• Hi Guest! Forum rules have been updated. All users please read here.

Opposed Piston Engine

Trust12002

ACCESS: Restricted
Joined
Oct 28, 2020
Messages
8
Reaction score
14
To clarify:
horizontally opposed boxer type engine: crankshaft in the middle, 2 cylinders, 2 pistons pointing outward. Normal cylinders with a cylinder head at the top.
opposed-piston engine: 2 crankshafts on the ends, 2 pistons share ONE cylinder. No cylinder head, so has to use ports in tthe cylinder wall. Very different.
 

Trust12002

ACCESS: Restricted
Joined
Oct 28, 2020
Messages
8
Reaction score
14
Opposed piston engines do not all have two crankshafts per cylinder. Some have had one crankshaft below vertical cylinders with the top pistons driving the crank via long paired connecting rods (in tension for the power stroke). Doxford marine engines for example.

Opposed piston engines have two world firsts to their credit. In 1903 Louis Rigolly took a 13.5 litre Gobron Brillie on to the sands at Oostende and was timed at 103 mph making the GB the first car to exceed 100mph. Its engine was of the single crankshaft type described . In 1971 Mitsubishi built "Ocean Prospector" the world's first self-propelled semi-submersible drilling rig. It was powered by four ex-US submarine Fairbanks Morse engines, which had two crankshafts geared together. These engines supplied all the rig power. For rig moves propulsion came from two ex-US submarine electric motors driving propellers in steerable Kort nozzles. In calm water these engines could drive the 12,000 ton rig at 6 knots although in practice it was always towed as well. This rig has recently been brought out of layup and is being prepared to go to work again after 50 years. I think it unlikely to have the same engines though.

A final opposed piston configuration was employed by Rootes for a truck engine. This had three horizontal cylinders with a central crankshaft beneath them. Force from the pistons was transmitted through big rockers at each end. The core engine ignoring accessory drives thus had 3 cylinders, 6 pistons, 6 rockers, 12 connecting rods, 1 crankshaft and 34 bearings. It went into service and reputedly performed well. One peculiarity was that at high power e.g. when climbing hills in low gear it emitted a banshee wail. Its drivers called it "the Commer Screamer".
 

robunos

You're Mad, You Are.....
Senior Member
Joined
May 1, 2007
Messages
1,968
Reaction score
365
That would be the Commer TS3 . . .



cheers,
Robin.
 

Basil

ACCESS: Secret
Joined
Aug 10, 2009
Messages
281
Reaction score
63
Are there any news about the Cummins /Achates ACE (advanced combat engine)? It has been quiet about its development from the companies for two years now ...
 

Trust12002

ACCESS: Restricted
Joined
Oct 28, 2020
Messages
8
Reaction score
14
The Junkers Jumo two-stroke diesel aero-engines had two crankshafts geared together. The aircraft propeller was driven from the upper shaft and the engine accessories - the fuel pump, injectors and scavenging compressor - from the lower. About three quarters of the output power came from the top crankshaft. The Junkers engineers realised that scavenging could be improved by not having the pistons reach TDC together. The intake ports were under the lower piston and the exhaust ports under the upper. The engine was designed so that the lower crank lagged 11° behind the upper. The exhaust ports thus opened first, allowing much more efficient scavenging. The Jumos were the first and for a long time the only diesel aero-engines in service. They powered the Junkers 86; which visited British skies in 1941/42 in bomber and photo reconnaissance roles. The engine was not popular with aircrews because of slow throttle response and poor reliability. The aircraft performed much better with Swedish-built Bristol Pegasus engines.

Jumo.D.JPG

Cutaway Jumo in the Louman Museum in The Hague. I apologise for the picture quality but flash photography is not allowed and the lighting is less than optimum.
 

Moose

ACCESS: Top Secret
Senior Member
Joined
Jul 4, 2010
Messages
1,390
Reaction score
377
Are there any news about the Cummins /Achates ACE (advanced combat engine)? It has been quiet about its development from the companies for two years now ...
There were a spate of articles about it around August.
The focus seems to be putting it into the next M88 refit at this time, though I bet it will be pitched to a number of programs.
 

1635yankee

ACCESS: Confidential
Joined
Aug 18, 2020
Messages
52
Reaction score
52
I was doing some checking on the enginehistory.org site. Junkers was the first company to build diesels for aircraft, with the MO-3 in 1913 (!) and the 500 hp FO-2 in 1916. I don't know if any of these flew, although the FO-2 was likely the grandparent of the 204.
 

SeaslugMk2

'Curator' of the Seaslug website.
Joined
Nov 10, 2012
Messages
78
Reaction score
159
Website
www.littlewars.org
I'm surprised no-one has mentioned the Napier Deltic; three banks of six cylinders (each with two pistons) arranged in a triangle, giving 1750Hp. The triangular arrangement meant each bank of cylinders had a crankshaft at each end but saved weight as there were only three crankshafts for three banks. It did need a supercharger (and compressed air starting) to work, and gave good service in the Dark class FPBs and, of course, the Deltic class Locomotives.

SRJ.
 

SeaslugMk2

'Curator' of the Seaslug website.
Joined
Nov 10, 2012
Messages
78
Reaction score
159
Website
www.littlewars.org
I'm surprised no-one has mentioned the Napier Deltic
You beat me to it - that is exactly what I was intending to post! One of the most interesting engines ever built IMO.
Napier's conceptual leap was the realisation that one of the crankshafts has to turn in the opposite direction to the other two for it to work. There are some good animations out there on the 'web, along with a Lego model.

SRJ.
 

Similar threads

Top