# Homework Help: How to Maximize a Stearin Engine

1. Aug 11, 2008

### Cgall24

The problem statement, all variables and given/known data:
A candle is balanced on a horizontal needle placed through it near its centre of mass. When the candle is lit at both ends, it may start to oscillate. Investigate the phenomenon. Maximize the output mechanical power of the system.

I have already conducted several experiments with candles of different diameters and have found that candles with smaller diameters generally oscillate better.

I would like to ask for experiments that could prove WHY this happens and other variables that can be tested. Also some suggestions of how to make the candle oscillate more

Thanks =D

2. Aug 11, 2008

### Topher925

Hmmm.....the only thing I can think of is the rate of melting wax given the angle of the candle. What axis is it oscillating on? Is it rotating planar to the surface of the earth or sort of a up and down motion tangent to the surface of the earth.

3. Aug 12, 2008

### Cgall24

Thanks Topher925.
It travels tanget to the earth. Much like an one of those classic rocking type oil well things without the pistons.

4. Aug 12, 2008

### Alfi

The candle on the lower side will burn faster till it loses mass and tips up and the other end begins to burn faster. and on and on

Have you tried drip-less candles?

5. Aug 12, 2008

### Cgall24

Yeah, that wa what we thought and no, we haven't even looked at drip-less candles. I didn't even know they existed. I have a look but knowing this town I'll have to order online. Ahwell. Anyway, thanks for your input.
With any luck we'll have a good case to argue with during the tournament.
Oh, and do you know of any candle that will burn faster?

thanks :D

6. Nov 2, 2008

### Cognol

Yo Yo

Well IYPT man,
Isn't obvious why the candle oscillates better with smaller diameters? It just eliminates the complected matter of dripping. This problem is very simple really. I'm from the australian team who won last year.

I solved this problem using two methods. One is simple kinematics and Euler's method for integration iterated ten thousand times. The other is simple kinematics and using the third derivative approximation to find a period for short times.

I have gone into thermodynamics, but it gets so incredibly complicated you could probably use an approximation for burn rates.

I haven't given my work to anyone so I won't really give an advantage to any team.

The mechanism is straightforward.

Have you taken a look at "hot ball." I would be interested to know what you found.

7. Nov 4, 2008

Hey I have to do this as a physics assignment atm and I'm using calculations such as, Moment of Inertia, Angular Velocity, Angular Momentum and Torque. Are these the main equations used in this experiment? Are there any more which I should consider?

Cheers.

8. Nov 4, 2008

### Cognol

Don't concern yourself with main equations, think about the concepts. Equations are merely quantitative mathematical tools to describe concepts in physics. Just think about the problem! Your dealing with rotational motion, so rotational kinematics is obviously going to concern you. You also have combustion, so thermodynamics will also be necessary. It sounds like you need to get to grips with rotational kinematics. I would suggest doing some problems out of a first year university text book, or maybe a high school one. Once you understand the concepts, the mathematics just comes out.

But heres your answer: Everything you said will be needed, that is obvious. There is also more. However, angular momentum could get complicated here, and isn't really needed to a first approximation.

Think in concepts(physics) not equations.

Are you an IYPT guy, or doing an EEI?

9. Nov 4, 2008

EEI, I'm doing it for a year 11 assignment so I don't think we'll need to go into ALL the details, but it would be nice to.

Guess I gotta do more reearch. :S

Thanks.

10. Nov 4, 2008

### Cognol

At a simple level, the kinematics of this problem is straightforward. A look at a single chapter in a text book would be enough to get to grips with it.

Theres not that much research you can do (except for learning rotational kinematics). You just have to nut it out yourself.

BGS?

11. Nov 5, 2008

Yea.

Alright I should be able to do it now, thanks for your help.

12. Nov 7, 2008

### mari-IYPT

huh here very interesting discussions are holding for me :D :D

So. i'm from the team of Georgia....... I had tournament of IYPT at my school and my team took 1-st place... I took part in IYPT 2008.... And I know Australians quite well. They are CUTE !!!

My team has already solved several probs...

But of course i won't help others :D :D :D

13. Apr 30, 2009

### Cognol

Hey mari.

Several problems? Is Dato on your team?