4 cylinder tin can engine

[antidartan]

I have been thinking about making a four cylinder tin can engine , just for kicks. I have decided that the flywheel will have to be a bit heavier. What I am wondering is should I make two sets of pistons 180 gegrees from each other or 4 sets that are 90 degrees apart.

Thanks
Anti

[theropod]

Hey,

I would think the smoothest production of power would be with 90° timing.

This could complicate the crank. A 4 throw setup might be easiest, but requires more bearings and stuff.

I wish you well and wanna see 'er when you're done.

Take care.

[antidartan]

Are you really 7 years of the grid?

[theropod]

Why not an "In-Line" four or six or however many? Instead of the "V" make a hot and cold manifold set along a conduit for each side, just like an internal combustion system. The cool end could be a shallow water tank, or half-pipe (cup-up) with a slight tilt to use gravity to help circulation. The hot side might be a length of thick steel pipe, with holes for the displacer hot ends, and carrying heat by convection. If one were capable of a good long precise crank with equally precise walking beams, and rods, and etc...., why not an in-line 12, 14, 50???

At the power levels we are talking about, per a "single" walking beam, one might be able to employ spring sections to make a composite crank. RC (remote control) hobbist use such a system in some applications pushing pretty considerable power. Much more than even 50 walking beams could produce. Surely lighter springs could be used here. Just an idea.



K?

[Administrator]

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DB

[spinningmagnets]

There are so many options depending on what your goals and preferred compromises are.

If you want 4 power pistons...

Having a single-throw crankshaft means you must use a cylinder layout that resembles a 4-spoke wheel.

having a 2-throw crank means you must use a flat four layout similar to a VW bug engine.

Hmmm, perhaps with vertical cylinders to reduce power-piston side friction? Maybe also with horizontal flat-4 displacers, run by eccentrics on the two ends. And the flywheel acting as a fan, ducted to cool the inner ends of the displacer cylinders? (horizontal displacers can have tiny wheels, too)

If each power piston has its own throw, the cylinders can be splayed at any angle you want. Though if you desire high-RPM's, you must take care to avoid complex balancing problems.

Regardless of layout, I would recommend seriously considering a 3-cylinder due to the sinusoidal "bell-curve" of each power pulse. This means that during 180 degrees of crank rotation, the middle 2/3rds have the most power transfer due to the crank arm leverage being close to 90 degrees in relation to the con-rod.

Though there is nothing at all wrong with a 4-piston.

[supertankerm60a3]

Just a thought: If you go with the "horizontal" style and 90 deg separation then you could use a single throw to operate one cylinders power piston and the adjacent cylinders displacment piston. Giving you a total of only 4 crank throws.