Elastic piston 5

[globi5]

I heard that Ford was working on elastic pistons at some point, but couldn't find any information online. Does anyone know more about this? What was it exactly and what were the results?
(There's supposed to be an elastic connection between the piston crown and the actual piston.)

Advantages:
* You can increase the compression ratio without increasing peak pressure. At peak pressure some of the heat energy (pV) would be transfered into spring energy which would then transfered back again at a lower pressure.
* Torque should go up, because pressure is reduced at TDC, but increased at a larger crank angle.

Disadvantages:
* The forces are tremendous so it might only work with smaller pistons (small diameter pistons).
* Material fatigue could be an issue.
* The mass and the complexity of the piston would increase.

 

[SomptingGuy]

Constant-volume combustion is MUCH favorable to constant-pressure combustion, from both a power output AND cycle efficiency standpoint!!

Agreed. But isn't this the opposite to the flexible-piston crew? They suggest that constant pressure combustion somehow reduces thermal losses. I scanned your website but couldn't find your 'big idea'. Care to disclose it here? It is patented after all.

 

[globi5]

Not quite on topic, but since linkage has also been mentioned I came across this buckling connecting rod engine (Picture 301):

http://www.technolab.org/Hako/Katalog-e/Section1.htm1

Brief description:

http://www.vegburner.co.uk/engines.htm

The point here is that if you can keep the piston longer at TDC, you can delay the ignition point (and therefore reduce pressure before crank reaches TDC) and complete combustion can be achieved before piston leaves TDC (which leads to increased peak pressure at the same compression ratio). In addition, since the piston spends more time at TDC it should be an advantage in expelling exhaust gases. Finally, the extra linkage reduces the side-forces on the piston.
The disadvantage is obviously more moving parts, more mass, larger engine and the maximum piston speed is also higher and if added together probably offset any merits that this concept could produce. (Note: this engine concept wouldn't have any advantage at all, if combustion was much faster (HCCI engine)).

 

[Tmoose]

Cool mechanical stuff is, well, cool, but part throttle engine efficiency seems to lie beyond the hardware, even imaginative hardware, or fun-to-compare published specs.

The impressive 30-ish highway gas mileage of late model V-8 2WD sedans and Corvettes was earned largely with steep rear gears, and strict fuel and ignition management (controlled by a CPU applying rules developed with hard work, and many R&D bucks financed by those of us who bought a heap of the less efficient cars). Put headers, a Holley carb and premium street manifold, and a magneto ignition on one of them, and I suspect the highway mileage and throttle response and maybe even power would plummet.