started planning a project that I hope could get finished in 4-5 years
It´s a plug in hybrid which means it´s main propulsion comes from electro motor and uses a small ICE for charging the batteries when needed.
My goal is 350+ bhp, 600+ Nm, 0-100 less then 4,5sec and V-max 270+kph

But I´m going to need some help from you concerning aero, suspension, component placement....
So there vill be quite a few questions from me on this topic, hope I´ll get help

My first question: should i locate the motors in the wheels and don´t use gearbox or to locate the motors inside and use a gearbox?

From what I see it´s like this:
Layout 1-with gearbox, will give the car better top speed and better braking but also it will weigh more, be more expensive, it won´t charge the batteries under braking like the second layout and the venturis at the back would be significiantly smaller

Layout 2-in wheel motors
Less expansive, weights less, lives place for other stuff and charges the batteries under braking

Layout 1 [IMG:150:112]http://img442.imageshack.us/img442/1760 ... xq6.th.jpg[/img]

Layout 2 [IMG:150:112]http://img376.imageshack.us/img376/2559 ... qc1.th.jpg[/img]

What do you think guys?

[tomislavp4]

No one? OK

[joseff]

OK, I'll bite...

If you want to do 0-100 in 4.5sec, you'll need the weight < 1200kg, giving a power/weight ratio of 4.6kg/kW, roughly in Porsche GT3 territory (quoted 0-100 4.1 sec)
- suspension and wheels = 150kg
- steering = 50kg
- driver + seat + belts + electronics = 120kg
- 260kW (350hp) electric motor + drivetrain = 200kg
- 100kW diesel + tank + fuel + generator = 200kg
- tube chassis + fiberglass body = 150kg

which leaves (optimistically) 250kg or so for batteries. Now you'll need something that can give you the 260kW without blowing up. Your best bet would be NiMH.

A typical NiMH battery has 50Wh of energy and 500W of power for a kilogram.

Given 250kg, you'll have around 125kW max, which is far below the 260kW needed. You could, of course, supply extra power from the 100kW diesel.

The total energy of the battery would be 12.5kWh. With moderate throttle application and regenerative braking, let's assume highway usage: constant 100km/h burning a constant 50kW. The batteries alone will give you a range of 25km.

Over to you...

[tomislavp4]

check: http://www.stefanoparis.com/piaev/pml-m ... -mini.html

the motors wheight 25kg each

There is a company that sales Lithium Ion batteries with form of a cylinder with height 65,50mm, diameter 26,15mm and approx. 70g weight which have 2,3Ah and 3,3V power and life of 1000+ cycles

[Tom]

I myself would use a gearbox because you could have high power high acceleration gears aswell as cruising gears which, if engineered correctly, create minimal power consumption.

There are alot of tried and tested methods used in cars but I think for a project like this I'd think outside the box. Maybe not a conventional gearbox with gear but instead a control which provides more or less power at different times depending on the selected option, this would allow the minimal weight and maximum space option of motors in wheels and only microchips as a 'gear'box.
Another possible system, inside the wheels you could experiment with an electric trye pump. For fast driving in spped gears pump the tyres up a little, for control, economy and comfort deflate them a little.
Make use of ultralight weight materials where possible, that's obviouse.
Perhaps a three wheel vehicle would be better, one wheel at the back would provide a well balanced yet powerful car, even under braking, and reduce drag.
Maybe even a design that uses four wheels for low speeds and cornering and 2 when the steering is straight, suspension sensors read a smooth road and speed is above x?
Good luck, I'll have a think and come up with some more ideas tommorrow.

[joseff]

the motors wheight 25kg each

There is a company that sales Lithium Ion batteries with form of a cylinder with height 65,50mm, diameter 26,15mm and approx. 70g weight which have 2,3Ah and 3,3V power and life of 1000+ cycles

Good point, mounting the motors in-wheel eliminates the tranny. Would you be able to do 270km/h without at least 2 gear ratios though?

using the 250kg battery example above, the Li-ion example given above would yield 27kWh capacity. What is the max current drain of the batteries? We still need 270kW. Wikipedia lists the power density as 1.8kW/kg. This gives 450kW which should be enough.

You have to remember that Li-ion batteries don't like heat. In fact they lose capacity when overheated, and in extreme cases go kaboom! (ask Sony)

[tomislavp4]

Yeah they dont like sun I guess

I was thinking to have a centrall tunnel in which the batteries will be monted. As the car travels trough the air the air goes in the tunnel cooling the batteries...

[img=http:150:128]http://img78.imageshack.us/img78/1116/u ... bj5.th.png[/img]

About the top speed, with motors capable of 2000RPM I think you could achieve 270, or am I wrong?

[Carlos]

You might consider a backbone chassis - as used in severl of the Lotus road cars - Europa and Elan - Lotus also made a sportscar with a composite monocoque - in the sixties - using fibreglass and a small subframe for the engine I believe - I think motor in wheels is a good approach - unsprung weight - within 5 years the electric motors will be lighter - as will batteries - front or rear engine - either - as long as weight distribution is 50/50 - have you read the hydristor thread - it may offer alternate ideas - an" I "shaped backbone frame of aluminum - surrounded by a composite monocoque for added strenght and anti - intrusion - a saftey cell - seems interesting - perhaps build it as a chassis for an aftermarket body - the Ferrari P4 is my favourite - althought you must have personal favouites - or design and build a body - in fact - the project must certainly be interesting just for the pleasure of desgn as self expression.

[Carlos]

Edited as I posted twice

[joseff]

About the top speed, with motors capable of 2000RPM I think you could achieve 270, or am I wrong?

Taking a typical 195/55-15 tire, we have 595mm diameter = 1869mm circumference. 2000rpm means 224km/h.

[tomislavp4]

I would think to put larger diameter tyres because the larger the rim diameter the larger the motor diameter will be

[Tom]

Larger tyre diameter requires more material and therefore more weight.

[tomislavp4]

But the bigger motor dellivers more power which will compensate for the added weight

[Tom]

Yeah, I wasn't meaning to be so patronising, I just meant that there must be an optimum power/weight because although a bigger motor has more power it also has the extra weight. I'm not so good a recurance relations so I'm not sure how you'd work it out but there will be a limit at which point you'll need more energy to push the weight of the motor and extra wheel weight than the motor can provide.
If you give me the power of each weight of motor I'll try and work it out for you.

[tomislavp4]

30kg motor gives 170hp 660Nm (approx. figures)