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Gyrojet Pistol 
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Joined: Thu Mar 24, 2011 12:44 am
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Post Re: Gyrojet Pistol
nemo:
fact: in just about every country in the world doctrine dictates that infantry advances using MBTs as mobile cover. fact: US infantry can't do that due to stupid design.
fact: in just about every country in the world MBTs move with infantry to cover each others weaknesses. fact: US MBTs can't do that due to the same stupid design flaw as the above(that friggin turbine)
so much of US tank doctrine is based around that turbine it's flipping silly, and there are reasons the russians dropped the experiment that was turbines for tanks and rejoined the rest of the world in using diesel.

fact: the M1 Abrams was designed to be stationed in germany using the infrastructure available there, and assumed that such infrastructure would be around. fact: using it elsewhere means that such well devolped infrastructure might not be around, creating serious issues with tactical and strategic mobility.(both in fuel usage and road/bridge usage)
fact: the M1 Abrams is very awesome on paper. Fact: in reality it is not very awesome.

there are two major problems for the Abrams as a combined arms vehicle, #1 turbine and #2 the lack of a tank/infantry phone(just about EVERY other tank since WW2 has this feature.) okey, they actually added it AGAIN in the latest version of the Abrams(SEP 2), i wonder where it is? can't be behind, that would fry the poor infantryman....must be on the side then? no, it is behind, on a corner, but better than none i suppose...only took 20 or so years to add it.

side note, checking the interwebs, apparently the british matilda II infantry tank had a phone as standard as early as 1940, by 1945 just about every tank had one.


Sun Sep 28, 2014 11:57 pm
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Post Re: Gyrojet Pistol
Quote:
fact: in just about every country in the world doctrine dictates that infantry advances using MBTs as mobile cover. fact: US infantry can't do that due to stupid design.


And in your eagerness to bash you missed it again. That tasking is offloaded to other, better suited platforms. The British and French style infantry tank was made obsolescent in WW2 in the face of the German Panzers. The infantry can use a light armored support vehicle, but not a MBT. Split them and focus them.


Mon Sep 29, 2014 4:06 pm
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Post Re: Gyrojet Pistol
nemo: and i am a follower of 'eliminate the not needed' to stream line things.
so, specialize....why not diesel the abrams, get a lightly armored truck(MRAP got this covered) and remove the bradleys altogether?
according to numbers i found, for two bradleys you could get one abrams and a truck...which together(assuming diesel abrams) would have a similar or slightly higher fuel usage, but better tactical mobility, more firepower and carry about as much troops/gear.

and might actually be cheaper in the long run due to mass production, and most assuredly could be cheaper to transport troops.

but, yes, you have a point about better platforms, but if you have a 155mm howitzer, why not have it capable of horizontal(direct) fire too? should not be an impossible(or even difficult) engineering feat.


Tue Sep 30, 2014 8:53 am
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Post Re: Gyrojet Pistol
You can use a large caliber artillery piece such as a Howitzer or field-gun for direct-fire and there have been times that that has happened.

There was even that one time in WWII when Allied ships (cruisers and destroyers) used their heavy guns in tank-pinking when the German's were over-running a harbour the ships were based in. I'll post the link here when I get home and can find it as was a pretty crazy battle.

But in-general direct-fire (tank gun) weapons are very different from in-direct fire weapons (artillery) and don't really work well when the roles are swapped. The shells have different velocities, trajectories, drop-over-distance, weight of the weapons system, and speed of re-targeting. The gas pressures, riffling and types of ammunition don't really carry over well.

Trying to design a weapon that works well for both roles has been done before with varying degrees of success but such things never really excelled in either role.


Tue Sep 30, 2014 12:07 pm
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Post Re: Gyrojet Pistol
discord wrote:
nemo: and i am a follower of 'eliminate the not needed' to stream line things.
so, specialize....why not diesel the abrams, get a lightly armored truck(MRAP got this covered) and remove the bradleys altogether?
according to numbers i found, for two bradleys you could get one abrams and a truck...which together(assuming diesel abrams) would have a similar or slightly higher fuel usage, but better tactical mobility, more firepower and carry about as much troops/gear.

and might actually be cheaper in the long run due to mass production, and most assuredly could be cheaper to transport troops.

but, yes, you have a point about better platforms, but if you have a 155mm howitzer, why not have it capable of horizontal(direct) fire too? should not be an impossible(or even difficult) engineering feat.

I can actually answer this... The AGT-1500 has several advantages over a diesel engine that are apparent if one looks at the tradeoff. And before I begin, I have to ask... How does using a turbine engine prevent a tank from doing what another with a diesel does?... (Hint: the exhaust 'issue' is only an issue because it's presented as such, yet not so in reality).

Now then, onwards...

1. The AGT-1500 is a true multifuel engine. Now, a diesel CAN be run as a multi-fuel system, but having worked on such in the past, I can tell you plainly... You do NOT want to do it. The injectors will be screwed in short order, and you'll lose a great deal of power while it does remain running, due to the simple fact that a diesel is mechanically optimized to run on diesel fuel. Biofuels of any sort are exceptionally bad about this. Turbines burn hot enough that pretty much anything combustible can be used as fuel without issue, from raw kerosene to gasoline to diesel to jet fuel. The Australians, for example, run their M1A1 AIM's on diesel without issue (Diesel Abrams, right here. ^.^). We run them on JP8, along with literally everything else, as a common fuel type.

2. A turbine engine has approximately 33% fewer moving parts, which in turn makes the engine less prone to failure. The record number of failures during Gulf War I was due to improperly fitted air filters, allowing sand into the engines... And surprise surprise, the other major MBT to see action then, the Challenger II, had the exact same issue with it's diesel. Let grit in, and it hardly matters what you've got under the hood, it WILL fail, fast. On a related note, that reduction in mechanical complexity makes for a smaller, lighter powerplant compared to a diesel of the same output. Look up a video of an M1's power pack being removed... Literally 70% of what you will see is the transmission, with the turbine looking like an afterthought bolted onto the end.

3. Power curve. A diesel has to spin up to speed, delivering peak horsepower only at a certain RPM, and not before or after. A turbine, from the moment it is spun up to operating speeds, delivers its full horsepower across the entirety of the power curve. Top speed is pretty much a hollow statistic, when it comes to an MBT, whereas acceleration, especially up a grade or over rough terrain, means everything when it comes to taking advantage of cover or getting out of the enemy's gunsights. Acceleration is something the M1 has in spades.

4. On the subject of RPM's... Revving an engine at high RPM's, outside of it's optimal range, kills it's service life. For a diesel, anything above about 2.5k is not good for it, and pushing along 50 plus tons of tank with a need for power will push it above that. As mentioned before, above a certain RPM gives you very little return, and steadily running above about 3k, you're likely to damage a diesel. The AGT-1500, by comparison, spins up to 20k to start (startup takes about fifteen seconds, FYI), and comfortably operates at 35k without ill effect. While the diesel looks more reliable on paper, it only remains as such in a certain operating range. After that you'll be replacing head gaskets, injectors, piston rings, and turbochargers regularly.

5. Quiet operation. While this may not sound like a serious advantage, it has proven to be as such. Diesel engines, even with proper mufflers, are noisy, rattling things in operation. By comparison, the M1 is very quiet, and has more than once quite literally snuck up on opposition both in training and in combat (early exercises earned it the nickname 'Whispering Death', and numerous near training accidents when one came crashing through the trees without warning).

6. Cold starting. Much like a gas engine, if you get a diesel cold enough, it will not start. Or, at best, will grudgingly do so and need a long warm up period. Turbines, unless literally frozen in a block of ice, will start every time in temperature ranges from cold to subzero, and have a shorter warm up period.

Now, there are some cons to using this sort of power plant, but that was well understood before it was ever used. It's a tradeoff, and wasn't done on a whim my friend. The higher fuel use was considered acceptable, since we've got the logistics to handle it. The more expensive replacement parts were also acceptable, since we've got the funding to keep them rolling. Beyond that, simple upgrades and operational procedures have largely taken care of other related shortfalls.

Also, on the subject of 'not needed', an MRAP, or any other armored truck, simply isn't suited to combat operations beyond a certain point. They lack the armor, crew protection, and firepower to even come close to taking over the role of a tracked IFV like the Bradley (for all it's flaws...). The concept of wheeled vehicles over rough terrain also presents problems that a tracked combat system just doesn't have. There is a place for both. Your thought there ignores the fact that literally every major military on Earth has a tracked IFV in their inventory, and is continuing to design and build new models, instead of using an MRAP like vehicle as a substitute.

And yes, it does have an infantry phone. It's on the aft quarter. Not every tank has been fitted with one, by the way... And I don't just mean the M1.

The exhaust 'issue' is vastly overrated, in all reality, merely as a talking point that has no actual bearing on the vehicles operations. You don't want to get near any exhaust, but nobody's ever cooked just standing there. It's a bit warm, I can tell you, but I didn't turn into a charred skeleton just standing in the wake, and infantry can walk right up without an issue to make use of the phone. The reason you see them so far back at times, at least 20 ft, is due to ricochets... Whatever hits that metal box has to go somewhere, and ricochets tend to travel parallel to the surface they hit. Would you stand near a bullet magnet? I wouldn't. And no responsible vehicle commander would let them.

As far as infrared signatures go, all armored vehicles have a high signature, and IR optics will pick out the exhaust of a diesel tank as brightly as a turbine, which has been proven (the difference between 299 degrees and 499 degrees on such optics is pretty much nil. Hot is hot, as far as the system is concerned). A less commonly known fact is that the AGT-1500 uses a recuperative exhaust system, scavenging it's own fumes to increase thermal efficiency by raising inlet temperature, which also cools it off a bit in the process.

Nemo has made all my other points for me. And no... I'm sorry... Blacktails "information" is not good for anything but a laugh. He cherrypicks, ignores any and all advantages that are present, and has more than once proven that he knows little more than talking points, which quickly fall apart in the face of anyone who has actual expertise or experience in the matter. You're free to believe him if you like, but I prefer to have the whole picture, myself.


Last edited by Senanthes on Mon Oct 20, 2014 7:09 pm, edited 10 times in total.



Tue Sep 30, 2014 3:36 pm
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Post Re: Gyrojet Pistol
pinheadh78 wrote:
But in-general direct-fire (tank gun) weapons are very different from in-direct fire weapons (artillery) and don't really work well when the roles are swapped.

The German 88mm anti-aircraft cannon was also used (famously and very successfully) both as direct-fire anti-tank weapon and as an indirect-fire artillery piece against infantry.

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Post Re: Gyrojet Pistol
Arioch wrote:
pinheadh78 wrote:
But in-general direct-fire (tank gun) weapons are very different from in-direct fire weapons (artillery) and don't really work well when the roles are swapped.

The German 88mm anti-aircraft cannon was also used (famously and very successfully) both as direct-fire anti-tank weapon and as an indirect-fire artillery piece against infantry.

It's all in the shell. :) A gun is but the mechanism to launch it.


Tue Sep 30, 2014 3:47 pm
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Post Re: Gyrojet Pistol
Ah! yes, the lighter weight and caliber guns such as the Bofers 40mm and Flak-88 series were indeed successful dual-purpose guns.

I was thinking more along the lines of the bigger stuff like an M198 howitzer field gun or M109 howitzer self propelled gun for the prior comment about dual-purpose artillery vs direct-fire.

Thanks :D


Tue Sep 30, 2014 4:05 pm
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Post Re: Gyrojet Pistol
Quote:
6. Cold starting. Much like a gas engine, if you get a diesel cold enough, it will not start. Or, at best, will grudgingly do so and need a long warm up period. Turbines, unless literally frozen in a block of ice, will start every time in temperature ranges from cold to subzero, and have a shorter warm up period.



I wanted to expand on this one a bit. Diesel has issues with operating at low temperatures because its viscosity changes dramatically as you dip below freezing. This actually causes it to be logistically complex because you require different fuel additives in different amounts as the environment changes.

These problems can be overcome if you build or adapt with a specific environment in mind and secure a stable supply of environment specific fuels for your armed forces. A local power can do that for local environments. The M1 is largely agnostic, allowing greater flexibility in deployment and power projection around the world. Soviets invade east Europe? Send tanks and gas. Soviets push into south Asia? Send the exact same tanks and the exact same gas. Or, like Sen pointed out, anything that burns.


Tue Sep 30, 2014 7:47 pm
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Post Re: Gyrojet Pistol
pinhead: i will accept that the 40mm is a lightweight gun, but the flak 88 was pretty much the heaviest gun put on a tank in its day, and still today would not exactly be a 'light weight', middle weight sure, but not light.

sen:
1. admitted. the turbine is also quite a bit thirstier.

2. fewer parts, yes, less maintenance, no. higher stress on high speed systems equals less tolerance.
in reality however, you get a failure you handle it the same way, lift out engine unit, plug in a new one, tank drives away engineers check faulty unit at leisure.
lighter, yes, smaller, yes, however, it is more sensitive to FOD and this is probably the major reason russia said 'fuck this shit!', they are not known for tolerating things with low grit tolerance.

3 turbines and diesel are different, yes, the abrams was designed in the 70's and since then the diesel has made rather amazing improvements, the turbine not so much.

4. this is a problem for the gearbox in a normal engine, it is STILL a gearbox(although includes a reductor on a turbine) problem for the turbine, since a turbine needs to operate at very high speeds, turbines have a slightly different problem, since what you generally want is torque, and the torque curve on a turbine IS peaky, which gives you basically the same problem of staying inside a rather small powerband for optimal performance in accel, and another for top speed...and as far as i know, neither is the optimal for fuel efficiency.

the powerplant was designed to run on autobahn, and do fast 'thunder runs' from base to base...that is basically what the design called for, it gets that job done, other scenarios....not so good.

5. not sure about acoustic differences, not had the opportunity to compare, but turbines in my experience are not exactly quiet, the signature is rather different, but not quiet.

6. cold weather problems? all the scandinavian countries use diesel, and it gets pretty damned cold here at times, and nemo is quite correct in that it can be managed.


Wed Oct 01, 2014 12:51 am
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Post Re: Gyrojet Pistol
discord wrote:
pinhead: i will accept that the 40mm is a lightweight gun, but the flak 88 was pretty much the heaviest gun put on a tank in its day, and still today would not exactly be a 'light weight', middle weight sure, but not light.

sen:
1. admitted. the turbine is also quite a bit thirstier.

2. fewer parts, yes, less maintenance, no. higher stress on high speed systems equals less tolerance.
in reality however, you get a failure you handle it the same way, lift out engine unit, plug in a new one, tank drives away engineers check faulty unit at leisure.
lighter, yes, smaller, yes, however, it is more sensitive to FOD and this is probably the major reason russia said 'fuck this shit!', they are not known for tolerating things with low grit tolerance.

3 turbines and diesel are different, yes, the abrams was designed in the 70's and since then the diesel has made rather amazing improvements, the turbine not so much.

4. this is a problem for the gearbox in a normal engine, it is STILL a gearbox(although includes a reductor on a turbine) problem for the turbine, since a turbine needs to operate at very high speeds, turbines have a slightly different problem, since what you generally want is torque, and the torque curve on a turbine IS peaky, which gives you basically the same problem of staying inside a rather small powerband for optimal performance in accel, and another for top speed...and as far as i know, neither is the optimal for fuel efficiency.

the powerplant was designed to run on autobahn, and do fast 'thunder runs' from base to base...that is basically what the design called for, it gets that job done, other scenarios....not so good.

5. not sure about acoustic differences, not had the opportunity to compare, but turbines in my experience are not exactly quiet, the signature is rather different, but not quiet.

6. cold weather problems? all the scandinavian countries use diesel, and it gets pretty damned cold here at times, and nemo is quite correct in that it can be managed.


1. Yes, yes it is. Part of the tradeoff, and a noted disadvantage.

2. You ignored that the Challenger 2 had the same issues, serving right alongside the M1. Since then, I've heard very little that didn't originate with those who have never used or worked on the M1 regarding any problems with reliability or maintenance. Honeywell didn't automatically build their engine with less tolerance to the requirements of it's own use for no particular reason. When you design a system to do something, you design it to withstand the stress of such to a reasonable degree, unless we're just assuming it's deliberately under-engineered? If so, why?

3. Have diesel engines stopped being piston driven when I stopped looking? And if not, how do they resolve the fact that a piston engine of any sort has to build up to it's optimal power band before generating maximum horsepower? I've not seen one yet that doesn't have an optimal range of operation, and a need to spin up to get there.

Turbines are spun up once, on start up, then spun back down on shutdown. Once in their operating range, which is narrow compared to a diesel, they can be kept there within a reasonable margin, delivering constant horsepower. The fact that they deliver very little deviation is the advantage in this case. Effectively, with a turbine, you're starting it, running it up, then dumping it into the drive train via reduction gears, wholesale, with the power plant delivering it's full output immediately, translating to a LOT of torque off the starting blocks with the right setup, but more importantly, a consistent power curve. With a diesel, you start it up, engage the transmission, then hit the accelerator, and the engine builds up it's RPM's from there. No question that diesel engines have excellent torque... But they don't deliver their full horsepower at lower RPM's, and thus don't have as consistent a power curve. Irony, really, that having a wider range, in terms of operational speed, means that a diesel, like all other piston engines, has a less consistent delivery of power.

On the subject of turbines not advancing... I suggest further reading on the matter.

4. It's actually a simple reference to the basic design of any piston engine setup. In all fairness, it's a point I should have rolled into 3. However, since we're on the subject... The only European MBT that has a better 0-20 mph rating is the LeClerc, which can do so in 6 seconds. Both the Leopard 2 and Abrams are rated at 7. Not too shabby.

When dealing with diesel, the ENGINE itself doesn't provide it's full, rated output until a certain RPM is reached. The MTU 873 only provides its full 1473 shp at 2,600 rpm (coincidentally, MTU's own information states that this is the maximum RPM for the engine, which is typical for a big turbo-diesel). Before you actually are getting 1473 shp, the engine has to get to 2,600 RPM. At a more modest 1000 RPM, you're getting approximately 740-870 shp (Rough calculation. MTU's site didn't have everything I needed, so I figured it from the displacement of 478.6 l, at 1000 RPM, both at 14:1 and 16:1 given that it's a direct injection engine. I'd favor the higher compression and resulting higher horsepower, given that I think highly of German engineering). The AGT-1500 is putting out 1500 shp from the moment you hit the gas, to the moment it peaks. Yes, it has a narrow powerband, which requires a slightly more complicated, heavier gearbox to regulate it, but the advantage is clear; the turbine runs entirely within it's powerband during operation, and has considerably more torque at lower speeds.

The resulting torque calculations from the shp comparison (effectively a situation where the tanks are accelerating) is;
M1 and variants using the AGT-1500 turbine: 3,939 ft-lb at 2,000 shaft RPM
Leo 2 using the MB 873 Ka-501 turbo-diesel: 2,284 ft-lb at 2,000 shaft RPM

Both numbers are a rough comparison, but the rating for the M1 is only 39 ft-lb off from whats officially claimed. It makes the point regarding torque, which equals acceleration, which equals life. For a 'thunder run' over any distance, I'd actually prefer the Leopard 2, with it's higher top speed. In the end, the M1, and Leopard 2A5, which are of similar weight in many instances (surprised? The Leo 2A5 lists it's weight as 55 t to 62.5 t, with the M1A2 listed at 62 t, and the original M1 at 54t), have similar specs on paper in regards to their power plant output. But the way those power plants deliver said horsepower is what sets them apart.

So...

You've got the choice of diesel, which doesn't give full power until it hits it's optimum range, or you've got the choice of a turbine, which provides it all from the get go but is less efficient.

And no, revving your engine to top speed is never optimal for fuel efficiency, regardless of what type of engine you have. One of the big drawbacks, as we agree, with turbines, is that they suck up gas no matter what, rather than sipping at idle. So, the tradeoff is efficiency versus capability. Pick your poison.

I'm not making a case of turbine engines being BETTER. Merely that they provide advantages that you can't match with diesel. There are situations in which a diesel is flat out better, in turn.

5. I have. It whines, with a slightly muffled quality to it, and a lot of examples can be found on Youtube. It doesn't sound like a jet airliner at full power, but it does have a high pitched whine. No tank is really 'stealthy' in terms of close range acoustics, but over the horizon? You won't hear it. You might not hear it at all if you're in a vehicle with a diesel running, until it drives up. During training exercises with Canadian units using diesel driven Leo 2 tanks, this happened time and again.

6. Nemo's entire post is correct, actually, including the part about it being a more complicated logistics chain. You can adapt a diesel to cold weather using additives, and building or adapting it for that region. Pre-heaters are a necessity... Now go and try and run that cold weather adapted diesel in the desert, or the subtropics... You'll have to change it up, every time.

You don't need to do anything for the M1's turbine to function just as well in the same conditions, without additives, or modifications, or much of a warm up period. That's the advantage. You paint the tank in the proper camouflage pattern, and send it off into the Sahara or Siberia with equal effectiveness. It won't make a difference in how the power pack functions.

His point regarding deployment is spot on. One type of fuel is all that's needed, regardless of where you're going, simplifying logistics. Can't get your fuel? No problem, burn whatever you can get your hands on from allied stockpiles until it gets there, or whatever you can scrounge up in the short term.

7. I feel the need to digress a moment. I'm not trying to make a case for the Abrams being some sort of godmobile... Nothing is invincible, perfect, or without drawbacks. It's simply one of many good tanks. And the reason I used the Leo 2 as the comparison here is simple; I consider it to be a monumentally fine example of modern armor in it's own right, and is my absolute favorite. It, too, has it's flaws.


Thu Oct 02, 2014 4:18 am
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Post Re: Gyrojet Pistol
sen:

1. done, over with, and we are in agreement.

2. turbines are due to how they operate inherently more susceptible to FOD, it is another of the disadvantages of the basic design, has to do with greater stress on air filters and delicately balanced internals.
that said, most engines will get effed up if you get sand and grit into it, question is how badly, how fast and how difficult it is to prevent.... Ramjet would probably not care though... but not really relevant for the discussion.

3. there are transmission solutions that will give pretty much the same effect to a piston engine(CVT, hydraulic torque converters, etc.), but it is not really all that important, the single most important issue is that it works and it does not matter one whit how great something is if it does not work, after being informed here, there are a few advantages to the turbine i had not considered before, specifically all weather/flex fuel issues.
sadly enough reliable MTBF numbers on military hardware in active service tend to be quite difficult to get a hold of.

4. well, given all that data, the abrams actually out powers the leopard 2 slightly, weighs in at about the same and if that instant power transfer mattered so much to acceleration why does it have such similar acceleration numbers?

5. I shall bow to your experience on that point.

6. so, there is an advantage while using turbines for an armed force that regularly go around and visit other nations on live fire drills, check.

7. i agree, the M1 is not a godmobile, it is a reasonably good MBT but i really dislike it's flaws, and i would go for a leopard 2 or a T-90 if i had the choice... T-72 would work, and interestingly enough i know a place you could BUY some t-72's as a civilian.


Thu Oct 02, 2014 10:34 am
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Post Re: Gyrojet Pistol
If you have a choice, take the T-90 into combat over the T-72. Just ask the Iraqi Republican Guard.

Been watching this debate from the side lines, its starting to look like the last one about the Zumwalt :roll: . Might be a good idea to split off into a separate topic.

Fun reading along though :D


Thu Oct 02, 2014 11:01 am
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Post Re: Gyrojet Pistol
Quote:
6. so, there is an advantage while using turbines for an armed force that regularly go around and visit other nations on live fire drills, check.


Sorry, that one begged for a small edit :roll:


discord wrote:
4. well, given all that data, the abrams actually out powers the leopard 2 slightly, weighs in at about the same and if that instant power transfer mattered so much to acceleration why does it have such similar acceleration numbers?



Picture, if you will, a sine wave oscillating around a line. The line is the M1 power outpout. The sine wave would be the Leo as it shifts gears and revs up.

If you ever bought a diesel engine car or truck and floored it you would see how this works. Come to think of it, its a pet peve of Clarkson on Top Gear. I will poke around and see if I can find footage of him showing the issue in a car. Basically this, when you ask a diesel to give it everything it can it gives you nothing, absolutely nothing, in terms of acceleration until the very top end of its power band/rev range. Then you get whomped in the back of the head as the power pours in at once. Then nothing again, because you had to shift and the power is gone away. Exaggerated, but thats the basic effect. The diesel has a narrow band where it delivers its power.



The other side of this is the potential to throw tracks or break out of a glut from a stand still. The wider power bands make it more likely to damage something and not have the power you need to break out from mud or what have you.

(edit: oh and the governor hits the performance pretty hard. It can be disabled but the tank, and crew, wont last long at its true top speed. )


Thu Oct 02, 2014 12:09 pm
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Post Re: Gyrojet Pistol
nemo:
you can get pretty much the same level power with CVT, torque converters and other complicated things.
my personal favorite when it comes to load leveling and perfect power, is power plant --> generator --> battery pack --> electrical drive motors. if you want lots of extra power, build in a bypass so you can shunt both the energy from the generator AND the battery pack into the motors...and electrical motors is pretty much the goto thing if you want instant power from idle.
a hybrid, most common one is diesel-electric as used in trains, boats.... trucks?

and a note, modern turbo diesels are pretty responsive.
a quick wikipedia quote from throttle response
"This changed recently with some modern diesel engines outperforming similar engine size petrol cars."

pinhead:
i totally agree, but you can get a T-72 for under 50k USD whereas the T-90 is somewhat more expensive, and rather restricted.
however, the T-72's the iraqi were using is....a interesting and somewhat funny story.
http://www.youtube.com/watch?v=j7NVRTlAkx0
man i love that guy, he's a riot.


Thu Oct 02, 2014 2:35 pm
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Post Re: Gyrojet Pistol
discord wrote:
sen:

1. done, over with, and we are in agreement.

2. turbines are due to how they operate inherently more susceptible to FOD, it is another of the disadvantages of the basic design, has to do with greater stress on air filters and delicately balanced internals.
that said, most engines will get effed up if you get sand and grit into it, question is how badly, how fast and how difficult it is to prevent.... Ramjet would probably not care though... but not really relevant for the discussion.

3. there are transmission solutions that will give pretty much the same effect to a piston engine(CVT, hydraulic torque converters, etc.), but it is not really all that important, the single most important issue is that it works and it does not matter one whit how great something is if it does not work, after being informed here, there are a few advantages to the turbine i had not considered before, specifically all weather/flex fuel issues.
sadly enough reliable MTBF numbers on military hardware in active service tend to be quite difficult to get a hold of.

4. well, given all that data, the abrams actually out powers the leopard 2 slightly, weighs in at about the same and if that instant power transfer mattered so much to acceleration why does it have such similar acceleration numbers?

5. I shall bow to your experience on that point.

6. so, there is an advantage while using turbines for an armed force that regularly go around and visit other nations on live fire drills, check.

7. i agree, the M1 is not a godmobile, it is a reasonably good MBT but i really dislike it's flaws, and i would go for a leopard 2 or a T-90 if i had the choice... T-72 would work, and interestingly enough i know a place you could BUY some t-72's as a civilian.


FIRST... I must fall upon my sword for a moment. I copy-pasted the wrong figures for the torque. My apologies...
Double the numbers, halve the RPM, and it's the correct figures. The torque for the MTU diesel would be off, since the mistaken figures weren't scaled with the horsepower increase as the RPM's rise. The side effect of multi-tasking at 3 AM XD. Note that the numbers are calculated for at-shaft, not to the road. Cut them in half again, and you'll have rough figures. It simply makes the point.

1. Yup.

2. My point exactly.

3. I'm looking for the MTBF's, actually. I found the information for the AGT-1500. A new build turbine has an average of 1,100 hours MTBF. I'll post the MTU numbers when/if I can find them.

Beyond that, I'm glad I got the point across. :) No solution is perfect. It's all about tradeoffs.

4. Nemo explained quite well. Nothing to add.

Also, Nemo, there are reviews in a couple auto mags about the M1, as well. One was in Diesel Power, the other... I forget. Makes for a little reading, is all. And yeah, I've heard a lot about what the governor limits... It's all hearsay, but I've had tankers claim to have had the governor removed, and attained speeds of 60-70 mph thereafter. The vibration through the drive train is pure hell on it though, and the tracks wear out quickly. I also came across an amusing little bit regarding the XM1 prototype...

True or not, I dunno, but amusing. But apparently, two MP's clocked a vehicle doing seventy plus down a dirt road towards a testing range, and immediately attempted to pull it over... They couldn't see what the hell it was through the talcum fine dust thrown up (and got COATED in it by following), and the XM1's driver couldn't see or hear the siren, so he kept going, hells bells, all the way to the range. Once they saw they'd been chasing a tank, there was apparently a lot of confusion.

For fun:
M1 stuck in mud ---> https://www.youtube.com/watch?v=p05mf6rk18A
T-90 stuck in mud ---> https://www.youtube.com/watch?v=jMwdQN-2f2w

5. I bow in turn to the pleasure of being able to reasonably debate. It's refreshing.

6. Pretty much. I have nothing to add here.

7. I could probably talk you out of the T-90... But we'd be in lockstep on the Leo 2. Superb machine. ^.^


Last edited by Senanthes on Fri Oct 03, 2014 1:31 am, edited 3 times in total.



Fri Oct 03, 2014 1:19 am
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Post Re: Gyrojet Pistol
Nemo wrote:
If you ever bought a diesel engine car or truck and floored it you would see how this works. Come to think of it, its a pet peve of Clarkson on Top Gear. I will poke around and see if I can find footage of him showing the issue in a car. Basically this, when you ask a diesel to give it everything it can it gives you nothing, absolutely nothing, in terms of acceleration until the very top end of its power band/rev range. Then you get whomped in the back of the head as the power pours in at once. Then nothing again, because you had to shift and the power is gone away. Exaggerated, but thats the basic effect. The diesel has a narrow band where it delivers its power.


That's also why big rigs can have something like 18 gears. Gotta stay in the maximum torque band.


Fri Oct 03, 2014 1:21 am
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Post Re: Gyrojet Pistol
sen: to be honest though, the T-90 had a slightly worse mud hole to get out of....


Fri Oct 03, 2014 1:51 am
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Post Re: Gyrojet Pistol
discord wrote:
sen: to be honest though, the T-90 had a slightly worse mud hole to get out of....

Somewhat. Those were for fun. Not to prove any point. :) Anything I'd say about the T-90 would have little to do with a mud hole that might as well have made grabby hands at the tank beforehand. Frankly, I'd have likely done the same. I wouldn't be able to resist trying XD.


Fri Oct 03, 2014 2:10 am
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Post Re: Gyrojet Pistol
Watching a video about tanks today and they had a pretty good segment on the M1 Abrams turbine engine.
https://www.youtube.com/watch?feature=p ... Aj5o#t=450

*Staying out of the debate, sharing some neat stuff* :D


Fri Oct 03, 2014 3:14 pm
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Post Re: Gyrojet Pistol
To be truly fair, the holes they were in were different. The M1 wound up in a rut that beached it. You can see when it went forward it picked itself up off its tracks and was sitting on its belly. A function of that damnable red clay we have all over the south east US.

The T-90 on the other hand couldn't find traction. The soil there looks really loose. Honestly, a heavier tank might have had an easier time getting out of that one if it could dig through the top and grip some of the harder packed sludge underneath. That or different tracks. Will pay real fake money for a Russian-English translation of that video. When they go in the hole and the tank stops, they didn't flood the engine intake did they? Couldn't hear it running in the second or two before it cuts away.


Fri Oct 03, 2014 3:56 pm
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Post Re: Gyrojet Pistol
just noticed a few things....
JP-8 flash point is at 38 celcius(or 100.4 fahrenheit), that means you need to either keep it in a hermetically sealed container or it might spontaneously burn in ambient temperature, admitted that is HOT weather, but not unheard of in the sandbox.
combine this with how hot the turbine runs, any fuel leak and you got instant tank BBQ.
this was basically the reason why diesel was so much preferred over gasoline for military vehicles way back when, less fire hazard...

addendum seems the difference in actual fire hazard is not so great, but still advantage to diesel.

the Honeywell AGT1500C weighs in at 1134kg(dry)
MTU MB 873 Ka-501 weighs in at 2200kg(dry)
now someone would say 'look, the turbine weighs less, much better!' hmm, lets look at fuel consumption and capacity.
M1 1900l 426km range
leo 2 1200l 550km range
at which point someone will say 'but aviation fuel weighs less!' which is true....
JP-8 0.775 to 0.840 at 15 C
diesel 0.825 to 0.845 at 15.6 C
so not so much difference, and besides, diesel has a higher energy density at 48MJ/Kg compared to JP-8 at 46.8MJ/Kg....so a higher density is actually GOOD, it means it takes less space and space is at a premium in a tank.

so to get similar range.... (apply mathemagic!) 2453l of JP-8, and pretty much nullifying any weight savings from the engine.

something i could not find however is powerpack volume, since volume is at a premium, it is kinda important, i do know that a newer diesel proposed for the leo got a 10% power increase in a package only 60% of the original size, that would free up enough space to double fuel reserves... if so wanted.


Fri Oct 03, 2014 5:05 pm
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Post Re: Gyrojet Pistol
discord wrote:
just noticed a few things....
JP-8 flash point is at 38 celcius(or 100.4 fahrenheit), that means you need to either keep it in a hermetically sealed container or it might spontaneously burn in ambient temperature, admitted that is HOT weather, but not unheard of in the sandbox.
combine this with how hot the turbine runs, any fuel leak and you got instant tank BBQ.
this was basically the reason why diesel was so much preferred over gasoline for military vehicles way back when, less fire hazard...

addendum seems the difference in actual fire hazard is not so great, but still advantage to diesel.

the Honeywell AGT1500C weighs in at 1134kg(dry)
MTU MB 873 Ka-501 weighs in at 2200kg(dry)
now someone would say 'look, the turbine weighs less, much better!' hmm, lets look at fuel consumption and capacity.
M1 1900l 426km range
leo 2 1200l 550km range
at which point someone will say 'but aviation fuel weighs less!' which is true....
JP-8 0.775 to 0.840 at 15 C
diesel 0.825 to 0.845 at 15.6 C
so not so much difference, and besides, diesel has a higher energy density at 48MJ/Kg compared to JP-8 at 46.8MJ/Kg....so a higher density is actually GOOD, it means it takes less space and space is at a premium in a tank.

so to get similar range.... (apply mathemagic!) 2453l of JP-8, and pretty much nullifying any weight savings from the engine.

something i could not find however is powerpack volume, since volume is at a premium, it is kinda important, i do know that a newer diesel proposed for the leo got a 10% power increase in a package only 60% of the original size, that would free up enough space to double fuel reserves... if so wanted.


Again, fellas, I only put the tanks in mud up for a giggle at the both of them... But no, Nemo, it didn't flood.

And yes, discord, you're entirely correct about the M1 carrying more fuel. Another tradeoff that was deemed acceptable. With the capability to burn pretty much anything, all you really have to do is cut the JP-8 with whatever you please to reduce the fire hazard.

There was one notable incident of a supposedly (to it's detractors) spontaneous engine fire on the M1 that I recall, which comes up pretty much every time; Cajone Eh. A lot of people claim it simply burst into flames... Every source I've managed to find states that it took a shell to the engine deck, then burst into flames after a tank ruptured, spilling the fuel all over the turbine.

Now, volume...

Here's the dimensions of the engines themselves;
AGT-1500: 67 inches (170 cm) long, 39 inches (99 cm) wide, and 32 inches (81.2 cm) high.
MTU MB 873 Ka-501: 70.9 inches (180 cm) long, 77.8 inches (197.5 cm) wide, and 41.7 inches (106 cm) high.

Rough volume is 1.378 cubic meters for the AGT-1500, and 3.76 cubic meters for the MB 873 Ka-501. The turbine takes up just over a third of the volume of the diesel. Both will need associated support apparatus (cooling systems, exhaust, ad nauseum). The net result is less under armor volume for the turbine.

Not bad for an engine that has it's origins in 1965... But still, I'd like to see what an updated turbine AND diesel could do in the M1, just for comparison.

Some numbers that I've seen thrown about for the LV-100-5, a possible AGT-1500 replacement, is 43% fewer moving parts, 50% improvement in idle fuel economy, and a 25% improvement in moving fuel economy according to Honeywell. I have no idea if it would be any smaller or lighter, though.


Sat Oct 04, 2014 2:42 am
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Post Re: Gyrojet Pistol
pinheadh78 wrote:
If you have a choice, take the T-90 into combat over the T-72. Just ask the Iraqi Republican Guard.

Been watching this debate from the side lines, its starting to look like the last one about the Zumwalt :roll: . Might be a good idea to split off into a separate topic.

Fun reading along though :D

Isn't the t90 a vastly modernised version of the t72 though in a sense? Comparable to the post warpac tvardy or t72m4cz


Wed Oct 15, 2014 8:01 am
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Post Re: Gyrojet Pistol
junk: yes probably.


Wed Oct 15, 2014 1:14 pm
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