Peter Fairbrother wrote:

Joe AutoDrill wrote:

Check This Out:

http://www.bath.ac.uk/~ccsshb/12cyl/

That's my new motorcycle engine.

That would be pretty slow.

Now the turbines on a SSME have about the same shaft BHP, and have a
power-to-weight ratio over 2,000 times better - far more suited to a mobike


BTW, from that link:

" The top of the connecting rod is not attached directly to the piston. The
top of the connecting rod attaches to a "crosshead" which rides in guide
channels. A long piston rod then connects the crosshead to the piston.
I assume this is done so the the sideways forces produced by the
connecting rod are absorbed by the crosshead and not by the piston. Those
sideways forces are what makes the cylinders in an auto engine get
oval-shaped over time."

That's maybe a small part of it, but the real reason is that the stroke is
about three times the bore (needed to make it so efficient), and conrods of
any reasonable length would have to somehow occupy the same space as the
cylinders if a crosshead was not used.

(just been desiging compressors, and had the same need for a crosshead-ish
arrangement on the hp cylinders, with large stroke/bore ratios. They used to
do the same thing on triple expansion steam engines.)

--
Peter Fairbrother

Without the crosshead and attendant piston rod the engine as a design
would fail to function. As it is a two stroke where the intake air is
admitted under the piston and sealed by a gland on the piston rod from
the crankcase, a crosshead is mandatory and normal practice on large
diesel engines.

Tom