Energy from reciprocating beam

Thread Starter

JulesP

Joined Dec 7, 2018
251
I have an oscillating beam with a counterweight on it of about 1.5kg, driven by a pendulum (see diagram).

I would like to extract and measure the energy available from the beam’s reciprocating movement by using perhaps a load cell, piezo electric device or even a magnet moving in a solenoid and storing the energy in a capacitor/battery.

The mass on the left moves a vertical distance of about 2cm at a frequency of 2Hz.

The advice I am seeking is which method, or another, would be best suited to this task?

Thanks

F2F7A3B7-77A9-4B2B-B555-6CDC14854827.jpeg
 

shortbus

Joined Sep 30, 2009
7,780
Do an experiment before spending too much time or money on this. Make the balance out of something you have around the workshop. And see how long it will keep moving by it's self after being put in motion. Then imagine that being cut in half or more time wise, that would be a best case scenario for energy production(it probably be a lot more than 1/2) That will show you that there is a reason perpetual motion or over energy won't/doesn't work. At least no on this planet.
 

jpanhalt

Joined Jan 18, 2008
9,807
Simple. Take the energy you put into it and multiply by some factor, like <=50% to 80%. That will tell you what you can get out of it.

Are you expecting more? Why?
 

Thread Starter

JulesP

Joined Dec 7, 2018
251
Do an experiment before spending too much time or money on this. Make the balance out of something you have around the workshop. And see how long it will keep moving by it's self after being put in motion. Then imagine that being cut in half or more time wise, that would be a best case scenario for energy production(it probably be a lot more than 1/2) That will show you that there is a reason perpetual motion or over energy won't/doesn't work. At least no on this planet.
This has nothing to do with what I’m investigating. I’ll go elsewhere for some sensible suggestions
 

Papabravo

Joined Feb 24, 2006
13,973
The energy you get out will be equal to the energy you put in minus the losses.
I'm not sure there are any sensible suggestions, but knock yourself out and good luck finding one.
 
Last edited:

DarthVolta

Joined Jan 27, 2015
477
Op ignore the confusion, as for doing a lab experiment ...if you already have it made.....no one said free anything, relax people, it's just a machine

What about just using visual methods to track the motion and calculate the kinematics ? What about the software that does that stuff from video ?

As for doing it with physical sensors, soon I'll be experimenting with lots of that stuff too, I can't wait. I want to make little robots and stuff.
 

Thread Starter

JulesP

Joined Dec 7, 2018
251
Yes I could do a calculation based on its motion but ideally I’d like to try and extract the kinetic energy. I’ve heard there are now cantilever piezo strips that produce a voltage when they are flexed or vibrate.
 

hrs

Joined Jun 13, 2014
236
If you take the solenoid idea and load it with a resistor, then log the voltage over the resistor, maybe you can integrate V^2/R over time to get the energy extracted until it stops oscillating.
 

Alec_t

Joined Sep 17, 2013
11,419
Piezo elements are ok for generating voltage, but because of their very high impedance they're poor energy harvesters.
A 1cm amplitude oscillation of a 1.5kg mass involves a change in energy of only about ±0.15 Joules by my calculation, so the transducer would need to be very efficient to extract useful energy from what little there is available.
 

Thread Starter

JulesP

Joined Dec 7, 2018
251
If you take the solenoid idea and load it with a resistor, then log the voltage over the resistor, maybe you can integrate V^2/R over time to get the energy extracted until it stops oscillating.
Interesting idea. Worth a look at.
 

Thread Starter

JulesP

Joined Dec 7, 2018
251
Piezo elements are ok for generating voltage, but because of their very high impedance they're poor energy harvesters.
A 1cm amplitude oscillation of a 1.5kg mass involves a change in energy of only about ±0.15 Joules by my calculation, so the transducer would need to be very efficient to extract useful energy from what little there is available.
So a calculation approach is probably more valuable. Thanks for thoughts.
 

jpanhalt

Joined Jan 18, 2008
9,807
Free energy similar concept to this:
Op ignore the confusion, as for doing a lab experiment ...if you already have it made.....no one said free anything, relax people, it's just a machine

What about just using visual methods to track the motion and calculate the kinematics ? What about the software that does that stuff from video ?

As for doing it with physical sensors, soon I'll be experimenting with lots of that stuff too, I can't wait. I want to make little robots and stuff.
Anytime a poster presents a gadget and asks about extracting energy without showing an energy source, they are usually asking about free-energy (extracting from the environment contrary to thermodynamics) or perpetual motion. That suspicion is raised when there are combinations of pendulums with variable lengths, sliding weights, springs, or ropes through buckets with holes.

So, to follow up, perhaps the OP will tell us first how his machine is energized.
 

Thread Starter

JulesP

Joined Dec 7, 2018
251
Free energy similar concept to this:


Anytime a poster presents a gadget and asks about extracting energy without showing an energy source, they are usually asking about free-energy (extracting from the environment contrary to thermodynamics) or perpetual motion. That suspicion is raised when there are combinations of pendulums with variable lengths, sliding weights, springs, or ropes through buckets with holes.

So, to follow up, perhaps the OP will tell us first how his machine is energized.
Mine is energised by a small motor pulsed by a 555 timer circuit so I can reciprocate the beam. Energy comes from the mains
 

jpanhalt

Joined Jan 18, 2008
9,807
Here are a few related ideas to consider:
1) Power to the gadget: Consider using "muscle wire" (https://en.wikipedia.org/wiki/Shape-memory_alloy ) for the spring. That could be powered directly from low voltage. Ambient cooling for the return. Such wire is used in ultralight indoor models to move control surfaces without servos.
2) For any reciprocating linear motion to rotation conversion, consider a connecting rod and crankshaft. More recent engines (circa 1950's and later) have used cams directly from pistons, but the cam contours are difficult to machine.
3) For reciprocating rotation like a pendulum, consider an escapement to give a full rotation, as has been used in clocks and watches for centuries.
4) And, of course, you can also use a magnet in a coil and some electronics to give DC.
 

Thread Starter

JulesP

Joined Dec 7, 2018
251
Here are a few related ideas to consider:
1) Power to the gadget: Consider using "muscle wire" (https://en.wikipedia.org/wiki/Shape-memory_alloy ) for the spring. That could be powered directly from low voltage. Ambient cooling for the return. Such wire is used in ultralight indoor models to move control surfaces without servos.
2) For any reciprocating linear motion to rotation conversion, consider a connecting rod and crankshaft. More recent engines (circa 1950's and later) have used cams directly from pistons, but the cam contours are difficult to machine.
3) For reciprocating rotation like a pendulum, consider an escapement to give a full rotation, as has been used in clocks and watches for centuries.
4) And, of course, you can also use a magnet in a coil and some electronics to give DC.
Thanks for some good ideas. I’m particularly interested in e magnet moving in a solenoid option but with say 2cm of movement and, I think, the magnet needing to move fully out of the solenoid with each pass, it’s going to be a very short solenoid around 1cm long. If that’s so then it will need to be very fine wire to get enough turns to create a significant voltage.
 

shortbus

Joined Sep 30, 2009
7,780
This has nothing to do with what I’m investigating. I’ll go elsewhere for some sensible suggestions
Mine is energised by a small motor pulsed by a 555 timer circuit so I can reciprocate the beam.
Why didn't you say you were using a "small motor pulsed by a 555 timer circuit", in the first post? Your illustration doesn't show such a motor.

But it still comes down to losses, you never will git more out than you put in. In either mechanical or electrical terms.
 

Tonyr1084

Joined Sep 24, 2015
4,738
This has nothing to do with what I’m investigating. I’ll go elsewhere for some sensible suggestions
Have heard that before. What constitutes sensible suggestions can often be suggestions that support the hypothesis as opposed to "Good" suggestions.
The energy you get out will be equal to the energy you put in minus the losses.
I'm not sure there are any sensible suggestions, but knock yourself out and good luck finding one.
100% agree. You can never get more energy out of something than you put into it. Example of energy in and energy lost - take a basket ball. Lift it six feet high. Drop it. The ball will not bounce back to the original height. The reason is because of the heat energy generated (converted from kinetic energy) when the ball bounces. Also, there's the wind resistance that also rob energy from the falling ball. Since simply falling through the air from six feet doesn't generate heat (actually there IS some heat generation from friction but it's too small to measure) another form of energy is being converted - wind energy. Wind is energy. We convert that energy into motion. Sailing ships and windmills were such devices. Today we convert wind energy into electrical energy. The reason why they're so big (and don't cause cancer) is because the amount of energy needed to create a kilowatt requires a certain amount of wind against a surface such as a windmill blade. To get two kilowatts out you need four times the surface area. I have no idea what those numbers are, but physics can explain it. And no - I'm not a physics expert either.

If you truly want sensible advice - take your mains power and convert it into whatever voltage you want. Then store that. When the storage has reached its capacity - shut off the mains. That way you don't waste energy. Or should I say "convert it into another form of energy, most typically heat."
 
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