Xoon

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Xoon last won the day on September 21 2016

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  1. The propaganda video uses quite old footage, including the one of the T-90 that caught fire (the remote MG's ammunition caught fire). Here is the video for those that are curious (The Leopard is seens at 08:20) (WARING, GRAPHIC): http://videos.videopress.com/wutY8cZC/the-islamic-state-22stay-for-the-end-times-wilacc84yat-hcca3alab22_hd.mp4
  2. Probably not the same tank when I think about it, might be another picture I was talking about. Anyways, another disabled Leopard 2?
  3. Just a two pictures I found interesting from a drone in a ISIS propaganda video: A little closer: Same tank?
  4. So the reason for adding the heavy and bulky copula was so that the commander could service and reload the MG under armor and with NBC protection. Not really worth it in my opinion. Thanks for the info though!
  5. Might be a bit off-topic but: Why did the US engineers chose such a huge copula? If they wanted protection for the operator of the machine gun, why not use a remote operated one? And if they wanted a high vantage point with good vision, why not use periscopes? And, what is the protection requirement for a copula? Minimum against HMGs?
  6. But does this mean that after a week, all the pressure would be gone? You should be careful when comparing bulldozers and bobcats to tanks. First of all, those vehicles use actuators. Since hydraulic actuators are much cheaper than electric actuators, also electric actuators require cooling in some cases, the hydraulic actuator reigns supreme. Now, this means you need a pump to power the hydraulic circuit, so why not make the motors hydraulic too? This saves complexity, time and money. Now, in modern tanks we do have some hydraulic systems like the turret traverse and elevation, but these are required to run even when the engine is off, aka silent overwatch. So you can't combine the transmission circuit with the rest. Also, tanks are slowly switching over to electric traverse and elevation mechanisms for safety reasons. I was mainly wondering if you had some rough numbers on the power factor of the hydraulic transmission parts. Something like this: No problem, all contribution are welcome.
  7. Yeah, I am a to-be-tradesman, not a engineer, at least yet. So this is more advanced than we are taught. We work generally with PSUs (24V, 2.5A) and your typical out-of-the-socket voltage types (230V, 380V, 400V, 440V and 690V). Here the current is constant, and will fill out the path of least resistance. Burning out anything not strong enough to handle it. We can manually adjust the PSUs, but we usually just keep them at max. And we are thought to never mix voltages, usually to avoid fusing switches and melting coils. I have touched on some more dynamic formulas, but never put them into practice. A few quick questions: 1. For how long can the accumulator keep the stored energy? 2. How much of the energy can the hydraulic regenerative breaks recover? 3. What makes a hydraulic system more suited for heavy vehicles? 4. The ultra caps can only store the energy for a short period of time right? So when traveling downhill for long amounts of time, the energy is lost? 5. Do you know how efficient the system would be? 6. Could you draw a hydraulic circuit to show how you can vary the speed of the motors and mix power? Though not terribly convincing, it is always worth a look. You never know if a breakthrough makes it viable in the future.
  8. Well, a small leak would still probably rupture the hose and spew hydraulic liquids everywhere. In a component it would not be a issue, well other than having to constantly refill the reservoir. Normally, you would have two circuits per sprocket, meaning that if one circuit fails, you can still limp back to base with the other. But of course this comes with the issue of needing two reservoirs, two pumps and two of any control valves per sprocket. Which could get complex. Without a duplicated circuit, the system would be just as vulnerable, if not more vulnerable. Ok, so I just found out I was completely off about grounding in vehicles. Turns out, they have nothing in common with house grounding systems. Quite simply, you connect one of the poles from the battery to the chassis, and this way you only need one wire to components in the vehicle. Like headlights, spark plugs, starter motors and electronics. The reason electric vehicles do not ground their batteries that power the motors is so that they don't mix the high and low voltage. So the reason a 787 or 380 has a 400V system is because the entire system is 400V, while in a car the headlights, starter, electronics and such are 6-48V.
  9. Well of course, the motors won't last forever. And yes, rewinding electric motors is becoming rarer and rarer, but you can still do it if needed. But most of the time you just replace the entire thing. When it comes to hydraulic transmissions, I can't say for sure. I am used to pneumatic systems, which are very similar. My problem with hydraulics is the chance of leakage, any leakage would cause the entire system to fail, if the pump failed, the system fails. And in practice, you would use the same control systems for the hydraulics, magnet valves and such. Here the sealing could rupture, and they need regular maintenance. Honestly, if anyone could cover hydraulic transmissions, that would be great. Does hydraulic system have the ability to recover and store power? Like regenerative breaking? Well, I am no mechanic (sadly), but I know that 6-48V systems can safely be grounded to the vehicle chassis. I suspect this is because the low voltage is too weak to flow through the steel of the chassis, simply because of the high resistance of steel. This helps dissipating the current, like when grounding a house, you run a wire through the soil, at the dept deep enough so that I can't electrocute a person on the surface. When using higher voltage systems however, the chassis is not used to ground the vehicle. I guess 400V is enough to penetrate through the chassis and electrocute a person touching it. This is why I suggested double isolating the electric components, which at least by Norwegian standards, removes the need for grounding.
  10. Yes, efficiency of electric motors have dramatically increased. Probably the main reason the motors were so heavy is because the cast iron frame. Nowadays we can use aluminum and titanium. Though, a hybrid electric drivetrain would probably be a bit bigger than a conventional transmission. If money was not a issue, we could wind the motors with silver, and make casings out of ceramics or some high strength alloy and the transmission would probably be around 40% more efficient and twice as light. Though the price would be around 20 times as high. Electric motors in general don't need gearing. Simply because of their excellent torque curve and output. Considering anything that is done in a differential or transmission can be done though a control circuit I see not reason to add unnecessary complexity. Though, for optimal efficiency, you should have a single gear, converting down the electric motors high RPM to something the sprocket can use. At least in AC motors, to reduce the RPM of the motor, you add more pole pars, however this also reduces the efficiency of the motor. A better alternative is to just use as little poles as possible (1 par) and then use a single gear, since from what I have learned, it should be more efficient. To give a overview, a AC electric motor with 1 pole par runs at 3000RPM, minus slip. And I think the sprocket has to rotate at 800ish RPM for the tank to reach 80-100km/h . So a ratio of roughly 1:3,75 should be enough. When you start working on these things, you will realize how resilient these things are. And no need for a soldier to be precise, just plug and play. A brush motor would be a very bad idea in a tank, since Brushless DC or AC motors are MUCH better. If you are concerned about springs and switches, we have solid state versions or all components, no moving parts. Grounding would not be a issue either, since you can't ground a 400V+ system into the chassis of the vehicle, you just double isolate it. Unless the engine compartment takes some damage from enemy fire, which breaks the protection of the equipment, shorts should be impossible, since all military spec electronics need to be dust proof and waterproof. And if a winding is partially severed, you just lift out the motor, unbolt a few bolts, remove the rotor, remove the broken winding, and add a new one. As long as the electric motors are IP67 or higher, you can lose as much crap you want into the engine compartment without worrying. Engine compartment flooded? No problem as long as the IEC does not get affected. Dust storm filled it with sand? No problem, dust proof. When speaking about cooling, external cooling would defiantly be the best, since it makes the motor a lot less bulky and makes possible to have a higher IP grade. Interesting.
  11. Thanks Coll, just what I needed. So if you don't mind I have a few questions on some points: The ideal tank steering mechanism is as simple as possible; or else the tank will be hard to maintain in the field. A tank that's stuck in the repair shop most of the time is no good for fighting. From my point of view at least, a electric transmission would be the most simple of them all, a little ironic considering that the dual drive system is one of the most complex ones. Why? Because the system can be broken into a few parts: 2 electric motors 2 VSDs 1 generator 1 engine Wires. And the control system. Electric motors are very simple in construction, the casing, stator and a rotor. And the only part that needs maintenance is the two bearings on the motor shaft. You can simply view the motors as a module, since if a enemy round pierces the motor, you can probably guarantee that it needs replacement, or rewinding, like a transmission. So when it comes to maintenance, you can probably ignore the motors. And when you need to maintain them, you simply lift out the powerpack or electric motor, loosen a few bolts on the front and rear, pull out the rotor, and inspect the stator. And switch the bearings if needed, which are located on each side of the rotor. The Variable speed drives or VSDs would most of the time be integrated into the motor. They last just as long as the motor if not longer, and again comes in a module form. They are simply electronics. The generator is in practice a electric motor in reverse, to say it in a simple manner. The wires can be made to simply be plug and play, so when one is severed you can just unplug it, and add a new one, and it should not require a crane or removal of any parts. You could also combine the severed ends if needed. Also, wires last forever, almost. Lastly, the control system, quite simply, 1 PLC or computer, two high speed pulse counters and a few sensors. All of them lasting practically as long as the VSDs, except the pulse counters which may need a bearing switch. If we could remove the IEC, the we could remove the generator, which would make the system MUCH simpler, but that is not possible with the current battery technology. (Just a note, there are a few small sub components in the system which are irrelevant that i did not mention) The ideal tank steering mechanism should be as mechanically efficient as possible. There's no point in having a massive, powerful engine in a tank if its transmission wastes most of the horsepower. I think a electric transmission scores best here, when I calculated it I think we ended up with the system being roughly 3% more efficient, not considering regenerative breaking and such. The ideal tank steering mechanism makes driving in a straight line easy; the tank should not tend to veer off course. This should not be hard to accomplish with modern electronics. With a sensor on each sprocket, we can measure the RPM and then adjust the motors accordingly. Alternatively we could have a clutch in between them, however this would be more complex and only work when driving straight forward, and not during turning. If we oversize the electric motors, we can simply transfer power from one motor to the other, and measure the load on the electric motor to avoid the track slipping on the terrain. The ideal tank steering mechanism is additive; that is, when transitioning from moving at full speed forwards to a turn, the mean track velocity remains the same. This helps a tank maintain its speed as it turns, instead of bleeding it off. In addition, tests have shown that additive steering works better when the tank is in deep mud, since keeping both tracks moving helps prevent the tank from getting stuck. By oversizing the electric motors, we can make them adaptive, simply allocate more power to the other electric motor. A alternative would be to overload the motor. A electric motor can produce 250% of its max torque, well at the cost of reliability and a no so slight chance of catching fire and/or melting. The higher the overload, the worse. Though by adding extra external cooling you could overload the motors for short periods of time like turning, without impacting the motors. This option has to be compared to a conventional transmission to weigh the pros and cons though when it comes to bulk. Or you could make the steering subtractive and make it more compact and lighter. The ideal tank steering mechanism allows neutral steering, that is, that the tank can turn within its own length. By simply adding a neutral mode, you can just make one of the electric motors go in reverse, and throttle them according to how fast you want to turn. Additionally, a tank steering mechanism should be regenerative, which is to say that the kinetic energy from the inside (slowed) track should be transferred to the outside (sped up) track. This also helps the tank maintain its speed as it turns. As you said, by running the electric motor in reverse, you can recover the power for later use, same with braking. Tank steering works best when it is continuous, that is, that power is delivered constantly to the tracks while the turn is performed. This is especially important when driving in hilly terrain, as the loss of power can cause the tank to slide downhill. A digital system should allow 255 states, which for the human mind is continues. Finally, the ideal tank steering mechanism provides multiple turn radii. Sometimes the driver needs to make a wide turn, while at other times they might need to turn quickly. In the most refined tank steering mechanisms, the steering is infinitely variable, which means that arbitrary, fractional turn radii can be selected, just like driving a car. Don't quote me on this one, but it should have infinitetly variable turn radius.
  12. I've been thinking about projecting a electric transmission just for fun, so I was wondering if you guys could tell me about the different steering systems in tanks. A short explanation of the concept would be enough, though you could link me to a article or post if you got one.
  13. What about a two stage swingfire-like top attack missile? Launch the missile upwards around 45-70 degrees with the first booster, then ignite the second soild-fuel rocket to accelerate it towards the target. If the arch is high enough, then it should simply need to be pointed towards the target and it would hit it at 30 degrees, from horizontal. But all things considered, wouldn't KEP missiles be quite bulky? Thereby limiting them to long range AT role, most likely vehicle mounted. But I have to say, 3 meter long missile sounds like a pain in the ass to work with for a AFV designer, if you want to protect the missile.