Designing a Non-Mechanical Timing Device: Ideas Needed!

[k_2_the_arma]

I need to design and create some sort of device to measure an interval of time between 10 and 40 seconds. I can't use any electrical or mechanical things. I had ideas of puting water in a funnel and letting it fill up a cup in which I've measured how much water equals a second for example. I also thought of dropping marbles off of a low-incline ramp and timing it's drop to the base. The catch is my physics teacher is making everyone in the class do a different project, the water measuring one has been taken and so have the marbles.
Does anybody have any ideas on what I can do? I have no problem designing, building and testing the device I just need to get going here.

Thanks All

 

[quantumdude]

Given that both the water and marble clocks are "mechanical", I am at a total loss. What exactly is ruled out by that term?

 

[k_2_the_arma]

I used the wrong term. We can't use anything electronic appliances such as fans, dremel tools etc.

 

[quantumdude]

A-ha. In that case, how about a pendulum? Has that idea been taken?

 

[k_2_the_arma]

well i was considering using a pendulum, but the period is bound to change during a duration of up to 40 seconds - I am allowed only a 2 second grace period

 

[k_2_the_arma]

It's still a possibility to do something involving marbles. One other person is already doing something where they mark on a track every second, and as the marble falls they count how many seconds the marble passes through. A good idea, but unfortunately I can't do the same thing

 

[brewnog]

Sand timer? If sand's taken, how about a sugar timer? Or a salt timer?

 

[k_2_the_arma]

Sand timer? If sand's taken, how about a sugar timer? Or a salt timer?

I am always one for cutting corners, but yup somebody is connecting two 2-liter soda bottles and filling it with sand. his friend tried to do sugar and it's not allowed

 

[arildno]

Why do you dismiss pendulums so easily?

You've got other versions than the grandfather clock variety, you know..
Look up, for example, torsional pendulums to get another pendulum type

 

[k_2_the_arma]

Why do you dismiss pendulums so easily?

You've got other versions than the grandfather clock variety, you know..
Look up, for example, torsional pendulums to get another pendulum type

a torsional pendulum might work, I'm researching them as we speak

 

[quantumdude]

Also, there are other types of harmonic motion: like a mass and spring.

 

[k_2_the_arma]

bump

any

 

[k_2_the_arma]

I came up with another idea that hadn't been taken - it's hanging a slinky from a hanger with a mass on the bottom and letting it stretch vertically, something like in the diagram seen here

link

do you think that this could be semi-accurate?