Flywheels achieving linear motion [Archive]

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mechanicalbrain

28-12-2005, 19:19

I need a little help with an idea of mine. I want to take a flywheel (10 pound disk with 10" diameter) and apply all of its stored energy into a single linear movement of a rod. I guess not unlike how a camshaft causes a linear motion with the engine cylinders. I really want to put quite a bit of force into a single thrust, and I really need to be able to spin this up to full potential fairly quickly. I already know the Kinetic Energy = 1/2*I*rpm*rpm equation and I'm making I = 1*Mass*Radius*Radius with a conversion efficiency of 60% (I know optimum is 80% but this is homemade after all). I'm kind of looking for a good guide for making flywheel devices along with any advice people might have.

gniticxe

28-12-2005, 22:22

Hi,
It sounds like you may have a cool project behind this, I'll help where I can:

If you have a disc, and not mass on a ring, I = 1/2*M*R*R

I'm sure you know already, but Ek = 1/2*I*(rad/s)*(rad/s), instead of rpm

As far as a physical way to transfer the energy, how about using a commutated shaft and using an electro magnet to extend a piece of steel past the radius of the wheel (you'll need a spring to keep it from deploying early and also a balancing weight on the opposite side, depending on how large/fast this is). In less than a revolution, you'll have contact with the waiting rod.

Using an efficiency of 0.6 for energy transfer calculations is probably plenty conservative, especially since the disc may spin backwards after hitting the rod.

KenWittlief

29-12-2005, 10:13

my father use to work at a factory that had big presses. A belt spun a large flywheel (very large - hundreds of pounds) and the energy of the flywheel was transferred to the press (to stamp a piece of metal to an extact length).

Im afraid I dont know the mechanics of how it worked, but since it was a standard factory machine you should be able to look it up and learn the basics behind its operation.

mechanicalbrain

29-12-2005, 13:39

Thanks both. yeah I meant a disk with most mass on the outside. Thats an interesting idea about turning a flywheel to transfer to a electromagnet though I wonder if I guess it would work better then an electromagnet powered directly from a battery since the potential power can possibly be greater then that of the battery alone if I'm efficient. Yeah as to the machine press I'm not surprised, if you do the mathematics you realize flywheels can store massive amounts of energy. Actually the centripetal force on it is so great that they can explode if not balanced right (happens in the racing cars sometimes :ahh: ) I'm looking at carbon composite but I'm also looking at using a medium power motor to power it, hopefully I won't have to worry about it. If I were to use electromagnets would I want to repel the rod or attract it? I'm kind of unsure on how that part would work, this is starting to sound like a rail gun. :D

dlavery

29-12-2005, 14:51

What is the stroke length of the rod motion you are trying to achieve (as an absolute length, and a percentage of the flywheel diameter)? Depending upon the desired output, there are a few neat little examples that I may be able to point you toward.

-dave

gniticxe

29-12-2005, 17:05

If dlavery has some examples for you, I'd go with them. But from what you said about the electromagnet, I don't think that I was clear in explaining the idea.

A battery is connected to the flywheel via a commutated shaft and brushes. Once the disc is up to speed, a switch is thrown to allow power to flow from the battery, through the commutator, and through an electromagnet. The magnetic field then pulls a ferromagnetic rod out past the outside of the disc. The rod you want to transfer the energy to is positioned so that the ferromagnetic rod will impact it.

Because of the centripetal force you spoke of, a spring will need to be attached to the disc and the rod to prevent it from extending prematurely.

Be careful in using this especially if you're turning it at speeds where the stress on the materials is close to their yield strength! Is your “medium size” motor a hobby or industrial “medium” ie 0.25hp or 100hp?

Elgin Clock

29-12-2005, 18:00

Hmm....

I think I know what you mean. maybe.

Would a modified version of a Geneva Wheel (http://www.cabaret.co.uk/education/geneva.htm) work?

I could be way off base in this I know, if I am, I'm sorry.

Rickertsen2

29-12-2005, 18:40

What is this device intended to do? Could you give us some more specifics?

sciguy125

29-12-2005, 19:16

This is sort of along the same lines as gniticxe's idea, but what about making the disk with teeth, something like a saw blade. Then, you push the rod toward the disk and it catches on the teeth.

Or, if your rod has relatively low inertia (and friction), you could use a friction disk to connect the flywheel to your rod assembly. Same idea as the clutch on a car, but with a thrusting rod of death.

mechanicalbrain

30-12-2005, 14:15

Rickertsen2

30-12-2005, 14:38

greencactus3

30-12-2005, 15:59

What I want to do is take a 2' bar and move it 1' forward with a ton of force. Yeah I'm looking at using a motor with roughly 100 rpm. My goal it to be able to puncture 1/10" to 1/8" steel. Right now its part of science fair project for centripetal motion but I also am doing this to really learn about flywheels... oh and eventually im going to apply it to a Battlebot :D
100rpm isnt enough info. my cellphone vibration motor can be geared down to 100 rpm and my truck can also run its wheels at 100rpm.
and 2 feet bar to move it 1 foot?
the lighter the "ram", the more speed it will gain. but well. less mass.
will it just be a bar? or sharpened?
andas for going into battlebots. i would just use the flywheel itself as the weapon rather than add extra stuff which will be less efficient.

nother idea... with not exactly a disk but maybe a disk with large "bars" coming out as the flywheel.. and then somthing moves the "ram" into contact with the flywheel bars. so the bars crash into the back of the ram and it flies forwards. the cool thing about this would be multiple shots.

or just friction on the edge of the flywheel touching the ram. i had a foam dartgun that worked on this priciple a long time ago. although it had 2 flywheels. on on each side of the dart.

KenWittlief

30-12-2005, 16:06

you need to start working out the physics equations for this: Force, energy, power...

if you want to puncture 1/8" steel the rod only needs to move about 1/4", right? The idea you are grasping at is getting all the energy from the flywheel into the 1/4" movement of the punch

work out the physics: a 12" movement with one ton of force the whole distance takes 48 times the energy as a 1/4" movement with one ton of force.

Rickertsen2

30-12-2005, 16:20

100rpm isnt enough info. my cellphone vibration motor can be geared down to 100 rpm and my truck can also run its wheels at 100rpm.

Why is 100 rpm not enough? depending on the design of the flywheel, 100rpm could be more than enough. How much energy would be contained in a planet spinning 100rpm!!!!!

Andrew Blair

30-12-2005, 19:22

Ah, I've got an idea! You could just use the HotWheels priciple. Have a spinning flywheel with some sort of grippy surface on it, even knurled slightly. Then have it spin a bit below 2" above a slide table. Then just slide the bar into it! Along the table. However, unless you like blood, you will want some sort of very strong stop behind the bar to prevent it from going AWOL.

greencactus3

30-12-2005, 21:05

Why is 100 rpm not enough? depending on the design of the flywheel, 100rpm could be more than enough. How much energy would be contained in a planet spinning 100rpm!!!!!
i never said its not enough revs. please reread my post. it says not enough info on the motor he wants to use.
that hotwheels principle is what i was attempting to explain too.

KenWittlief has a good point. other than the whole coolness of a rod flying 30feet to go through a sheet of metal, why do you need it to move so much?
and how about having a spike on the flywheel itslef and move that flywheel closer to the sheetmetal. and then itll more rip the sheet than just puncture (well not necessarily i know)

mechanicalbrain

31-12-2005, 01:26

First and foremost I'm doing a project to show the given force in centripetal motion, I wanted to develop this whole concept as a side project for future use, yes I do have reasons for wanting it to work this way. I think I have some general ideas for what I should look at doing and I have some ideas to play with.
So far my biggest worry is that to take the amount of force stored in a flywheel and transfer all at once would shred whatever I used... :(

Bill Beatty

31-12-2005, 11:30

Our company has been designing and building flywheel driven punching and shearing machines for more than 85 years. To produce a good punched hole you must have a die opposite the punch on the other side of the material. The force necessary to punch mild (C1020) steel is approximately 50,000 lbs per square inch of sheared area. Therefore to punch a 2 inch diameter hole through .125 thick steel will take 2 x 3.14 x .125 x 50,000 lbs. of force. This is the force in a blanking operation. Mild steel will fracture after approximately 33% break through. The energy to produce this hole will be the force X .125/3.

Hope this helps.

Mr. Bill

KenWittlief

31-12-2005, 13:59

First and foremost I'm doing a project to show the given force in centripetal motion...(

Im not sure the system you have been describing demonstrates the force in centripetal motion

we have been talking about converting the inertia in a flywheel into a linear motion

a good demonstration of centripetal motion is something we use to do on those little merry-go-round things they USE to put in playgrounds. You get about 8 people to hang off the edge, pushing their behinds out as far as possible. Then one person spins the ride around as fast as he can, then jumps onboard.

Now the fun part: everyone pulls themselves towards the center. You would not believe how fast the thing starts spinning, and how hard it is to hang on if you are the last person hanging onto the outer part of the railings.

They dont put these in playgrounds anymore (I wonder why?!)

DonRotolo

31-12-2005, 15:32

I need a little help with an idea of mine. I want to take a flywheel (10 pound disk with 10" diameter) and apply all of its stored energy into a single linear movement of a rod. ..... I really want to put quite a bit of force into a single thrust, and I really need to be able to spin this up to full potential fairly quickly.
Two issues here:

First, spinning it up quickly: The stronger the motor, the faster it spins up. Remember there's a maximum speed for your disk, maybe 10 or 20,000 RPM. Build a safety cage just in case it does blow up...

Second, extracting the energy: Some kind of a clutch. You need to move your rod ('punch') only 1/4"

A magnetic clutch (like used for a car's air conditioning compressor) will allow far too much slippage, even though it can transmit 7 or 8 Horsepower, not as a shock load.

Trying to mesh gears will only break the gears. Again, shock load it far too high.

How about how big punch presses do it? They take the flywheel energy and gear it down a zillion times, and the 'punch' rod moves only 1/4" every five to 10 seconds. When you're ready to extract the energy, just put a 1/8" piece of metal between the punch and die and WHAM (or more like Crrrunch). Need very strong gears though - wide teeth at the slow speeds, can be expen$ive. Belts and pulleys at the fast speeds should be OK, since you are trading torque for speed.

Oh, to make the demo really cool, you can set the "full" speed of the flywheel to some point where the energy extracted is nearly 100%, so the disk almost comes to a complete halt while punching the hole... Very dramatic.

Good luck

Don

greencactus3

01-01-2006, 13:17

Oh, to make the demo really cool, you can set the "full" speed of the flywheel to some point where the energy extracted is nearly 100%, so the disk almost comes to a complete halt while punching the hole... Very dramatic.

and very painful for those last few gears.

Gary Dillard

13-01-2006, 11:50

Hmmmm.... I see all the previous posts here were before kickoff.

Dave Lavery offered that he has some ideas.

Chef Bill's company has been doing this for years.

Too bad the only application for this (achieving linear motion from a flywheel) is to punch holes ;)

Jimbo5051

31-01-2006, 20:27