Opposed Piston/Opposed Cylinder 2-stroke engines - Steel Soldiers::Military Vehicles Supersite

Wrench Wench · 03-10-2009, 02:04

Has anybody heard of the OPOC engine? Opposed Piston/Opposed Cylinder turbo 2-stroke diesel engine.

Opposed Piston Opposed Cylinder Engine - Engineering TV

I'm be interested in everyone's opinion of it from these articles.

EZFEED · 03-10-2009, 02:15

Neat!

Jones · 03-10-2009, 02:35

Fairbanks-Morse used the opposed piston idea years ago in their prime movers for locomotives; although the top and bottom piston sets had their own crankshafts connected by a gear train.
This new offshoot looks interesting but may have a weak link in the long rod(s) connecting the outer pistons. Anything with lots of moving parts has that many more parts to break.

I've personally always thought that the gas turbine was the ultimate internal combustion engine-- no reciprocating parts... everything turns the same direction all the time, just faster or slower.
Unfortunately, early on they were expensive to build and for some reason, people got nervous around something with a 92,000 rpm shaft speed.

That's my two-cents worth.

JDToumanian · 03-10-2009, 02:36

Looks like a merging of several previously used diesel engine designs...

The first is the Fairbanks-Morse opposed piston engines, in which there were two pistons in each cylinder, the ports were arranged the same as this new OPOC engine and the pistons fired away from each other.... But there were two crankshafts, one at each end of the cylinder, and they were geared to a common shaft in the middle. They were made in a number of configurations up to 8 cylinder (16 pistons) and were used in ships and locomotives.

The second is the Commer "Knocker", made in England in the 1950s. Similar to the Fairbanks-Morse, except that they were much smaller (truck-engine sized) and instead of two cranks, it had rockers that reversed the motion of the connecting rods, to a crank mounted below the middle of each cylinder.

The Fairbanks-Morse fell out of favor due to expense of maintenance - you could not easily replace a single "power assembly" (cylinder with it's liner and head, piston, and rod). As for the Commer Knocker... I think it was just ahead of it's time. Brilliant engines... Very similar to Detroit Diesel 2-strokes, but more compact for the same horsepower.

I don't think that OPOC engine will catch on, but there's no reason it would not succeed if it did... It's based on sound designs that date back over 60 years.

Regards,
Jon

kroctec · 03-10-2009, 09:08

Well WrenchWench you have opened up a very interesting aspect of diesel engine development.

To the best of my knowledge this technology dates back to the late 1920s when the German airplane manufacturer produced a design for this type of engine "Junkers Jumo 204' which was first flown in a Junkers G24 in 1929. Junkers further developed their original designs which were 2 stroke super-charged type having very high output, with high power to weight ratios. There was further advantage in that these large capacity engines comprised small components which were easily hardened for better strength/wear characteristics.

In the 1930s Junkers licenced the design to the British company Napier who produced the Napier 'Culverin' engine at the beginning of WW2 and continued development culminating with the English Electric 'Napier' Deltic engines - these had 3 banks of 12 opposed pistons in 6 cylinders (total of 36 pistons in 18 cylinders), driving 3 crankshafts geared to a common output. These engines were super-charged 2stroke and by an ingenious arrangement of porting largely overcame the problems of poor exhaust scavenging.

With the advent of much improved materials and superior machining it is not surprising that these 85 years old designs are being once again looked at.

Anyone who is interested can find lots of further reading and illustraions in Wiki. Further information and photos can be found by various searches of Google Images.

best regards from Davce Gudmunsen

MWMULES · 03-10-2009, 17:19

Back in the cold war, we used them on our fast attack subs. I was getting ready to relieve the generator watch on a 637 class sub when the blower on one locked-up.

kroctec · 03-10-2009, 21:01

Sorry wrenchwench - you asked for an opinion and not a potted history.

In my opinion this is a design which remains to be properly fulfilled. I would hazard a guess that with the combination of more advanced machining, advances in materials science combined with superior math modelling then it seems quite likely that this engine will rock.

I hope it is a success and will watch the space to see just what happens.

rmgill · 03-10-2009, 22:59

One other thing is that this looks like it would be a very compact engine design ideal for armoured vehicles where space is at a premium.

The British FV432 and Abbot SPG's both use an opposed piston setup, the Rolls Royce K60.

juha_teuvonnen · 11-25-2009, 17:50

Russians used these in their tanks

T-64 was equipped with 5TDF engines
T-80UD was equipped with 6TDF

These engines required more careful maintenance when compared to Russian V12 diesels (T-55, T-62, T-72). The early 5TD series engines required to be fully heated up prior to driving. This rendered them close to useless in winter, because the enemy forces generally don't have a habit of give you advance notice about their attack.