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  1. J

    Educated opinions please: Are seats in rear crumple zones unsafe?

    I understand, but by working with the wrong units, the calculated force is 1 order of magnitude higher. By the way, even calculating with the wrong units, the answer should be 2x10^7 N instead of 2x10^8 N, which leads to a total error of two orders of magnitude higher. I see that you are...
  2. J

    Educated opinions please: Are seats in rear crumple zones unsafe?

    I am not sure about what you are trying to calculate, but the velocity term should be in [m/s] instead of [km/s] or [kph] to keep units consistent.
  3. J

    FredGarvin - Question For You Please

    The book is "Roark's Formulas for Stress and Strain" and the equation comes from Table 14-1, chapter 14, p.702 (7th edition, 2002). For background information, look for hertzian stress or contact stress.
  4. J

    Uranus and Neptune Orbiters

    As you stated, Neptune and Uranus are unarguably invaluable to science for several reasons and the community knows it, but have been left out of probe missions due to current propulsion technology limits and budget. There are future missions planned to be launched around 2020 and beyond, but...
  5. J

    Flying wing aircraft.

    Not exactly, load the second video and seek to 01:44, look carefully at the glider, what do you see ? Please, continue reading this post after you did that. In the first video you can see the delta gliders soaring, and feel their instability under low speed, which is expected. Danger might add...
  6. J

    Blow Out Preventers

    russ_watters is right. The BOP knives must have the force to cut through the drilling column. Any accidental closing is always undesirable, because going back to drilling means running lengthy systems and equipments checkups and also one would have to face the problem of trying to fish the...
  7. J

    A plan for the private colonization of the moon

    I think you should move on to cost estimates. Next, what do you think about outlining your enterprise with the help of PMBOK ?
  8. J

    Flying wing aircraft.

    Ops, sorry about the ride.
  9. J

    Flying wing aircraft.

    These are RC hand launched gliders:
  10. J

    Pressure Vessel End Cap Velocity

    Hydrostatic pressure limits the amount of kinetic energy transferred to the end-cap, as the water will not push the end-cap further after the breach, instead, the water will drop and flow to the ground. If the flow rate is too high, the water flow will become as hazardous as the end-cap...
  11. J

    Force in a static member

    Draw a free body diagram for the tip of the beam, decomposing W and check where is theta.
  12. J

    Calculating the energy of a stopping vehicle

    As they are structural consultants, either they are trying to figure out what will be the size of the restraints, or they might be questioning the plate thickness you provided. During break, most of the fork lift weight will be directed to the front axle and depending on the pit size...
  13. J

    Calculating the energy of a stopping vehicle

    I second sophiecentaur, if you are required to apply a code, stick to the code. I'm considering your question as being more to the curiosity side.
  14. J

    Centre of buoyancy

    If the fully immersed body is homogeneous it will be stable as you predicted. If the body has off-center internal cavities, the mass distibution will be uneven giving it a righting arm in respect to the center of bouyancy.
  15. J

    Building a water tunnel

    We worked with straws when we built a wind tunnel some time ago, it served well to our purpose. I'm not sure whether it will work for you, but you should try out. I remember a tricky part was to build the transition between the blower round pipe and the square test section, we applied a cubic...
  16. J

    Calculating the energy of a stopping vehicle

    The correct unit is [N]: 9800 x 3.75 = 36750N (3746kgf) I'm not sure what you are trying here, but this equation is unbalanced: [(9800 x 9.81) x 0.2] – [(9800 x 9.81) x 3.75] = 341289.9N. The first term will give [N] and the second term [N x m/s²], so you cannot add them together because they...
  17. J

    Building a water tunnel

    You can experiment and design one, or you might buy some flow conditioners for flow meters and try out the best arrangement to limit the turbulence intensity within the levels you are looking for.
  18. J

    Building a water tunnel

    You need a flow conditioner. Is this tunnel about the size you're looking for ?
  19. J

    The properties of Superheated steam

    I might be wrong, but I could not find where Andrew stated his design was better or revolutionary. Although we all know this is not the usual way products are developed, I think he is very creative and might one day come up with something really useful, until then, at least inventing is a very...
  20. J

    Calculating the energy of a stopping vehicle

    Ignoring the rotative inertia of the wheels and drivetrain, the maximum breaking force will be dictated by the maximum friction coefficient. Asssuming a maximum friction coefficient of mi=1, the maximum possible force would be Bf=weight x mi=96138N The deceleration will be a = -Bf/mass =...
  21. J

    Weibull with divergent pdf

    "The Weibull failure rate for 0 < β < 1 is unbounded at T = 0 (or γ). The failure rate, λ(T), decreases thereafter monotonically and is convex, approaching the value of zero as MATH or λ() = 0. This behavior makes it suitable for representing the failure rate of units exhibiting early-type...
  22. J

    Calculating Heat Transfer

    Start by drawing a diagram showing the heat flux from the source to the water exiting the block. Write the heat balance equation, you should consider the energy source, the heat transferred to the block through radiation, the heat lost by the block surface through radiation and due to...
  23. J

    Tractive force exerted by a lorry

    This thread should go to the homework section. Start with a freebody diagram, can you tell all the forces involved ? How can you relate the given mass and the given resultant acceleration ? How can you relate self weight, slope effect on weight vector components, motion resistance and the...
  24. J

    Calculating Generator Shaft Torque

    Apply the equation to 2.2kW@3600 to get the input torque. Using the 18:1 reduction, the output torque will be greatly increased. Will this increased output torque supply the required torque of 252.6N.m for the generator ? If not, what would be the generated power, disregarding transmission...
  25. J

    Calculating Generator Shaft Torque

    5kW@189RPM = 252.6N.m 350N.m@189RPM = 6.93kW Using Power [W] and Rot [RPM] to get Torque [N.m], the equation will be: Torque = Power x 60 / (2 x PI x Rot)
  26. J

    Difference between coupling and constrain equations in ansys

    Try solving the following equation using [kg] and [m/s²] to get [N]: F = m.a Now try again combining [kg] or [tonne] and [m/s²] or [mm/s²]. Which mass and acceleration units can be combined to give the same numerical result as [kg] and [m/s²] ? Which combination returns consistent units ?
  27. J

    Dyna result doesn't match Test result

    In the first figure, when you define the stress x plastic strain for the material, the maximum inputed value is around 0.5GPa for a strain of 0.3, but when you show the lab test stress x strain graph in the last figure, the maximum stress is around 0.37GPa for the same strain.
  28. J

    Pole fatigue calc

    One thing you are doing wrong, self weight is a static load and cannot induce fatigue damage. It is not possible to verify the equations in your spreadsheet, but you might be working with the wrong units.
  29. J

    Pneumatic/hydraulic simulation software?

    you may try Festo's Software: