Carb image

Carburetor

Carburetor

Carburetor Theory

The carburetor has one main function: to regulate engine speed. It accomplishes this by adjusting the amount of air and fuel that reaches the engine chamber, which then sustains combustion.

For a low-speed idle you have a small amount of air and fuel entering the engine. This lowers the chemical mixture entering the combustion chamber, and thus lessens engine power and subsequently lowers the RPM (revolutions per minute). As we open the throttle, the carb allows more air and fuel into the combustion chamber, thus increasing engine power and RPM's.

The Venturi Effect

What allows the carb to pull fuel from the fuel tank is the Venturi effect, a phenomena related to the Bernoulli principle. This states the velocity of a fluid entering a tube increases as it passes through a smaller diameter region.

Fluids are generally incompressible, so the same amount of fluid (volume) is going to try to get through a volumetric cross-section of tube - if you make the diameter smaller, the fluid has to move faster to get through.

In a carburetor, this increase in air speed allows more fuel to be drawn from the float chamber (a fuel reservoir) through the jet, where it is somewhat atomized.

This low pressure region is precisely where fuel enters the carburetor throat. This is what allows the engine to "suck" fuel from the gas tank.

http://static.howstuffworks.com/mpeg/chainsaw3.mpg

http://auto.howstuffworks.com/question377.htm

Engine stuff.

Engines galore!

Steam Engines:

http://science.howstuffworks.com/transport/engines-equipment/steam.htm

http://www.animatedengines.com/locomotive.html

Stirling Engines:

http://auto.howstuffworks.com/stirling-engine.htm

http://www.animatedengines.com/vstirling.html

http://www.animatedengines.com/stirling.html

http://www.animatedengines.com/ross.html

2-stroke Engines:

http://science.howstuffworks.com/transport/engines-equipment/two-stroke1.htm

http://science.howstuffworks.com/transport/engines-equipment/two-stroke2.htm

4-cycle Engines:

http://auto.howstuffworks.com/engine1.htm

(single cylinder)

Intake, Compression, Combustion, Exhaust

http://auto.howstuffworks.com/engine2.htm

(more typical, and more complex)

http://auto.howstuffworks.com/engine4.htm

What goes wrong typically?

http://auto.howstuffworks.com/engine3.htm

car review / field trip

FOLKS:

Car review will be due on Tuesday.  Feel free to turn it in early. This is such a crazy week for many people - it seemed safer to extend the deadline by a class.  Remember - it should resemble a pro review that you might see in places like this:

http://www.edmunds.com/car-reviews/

http://www.caranddriver.com/

http://www.consumerreports.org/cro/cars/index.htm

We're doing the field trip next Thursday (Oct 4) to DC.  My astro class will hit the air/space museum while you'll hit the American history museum.  Let me know if this presents problems.

moped parts, etc.

It's a place called Treatland - treatland.tv

For next class, I anticipate having a go-cart frame and engine.

Hopefully also handlebars for the bike.

I should have ordered a moped (Puch) throttle cable by then.

Enjoy the weekend!

Go-ped folks -- decide what is next.  Two Go-peds are basically running.  They could definitely stand tune-ups, etc.  The third one (with the seat) needs work.  Think about that one.

Josh and Chris - keep up your spirits!

Check out the Stirling stuff on the previous post.

Other info:

The bike engine kit is on order.  I hope it's here by the end of next week.

Still looking for a go-cart.

It looks as though I'm going to have some donor bicycle(s).

Stirling Engines

Have a look.  Have a read.

http://auto.howstuffworks.com/stirling-engine.htm

http://www.animatedengines.com/vstirling.html

http://www.animatedengines.com/stirling.html

http://www.animatedengines.com/ross.html

http://www.animatedengines.com/ltdstirling.html

Also, if you have time - look on youtube for some Stirling engines.