Happy medium between 2 and 4 stroke?

[87Octane]

That's going to be rpm limited by the speed of the piston head. That's a fair bit of mass to be accelerated quickly on its exhaust/intake stroke. I'd also worry about deposit buildup between the piston halves. Maybe they could add another oil ring to the piston base to control that, but the acceleration of the head is going to be harder to overcome.

One good thing is that "mini connecting rod" doesn't have much an angle on the piston.....so there will be less friction on the intake and exhaust stroke than there is on the power and compression strokes.

 

[mark20]

Main problem i see with it is that once you get into the higher rpm, the main piston conrod is going to stretch and make the clearance for the mini dome less, also might interfer with the down stroke causing a bad time.

Also don't think it'll be able to use multiple pistons in the same space as a regular piston engine (although i totally want to be wrong)

Although looks kewl, like with most things, its going to be expensive as he'll to make.

 

[87Octane]

Main problem i see with it is that once you get into the higher rpm, the main piston conrod is going to stretch and make the clearance for the mini dome less, also might interfer with the down stroke causing a bad time.

If you look at the above picture the main rod isn't under tension when it re-connects with the piston top (or "mini part of the piston" as some are calling it).

The main connecting rod which deals with both the power and compression cycles is only under a compressive force. (The mini-connecting rod dealing with the intake and exhaust is the rod that must handle stretching.)

 

[CrazyDan]

What about the duke engine? We have a running prototype video at least:

 

[mark20]

If you look at the above picture the main rod isn't under tension when it re-connects with the piston top (or "mini part of the piston" as some are calling it).

The main connecting rod which deals with both the power and compression cycles is only under a compressive force. (The mini-connecting rod dealing with the intake and exhaust is the rod that must handle stretching.)

Eh, thats on paper, id say that with heat expansion and proper rpm itll be close as the main piston has some weight and force on it (ie crankshaft and cam assembly), also, the piston will have some kinda timing issue as it rides on a cam with basically no pressure to bring it down on the intake stroke. (Top of cam)

 

[Will'smotobikes19]

Yes the duke, dan you can make a motorized bike sized one out of an AC compressor.
Check out this piston action its like a kaleidoscope. 2 stroke and 4 stroke is possible, the 4 stroke uses a cental cam that actuates the valves. There was a german video showing the head with valves but I can't find it.

 

[87Octane]

the piston will have some kinda timing issue as it rides on a cam with basically no pressure to bring it down on the intake stroke. (Top of cam)

There must be something not shown in either the video or picture that keeps the follower in contact with the D-cycle cam lobe.

 

[Will'smotobikes19]

Just to prove it's possible here is a 3 cylinder but he made it a 2 stroke

 

[Will'smotobikes19]

found a 4 stroke one

 

[87Octane]

With this engine having two connecting rods per piston:

1. One main connecting rod for the piston skirt with a normal rod to piston angle

2. One mini connecting rod for the piston top/ring pack with a very small rod to piston angle

I wonder if a longer than normal stroke could used for any given block deck height? That is could the engine get away with a much lower than normal connecting rod length to stroke ratio because of the extra stabilizing effect of the mini connecting rod? This because the mini connecting rod has such a small angle on the piston top/ring pack. If so, then the maximum displacement for any given deck height could be larger than what is normally seen.

Block deck height = piston pin height + connecting rod length + 1/2 stroke length.