How can I create a constant flow? (not sure where to post)

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Parker Hame
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I am doing a STEM project where we need to make a timer without any chemical reactions or electricity, and I think the best way to do this is to create a constant flow for a certain amount of time and weigh how much water comes out. What is the best way to create a constant flow of water for 10-300 seconds?
I am doing a STEM project where we need to make a timer without any chemical reactions or electricity, and I think the best way to do this is to create a constant flow for a certain amount of time and weigh how much water comes out. What is the best way to create a constant flow of water for 10-300 seconds?
 
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Fun project. What are your thoughts so far?

I can think of one way to do it fairly accurately...
 
anorlunda said:
Google "water clock" there is an ancient and venerable tradition of designing clocks that use water. There are dozens and dozens of basic designs.
The hard part about those is that I have no idea what the angle needs to be for it to work properly, or where to get a hollow cone.
 
berkeman said:
Fun project. What are your thoughts so far?

I can think of one way to do it fairly accurately...
I’m thinking maybe using a throttle type device and two tanks of water
 
Parker Hame said:
The hard part about those is that I have no idea what the angle needs to be for it to work properly, or where to get a hollow cone.
The cone was only one of many. Here's a simpler one.

1570827232084.png


And another.
1570827384201.png
 
Did anyone suggest a pendulum clock?
A saw blade (hacksaw) could be lowered tooth by tooth by an escapement attached to a fixed length pendulum, that repeats a cycle every second. The blade will fall out when the number of teeth initially engaged have passed down through the escapement. You would need a blade with over 300 teeth for 1 second accuracy.
 
Does it have to be water.
Other options.
An egg timer perhaps.
https://en.wikipedia.org/wiki/Hourglass
If water, one could set the faucet to drip, drip, drip, and do counting instead of weighing.
 
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Parker Hame said:
What is the best way to create a constant flow of water for 10-300 seconds?

One thought is to have a container where inflowing water at the top of the continer keeps it overflowing, so the water level is in the container is approximately constant. Near the bottom of the container, have an outlet pipe whose outflow is much less than the inflow at the top. The outflow would be driven by an approximately constant pressure.
 
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Stephen Tashi said:
One thought is to have a container where inflowing water at the top of the continer keeps it overflowing, so the water level is in the container is approximately constant. Near the bottom of the container, have an outlet pipe whose outflow is much less than the inflow at the top. The outflow would be driven by an approximately constant pressure.
This idea sounds great! I think this is what we will do, red solo cups and graduated cylinders to the rescue!
 
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Stephen Tashi said:
Near the bottom of the container, have an outlet pipe whose outflow is much less than the inflow at the top.
The overflow only has to remain positive, it does not need to exceed the regulated outflow.
The reservoir could have a large surface area of water to reduce sensitivity to flow regulation.