Achates Engine - 2 Stroke Diesel.

Dr Who · 27 Jul 2018 at 16:49

So opposed piston engines are looking like they might make a comeback.

The Original Commer TS3 was one of the most fuel efficient (if not the most) engines ever made.

3 Cylinders, 6 Pistons, horizontally opposed, one crankshaft, 2 stroke, supercharged. (and they sound insane

)

Achates in the US has reinvented the wheel of opposed piston engines and it is looking very impresive.

3 Cylinders, 6 pisons, vertically opposed, 2 crankshafts (one flywheel) 2 stroke, supercharged and turbo charged and might possibly hit 60% thermal efficiency, figures only usually seen in huge marine engines!

https://www.youtube.com/watch?v=2RwqL-7G-3c

https://www.youtube.com/watch?v=UF5j1DvC954

Not sure the worldwide market for small diesels will last long but this thing puts out very low levels of NOx apparently so ideally suited to Large Goods vehicles and buses and military vehicles due to light weight.

Lubrication does not go out the ports, scavenging is perfect on a diesel as no fuel enters the combustion chamber while the ports are open. Looks impressive and I have always been a fan of the TS3 and believe 2 stroke to be a perfect platform for diesels (and they sound awesome imho).

Dis86 · 27 Jul 2018 at 16:58

Why did opposed piston engines bum out in the first place?

sovietspybob · 27 Jul 2018 at 17:01

I saw that EE video the other night, very interesting that someone is seemingly seriously trying to bring that engine design back around again.

In one way it looks really good especially the efficiency band the engine has, but on the other why bother when electric motors are like 95%+ efficient and that's the way the world is quickly going so it almost seems a bit too late to bother in some senses.

Nasher · 27 Jul 2018 at 17:18

Dis86 said:
Why did opposed piston engines bum out in the first place?

I'm guessing cost. Most engines are V or inline because they are cheaper to make. Even though they may not necessarily be the best.

Dr Who · 27 Jul 2018 at 18:32

Dis86 said:
Why did opposed piston engines bum out in the first place?

Good question, probably because of the issues of gearing the 2 sides together and the success of otto cycle engines, but with increased efficiency demands and modern materials and metallurgy there is no reason why they cannot make a comeback now.
Bear in mind the 1950's Commer Diesel TS3 3.25ltr put out nearly 300ft.lbs of torque which was equivalent to much larger engines at the time with a power delivery of a Flat12 from 3 cylinders (assuming 2 cylinders firing at once on the 12 cylinder) Imagine that kind of smoothness on a diesel car!

I think mostly in commercial applications, battery technology isn't good enough yet for the increased demands of commercial use. Our hybrid buses need replacement power packs every 3-6 months, very expensive so we are converting them back to diesel power

Personally I think trolley bus is the way forward for inner city use, much cheaper than trams, but diesel still has a place if it can meet emissions in the stringent new world.

Will these ever make it into cars? Possibly for a short while.

adolf hamster · 28 Jul 2018 at 03:10

sovietspybob said:
I saw that EE video the other night, very interesting that someone is seemingly seriously trying to bring that engine design back around again.

In one way it looks really good especially the efficiency band the engine has, but on the other why bother when electric motors are like 95%+ efficient and that's the way the world is quickly going so it almost seems a bit too late to bother in some senses.

The motor itself might be 95% effecient, but there's the power station, power grid, charging circuit, battery losses and power controller losses to consider if you want to compare directly with an ic engine.

I dont think opposed will make it to cars, maybe for agricultural equipment but cars have packaging issues to consider and public opinion seems to have thoroughly demonised diesel now.