The REAL M1 Abrams! Chapter 2: Mobility (Part 3/4)

[MingGuoLi]

Jet fuel is a good thing if it's military grade. JP-5 doesn't burn easily, at least not as easily as diesel.

[BlacktailDefense]

@MingGuoLi Let's hope that's true then, because the M1 carries 505 gallons of it.

[dudejo]

i heard that turbine engines guzzled more gas than piston engines on idle but even at slow cruising speeds???

that IS bad. then again, that's what you get for wanting a 1500 hp engine that only makes that power at high RPMs.

[BlacktailDefense]

@dudejo 1500hp at a non-stop 30000rpm is going to drain a 505-gallon tank pretty fast, no matter how much power you transfer to the Drive Sprockets.

It's just not worth the effort.

[beltar2]

Soviet T-80 with gas turbine could drive at 50 mph. But we can say for sure now that it was temporary fashion. Everybody want only diesel engine now.

[TheKifinas]

@beltar2 that's why they made the t-90 the t-80 was draining gas like a bicht sucking a cock !!!

[MatoVuc]

I'm somewhat surprised that deisel-electric engines have never been considered for tank propulsion (Ferdinand Porsche's 2 failed excursions not withstanding)

they develope more power with less "horses" and provide direct torque(i.e. cut out the transmision)

it can be broken down into 3 parts: power unit (diezel motor), power storage (a number of capacitors to store extra electrical charge) and electric motor propulsion unit, all simple, reliable and easily replacable and repairable

[BlacktailDefense]

@MatoVuc I'm not sure why the idea never took-off either, but I have a couple of theories;

1- A hybrid engine that powerful and rugged would be HUGE.

2- While the engine you describe has 3 main subcomponents, a regular diesel has 2 (engine block assembly & transmission assembly).

3- It would be more expensive to build than a direct-diesel.

I still think it's a concept that needs to be explored, though --- especially for smaller AFVs and softskin vehicles.

[MatoVuc]

@BlacktailDefense technically, it could work even without the storage units, they are just a falesafe (if the engine dies, you at least have a minute or so to find cover) and a "quickstart" (moving on baterry power for a short period even before the diezel starts generating electricity, basically runing from a dead engine instantly)

Even so, an electric motor is significantly less complex than a transmission system and wastes less energy

[MatoVuc]

@BlacktailDefense as for the size argument, i can ceratinly see how that would apply way back when, but this technology has advanced significantly by today and could have been even better, as it was basically stunned in it's evolution for at least a decades worth of technological improvement (oil mafia and profit mongering)

Supposedly it's being fitted into the XM1203, but i think it'd take probably 3-5 years of concerted research and effort to produce a viable tank diezel-el. engine

[SpecialKLSX]

@BlacktailDefense Lets not forget that a system like that would have countess battery failures. Just imagine if in a block of 20 batteries one went down. now you gotta go in there and pull that one failed battery out at the very min, if not more because the fialed battery has damaged others nearby.

A hybrid drive in theory is a great idea, but in practice it's gonna bite you in the ass.

[52111centrumcz]

@SpecialKLSX

Oh hybrid powertrain is going to bite you in the ass...well I don't know but the railroad company that works near me has 29 diesel-electric locomotives that are 35 years old and they are going strong...

[SpecialKLSX]

@52111centrumcz That's a Train riding on smooth tracks, not a tank going overland. Also. Unlike a Tank, Trains get proper routine maintenance, and can go with a little neglect for a long time. Military vehicles need to be overbuilt like they are because of the idiots that they train to use them every day, letalone the abuse they would endure in severe conditions during combat.

I'm not saying it's a bad idea I'm just worried about longevity in combat.

[52111centrumcz]

@SpecialKLSX

These are Skoda locomotives: cs(.)wikipedia(.)org/wiki/Loko­motiva_751

Sorry no english pages for it. They have due to their reliability have only undergone oil changes and replacement of leaking fuel and pressure lines. The guy next to me is a former engineer of the CD railroad, and he served on one locomotive - he said maintanance(as in overhaul) was done only three times on the thing before it was retired in its 60 year lifetime.

[52111centrumcz]

@BlacktailDefense

I am not so sure. You are eliminating one of the most expensive and difficult parts to build on a tank, the differential gearbox! with suficient battery power, you can use a smaller engine cranking out DC power. 

[BitnikGr]

Advantages of gas-turbine engine:

1) Very high Power/Weight ration comparing with any piston engine.

2) Movement friction only in one direction, which significantly reduce vibrations, always comparing to piston engines.

3) Less moving pars

4) Low usage loads

5) High speed of rotation (RPM)

6) Low cost and use of oil

7) Low demands to fuel quality. Gas Turbine can use any fuel which can be spread in form of dust. Any petroleum products, organic compounds and dust-like coil

[BitnikGr]

@BitnikGr 8) Much easier start-up (ignition) at extremely low temperatures. Gas turbine engine will not have trouble to start even with -30degrees Celcium

-

Disadvantages of GTE:

1) Much more expensive compared to similar size piston engines, because materials used in turbine must have high heat-endurance and must be much more tough. Principle of co-operation with transmission is also more complex.

2) As a rule they have less Energy Conversion Efficiency... especially on partial powerload...

[BitnikGr]

@BitnikGr (something you have stated here already).

3) Reaction lag on changing power settings

4) Much bigger heat signature for IR homing ATGMs and thermal vision sights

5) The most well known and the most obvious! It is less fuel efficient! Something which limitates range and tactical mobility on battlefield.

-

The first three drawbacks explain why all tranportational means, which are smaller, cheaper and requires less maintenance than tanks, helicopters, coast boats etc don't use GTE ...

[BitnikGr]

@BitnikGr Two more advantages of Gas Turbine Engines:

8) They don't "choke". They don't shut down if find an obstacle or if driver make poor start. Everyone who drive car with manual gears understand what I am talking about.

9) Very important factor of MBT is its repairability (especially on the field). GTE can be replaced in 3 hours. Diesel engines are much more complex and require a lot more time.

[52111centrumcz]

@BitnikGr

Diesel engine powerpacks on the L2 can be replaced with hand tools and a 2-ton crane in 30 minutes.

[BitnikGr]

@52111centrumcz Well, like it seems, we can't generally say that diesels are more easily replaced than gas-turbines or vice versa. Since, there are diesels which requires almost 2.5 hours in order to be replaced by crew, and there are diesels which requires only 1hour (Leclerc Europack).

Probably same could be applied to gas-turbines as well.

[52111centrumcz]

@52111centrumcz

A diesel requires only a couple of inputs: therefore a fuel line and a communication line to bring commands along a wire, and a connection to a gearbox/ or a connection to the driveshafts if the powerpack incorporates the gearbox. I would say diesels are either the same, or more easily replaced then jets.

[BlacktailDefense]

@52111centrumcz

@BitnikGr

Those are pretty solid points; Diesels have a simpler interface that Gas Turbines, and the average amount of time required to hop the powerpack varies widely within Diesels alone.

It goes to show that the notion that "Gas Tubines can be changed faster" is at best a HUGE oversimplification.