LINEAR MOTION / ROTARY MOTION

I certainly am not an engineer but I am confident that you haven't given these folks much information. Have you ever looked at the design of an engine crank shaft?

A 6 inch stroke on a 24 inch flywheel?

Can you get us a diagram?

A few of the terms you will need to understand before you can do the calculations. Torque, lever arm, moment of inertia, angular acceleration, Work as a function of force and linear displacement, work as a function of torque and angular displacement.

Take a close look at how a piston is attached to a cam shaft. As rotation takes place the effective lever arm changes as a function of the angle relative to the shaft.

On a reciprocating engine the time it takes for the shaft to rotate 360 degrees is the same as it takes the piston to move from top dead center back to top dead center. Regardless of how you are powering your piston you are only doing effective work during the power stroke.

Depending on how far you are into electronics you will enjoy the similar trigonometric relationships that are inherent to mechanics and electronics.

Gavilan

Hi Gavilan,

I'm not sure how to get a drawing to this medium,

but I'm trying to design a small low pressure steam engine for a small paddle boat.

There is a small market for such "toys" up here in Canada.

I don't mean the the small steam engines my kids used to have, the ones you fire up with a candle, but something in the order of 5 HP.

regards

Jens

"Regardless of how you are powering your piston you are only doing effective work during the pwer stroke"? It sounds like this guy is talking about a steam engine as the flywheel is 24" dia. If this is the case and if it is a double acting engine then the power is obtained by both an upward stroke as well as the downward stroke! Spencer.

You should give us your diagram.

However you can use bellow formula to calculate Power (HP) and angular velocity:

P(HP)~Torque(lbs.ft)*Rotation Speed(rpm)/5252.

Torque~Force(lbs)*Radius(ft).

If your piston motion is up and down F~m*a~100(lbs)*32.17 ft/s²~3217 lbf

Therefore you must to define rotation speed.

http://en.wikipedia.org/wiki/Torque

Thanks for the fomulas

all the best

Jens

Jens,

Do a GOOGLE for steam engine clubs and associations.

There are hundreds of them and they will welcome you into their fold and teach you more about steam engines than you ever thought was possible. It is what I did when I was helping my Dad build a Steam Launch. We ended up buying a Kit and doing all the machine work ourselves. It worked! Dad trailered it around to various Steam Meets, and had a great time with it.

Where are you located on NC coast. I am a retired ME with a complete workshop for hobby work. Maybe we have something in common??

Hi,

I live in northern Ontario.

And you are in North Carolina

I don't know the distance, but it must be at least 2 days travel.

I'm 5 hours (by car) north of Niagra Falls in Canada.

In a small country town called Worthington.

Would have been nice to be a bit closer

Best regards

Jens

I am in New Bern, NC.

prbarry@suddenlink.net

When will the world change over to Metric system, which is such a friendly and easy to understand system rather than confusing with fractions and decimals throughout the calculations.....and eventually ending up in shapeless designs :-).

Hi Guest,

Probably never, but it doesn't matter to me.

I was born in a country which was and is metric.

I emigrated to Canada (1966) and I can work in both systems.

But I do agree with you, that the metric system makes calculations

much faster and easier. And it makes much more sense.

all the best

Jens

I don't think you need to be a mech engineer to solve most of this, it is introductory college physics. Try converting this to metric system and solving, then convert back for HP. RPMs? you do 5 strokes per second (=5 cycles per second), 60 seconds in a minute. The rotational lever arm is 3" around the center and force is 100 lbs= 300 in lb, or 25 ft lb, 5 times per second, or 125 ft lb/sec. There are 550 HP per ft lb/sec. The fly wheel represents a rotational inertia that must be overcome until you reach a constant angular velocity. Since there is some loss due to friction, at this point yuou will need to evaluate the angular deceleration between forcing cycles due to frictional losses. The forcing cycle will need to re-accelerate the flywheel to maintain the rotation.

Hi guest,

Thanks a million, I should have seen that myself.

I went through college, but I was never taught any thing like this,

but thanks you made it quite simple.

I'm an electronics communications/navaids and instrumentations guy.

best regards

Jens