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Gerrit Grundling

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About Gerrit Grundling

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  1. It sounds to me like "shake allowance" and "shrinkage allowance" are conflicting requirements. Could you please elaborate?
  2. Without a thermostat, the engine block would swell and shrink as the temperature varies with load. This would make the pistons wear quickly and irregularly. Ever notice how an engine is somewhat noisier when it is cold that when it is at operating temperature?
  3. The diesel lubricates the injectors and the pump. If you run out of diesel, you damage the injectors and the pump, which may either cause sensors to prevent the engine from running, or cause sufficient physical damage to cause the injectors or pump to not work.
  4. 1. Diesel lubricates the diesel pump and injectors. Petrol has no or little lubricity, so the components will seize. 2. Petrol is designed to prevent spontaneous combustion. Diesel is designed to promote it. Without spontaneous combustion, a diesel won't run. Diesel has a higher flashpoint than petrol, but diesel also has a lower auto-ignition temperature than petrol.
  5. Both maneouvre by moments around 3 axis: roll (around the longitudinal axis), pitch (around the lateral axis) and yaw (around the vertical axis)
  6. I could be wrong, but I don't think you get a knee-and-column CNC mill. The bed-type mill can move much faster, especially in the z-axis, so it should be the more productive machine. As I said, I could be wrong.
  7. Stress concentration factor is dependent on the geometry, such as a hole, notch or fillet in the component. This can be designed for as it only depends on the geometry. Stress intensity factor is dependent on geometry and load. This can only be determined experimentally. The stress intensity factor is highly dependent on cracks and other material and geometric defects. Tables for the stress intensity factor is hard to obtain, while stress concentration factors are tabulated and graphed in literature.
  8. Are you expecting answers, or drawing up a study guide?
  9. The surface speed between two gears are exactly the same, otherwise there would be slip. The load, or force, between two gear teeth are exactly the same, otherwise they would violate the conservation of force. The larger of the two (in this case, the gear) has a much greater shear area, which means it sees a lower toque-induced shear stress. Recall that the stress = torque / polar moment i.e. Tau = torque / J, where J = pi * (D^4-d^4) /32. It is true that each tooth on the larger gear has more time to cool down after making contact with the pinion because there are more teeth. But it is also usually true that the pinion's teeth are in contact with cooling oil for longer and more often.
  10. The Twin Charger uses both a turbocharger (driven off the exhaust gas) and a supercharger (driven off the engine) in sequence. First, the supercharger is engaged at low speeds where the exhaust is too weak to drive the turbos. Then, at higher speeds when the turbos are generating boost, the supercharger is disengaged. The idea is to overcome the inevitable "turbo lag" at low speeds. This is not the same as the turbocharged 2-stroke diesels, which rely on supercharging for scavenging, but may have a turbo to produce intake boost upstream of the supercharger.
  11. I have tried to find proof of the claims that direct injection is more efficient, but all I get are claims and phrases such as "direct injection is more efficient than indirect injection". I would like to do a side-by-side comparison of the two technologies. I would require two engines which are identical in every way, except the one is direct injected and the other one is indirect injected. The only such report I found was for the OM322 and OM352 truck engines, but those engines run at speeds below 2500RPM. I am not convinced that direct injection is better, as the components cost more, and there are more components, the systems are incredibly sensitive to maintenance and fuel quality, and the very high pressures require sturdier (which means heavier and more expensive) construction.
  12. The text books you use while studying mechanical engineering will be good enough. The rest of it is down to regulations and proprietary knowledge. All of it is just a combination of thermal design, kinematic and dynamic design, and material selection.
  13. "To allow slip and creep chain drive is used over belt or rope drive." That makes no sense. A chain drive is used to prevent slip and creep. Chain drives require almost no pretension, unlike belt drive and rope drives. However, the chain will require guides to prevent it from coming off of the sprocket. Too little tension will also see the chain flung out under centripetal force at higher RPM. Toothed belts also offer synchronicity like chains, but without the need for lubrication. They also weigh much less. However, they do not take shock loads too well, and they need periodic replacement, while a well-designed chain system can last decades.
  14. It is interesting to see the inlet valve close BBDC.
  15. I am inclined to agree that the 6-stroke engine is unfeasible. Water injection was used in 4-stroke engines to reduce combustion temperatures and increase combustion pressures in high-powered aircraft during WW2. The evaporation of the water would increase the constant pressure component of the mixed-cycle operation of the engine, exchanging heat for pressure. Unfortunately, this meant that water had to be carried on board as well, and water is heavier than fuel. If the 6-stroke engine manages to run at all, I believe that it wouldn't be very efficient. Or it wouldn't be very powerful. Either way, it wouldn't be useful as a total system.
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