[Big Dave]

All things old are new again. The engine described on the Engineering TV link amounts to doubling the old Junkers Jumo or Fairbanks-Morse two stroke diesel engines.

The Junkers Jumo had a good power-to-weight ratio – so much so it was used on high-altitude reconnaissance planes in the 1940s. The Fairbanks-Morse was uber-reliable (there are seventy year old engines still running today making rated power) and would run on anything sorta oily.

The opposed-piston engine gets around one of the major manufacturing problems of the internal combustion engine: the complex cylinder head. The opposed engine simply uses another piston to provide the “equal and opposite” for the piston. I noticed the guy did pay special attention to a known weakness of piston-ported engines – heat buildup in the ports.

I have some reservations.

The Fairbanks-Morse and Junkers Jumo used a gear train to synchronize the motion of the pistons. This engine uses a Scotch yoke mechanism instead. The Scotch yoke is definitely less expensive, especially in the US where so few gear manufacturers survive, but the Scotch yoke is a notoriously weak mechanism that relies on a high-wear connection to the crankshaft. In most applications the Scotch yoke was out of general use before the second World War. Even I am not so old that I can even remember seeing a mass-produced Scotch yoke device. Maybe a Singer sewing machine of the 1950s. Early Singers used a Scotch yoke for the co-ordinated motion of their needle, but sewing machines are hardly high-stress machines.

I have absolutely no idea how you would package this engine in any vehicle other than a sidewheel paddle riverboat. The engine is long and low with the crank in the middle.

Trump card. It is a two-stroke diesel and sooner or later to be mass-produced it would have to meet Tier II emissions requirements. No chance whatsoever. Piston-ported two-strokers are notoriously dirty – emitting scads of unburned hydrocarbons (VOC), particulates, NOx, and carbon monoxide. That’s why they have all but disappeared from the market.