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Neander Motors

Posted by jandp 
Re: Neander Motors
November 05, 2014 07:56AM
Hi Rolly,

Mike is right. Really, they probably shouldn't even use the term "harmonic balancer", some call it a "torsional damper" which seems much more accurate.

Just to make things confusing, however, there actually ARE such things as external balance masses on some engines. These devices are used when the size of the required crank counterweights are larger than the available volume of the crankcase or if there is insufficient clearance between the top of the counterweight and the bottom of the piston. In these cases a flywheel with a precisely calculated unbalance is bolted onto the engine, this unbalance causes the heavy spot to align with the position on the end most crank counterweight that requires more mass to balance the engine. The torsional damper pulley on the other end also has a similar unbalance manufactured into it which supplements the forces generated by the crank counterweights.

This is where some motor heads get to debating the relative advantages of "external" vs "internal" balance. Generally manufacturers prefer internal balance for a variety of reasons associated with mass production. External balance is usually found on some, but not all, big block V-8 engines and truck Diesels; engines where the reciprocating masses are high enough that there is insufficient room in the crankcase, and between the counterweight and piston, to permit internal balance.

It's an interesting experience to balance an externally balanced flywheel or damper. The print will specify the amount of unbalance in either inch-ounces or millimeter-kilograms and also give a very precise vector along which the force must be manifested. For example, 18.72 inch-ounces at 197.3 degrees. Realistically, there is no way to drop this flywheel into a balancer, spin it up and get this unbalance. For one thing, those kinds of forces tend to overwhelm the machine, the onboard electronics drop the accelerometer amplifier gain to compensate and accuracy falls with it. What I do is find some tapped holes already machined into the part at tightly specified places (or put in a couple myself on a milling machine). If I have two holes bracketing the line along which the part should be "light", I can take the angles of the holes and their radii to calculate exactly the masses that could be placed at these holes to produce exactly the desired amount of force; only it will be 180 degrees off. Since these weights almost perfectly cancel out the desired unbalance, whatever is left for the machine to read is the amount that must be removed to achieve ideal balance.....just another day at the shop, now. It's not much more than applied trig although with a CAD program you can draw out a vector diagram and measure the lengths of the rays to calculate the mass without having to know trig at all. But I'm wary of anyone doing a lot of balance who can't do the math for himself.

At one time externally balanced components were bolted to the crank and installed into the engine, the entire block was suspended with accelerometers stuck on with magnets (and oil pan not installed). The engine could be spun with an electric motor and the crankshaft could be balanced by drilling the exposed crank counterweights. This assembly balance gives a very good result if done properly. Most modern engines rely on balancing the crank, flywheel and damper independently but so accurately that the worst case stack-up of forces is still tolerable. This is cheaper and easier to manufacture in the long run. It's also easier on guys rebuilding an engine. If you replace the crank on an externally balanced engine, there is no guarantee that the combination of old damper and flywheel mounted onto the new crank will be balanced correctly.

OK, probably drifted a bit off topic, but it IS an engine forum.

Ken
Re: Neander Motors
November 12, 2014 12:51PM
The concepts of zero compression and clearance were bought up earlier.

"The Unaflow Steam Engine", 1922 printing


Page 37

Just thought I'd point out some historical antecedents.

Ken



Edited 1 time(s). Last edit at 11/12/2014 05:10PM by frustrated.


Re: Neander Motors
November 12, 2014 06:04PM
The problem with zero clearance - zero compression, as I see it for a unaflow, zero compression would require an exhaust valve in the cylinder head to vent the residual steam out of. Thus the engine would revert to a counterflow configuration.

To effectively gain zero clearance re-compression is to initial pressure, -p1. That or exhaust at p2 is vented while the piston would otherwise be re-compressing.

Re-compressing the residual steam from p2 back to p1 is a reversible process. (theoretically) There is no energy loss as one could re-expand the residual steam back to p2 where it started. So the re-compression is not an energy loss in and of itself. Clearance space is a loss however even considering re-compression back to p1.

This loss is in the loss of efficiency due to a lower expansion ratio just because the clearance space is there. A more modern engine running with initial pressures upward from 1,000 psia needs a higher expansion ratio than is easily obtained with an engine using clearance.

Now the re-compression process is reversible but the clearance space needed for it is a tax on efficiency. So get rid of the clearance space by re-compressing back into the steam port. The steam at p1 will just be turned around and head back into the cylinder along with the fresh charge but now without the clearance space our expansion ratio is higher.

The advantage of doing it with a unaflow engine vs. a counterflow is that for the same initial conditions and efficiency a unaflow is smaller. A counterflow has to expand further. It expands to near exhaust manifold pressure while a unaflow expands to greater than exhaust manifold pressure otherwise the unaflow could not move the exhaust out and would try to re-compress the whole thing. That's the cycle, but of course a counterflow could open it's exhaust well above manifold pressure and mimic the unaflow, but then it may as well have occulting exhaust ports like a unaflow anyway.


Best,

Bill G.
Re: Neander Motors
November 12, 2014 06:57PM
In figuring a full Rankine cycle including clearance and compression there is no difference between in engine types. It is only valve event timing. The engine cylinder wall may of course exhibit different temperature that is not part of the cycle.

What I am trying to do is maintain an effective zero clearance by dynamically controlling valve timing. It is a counter flow engine which seams the only practical way of varying exhaust timing. The concept is a full expansion with compression back to inlet pressure. Turbine efficiency as described above. That is the ideal. One must consider practical limits. A pressure difference is need for steam to flow. In theory it is doable by varying the clearance, cutoff and clearance.

Andy
Re: Neander Motors
November 12, 2014 09:53PM
Hi Bill,

There is one way to approach zero compression and not exhaust through the head. That is by using a special class of uniflow engine equipped with a valve in the piston itself. Said valve routes steam through the piston and down to the uniflow port. Since the flow is in the right direction, it's a uniflow....don't take my word, Dr. Stumpf said so hisself!

After carefully reading through what Stumpf said, the physics seem to be about what common sense would suggest, absolutely zero compression or clearance is the most efficient possible design but his math would suggest the laws of diminishing returns are kicking in as you reach zero.

Regards,

Ken

The Una-Flow Steam-Engine, 1912 printing.


Re: Neander Motors
November 13, 2014 04:35AM
Atkinson steam lorries used this valve in piston uniflow idea in the 1920's. If I can find a drawing I'll post it.

Mike
Re: Neander Motors
April 18, 2015 12:32PM
I am not sure that the Lanchester crank mechanism can be used to cancel piston sideforce, unless there are two equal loads on the engine.
Given the requirement of lash in the gears connecting the crankshafts, are you then going to provide some sort of sideways floating smallend connexion?

If not, what is the Lanchester crank (as per Neander) except a primary balance shaft with a lot of unnecessary moving parts?

If on the other hand if it is an opposed engine, as Jim defines it, then like Ken says it would obsolete the two double-speed secondary balance shafts.
Re: Neander Motors
April 18, 2015 06:50PM
Sidrug,
Why the question, does no one read the books? The early Lanchester was an 180° opposed two cylinder engine. It proves the Sir Isaac Newton was right, "Equal masses going in exactly opposite motion at the same time cancel each other out." The F.M. submarine and railroad engines too.
There is or was a great book: "Unusual engines" by Setright, read it.

It does cancel because it uses two connecting rods per piston, each developing opposite side thrust.
What would be of interest is if he used the desaxe principal too.

Lanchester used herringbone gears, at least the one I examined had them. Or maybe they were helical gears installed in opposition.
Andre Citroen didn't invent them, he developed the way to make them commercially.
Jim



Edited 1 time(s). Last edit at 04/18/2015 06:56PM by Jim Crank.
Re: Neander Motors
April 19, 2015 06:19AM
My meager knowledge about gears leads me to think that they usually have to have some lash, due to thermal expansion and manufacturing tolerance. Given some lash, all the force is through one of the two rods, its bearings and so on - it is the ones associated with the shaft that power is taken from. Are you implying that the Lanchester engine have lashless gears? Or else, what is the mechanism that cancels the lash?

The thread title is Neander Motors, and as far as I can see the Neander engines are not opposed, so I'm puzzled; why are they using the double crank? Does it do anything that a primary balance shaft would not do - with less friction, complexity and cost?
Re: Neander Motors
April 19, 2015 11:37AM
The Neander engine is balanced for primary shaking forces but not for secondary.

Lanchester crank setups can be for opposed or unopposed engines.

The idea behind the Lanchester crank was to balance primary forces, the counter rotating cranks do this even in a single cylinder engine.

Lanchester dropped the Lanchester crank when he invented the balance shaft. The only advantage of the dual crank setup is that it neutralizes side forces on the piston. There will be a bit of lash in such gears but it is usually acceptable except in ultra-precise applications such as CNC positioning.

The down sides of the Lanchester crank are many. Cranks built to modern tolerances of +/- 5 microns are expensive and nitpicking to manufacture, one per engine is hassle and cost enough. Another problem is the use of two connecting rods. The typical modern engine has a healthy stroke in relation to bore and the rod is relatively short in relation to stroke; this makes for a very compact machine. When the piston travels to and from TDC there is a point where the distance between the rod and the cylinder wall is at its minimum, this sets the minimum bore diameter for an engine with that rod to stroke ratio. The two Lanchester crankpins are significantly displaced from the piston center, the bore must be much greater in relation to the rod/stroke ration, limiting your design choices and making the engine very oversquare by necessity rather than choice. The same rod placement causes the cranks to be displaced quite a ways side ways off the cylinder centerline, further increasing the amount of oversquare. Another thing to consider is that the rods will never achieve a vertical position, even at TDC and BDC they will be significantly inclined. Such inclination reduces the compession load on the rods and adds a shear component instead. Given my drathers, I would prefer compressive to shear loads.

The Neander engine simplifies the crank construction by using overhung cranks, just like a Stanley. Overhung cranks have a problem in that the load is not even shared by bearings on each side of the piston. The nearest bearing is absorbing much more of the load from a piston than is the one further away, so a more massive bearing is needed. The overhung cranks also mean that power must be taken off from the center, again like a Stanley, not the most convenient place to extract power.

I dunno, I tend to view this engine (and any having dual parallel cranks) as being different so as to attract buyers with its novelty; I really don't see any advantages over the traditional single crank and rod design. The bottom end is going to be big, heavy and expensive; for a given bore the stroke will have to be short regardless of the designers wishes. I think it is easy to see why Lanchester dropped the crank and invented the balance shaft and torsion damper.

Regards,

Ken
Re: Neander Motors
April 19, 2015 03:31PM
Ken

I learn more from your posts than any others on this forum. This is the best education anyone could ask for. Thank you for your time.

Kerry
Re: Neander Motors
April 21, 2015 11:57AM
Hi Kerry,

While I don't agree with your conclusion, I sincerely appreciate the sentiment. Thanks very much.

Ken
Re: Neander Motors
April 26, 2015 12:50PM
Ken posted:

After carefully reading through what Stumpf said, the physics seem to be about what common sense would suggest, absolutely zero compression or clearance is the most efficient possible design but his math would suggest the laws of diminishing returns are kicking in as you reach zero.

Stumpf is absolutely right. (Except I think it is zero compression and clearance) But there is one problem. He is considering ideal cycles. It wasn't really anything new as far as thermodynamics. The most efficient ideal cycle is full expansion with zero comprrssion. And for a piston engine that would be unthrottled.

Designing a variable power output engine is another layer of problem. One needs to vary the power and that is the hard part.

I have shown that a partial expansion idealy can be throttled between full pressure to the point of a full expansion cycle with little change in efficiency. But a full expansion from full presume would be more efficient.

The most efficient engine would take steam at boiler pressure and fully expand it. That is the most efficiency is a full expansion cycle from boiler pressure.

A turbine can be flow throttled so it is always running a full expansion cycke. A throttled piston engine is different. Throttling a piston engine reduces the steam pressure in the cylander. The efficiency is primarily a function of expansions. However over expanding means part of the stroke is taking shafts work to continue the stroke. I simular to a compresser. Instead of steam exiting, flowing out of the cylander. when the exhaust opens it first flows into the cylander and then must be pumped out by the piston exhaust stroke.

It is the nature of the positive displacement engine. The main reason power generation plants went to turbine power. Normally a positive displacement (piston) engine can not always run a full expansion cycle.

Clearance is normally a loss in a piston engine. The high compression uniflow engine greatly reduces clearance loss. But does little to solve getting high efficiency over a wide power range. You can run full expansion with compression eliminating clearance getting near ideal efficiency. But as soon as you make it variable power you have to reduce the expansion to have throttling room. Stumpf work doesn't consider how to run constant full expansion over a wide power range.

A steam engine utilizing compression to eliminate clearance loss can run, close to as pritical, a full expansion cycle. The problem is how to vary the power while doing so.

Jerry did some great work on analyzing the compression Rankin cycle. It a great read but you have to realize he uses the turm cutoff in a non-standard way.

In Jerry's paper he explains that the steam at cutoff is made up of two parts. The residule or recycled steam and admitted steam. The residule part is the compressed steam. The steam in the cylander when the exhaust closes. Ignoring specific engines it ideally doesn't matter wether the engine is a counter flow or uniflow. Both are capable of variable exhaust timmings. The idle compression cycle simple expels steam for some part of the stroke an compresses for the rest. The exhaust can open before the end of the stroke in a counter flow engine. Ignoring heat flow in the engines as the ideal cycle does only considering the working fluid the analysis is the same.

What such an analysis shows is that an engines power can be controlled by varying the ratio of residual and fresh steam going through the cycle. If we can vary the clearance the residual part can be varied and less admitted steam is in the full expansion cycle. The shafts power comes from the admitted steam going through the cycle. The residule or recycled steam work is a net zero output. The compression work is ideally equal to its output work part. A variable clearance mechanism can with corrousponding valve timmings maintain a full expansion cycle with a variable amount of fresh steam going through the cycle broducing a corosponding amount of work proportional to the admitted steam.

That is the engine concept I am trying to design. Many ways to do so. Varying the displacement can vary the clearance and give an increased power range keeping a constant expansion ratio. Opposed piston engines can achieve this by varinag the phasing between the crank shafts. A warble plate can also a compliance the requirement of varinag displacement and clearance. The multi crank opposed piston engine wold have gear slop. The wobble plate engine doesn't have gear slop problems. Torque may be a problem. But the can be vary compact. A double oposed piston wobble plate engine maintains perfect balance.

At low speed you need longer cutoff for smooth running and overlapped cutoff for starting from a dead stop.

Stumpf is a great read and perfectly right as far as it goes. But does not address variable power required for automobile use were we have an arodynamic cube power requirement. 20 to 60 MPH is a 27:1 power range. Modern car designs cheat the arodynamic power laws. But only by shifting the arodynamic drag. There is no free lunch in the laws of physics.

In Stumpf's book there is a comparison between his uniflow and a Corliss engine. That comparison shows the effect of high compression. Otherwise there is not that much differance. The increased temperature of the residual compressrx steam is quite apparent in that chart. Otherwise the the charts are very close. The Coriless shows a simular temperature increass only for a much shorter compression.
Re: Neander Motors
April 26, 2015 01:07PM
Ken posted:

After carefully reading through what Stumpf said, the physics seem to be about what common sense would suggest, absolutely zero compression or clearance is the most efficient possible design but his math would suggest the laws of diminishing returns are kicking in as you reach zero.

Stumpf is absolutely right. (Except I think it is zero compression and clearance) But there is one problem. He is considering ideal cycles. It wasn't really anything new as far as thermodynamics. The most efficient ideal cycle is full expansion with zero comprrssion. And for a piston engine that would be unthrottled.

Designing a variable power output engine is another layer of problem. One needs to vary the power and that is the hard part.

I have shown that a partial expansion idealy can be throttled between full pressure to the point of a full expansion cycle with little change in efficiency. But a full expansion from full presume would be more efficient.

The most efficient engine would take steam at boiler pressure and fully expand it. That is the most efficiency is a full expansion cycle from boiler pressure.

A turbine can be flow throttled so it is always running a full expansion cycke. A throttled piston engine is different. Throttling a piston engine reduces the steam pressure in the cylander. The efficiency is primarily a function of expansions. However over expanding means part of the stroke is taking shafts work to continue the stroke. I simular to a compresser. Instead of steam exiting, flowing out of the cylander. when the exhaust opens it first flows into the cylander and then must be pumped out by the piston exhaust stroke.

It is the nature of the positive displacement engine. The main reason power generation plants went to turbine power. Normally a positive displacement (piston) engine can not always run a full expansion cycle.

Clearance is normally a loss in a piston engine. The high compression uniflow engine greatly reduces clearance loss. But does little to solve getting high efficiency over a wide power range. You can run full expansion with compression eliminating clearance getting near ideal efficiency. But as soon as you make it variable power you have to reduce the expansion to have throttling room. Stumpf work doesn't consider how to run constant full expansion over a wide power range.

A steam engine utilizing compression to eliminate clearance loss can run, close to as pritical, a full expansion cycle. The problem is how to vary the power while doing so.

Jerry did some great work on analyzing the compression Rankin cycle. It a great read but you have to realize he uses the turm cutoff in a non-standard way.

In Jerry's paper he explains that the steam at cutoff is made up of two parts. The residule or recycled steam and admitted steam. The residule part is the compressed steam. The steam in the cylander when the exhaust closes. Ignoring specific engines it ideally doesn't matter wether the engine is a counter flow or uniflow. Both are capable of variable exhaust timmings. The idle compression cycle simple expels steam for some part of the stroke an compresses for the rest. The exhaust can open before the end of the stroke in a counter flow engine. Ignoring heat flow in the engines as the ideal cycle does only considering the working fluid the analysis is the same.

What such an analysis shows is that an engines power can be controlled by varying the ratio of residual and fresh steam going through the cycle. If we can vary the clearance the residual part can be varied and less admitted steam is in the full expansion cycle. The shafts power comes from the admitted steam going through the cycle. The residule or recycled steam work is a net zero output. The compression work is ideally equal to its output work part. A variable clearance mechanism can with corrousponding valve timmings maintain a full expansion cycle with a variable amount of fresh steam going through the cycle broducing a corosponding amount of work proportional to the admitted steam.

That is the engine concept I am trying to design. Many ways to do so. Varying the displacement can vary the clearance and give an increased power range keeping a constant expansion ratio. Opposed piston engines can achieve this by varinag the phasing between the crank shafts. A warble plate can also a compliance the requirement of varinag displacement and clearance. The multi crank opposed piston engine wold have gear slop. The wobble plate engine doesn't have gear slop problems. Torque may be a problem. But the can be vary compact. A double oposed piston wobble plate engine maintains perfect balance.

At low speed you need longer cutoff for smooth running and overlapped cutoff for starting from a dead stop.

Stumpf is a great read and perfectly right as far as it goes. But does not address variable power required for automobile use were we have an arodynamic cube power requirement. 20 to 60 MPH is a 27:1 power range. Modern car designs cheat the arodynamic power laws. But only by shifting the arodynamic drag. There is no free lunch in the laws of physics.

In Stumpf's book there is a comparison between his uniflow and a Corliss engine. That comparison shows the effect of high compression. Otherwise there is not that much differance. The increased temperature of the residual compressrx steam is quite apparent in that chart. Otherwise the the charts are very close. The Coriless shows a simular temperature increass only for a much shorter compression duration.

It is not so much the uniflow exhaust as the compression eliminating clearance loss making the uniflow engine efficient. You can see the compression temperature increase above the inlet temperature in those temperature charts. I do wonder why the temperature drops so quickly on admission opening. Why do we not see some temperature effect on the mixing. Me static analysis shows the should be a higher temperature at cutoff then the inlet steam temperature. What happened to that residual steam heat? The Stumpf book shows a short cutoff uniflow engine. The compression temperature is significantly greater then the inlet fresh steam temperature yet the temp almost immediately drops to inlet temperature on opening.

Anyway Stumpf didn'the analyze an engine over a significant power range.

Andy
Re: Neander Motors
April 27, 2015 09:50AM
Andy: Where was the temp sensor, and how fast was that engine?
Re: Neander Motors
April 27, 2015 04:09PM
I do not remember if it stated the RPM of the engines. You can find the books on google.

The only explanation for the temperature action on inlet opening, I can think of right off, is over compression. If the compression temperature was significantly higher then the inlet. Over compression would cause an initial outflow mixing with.steam chest steam. In stable running state that would have a steam chest mix that would be stable. It might be possible that the over compression steam and heat is transfered to the steam chest mostly. If over compression caused some part of that compression temperature it wouldn't increase the inlet temperature as upon expansion to equilize pressure most of that heat would go into that expansion back to inlet pressure.

My cycle calculator figured the mix of compressed steam and inlet steam by the mass and enthalpy sums, calculating the state point at inlet pressure and enthalpy.

Anyway my calculations were not programed to handle over compression above inlet pressure. Just the opsite. Lower pressure could be handled by figuring it being compressed in the cylinder as part of the mixing process. It could be a constant enthalpy, entropy mix. A 0 to 1 determined the relation from totally an isentropy process to totally isenthalp or any combined mix.

Andy
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