elictric powerd car matierals, gears, aerodynamics, anythig

[wendy1993]

Hi im entering a computition for a electric powerd car im just geting started and Ineed some help or ideas. The engin is 24 volts and its an indurance race (we have got to see how many laps we can do in 6 hours). If you could give me any help on any thing it would be greatly appritiated espicly on matirals as I need something light but strong. thanks
thanks wendy.

[deleted-71576]

Wendy:

Sounds like a lot of fun. It would probably help us if you could be more specific about the rules.

Generally, when you think of light, strong materials you think of carbon fiber, titanium, aluminum, fiberglass. Obviously, cost and knowledge of techniques in working with these materials is helpful. There are lots of tricks like hollowing out pieces, adding glass microspheres, etc.. which can be used to decrease weight.

Light weight is clearly important. Strong may not be as important as you think. While the car does need to last the 6hours, it shouldn't have to survive a crash, should it? If not, materials like balsa and bamboo come to mind. How will the car turn around the laps? Is it on a track/rails, or does it need to be able to turn on its own?

Is your car going to be solar powered, or battery powered? In either case, battery choice/technology is going to be extremely important to your success.

Your first start should be using the search engines. Google, wikipedia, Ask.com, answers.com, yahoo, etc. Search on as many terms as you can think of. These terms will send you off in other helpful directions. This is the fun part of the learning of the project. You never know what interesting ideas you will come up with.

Give us some more details, and we'll be happy to guide you in the right direction. There are experts here in a wide variety of fields, whose knowledge is quite impressive. We're here to help.

[jamescjb]

wendy:

It sounds really interesting for me that your car is going to run for 6 hours. As zzzzdoc said something about materials, which is really important for your car, I think you should also think about what kind of tire are you going to use. It is a challenge for the endurance of your tires. It depends on the ground situation of the laps. Sponge tires are good choices for hard ground. I would like to know more information about your project. It is a good start!

James

[wendy1993]

we have a 24 volt engine and battery all competetors have the same so i cant change that it will be on a tarmac track.

here are some other specs
Wheels:
The wheels must be pneumatic and capable of sustaining the loads imposed on them with respect to both vehicle weight and cornering loads. They must comply with the following wheel sizes (front and rear):
Max 500mm (20in.) Min 200mm (8in.)

Size and Configuration:
The vehicle must not exceed 2500mm in length and 1200mm in width overall. The vehicle must be able to pass under a 1200mm high horizontal pole.
It must have a minimum ground clearance of no less than 40mm.

if you would like to look at more try on http://www.greenpower.co.uk/racing/rules_f24.php
thanks for helping

[deleted-71588]

I looked at the specifications and they cover the car and some aspects of the road course. What isn't clear are the charging rules for your particular race and if you are intending to augment the battery power with solar power. The motor takes 10Amps, so a 6 hour race = 60 Amp-hours of power. I wasn't able to find specifications for the specified "Yuasa battery. If it is less than 100 Amp-hour and the race is on a single charge, it may not have enough power to get the car started after the last driver exchange if you do it too late.

You have some interesting engineering challenges in terms of a clutch, gear box, steering, brakes, disapating 240 W of heat to keep the motor cool, power controller, and all of the safety issues.

0.3 horsepower at 2000 RPM means weight will be a major factor. Most of the forces that affect the clutch, gears, steering, brakes, and tire rolling resistance all result from the mass of the car.

Figure out the weight of the things you can't change and go from there.

[deleted-71576]

Wow! Quite the challenge. As Craig said, weight is key. Since you will be having a driver, the driver's weight is key also. I wouldn't choose the largest student in your class as the driver.

Weight, rolling resistance, engine cooling, gearing, stability, to a small degree aerodynamics (I'm not sure that's incredibly important at your likely slow speeds, but it can't hurt), ability to add additional power (solar), all matter.

Looking at some of the previous cars, you can see that a number of teams built cars with a fairing to reduce air resistance. Bet it was hot in there. Some really beautiful cars by the looks of things.

You can get a number of hints by looking at the pictures of the cars. Look at the tires/wheels. If money is no object, look at racing bicycle tires/wheels (tubulars). Recumbent bicycles share much of the design goals as to what you are attempting. High pressure, low rolling resistance.

The shape of the cars should also give you ideas.

I didn't realize the large scale of this project. It's quite the competition.

There is a forum on their website. I would get involved there. Nothing like advice from people who have done this before.

Good luck.