Quote:
Originally Posted by Ecky
The answer(s) nobody brought up in this thread are "offset crankshaft" and "combustion speed". An offset crankshaft imbalances an engine (not great for very high RPM operation) but greatly reduces stresses on both the cylinder liners, and on the conrods, and it also repositions TDC to a non zero crank angle.
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Yes!
Offset is used and a lot has gone into keeping offset engines balanced.
While Obrist says/admits nothing of the sort, the Obrist Engine completely solves the vibration issue by having 2 counter rotating engines, joined by gears.
So any vibrational force has an exact, opposite, equal, canceling it out at any given time or point of rotation.
ie: A sum total of 'zero' vibration... (due to offset)
IF this has NOT in fact occurred to Obrist, it damn well should!
I think it's their little 'secret advantage' they're hoping 'no one will notice' or 'see'.
(I like the idea of a series PHEV Tesla btw. As the Bunny Hugger market is now saturated and regretting their choice; it's time IMHO. I hope Musk realizes that!)
Quote:
Originally Posted by Ecky
Modern combustion chambers aim to speed up combustion above all else. The faster combustion completes, the less of it needs to happen before the piston reaches TDC, and the less negative work, and less conrod stress, there is.
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Yes, but I think you're missing the point here:
Lets say you have the head off an engine and have turned one of the pistons to exactly TDC.
Pushing down on the piston (by hand) has exactly zero effect on rotating the cankshaft as there is zero 'horizontal' component to the applied force.
The ONLY way you'll get the piston to move down is by loosening the main crankshaft bearings.
Now take the cylinder/s off too and turn the piston and conrod 90 degrees.
Now pushing on them applies a force that is at 90 degrees to the crankshaft where your push applies maximum torque to it.
Another way of looking at it:
With the cylinder/s on: Turn the crank till the same piston is 1/3rd to halfway down.
Now your push on the piston easily turns the crank.
That is the issue the OP was trying to ameliorate:
Ideally he/we wants TDC to be when the crank's at 90 degrees to the conrod...
Linear piston generator anyone!?