Build a Battery-Powered Dragster for Physics Class

[midcourtassassin]

Hey there! I need to make a battery powered dragster for my physics class! Here are so requirements...

Only AA batteries, but any number is allowed.
Only commercial motor and gears are permitted.
Everything else on the car must be materials not meant for their use (ex. car wheels must not be wheels. They can be thread spools or CDs, etc.)

Any ideas as to how I could make this work? Or what's the best engine to use? My partner and I took an engine from a AA battery powered RC car at the local toy store. Are there any faster ideas, though?

I'd appreciate it. Thanks! :)!

 

[Cliff_J]

Well, apply the basic forumlas:

F = MA or better said A = F/M

From that, you can see why people talk about power-to-weight ratios of cars or motorcycles as a measure of their performance, the two oppose each other in regards to acceleration.

More batteries means more power, but also more weight!

Now, where does the electric motor you have make the most power for a given amount of weight?

Also, what voltage is the motor you have designed to run at? This may be a good point to start experimenting but a lower voltage may or may not work better.

You may want to experiment with a small car and vary the number of batteries and see how it affects performance.

You'll likely find that small o-rings or rubber bands would work as tires on whatever wheels you find to get more traction.

Getting the correct balance is going to be the key to make the best compromise. You may want to use a larger motor that will significantly reduce battery life (since this is a dragster) but this may be a problem over many races. So it really is just going to be a matter of finding the best results with the resources you have at hand, and rechargable batteries and a stopwatch is about all you really need.

 

[brewnog]

I made one of these when I was about 16, it was one of the scariest things I've ever created! It probably weighed about 400 grams, and I think we clocked it doing about 55mph.

Go and get a motor designed specifically for model cars. They tend to like 7.2V, though I think 8.6V ones are not uncommon. You're probably looking at about 20 GPB for a half-decent motor. Don't underestimate your battery selection either, invest in some decent recargables. Speeds of 70mph+ are perfectly feasible, so be careful! A balsawood chassis will do nicely, laminate it for stiffness. Try and get your batteries mounted just in front of whatever drive mechanism you use.

Your wheels and tyres will probably be your weakness here, you will definitely need all the traction you can get. Think about the surface you're racing on, - foam tyres work well on carpet, rubber tyres on tarmac or concrete. Superglue them to whatever you end up using for wheels.

Experimenting is definitely the key with this project, especially with gear ratios.

 

[midcourtassassin]

Yeah, the battery MUST run on AA's only. That's a requirement... I just don't know what motor to use! It is so unfortunate. :( Like I said above, my partner and I just pulled one out of a toy RC. But.. do you have any other suggestions as to what motor we should use? It HAS to run on AA's! The motor and the gears can be commercial.. And the wheels are a tougher challenge. I don't know WHAT to use!

 

[brewnog]

As I said, use a motor designed for radio control cars, such as one of these.

 

[FredGarvin]

Do a google search on RC cars. You will find plenty of hobby shops on line that will sell the items you need.