Building a better crankshaft (crank and slider)

[paradisePhysicist]

Make the little circle a slot : same placement, same width but say a length of 3x, the diameter of the original. Angled, as measured at BDC(or TDC), at 45deg.

Works fine in 2d ; probably too messy in 3d, but might give you something to work off of.

Hmm, can you draw me a rough sketch, I'm not quite sure what the visualization of this is. Are you saying to cut a slot into the gear, put the conrod into the slot, or something else?

 

[hmmm27]

Something like...

The first one is normal, it's the one you have issue with. The second one uses a slot, not a circular hole, to hold the crankpin.

 

[Averagesupernova]

Something like...

View attachment 285613The first one is normal, it's the one you have issue with. The second one uses a slot, not a circular hole, to hold the crankpin.

What happens at the top of the stroke?

 

[hmmm27]

What happens at the top of the stroke?

Same as what happens at the bottom... except upside-down. 45deg before tdc/bdc, the pin switches from the inside end of the slot to the outside.

 

[paradisePhysicist]

Something like...

View attachment 285613The first one is normal, it's the one you have issue with. The second one uses a slot, not a circular hole, to hold the crankpin.

I will try running this in the simulation.

I tried this idea (post #21) into the sim, and it cannot work for linear input, no matter how many teeth are in the circular gear (the simulation is very forgiving).
https://grabcad.com/library/reciprocating-mechanism-1

I attempted to put post #44 into the sim but the instructions seem unclear, is the small gear anchored to the world space or supposed to slide around the big circle, I am not sure, I have a lot of questions about that drawing.

 

[hmmm27]

I will try running this in the simulation.

#55[edit: #52] * idea does rely on inertia ; if the piston-arm is comparatively too heavy, you'll still be stuck.

* so, how does one link to a specific post in a thread ?

 

[paradisePhysicist]

#55 * idea does rely on inertia ; if the piston-arm is comparatively too heavy, you'll still be stuck.

I tried post #52 it in the sim, it works if the friction is low, but if there is a decent amount of friction it won't work, gets stuck when the diagonal is in the outer region. Post #55 contains different concepts so idk which one you are referring to.

* so, how does one link to a specific post in a thread ?

You can use the quote button.

Also, I tried the idea I said was my favorite (post #38) and it sucks for linear input, back to the drawing board ig.

 

[hmmm27]

I tried post #52 it in the sim, it works if the friction is low, but if there is a decent amount of friction it won't work, gets stuck when the diagonal is in the outer region. Post #55 contains different concepts so idk which one you are referring to.

Sry, meant #52, not #55. post amended. Given length of slot was for an example, not a calculation.

 

[some bloke]

Hmm, based on this I tried to put two gears in the same spot in the simulation. Then a rod at then minimum location to gear 1, then a rod at 90° location to gear 2, both attached to the same piston. It will not work and how do I explain this... I used springs to give it some leeway incase the rotations and positions were not exactly precise, still didn't work, I think the reason is because when gear 2 reaches the maximum position, it wants the piston to go in reverse, but at the same time, gear 1 wants the piston to still go forward, therefore it can't rotate. I will draw a picture to make it clearer.
View attachment 285607
Actually I think I could have just used 1 gear for this actually, but in the simulation I used 2 gears stacked on top of each other.

I haven't tried your doodle yet but I will try that next.

Yes, this was similar to my first thought before I dismissed it for the same reasons!

The trick is finding a way to have 2 cranks which can be turned by a single con-rod. That's where my design came in, though I am struggling to find a way to make it on any online gear generators - none of them assume a gear is fixed and the rest rotate around it!

 

[paradisePhysicist]

Sry, meant #52, not #55. post amended. Given length of slot was for an example, not a calculation.

I will post gif of experiment, I don't think it will work at any length or configuration without assistance from rotational inertia (ie., a heavier gear or flywheel needs to be added.)

I am looking into the one cylinder locomotive, the only website I can find is this website, which says the diagram is wrong, so I haven't figured out how they built it yet. http://www.douglas-self.com/MUSEUM/LOCOLOCO/onecylinder/onecylinder.htm

Yes, this was similar to my first thought before I dismissed it for the same reasons! The trick is finding a way to have 2 cranks which can be turned by a single con-rod. That's where my design came in, though I am struggling to find a way to make it on any online gear generators - none of them assume a gear is fixed and the rest rotate around it!

Hmm can you edit your diagram because I'm a bit confused about it.

 

[some bloke]

I will post gif of experiment, I don't think it will work at any length or configuration without assistance from rotational inertia (ie., a heavier gear or flywheel needs to be added.)
View attachment 285646I am looking into the one cylinder locomotive, the only website I can find is this website, which says the diagram is wrong, so I haven't figured out how they built it yet. http://www.douglas-self.com/MUSEUM/LOCOLOCO/onecylinder/onecylinder.htm
Hmm can you edit your diagram because I'm a bit confused about it.

I think you have too long a slot on the gear there. I would have the slot at 45° from the radius, and significantly shorter than that!

The goal of the motion there is that when the crank stops turning from the forward motion, when the piston pulls back the connection slides along the slot and downwards, so that it is below the crankshaft axis and therefore will now pull the crank in the correct direction.

The issue there is that the crank will be turning & stopping throughout the cycle as the con rod stops driving it and instead slides through it.

I will try to come up with a clearer way to convey my idea, but it will probably involve making an animation to explain it as it's a bit hard to picture the way everything moves! This is an adaptation of a mechanism I designed years ago to create a long linear motion from rotary motion within a confined space. It effectively doubles the piston motion for the crank diameter, and also creates exact linear motion rather than rotary for the con rod. I'm adjusting it with an offset in the idea that it would create the dual crank effect I'm trying to come up with for you!

Can you explain which design you're trying to figure out on the link, as there are loads on there, and all of them seem to involve flywheels!

Can you also explain why a flywheel is not wanted if you are trying to create an engine which will turn continuously in one direction?

Ignore that, I re-read the thread and you're goal seems to be about creating a reversible cam & slider mechanism without relying on a flywheel. I wonder if this is one of those things which may prove mathematically impossible...

I'll look forward to trying to find out...

 

[gmax137]

Can you also explain why a flywheel is not wanted if you are trying to create an engine which will turn continuously in one direction?

I think everyone reading this thread would like to know this! Especially in light of this:

The issue there is that the crank will be turning & stopping throughout the cycle as the con rod stops driving it and instead slides through it.

That seems a fatal flaw for any useful slider crank mechanism.

 

[paradisePhysicist]

I think you have too long a slot on the gear there. I would have the slot at 45° from the radius, and significantly shorter than that!

What is 45° from the radius lol, a radius is a scalar with no angle.

The goal of the motion there is that when the crank stops turning from the forward motion, when the piston pulls back the connection slides along the slot and downwards, so that it is below the crankshaft axis and therefore will now pull the crank in the correct direction.

I will try another configuration of that but I don't think it will work.

The issue there is that the crank will be turning & stopping throughout the cycle as the con rod stops driving it and instead slides through it.

Yes, some efficiency will be lost with that as well.

I will try to come up with a clearer way to convey my idea, but it will probably involve making an animation to explain it as it's a bit hard to picture the way everything moves! This is an adaptation of a mechanism I designed years ago to create a long linear motion from rotary motion within a confined space. It effectively doubles the piston motion for the crank diameter, and also creates exact linear motion rather than rotary for the con rod. I'm adjusting it with an offset in the idea that it would create the dual crank effect I'm trying to come up with for you!

Ok cool. Looking forward to the animation but also in the meantime you could add more labels with the diagram, with the current diagram I'm not quite sure how to build it.

Can you explain which design you're trying to figure out on the link, as there are loads on there, and all of them seem to involve flywheels!

Oh the design that was suggested is the Neilson one-cylinder locomotive. The only problem is that seems to be the only website I've found of it online, and the book about it doesn't seem to exist.

Can you also explain why a flywheel is not wanted if you are trying to create an engine which will turn continuously in one direction?

Ignore that, I re-read the thread and you're goal seems to be about creating a reversible cam & slider mechanism without relying on a flywheel. I wonder if this is one of those things which may prove mathematically impossible...

Yes. I don't think it is mathematically impossible, but would be interesting to see some kind of mathematical theorem or axiom saying it is impossible.

I'll look forward to trying to find out...

Thanks.

I think everyone reading this thread would like to know this! Especially in light of this:

Flywheels reduce acceleration and require more force to move. Also would be nice to just have a device that converts linear to full rotational motion inherently.

That seems a fatal flaw for any useful slider crank mechanism.

True but if the slide is short enough maybe the efficiency lost is not so bad.

 

[hmmm27]

seems a fatal flaw for any useful slider crank mechanism.

Ball bearing in a tube crossing the crankshaft axis at the appropriate angle.

----------

Heheh, the actual(ish) solution is to use the concept in the DWFTTABCWHATEVER thread (but not the propeller implementation) to scoot a weight around the outside of the crankarm at twice the crank angular velocity,

Easy peasy.

 

[paradisePhysicist]

Ball bearing in a tube crossing the crankshaft axis at the appropriate angle.

Sort of a diagonal 3d angle or is the angle purely 2d?

Heheh, the actual(ish) solution is to use the concept in the DWFTTABCWHATEVER thread (but not the propeller implementation) to scoot a weight around the outside of the crankarm at twice the crank angular velocity,

Hmmm what thread is this? Also adding a weight seems to be a bit like a flywheel lol...

The issue there is that the crank will be turning & stopping throughout the cycle as the con rod stops driving it and instead slides through it.

I tested this in a new configuration as suggested it still locks up. The simulation is very forgiving so at first this isn't apparent, but if you test it by letting go of the throttle and only applying it periodically in bursts, then it will lock up at the 2 stagnant regions.

I think I can now define it as an axiom or more clear definition, an inherent linear-to-rotary mechanism can do full rotations without the use of momentum, a non-inherent linear-to-rotary mechanism must be boosted by momentum to do full rotations. Full rotations is kinda vague also cause you can just attach a little gear and get full rotations on the little gear, I think maybe the phrase "continuous rotations" is the ticket.

Anyway, as predicted, after looking at the graphs, the crank with the groove in it is somewhat less efficient, still does useful work though. The standard model rotates for about 53 seconds the crank with groove rotates for only 48 seconds when both start with the same velocity. Also the graph curves are not as smooth.

 

[gmax137]

Flywheels reduce acceleration and require more force to move. Also would be nice to just have a device that converts linear to full rotational motion inherently.

OK.

I think you always have some flywheel effect: the crankpin and the big end bearing are orbiting the crank centerline, plus there has to be a connection between the crank and the crankpin. This may not "look" like a flywheel but there will be some rotational inertia. How much is needed to get the crank to rotate past the top & bottom dead centers? I concede, there is not always enough without a flywheel (eg, the gas model airplane engines won't run unless the propeller is on the shaft).

 

[hmmm27]

Sort of a diagonal 3d angle or is the angle purely 2d?

2d : at two points in a full crank-rotation, the bb rolls to the other side, providing weight to push the crank rotationally.

[note: the next bit of the conversation regards a different mechanism]

Hmmm what thread is this?

Something about an unpowered vehicle moving faster straight downwind than the wind itself. Unintuitive... and nifty.

Here's the relevant vid.

Using that as a reference, imagine two concentric circles: a static one on the outside, a rotating one on the inside, with a little go-buggy in-between, whizzing around (exactly)twice as fast as the inside circle : for each one revolution of the circle, the go-buggy completes two revolutions.

Also adding a weight seems to be a bit like a flywheel lol...

Like everything else in the system which has a rotational component, it acts as a flywheel. Which has nothing to do with how it gets the crank through both tdc and bdc.

Basically, just like the ball bearing rolls over to the other side to add its weight at the right placement to push the crank through both tdc and bdc, the go-buggy manages to be in the right place at the right time twice during a crank revolution.

I think I can now define it as an axiom or more clear definition, an inherent linear-to-rotary mechanism can do full rotations without the use of momentum, a non-inherent linear-to-rotary mechanism must be boosted by momentum to do full rotations. Full rotations is kinda vague also cause you can just attach a little gear and get full rotations on the little gear, I think maybe the phrase "continuous rotations" is the ticket.

And you mean what by "inherent" and "non-inherent" ?

 

[paradisePhysicist]

2d : at two points in a full crank-rotation, the bb rolls to the other side, providing weight to push the crank rotationally.

Hmm I will try various configurations and see if it works, but I'm suspecting it will either help the device get past the 179 angle and hinder it getting past the 359 angle, or vice versa.

[note: the next bit of the conversation regards a different mechanism]

Something about an unpowered vehicle moving faster straight downwind than the wind itself. Unintuitive... and nifty.

Lol.

Here's the relevant vid.

Cool vid, seen it the other day. Didn't study it to 100% see how it works but I shall study this.

Using that as a reference, imagine two concentric circles: a static one on the outside, a rotating one on the inside, with a little go-buggy in-between, whizzing around (exactly)twice as fast as the inside circle : for each one revolution of the circle, the go-buggy completes two revolutions.

Like everything else in the system which has a rotational component, it acts as a flywheel. Which has nothing to do with how it gets the crank through both tdc and bdc.

Looking for non flywheel solutions but this idea does seem interesting for experimentations.

Basically, just like the ball bearing rolls over to the other side to add its weight at the right placement to push the crank through both tdc and bdc, the go-buggy manages to be in the right place at the right time twice during a crank revolution.

And you mean what by "inherent" and "non-inherent" ?

inherent means the system works without an external boost. A working inherent system gives continuous rotations even with heavy friction and no momentum boost. The flywheel acts kind of like a boost mechanism to get past the limitations of the system. An loose example is a car that goes 190 kph topspeed, does not go 200 inherently, but you can use a nitro boost to go to 200 kph.

 

[hmmm27]

Looking for non flywheel solutions

So, since it isn't actually a flywheel, beyond having a rotational component, like many other bits and pieces of the system like the crankshaft, crankarm, piston-rod, etc...

inherent means the system works without an external boost. A working inherent system gives continuous rotations even with heavy friction and no momentum boost. The flywheel acts kind of like a boost mechanism to get past the limitations of the system. An loose example is a car that goes 190 kph topspeed, does not go 200 inherently, but you can use a nitro boost to go to 200 kph.

Without rotational momentum, a basic system (piston->piston-rod->crank-arm->crankshaft) is never getting past tdc/bdc, regardless of how friction-free the bearings are.

 

[some bloke]

Here's a mechanism which I think would work. You could have the central oval cam (which doesn't rotate) rock back & forth to change direction.

I am imagining the piston to the right of the wheel, pushing the pin to the left. The pin interferes with the fixed cam, so cannot move past it. The pin is in a slider. The image is the 4 stages of half a stroke, and it behaves the same on the way back.

The idea is to have a mechanical movement where the first parts of the pistons stroke are converted into non-linear motion - in this case, the pin is deflected sideways by the central cam, and starts the wheel rotating anti-clockwise. At the start of each rotation, the pin slides along the cam and starts the wheel going in the correct direction.

If you're interested, this was inspired by the mechanism inside of a clicky pen, which converts repeated reciprocating motion to rotary in a similar way to what you are requesting - have a look at a transparent clicky pen and you'll see the mechanism spins as you click it!

 

[paradisePhysicist]

Here's a mechanism which I think would work. You could have the central oval cam (which doesn't rotate) rock back & forth to change direction.

View attachment 285697

I am imagining the piston to the right of the wheel, pushing the pin to the left. The pin interferes with the fixed cam, so cannot move past it. The pin is in a slider. The image is the 4 stages of half a stroke, and it behaves the same on the way back.

The idea is to have a mechanical movement where the first parts of the pistons stroke are converted into non-linear motion - in this case, the pin is deflected sideways by the central cam, and starts the wheel rotating anti-clockwise. At the start of each rotation, the pin slides along the cam and starts the wheel going in the correct direction.

I am still not understanding your diagram lol.

These are my questions on the first diagram also:

If you're interested, this was inspired by the mechanism inside of a clicky pen, which converts repeated reciprocating motion to rotary in a similar way to what you are requesting - have a look at a transparent clicky pen and you'll see the mechanism spins as you click it!

This implies that the concept is mathematically possible.

So, since it isn't actually a flywheel, beyond having a rotational component, like many other bits and pieces of the system like the crankshaft, crankarm, piston-rod, etc...Without rotational momentum, a basic system (piston->piston-rod->crank-arm->crankshaft) is never getting past tdc/bdc, regardless of how friction-free the bearings are.

There is another concept that proves it is mathematically possible without adding a flywheel type extra weight. While this contraption is not exactly ideal, with collisions on the walls at 90 degree angles, and not exactly 100% the same as a typical crank, but does imply it is mathematical possible.

 

[hmmm27]

What does Charlie Brown's shirt have to do with anything ?

 

[paradisePhysicist]

What does Charlie Brown's shirt have to do with anything ?

Lol it is a 2d overlay but that is the shape you put on a 3d cylinder to give 1 way rotations (you put a disk into the slot from the piston.)

 

[hmmm27]

Lol it is a 2d overlay but that is the shape you put on a 3d cylinder to give 1 way rotations (you put a disk into the slot from the piston.)

Ah, so now you're powering the piston from the crankshaft ? Or, a rotary motor connected to the zig-zag on a cylinder (or perhaps The cylinder), powering the piston through the zig-zag, thence to the crank, etc.

Were you traumatized by a flywheel as a child ?

 

[paradisePhysicist]

Ah, so now you're powering the piston from the crankshaft ? Or, a rotary motor connected to the zig-zag on a cylinder (or perhaps The cylinder), powering the piston through the zig-zag, thence to the crank, etc.

No, the piston is supposed to power the zig zag cylinder, but it could work the other way around.

Were you traumatized by a flywheel as a child ?

-_- No and let's keep the convo on physics... let's steer the convo away from talking about traumas...

 

[Dr.D]

No and let's keep the convo on physics... let's steer the convo away from talking about traumas...

Great! When does it start?

 

[jrmichler]

This thread was discussed in the Mentor forum, and the decision was made to allow it to continue.

There are many mechanisms for converting linear to rotational motion, some of which do not require flywheels. I'm not aware of any mechanism that can convert a linear motion with sinusoidal velocity to smooth rotational motion without rotational inertia (flywheel).

An earlier post linked to a mechanism consisting of a slot with two racks and a pair of half gears. That mechanism could convert linear to rotation motion without a flywheel, but has two fundamental shortcomings:

1) There is a point at each end of travel where neither gear is in contact with its rack.
2) Getting smooth rotational motion requires the rack to have infinite acceleration at each end of travel.

If a requirement is smooth (constant angular velocity) rotation output with a smooth (minimum peak acceleration) linear input, then a flywheel is necessary. If herky jerky input and/or output are acceptable, then there should be mechanisms that will work.

There is an old book available online and free that consists entirely of various mechanisms. Search 507 Mechanical Movements to find a copy. It's a good read for anybody who finds this thread interesting.

 

[paradisePhysicist]

This thread was discussed in the Mentor forum, and the decision was made to allow it to continue.

Thanks

There are many mechanisms for converting linear to rotational motion, some of which do not require flywheels. I'm not aware of any mechanism that can convert a linear motion with sinusoidal velocity to smooth rotational motion without rotational inertia (flywheel).

An earlier post linked to a mechanism consisting of a slot with two racks and a pair of half gears. That mechanism could convert linear to rotation motion without a flywheel, but has two fundamental shortcomings:

1) There is a point at each end of travel where neither gear is in contact with its rack.
2) Getting smooth rotational motion requires the rack to have infinite acceleration at each end of travel.

If a requirement is smooth (constant angular velocity) rotation output with a smooth (minimum peak acceleration) linear input, then a flywheel is necessary. If herky jerky input and/or output are acceptable, then there should be mechanisms that will work.

There is an old book available online and free that consists entirely of various mechanisms. Search 507 Mechanical Movements to find a copy. It's a good read for anybody who finds this thread interesting.

Yesterday I found a vid that overcomes 1) , haven't had time to test it in the sim yet but I think it can produce smooth or almost smooth rotational movement. The problem is that in order for it to be smooth it needs sawwave type input instead of sine wave.



I also tried to build another concept someone had, I put it in the simulation and my current implementation of it somewhat sucks, but it at least shows something like this maybe can be done.

 

[some bloke]

I am still not understanding your diagram lol.
View attachment 285700

These are my questions on the first diagram also:
View attachment 285704

I'll try to describe them better!

In the first one (the sequential images):

• Yes, it's a side view, not 3d
• That thing is a slot in which the connector can slide inwards and outwards along the radius of the crank. The circle inside is both where the con-rod would attach, and what interferes with the fixed oval cam inside.
• The arrows were just what was available in powerpoint, don't pay any heed to their 3dness!
• The piston does attach to the little circle, it is being pushed left & right.
• The big circle is the crank, so it rotate about its center.
• There's no piston pictured as it's simply pushing the little circle left and right, I didn't think it was needed to draw it! My mistake!

The second one (crank in a crank):

• 3d arrow is not relevant, the design is drawn in 2d!
• "Fixed Gear Around Crankshaft" means it is fixed to the engine casing and doesn't turn, and the crankshaft passes through it to reach the first crank (larger circle)
• The little circle is a gear which is fixed to the crank, and orbits around the fixed gear as the crank turns. It turns the secondary crank in the opposite direction, with a ratio of 1:1 (so it turns once backwards whilst the crank turns once forwards).
• "is it just to show where not to put the conrod..." that circle is the central axis of the second crank, which is attached to the first crank, so the secondary crank orbits the crankshaft whilst also cranking on its own.
• <Piston here> Yes, that's right. The piston connects to the small circle and pushes it around.
• "what is this rod for" - it was just visual to mark that the final conrod position is fixed to the secondary crank and not to the first.

One day I will animate this, and it will make more sense!

 

[paradisePhysicist]

I'll try to describe them better!

In the first one (the sequential images):

• Yes, it's a side view, not 3d
• That thing is a slot in which the connector can slide inwards and outwards along the radius of the crank. The circle inside is both where the con-rod would attach, and what interferes with the fixed oval cam inside.
• The arrows were just what was available in powerpoint, don't pay any heed to their 3dness!
• The piston does attach to the little circle, it is being pushed left & right.
• The big circle is the crank, so it rotate about its center.
• There's no piston pictured as it's simply pushing the little circle left and right, I didn't think it was needed to draw it! My mistake!

I guess I am confused about the elongated ellipsoid in the middle, what is its function? Is that the central oval cam you refer to that rocks back and forth? I do not see it rocking back and forth in the image, and I'm wondering how it is connected to the pin. In the first one also the center circle seems offset from the others, I am wondering if there is a significance for that.

The second one (crank in a crank):

• 3d arrow is not relevant, the design is drawn in 2d!
• "Fixed Gear Around Crankshaft" means it is fixed to the engine casing and doesn't turn, and the crankshaft passes through it to reach the first crank (larger circle)
• The little circle is a gear which is fixed to the crank, and orbits around the fixed gear as the crank turns. It turns the secondary crank in the opposite direction, with a ratio of 1:1 (so it turns once backwards whilst the crank turns once forwards).
• "is it just to show where not to put the conrod..." that circle is the central axis of the second crank, which is attached to the first crank, so the secondary crank orbits the crankshaft whilst also cranking on its own.
• <Piston here> Yes, that's right. The piston connects to the small circle and pushes it around.
• "what is this rod for" - it was just visual to mark that the final conrod position is fixed to the secondary crank and not to the first.

One day I will animate this, and it will make more sense!

Ok I think I have a clear blueprints of how to build this one now, one of these days if I get some energy if I will try to build an animation of it.

Well, there you go.

After 4 pages, and coming in with that specific problem, by now you should be able to tell whether charlie-browns-t-shirt, sliding-siding, or gearpunk-porno-123 meet your requirements or not, those being - if you'll pardon the assumption -

Create a mechanism to translate (reciprocal) linear motion to continuous rotational, without using rotational momentum in any manner.

Some_bloke's solution is the most mathematically sound method.

If I may be allowed a slightly different instantiation of the concept . . .

For reference draw vertical and horizontal axes, and a circle centered on their origin.

For the mechanism of the "second input", picture
- an ellipse, similarly centered, touching the reference-circle from the inside ;
- a tiny circle, resting on top of the ellipse, centered on the vertical axis : and
- a 6,371km radius circle underneath the big circle, not touching, centered along the vertical axis (or you may want to simply assume it's there)

Movement of the ellipse is rotation around its centerpoint ; movement of the small circle - forced against the top side of the ellipse by gravity - is to be restricted to up and down, only.

(tldr; same as some_bloke's except inside-out : the cam moves, the follower is fixed)

Sorry, M$-Paint plus a Trackpoint isn't a terribly good combination.

6,371km radius? Is that a typo, or what?

 

[some bloke]

I guess I am confused about the elongated ellipsoid in the middle, what is its function? Is that the central oval cam you refer to that rocks back and forth? I do not see it rocking back and forth in the image, and I'm wondering how it is connected to the pin. In the first one also the center circle seems offset from the others, I am wondering if there is a significance for that.

Firstly, the central circle being out of position in the first one is not relevant, that's a mistake!

So, the oval piece in the middle doesn't move - it's fixed to the engine casing, no rocking or anything, it's just there to get in the way of the pin.

The pin is where the piston's con-rod attaches. When the piston pushes it to the left, the pin slides inwards on the slot (towards the middle of the crank) and it knocks into the oval cam. The oval cam being angled means this causes the pin to be pushed upwards, and this gets the crank past its initial few degrees.

From there the crank operates as normal, pushing it around to the 180° mark. As it reaches the far point, the pin slides back outwards on the slot, allowing it to clear the oval cam.

Then the process repeats in the other direction (not pictured). The pin is pulled back to the right, it collides with the cam and moves downwards, rotates the crank past the ambiguous point where it could turn either way, and starts it rotating in the same direction.

 

[paradisePhysicist]

Firstly, the central circle being out of position in the first one is not relevant, that's a mistake!

View attachment 286355
So, the oval piece in the middle doesn't move - it's fixed to the engine casing, no rocking or anything, it's just there to get in the way of the pin.

The pin is where the piston's con-rod attaches. When the piston pushes it to the left, the pin slides inwards on the slot (towards the middle of the crank) and it knocks into the oval cam. The oval cam being angled means this causes the pin to be pushed upwards, and this gets the crank past its initial few degrees.

From there the crank operates as normal, pushing it around to the 180° mark. As it reaches the far point, the pin slides back outwards on the slot, allowing it to clear the oval cam.

Then the process repeats in the other direction (not pictured). The pin is pulled back to the right, it collides with the cam and moves downwards, rotates the crank past the ambiguous point where it could turn either way, and starts it rotating in the same direction.

this idea is bloody brilliant.
https://www.myinstants.com/search/?name=brilliant2

if i ever get rich from this contraption (or at least make a decent profit) i shall try to give u a reasonable reward. not trying to "general electric" people out of their fair share.

had this been invented 200 years ago, this may have revolutionized society, the steam industry, cars, everything.

 

[Baluncore]

A single cylinder engine cannot be dynamically balanced without a flywheel, so it will shake itself, whatever it is attached to, and you, to pieces. That is why we use multi-cylinder engines, they can be balanced. Happily, multi-cylinder also resolves the stationary problem at BDC and TDC.

Single cylinder steam engines were inefficient, so were rapidly replaced by compound engines having both a high and a low pressure cylinder. The most efficient steam-driven piston engines are tripple expansion engines.
https://en.wikipedia.org/wiki/Compound_steam_engine#Multiple-expansion_engines

had this been invented 200 years ago, this may have revolutionized society, the steam industry, cars, everything.

Don't kid yourself. You are so far behind, that you think you are first.
I repeat.

Before setting out to discover a better solution you need to understand the existing solutions. Replace the excitement of "uninformed independent re-discovery" with the excitement of "historical research" into the technology.

More than half of science and technology is the review of literature.

 

[jrmichler]

That's a very nice animation in Post #82, but it does not work. Keeping in mind that the goal is to convert linear motion to rotary motion without using rotational inertia (a flywheel), let's take a close look at the process.

Start with the system in this position:

The pin is bottomed in the slot. The piston decelerates to a near stop because the moment arm is very small. Small movement of the piston with large rotation means that the output torque decreases to near zero.

Next, look at the pin sliding outward in the slot:

Again, the piston slows almost to a stop. The output torque decreases to near zero. And what is moving the pin outward in the slot?

Next, at bottom dead center (BDC):

There is an instant where the pin is at the extreme tip of the elliptical cam. At that instant, the output torque is zero. Since the assumption is zero rotational inertia, the mechanism stops at this point. There is a similar, but not shown, effect at TDC.

Next, the pin is sliding outward as the piston moves away from the crankshaft:

The animation shows the piston at a dead stop while the pin slides outward, and does not show what is making the pin slide outward. With the piston at a dead stop, the output torque is zero, and the mechanism stops.

These types of mechanism can be analyzed by starting at a point, typically TDC, rotating the output shaft in small steps, and calculating the position of the piston at each step. Piston velocity and acceleration is calculated from the piston positions. Piston position, velocity, and acceleration is then plotted against output shaft position. Output torque is calculated from the ratio of piston velocity to crankshaft angular velocity.

Since you are comparing this to a conventional crankshaft with flywheel, you need to do the same analysis, using the same methodology, to a conventional piston with crankshaft and flywheel. Look closely at the peak piston acceleration (about 2000 G's), and the sizes of the wrist pin, connecting rod, and crankshaft. then consider the peak loads in your mechanism and the strength of the parts needed.

While this thread has been entertaining, it's time for the OP to do some actual analysis and less wishful thinking. The OP will do an analysis as indicated above, or this thread will be locked.

 

[paradisePhysicist]

Don't kid yourself. You are so far behind, that you think you are first.
I repeat.

Not me, but I think the user known as "some bloke" is the first to invent this. You may be right and maybe this was invented already, I'm not 100% sure.

Single cylinder steam engines were inefficient, so were rapidly replaced by compound engines having both a high and a low pressure cylinder. The most efficient steam-driven piston engines are triple expansion engines.

Early steam locomotives had a problem of getting stuck at BDC, then the locomotive would start to go in reverse, this invention would have revolutionized that. My comment about this potentially revolutionizing cars may have been hubris though.

More than half of science and technology is the review of literature

pbuk suggested looking into the Neilson steam locomotive, unfortunately the book about it seems to be missing. Maybe society needs to do a better job at preserving the literature?

https://openlibrary.org/books/OL14474327M/Neilson's_single_cylinder_locomotives.

That's a very nice animation in Post #82,

thankyou

but it does not work. Keeping in mind that the goal is to convert linear motion to rotary motion without using rotational inertia (a flywheel), let's take a close look at the process.

Start with the system in this position:
View attachment 286432
The pin is bottomed in the slot. The piston decelerates to a near stop because the moment arm is very small. Small movement of the piston with large rotation means that the output torque decreases to near zero.

Yes but this is a universal problem with all crankshafts not just this one, when near TDC or DBC its harder to create torque.

Next, look at the pin sliding outward in the slot:
View attachment 286433
Again, the piston slows almost to a stop. The output torque decreases to near zero. And what is moving the pin outward in the slot?

I stopped applying input to the piston, then it is being carried by inertia. Admittedly, not the best example to prove that this device works, could have uploaded a different test run with more friction and showing the action at BDC.

Next, at bottom dead center (BDC):
View attachment 286434
There is an instant where the pin is at the extreme tip of the elliptical cam. At that instant, the output torque is zero. Since the assumption is zero rotational inertia, the mechanism stops at this point. There is a similar, but not shown, effect at TDC.

That picture does not show the pin at the tip of the elliptical cam, but underneath the elliptical cam (ellipsoid). In this pic it is almost at TDC, when it is at TDC it will be underneath the ellipsoid.

Next, the pin is sliding outward as the piston moves away from the crankshaft:
View attachment 286435
The animation shows the piston at a dead stop while the pin slides outward, and does not show what is making the pin slide outward. With the piston at a dead stop, the output torque is zero, and the mechanism stops.

These types of mechanism can be analyzed by starting at a point, typically TDC, rotating the output shaft in small steps, and calculating the position of the piston at each step.

I performed that analysis as requested, the device works (depending on the friction inserted and the amount of power to the piston.)

Piston velocity and acceleration is calculated from the piston positions. Piston position, velocity, and acceleration is then plotted against output shaft position. Output torque is calculated from the ratio of piston velocity to crankshaft angular velocity.

Torque can only be calculated by force, momentum, mass of the piston, not velocity alone. A crankshaft made of styrofoam would have fast angular velocity but not much torque.

Since you are comparing this to a conventional crankshaft with flywheel, you need to do the same analysis, using the same methodology, to a conventional piston with crankshaft and flywheel. Look closely at the peak piston acceleration (about 2000 G's), and the sizes of the wrist pin, connecting rod, and crankshaft. then consider the peak loads in your mechanism and the strength of the parts needed.

I am not sure what the peak piston acceleration of a car engine is, but I am willing to consider my original comment that this could have revolutionized cars, may have been hubris. That being said, the device should in theory work, but maybe not as a car engine. A website on marine engines said 221 m/s/s which is 20x the acceleration of gravity.
http://marinediesels.info/Theory/piston_acceleration.htm

While this thread has been entertaining, it's time for the OP to do some actual analysis and less wishful thinking. The OP will do an analysis as indicated above, or this thread will be locked.

When I was analyzing this with a fine tooth comb, there was a brief moment I could see why you think it doesn't work. The reason why it works is because when at BDC when pushing the piston forwards it cannot decide to do a clockwise or counterclockwise rotation, but leading up to BDC it always chooses to do a clockwise rotation. Then when the piston retracts, it cannot decide either but the ellipsoid makes the decision for it.

that being said, when I increased the friction of the crank to 40nm it got stuck. But IRL it should work in theory if the parts are solid, well oiled and don't bend too much. How much it rotates is entirely dependent on friction and how much force is being applied to the piston. If there is too much friction it will get stuck and not rotate past the apex of the ellipsoid. This can be fixed by adjusting the ellipsoid angle more, reducing friction, or increasing power of the piston. Further optimizations could be done by experimenting with ellipsoid angles and slider lengths.

 

[Baluncore]

Early steam locomotives had a problem of getting stuck at BDC, then the locomotive would start to go in reverse, this invention would have revolutionized that.

That was not a problem. It is easy to rotate the flywheel through about 5 degrees over BDC or TDC since there is very little piston movement at that point in the cycle, and the wear in the bearings gives some freedom. Only in a new engine with tight bearings might it have been hard work to advance the phase by hand.

In single-cylinder steam engines there is little difference between BDC and TDC because steam pressure is applied alternately to both faces of the piston, in effect eliminating the dead point at BDC. I remember when starting and driving a steam traction engine in the late 1960s. It did not matter if the flywheel started and moved initially in the wrong direction, that just put it in a better position to start in the required direction. The direction was decided by the valve gear through a Stephenson linkage. If it stalled and did not start forwards, then flipping the valve drive linkage to reverse and then forwards again, always resolved the problem within a couple of seconds, and no one noticed the quickly-learned natural process.

Any single cylinder engine needs a flywheel, or a weighted crankshaft, simply to balance and smooth the power flow to the drive. Arguing that a flywheel is not needed, or can be eliminated, is pointless since we no longer use inefficient single cylinder steam engines, and the inertia of the driven load was sufficient to maintain rotation once things were moving.

 

[jrmichler]

Yes but this is a universal problem with all crankshafts not just this one, when near TDC or DBC its harder to create torque.

Which is the exact problem you are trying to solve. Any practical mechanism for converting linear to rotary motion without a flywheel must meet several requirements:

1) It must work with a significant friction load on the crankshaft.
2) It must work with a roughly constant input force. That's why I asked you to calculate the ratio of input force to output torque for a complete revolution, and compare to a conventional slider crank with flywheel.

You have not done so. Thread closed. If you want the thread reopened, PM me with the appropriate calculations.