Recently we reposted an article from November 2018 titled “Seven of the Strangest New Engines in the Industry” which covered some technologies which have actually started to prove themselves since we published the article.

However, it seems that everyone focused on the lead photo in the Facebook post (of the Achates 2.7-liter opposed-piston engine) and proceeded to talk about how opposed-piston engines aren’t new at all. While we mentioned that fact in the article itself (so we know who only comments based on the headline alone now), the fact that everyone seems so interested in the opposed-piston engine isn’t lost on us.

That leads us here, to a video showcasing six different opposed-piston engine designs in actual use. From delivery trucks to main battle tanks, train locomotives to aircraft engines, and even diesel submarines, the opposed-piston engine design has served with distinction for over 140 years, with the engine types in the video spanning almost eight decades.

Of the video’s six engines, we’ll briefly summarize three of them. And no, we aren’t backing down from calling opposing-piston engines “weird.”

Commer TS3

Recently, we featured the Rootes-Commer TS3 on our Facebook page for “Weird Engine Wednesday.” It wasn’t so much the engine’s opposed-piston design which earned it a spot on WEW, but rather it’s the use of a single crankshaft instead of the opposed-piston engine’s usual dual crankshafts.

Additionally, the TS3 utilized a Roots-style supercharger (not to be confused with the Rootes Group, the parent company of Commer) not as a power-adder, but to scavenge exhaust gasses from the engine’s valve-less cylinders. The three cylinders displaced 200 cubic inches thanks to its 3.250-inch bore and 4.00-inch stroke.

Making a whopping 105 horsepower at 2,400 rpm and 270 lb-ft of torque at 1,200 rpm, the engine has a very distinct exhaust sound, earning it the nickname, “The Commer Knocker.” Discontinued in the late 1960s, there are still some examples of the TS3 alive and kicking today.

Leyland L60

Moving to larger-displacement opposed-piston engines, we look at the Leyland L60. This 6-cylinder/12-piston layout displaced a whopping 1,200 cubic inches (19 liters), was more physically compact than less powerful engines of the time and was configured to run on a variety of fuels other than diesel in its role as the powerplant for the Chieftain main battle tank.

The L60 went through a number of design revisions, ultimately peaking at 750 horsepower and 1,460 lb-ft of torque from the factory, and getting an in-service boost at the end of its life cycle to 840 horsepower. The L60 was designed as part of an “engine pack” designed to be field-swappable and also used a Roots supercharger for scavenging purposes.

Napier Deltic

As if opposing piston designs weren’t already different enough, the Napier Deltic engine takes it a step further. Moving to a three-crank configuration. As the “Deltic” name alludes to, the cylinders are arranged in the form of a triangle, with each cylinder making up each side, and crankshafts at the triangle’s vertices.

Three triangular sections were combined to make for an 18-cylinder engine with 36 pistons. By staggering firing events across the banks of cylinders, the engine was particularly smooth-running. In Naval service, the Deltic made a peak of 2,500 horsepower at 2,000 rpm. In locomotive use, there Deltic made slightly less continuous power — 1,650 horsepower at 1,500 rpm versus the Naval variant’s 1,875 horsepower at 1,500 rpm.

Regardless of whether or not opposed-piston engine designs can rightly be called “weird” or not, they are definitely interesting. And while they have fallen out of favor in modern times, that could change, as the Achates company is actively finding modern applications for this well-proven engine design.

The Napier Deltic in operation. This is a single bank of cylinders, and the Deltic had six of them, while the “Baby Deltic” had three. By MigMigXII – Animated from CAD drawing, CC BY-SA 3.0,