[Womble]

[member=212379]naturelovingfarmer[/member] asked a question on another thread, but to avoid side-tracking that, here's a new thread:

Can you explain a ram pump? It uses momentum and weight of a large amount of falling water to lift a small amount of water high up. If the depth matters more than the weight, how does a ram pump actually work?

OK, ram pumps - that's easy (I've always wanted to build one, but unfortunately have no use for one here - gutted!). You've already got it - the key is momentum, and changing that momentum into pumping pressure.All you're doing with a ram pump is letting water flow until it's moving fast (i.e. it has built up momentum), and then stopping the flow suddenly. That's like driving along in your car with an object on the passenger seat, and then slamming on the brakes. The object will fly forward and hit the windscreen, converting its momentum into pressure against the windscreen.In engineer world, this momentum is known as "velocity head" - it's the head (sort of like having the potential for pressure*) which the water possesses because it's moving. When you suddenly stop the water from moving, the "velocity head" gets translated into a short spike in pressure which then 'relieves' via the side pipe. The side pipe has a non-return valve in it, so you get a pulse of water out at high pressure. The flow in the main pipe then starts up again, and the cycle repeats - it's really very ingenious - one of those incredibly simple applications of physics that I wish I'd thought of, only didn't!

*Mr Bernoulli is turning in his grave right now, but what the hell  . Does that help?  I can go into the physics a bit more if you like, but TBH I'll bet there's somebody on Youtube who explains it far better than I can!

[naturelovingfarmer]

That's super interesting. I was wondering if i could divert a small amount of water from a spring and raise (probably slowly) some water for a fountain. The idea was to use the ram pump to raise water to a header tank which has a bell siphon that is connected to the fountain, so when the header tank fills, the water gushes out all at once through the fountain. The point is to periodically make a bunch of noise that scares off wild animals without having to invest in electricity for it. 

[Womble]

Hell yes! That's a perfect application for a ram pump. All you need to make one work is a reasonable flow (velocity) of water through a pipe. I love the idea of coupling it with a bell syphon too. Loads of physics going on there! 

[naturelovingfarmer]

I love bell siphons. My mom tends to kill plants by overwatering, so I made her a flower pot with a bell siphon to make sure she didn't put in more than the recommended amount of water. First time she used it... got water all over. Learned not to do it. She repotted the plant and proceeded to drown it. Gave me the pot back. Apparently didn't want a plant pot that watered her back. To my credit, I told her to use it with a dish and not to overfill it. I even showed her how it worked. So she shouldn't have gotten watered. The idea was that she'd pour in enough water to wet the roots but not enough to drown it. And if there was accidentally too much it would drain into the dish underneath.

I once considered making a musical fountain using siphons, The water would flow through a series of chambers and the bottom of each siphon would contain a sort of reed like on a recorder flute. It doesn't make a sound while there's water in it, but once the water starts flowing through the next one down it sucks air past the reed and then it does. As the suction decreases with the increase of volume of air in the chambers, I sought to overcome it by pre-filling the chambers partially using other siphons with a one-way water only valve. The way to keep air from going through the pre-fill was to have them lock with a counterweight, but then I couldn't just make it out of clay in a single piece with no moving parts so I abandoned that idea and made a bong with a bell siphon in it instead. My brother was not amused.