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Ukrainian armor - Oplot-M, T-64M Bulat and other.


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Proper, god-fearing Soviet tanks use four-stroke diesel engines.  When the tank is cruising, the engine should be happy and produce very little smoke.  But when the engine is suddenly changing RPM, th

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Ukraine finally made it. Last Ololots were delivered to Thailand. Contract is done.

38788476_1923592664365849_6998355609162612736_n.jpg

 

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   According to the Thai web site Thadefense-News, on July 29, 2018, a historic event happened without much of publicity: the last shipment of BM "Oplot-T" tanks delivered from Ukraine was unloaded from the Thai port of Sattahip, completing the implementation of the long-suffering Ukrainian-Thai tank contract of 2011 . The last shipment delivered to Thailand by sea on July 29 included the last six BM Oplot-T tanks from 49 ordered under this contract, as well as both armored recovery vehicles (BREM) "Athlet" on the same base.

   On July 30 all the unloaded equipment of the last batch was delivered from Sattahip to the location of the 2nd division of the Thai army in Prachinburi, east of Bangkok. It is reported that the final official acceptance of this party by the Thai army will be made in September after the tests.

   The contract number USE-18.2-356-D / K-11 worth more than $ 240 million was signed by SC Ukrspetsexport on September 1, 2011 for the supply of the army of Thailand with 49 new tanks BM Oplot-T and two armored repair- evacuation vehicles "Athlet" on their base, with a deadline for the execution of the contract by the end of 2014.

 

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20 hours ago, Karamazov said:

a lot of smoke

 b3AhWIPTVko.jpg

 

 

why?

 

Proper, god-fearing Soviet tanks use four-stroke diesel engines.  When the tank is cruising, the engine should be happy and produce very little smoke.  But when the engine is suddenly changing RPM, the fuel/air mix usually isn't quite right, and there will be some un-burned fuel that creates the clouds of black smoke.  If you watch videos of Soviet tanks they usually smoke a bit whenever they turn, because Soviet tank steering mechanisms don't maintain the same average track velocity when the tank turns, which means that the engine changes RPM.  It's the same thing as the puff of smoke you usually see big rig semis produce when they accelerate.

The Kharkov design bureau favored two-stroke diesel engines for their tanks.  The advantage of a two-stroke diesel is that it produces a lot more power for a given size and weight of engine than a four-stroke diesel.  In theory they are also more fuel-efficient, although I am not sure they are in practice.  The disadvantage is... well, there are lots of disadvantages.

 

One other quirk of two-stroke diesels is that they aren't lubricated the same way as four-stroke diesel engines.  A normal four-stroke engine has separate oil and fuel.  You fill up your car with gas, and every once in a while you check the oil and replace the oil.

Two-stroke motors aren't like that.  They don't have separate fuel and lubrication systems.  Think of a chainsaw; the fuel and lubrication oil are mixed together, and the moving parts of the engine are lubricated using this fuel/oil mixture.  This further reduces the size of the engine, but it means that there's a bunch of oil mixed in with the fuel, which tends to produce a blue or white smoke as the motor runs.

If you look at pictures of Chieftains on parade, they're usually surrounded with a blue/white smoke for the same reason.

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46 minutes ago, Collimatrix said:

 

Proper, god-fearing Soviet tanks use four-stroke diesel engines.  When the tank is cruising, the engine should be happy and produce very little smoke.

 

Older tanks, like T-54/55/62, and anything that uses V2 derivative engines also produce lots of smoke. As far as I know, it has nothing to do with two and four stroke. M113 has a two stroke Detroit Diesel, and it barely produces smoke. Piston ring design for example, is much more important. Probably this is the case with 5TDF/6TD. 

There is a russian firm (Batmaster-Istra) that, among other things rebuilds engines. They developed a modernization package which involves replacing pistons. Result: much lower oil consumption (= less smoke) and significantly longer service life. https://web.archive.org/web/20170421001645/http://www.bmz.ru/disel/mdis.htm

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13 minutes ago, heretic88 said:

 

Older tanks, like T-54/55/62, and anything that uses V2 derivative engines also produce lots of smoke. As far as I know, it has nothing to do with two and four stroke. M113 has a two stroke Detroit Diesel, and it barely produces smoke. Piston ring design for example, is much more important. Probably this is the case with 5TDF/6TD. 

There is a russian firm (Batmaster-Istra) that, among other things rebuilds engines. They developed a modernization package which involves replacing pistons. Result: much lower oil consumption (= less smoke) and significantly longer service life. https://web.archive.org/web/20170421001645/http://www.bmz.ru/disel/mdis.htm

 

Older diesels smoke more.

 

Pretty sure the M113 has a four-stroke diesel.  It certainly doesn't sound like a two-stroke:
 

 

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On 8/25/2018 at 5:36 PM, Collimatrix said:

Pretty sure the M113 has a four-stroke diesel.  It certainly doesn't sound like a two-stroke:

 

Google Detroit Diesel 6V53. Its a quite successful, reliable two stroke diesel. M551 also uses this engine.

Old LVTP7 again had a two stroke engine, but a little bit bigger 8V53.  M109 uses a 8V71. 

 

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On 8/26/2018 at 9:42 AM, heretic88 said:

 

Google Detroit Diesel 6V53. Its a quite successful, reliable two stroke diesel. M551 also uses this engine.

Old LVTP7 again had a two stroke engine, but a little bit bigger 8V53.  M109 uses a 8V71. 

 

 

The M113's relative lack of smoke might be because it's lighter and has a smaller engine.

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On 8/25/2018 at 4:20 PM, Collimatrix said:

 

One other quirk of two-stroke diesels is that they aren't lubricated the same way as four-stroke diesel engines.  A normal four-stroke engine has separate oil and fuel.  You fill up your car with gas, and every once in a while you check the oil and replace the oil.

Two-stroke motors aren't like that.  They don't have separate fuel and lubrication systems.  Think of a chainsaw; the fuel and lubrication oil are mixed together, and the moving parts of the engine are lubricated using this fuel/oil mixture.  This further reduces the size of the engine, but it means that there's a bunch of oil mixed in with the fuel, which tends to produce a blue or white smoke as the motor runs.
 

 2 stroke diesels used in Tanks and APC's has a separate oil sump just like on a 4 stroke, it is not a moped engine. 2 strokes smoke more because of larger injectors and they always have pressure charged intake air by a compressor / Roots Blower. They usually have more torque at low RPM compared to a 4 stroke.
 

I was a Tank Mechanic in the Danish army, been working on Centurions, Leo 2, M113 and the M578 +  Centurion recovery vehicle.. 

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On 9/24/2018 at 3:43 PM, Mortenbandit said:

 2 stroke diesels used in Tanks and APC's has a separate oil sump just like on a 4 stroke, it is not a moped engine. 2 strokes smoke more because of larger injectors and they always have pressure charged intake air by a compressor / Roots Blower. They usually have more torque at low RPM compared to a 4 stroke.
 

I was a Tank Mechanic in the Danish army, been working on Centurions, Leo 2, M113 and the M578 +  Centurion recovery vehicle.. 

 

 

Interesting.  I didn't realize that the large 2 strokes were that different.

 

Why do 2 strokes have larger injectors?

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6 hours ago, Collimatrix said:

I didn't realize that the large 2 strokes were that different.

There are a few tricks that separate gasoline and diesel (and AFAIK supercharged and naturally aspirated) 2 stroke engines.

The problem with 2-stroke engines is that the moment the down-stroke is done, the entire cylinder has to be scavenged and filled with clean air (and fuel, for gasoline engines). And the cylinder is full of hot gas above atmospheric pressure.

So on small engines, the crankcase and piston are used as a pump, with the piston sliding also playing the role of the valves. On the up stroke air is drawn into the crankcase, on the down stroke it gets pressured and then pumped into the cylinder, ready to work.

clip_image0028_thumb.jpg?imgmax=800

This of course means you have a lot of air going through your crankcase and can't just spray oil on it, but mix it in with the fuel. You can also get iffy performance thanks to questionable scavenging, rich mixture (if its a diesel, the fuel is injected directly, regardless of the scavenging efficiency), and so on.

In larger 2-strokes, the overpressure problem is solved with a blower of some kind, usually an engine-powered supercharger (turbos don't work at low speed, but external blowing is also possible), which allows the crankcase to not be used for air pumping. This means it can be lubricated like a normal engine.

Additionally, with some cam-operated valves, and careful arrangement of the system, good axial scavenging can be achieved.

image154.jpg

Linear scavenging is even more useful for cylinders with a high stroke to bore ratio; such as are found on opposed-piston engines. These are tempermental beasts, but when properly tuned put out a lot of power for their weight and volume. 

Napier_deltic_animation_large.gif

The Napier Deltic took this to a whole new level, and it worked pretty well, but was very hard to maintain.

 

With modern CFD and CAD, the precise arrangement of ports, timing, and dimensions can be found to make this work reliably and efficiently. 

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