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  1. Andrea Vironda

    Calculating constraint reactions

    Thanks, it helped me a lot
  2. Andrea Vironda

    Calculating constraint reactions

    I would be interested in calculating the constraint reactions on the 6 pads in yellow in the figure, about 300mm apart among them and loaded with F=12500 kN in blue. Since the system is highly hyperstatic, I don't know how to calculate the constraints. Can you give me a hand? I've made a FEM...
  3. Andrea Vironda

    I Time required to cool down a botte of wine

    In post #16 there's a word, "here", that is in blue. Clic on it, it's stored on OneDrive. I put comments on all the variables i used
  4. Andrea Vironda

    I Time required to cool down a botte of wine

    You can Open the link and have a look 👍
  5. Andrea Vironda

    I Time required to cool down a botte of wine

    Ok got, i created a model here, but I notice the starting rate would be -1.1 °C/s, too many in my opinion. I think C or U must be revised.
  6. Andrea Vironda

    I Time required to cool down a botte of wine

    I have the second edition (2002). I can see in §10.9 FREE CONVECTION the theory, but I can't find the tables. Also appendix E is mute
  7. Andrea Vironda

    I Time required to cool down a botte of wine

    What is MC? and how to deal with U? around 1E-2 W/(m2·K) I think it's suitable. In this case I would have dT/dt=-0.004 °/s
  8. Andrea Vironda

    I Time required to cool down a botte of wine

    How can I estimate U and C? For U I think I have to use the resistance equivalent with thermal conductivity of the glass wall (W/(m·K)) and convection heat transfer coefficient (W/(m2·K)) For C can I assume 2.5 kj/kg/K ?
  9. Andrea Vironda

    I Time required to cool down a botte of wine

    I know ##\Delta=Q-W##. Here the work done is 0. ##Q## is function of external temperature, wine temperature, the bottle shape and the thickness of glass. Of course the substances are also important (maybe I can consider wine as water, as Jesus did). I can use conduction Heat Transfer formula to...
  10. Andrea Vironda

    I Time required to cool down a botte of wine

    Good morning sirs, I have a standard bottle of wine made by glass, 0.75l. I suppose it's 20deg and I'd like to know how much time I need to lower the temperature of 4deg, considering outside it's winter, no wind, simple convection. I read some theory and I discovered some reference to Nusselt...
  11. Andrea Vironda

    How best to heat my house?

    I think there's a limit below which living becomes unhealthy. I could control it with a thermometer and a hygrometer. 18C–21C is the comfort zone, i think below 18C is better not to go
  12. Andrea Vironda

    How best to heat my house?

    I have a lodging in a block of 4. Mine is in the lower floor. exposed to east in the living side and to north in the night side. The average italian consumption is 4% more than minee, but since I'm single and I work/run for the most of the day, my consumption is very high. A family living in...
  13. Andrea Vironda

    How best to heat my house?

    Good morning, I have a 90 mq house burning 1200 smc of methane every year. I live alone and i keep 20°C when I'm at home (evenings) and 18.5°C when I'm not. My window frames are quite old, and I don't know very well if it's the case to spend 8 monthly payments to update my hardware. What is...
  14. Andrea Vironda

    Is there something happening below 0°C in this daily temperature graph?

    This is the link I used for the screenshot
  15. Andrea Vironda

    Is there something happening below 0°C in this daily temperature graph?

    ahahaha, yes for example. But why does freezing should cause that weird shape?
  16. Andrea Vironda

    Is there something happening below 0°C in this daily temperature graph?

    Hi, I notice from the graph that every night when the temperature reaches -2/-3 °C the curve change first the slope and then the concavity. Is something special happening?
  17. Andrea Vironda

    I Current produced by a Dynamo

    Yes, it's like climbing a mountain and then descending to the same point, but with a different potential. How can I relate the spinning rotation of the disc with the produced fem? Since the produced current is proportional to the resistance, I think that I have to find a maximum of produced...
  18. Andrea Vironda

    I Current produced by a Dynamo

    Can you explain better the potential topic? And vortices... Maybe an exponential ##^{2}## is missing in the denominator? is ##\vec{f}## a versor?
  19. Andrea Vironda

    I Current produced by a Dynamo

    Hi, I was trying to read about the current produced by a dynamo in my physics books but I can't find any reference. I have a rotor rotating at a certain speed, air flow and with a certain inertia, but how can i find the power produced and related current and tension?
  20. Andrea Vironda

    Solving a standard integral

    Solving integrals is an art
  21. Andrea Vironda

    Solving a standard integral

    In my opinion I could define ##u=\sin^2(x)+1##, so ##du=2\sin(x)\cos(x)dx##. Then ##\int_0^{\pi/2}\sqrt{u}du=2(\sqrt2-1)## but this is not the right solution.
  22. Andrea Vironda

    Solving a standard integral

    Hi, I'd like to integrate this function: $$ \int _0^ {\pi/2} 2 \sin(x) \cos(x) \sqrt {1+\sin^{2}(x) } dx $$. I think I should introduce some substitution but I'm not sure. How should I proceed?
  23. Andrea Vironda

    I Position of a point as a function of angular position

    Consider that d1 and d3 are parallel at ##\alpha, \beta = 0##. In my attachment there's the correct position in M, but when i have ##\alpha = 90## I can't find the z position. I can't imagine in my mind how much d3 is raised by ##\alpha## rotation
  24. Andrea Vironda

    I Position of a point as a function of angular position

    Hi, sorry but I can't understand how you set up angles, etc.. I've found a better image. How to outline the possible movements on an excel file?
  25. Andrea Vironda

    I Position of a point as a function of angular position

    Hi, I noticed I used ## \alpha## twice. It's the angle of rotation of d2 and d3 around a axis. It's not the angle between d2 and d3 (that's a constant angle). The 2 degree of freedom are the rotations around a and c axis.
  26. Andrea Vironda

    I Position of a point as a function of angular position

    Hi, I have this scheme, in which there are 3 segments: - I is coaxial to c axis and free to rotate in the origin. Length d1 - II is coaxial with a axis and free to rotate around c axis. There a fixed angle θ between a and c axis. Length d2 - III is welded to II, it's the PM segment. α is fixed...
  27. Andrea Vironda

    Sensor for detecting piston axial position

    Hi, I made the proof and I notice the piston behaviour is not the same on the outward and inward travel. For example the damping time changes. How can I convert this information in a tension [V] on a machine?
  28. Andrea Vironda

    Sensor for detecting piston axial position

    I'm not native english, what do you mean for "inside the box"? Thinking like a robot?
  29. Andrea Vironda

    Sensor for detecting piston axial position

    Interesting, I was thinking to use an Arduino and a Hall sensor plus a magnet I can buy easily online
  30. Andrea Vironda

    Sensor for detecting piston axial position

    Thanks for suggestion. Can you be more clear here?
  31. Andrea Vironda

    Sensor for detecting piston axial position

    Is it possible to calculate how much a wall of steel dampers the magnetic field of a magnet?
  32. Andrea Vironda

    Sensor for detecting piston axial position

    Hi, the temperature stands between 20-120 °C, the stroke is about 30-40 mm and the speed is not so high (i think around 1" to perform the complete stroke). There are no oscillations, the stroke is performed around 10 times a hour, but the system is placed receive vibrations from machining...
  33. Andrea Vironda

    Sensor for detecting piston axial position

    Hi, I have a steel piston running below a 3-4 mm thick steel wall. I'd need to know the piston position below the wall without drilling the wall. I'm thinking to an inductive sensor but I think it will not work because it will detect all the time something in front of him (the fixed wall)...
  34. Andrea Vironda

    Question about angular contact bearing mounting

    This is an angular contact ball bearing. In the internal side there's a spring pushing to the left, and oil pressure pushing to the right. But the bearings to not bear load, in this case I don't know why they are angular and not straight. Maybe because the passage of the load is not smooth and...
  35. Andrea Vironda

    Question about angular contact bearing mounting

    There are 2 spacers: one between the 2 yellow marks (rotating) and the other just above, fixed. I think the internal is useless since forces are exchanged in other points.
  36. Andrea Vironda

    Question about angular contact bearing mounting

    Hi, In my memories there's the information that in a O shaped mounting, the bearings will work in diagonal (the forces will be transmitted following that path). But in many drawings I can see the presence of a spacer between internal rings. Is it necessary since no force should be transmitted to it?
  37. Andrea Vironda

    Hydrostatic Dampening System

    This table is used for machining. I have this marketing image in with you can see a general layout (column is around 6m tall). The main advantage in using hydrostatic technology is vibration dampening. The hydrostatic rotary tables are the 2 scrolling on the blue bases
  38. Andrea Vironda

    Hydrostatic Dampening System

    Thanks Baluncore. What's the law governing this behavior? Navier-Stokes?
  39. Andrea Vironda

    Hydrostatic Dampening System

    Hi, In some hydrostatic tables I can see many spring-shaped pipes that are traversed by oil. Spring is responsible for a kind of dampening that I ignore how to deal with. Do you have any idea of the physical principle behind it?
  40. Andrea Vironda

    Automotive Aerodynamic drag on a car and recovering some of that energy using a fan

    I think that driving at 130-140 km/h a car could dissipate 5-10 kW of energy only because of aerodynamic drag. Why cars don't have a fan somewhere to exploit the aerodynamic drag? For example a Pelton turbine
  41. Andrea Vironda

    I Polar moment of inertia

    Yeah, only part of deflection stress formula. Ok i think i understood. but why ##r^2## into the integral and not simply ##r##? If i integrate ##r## on ##dA## i will get something related to the area
  42. Andrea Vironda

    I Polar moment of inertia

    Hi, A well-known part of the formula for calculating the deflection stress is ##I_z=\int \int r^2 dA## Usually a moment of inertia is something related to how difficult is to move an object. In this case is understandable but i don't understand the meaning of the double integral. Using ##r^4##...
  43. Andrea Vironda

    Why in an RL circuit does the voltage anticipate the current?

    In my opinion the problem is similar for both circuits. When i switch on I and V should have the same phase. And then, after some time, they would be dephase by inductor or condensator Not only one? for example the 50Hz at home
  44. Andrea Vironda

    Why in an RL circuit does the voltage anticipate the current?

    At this point i understand the phase practically speaking, for example when some AC motor is not well connected, it will turn in the wrong direction. But in a circuit what does it mean? V and I shifted by 90deg, what does it mean?
  45. Andrea Vironda

    Why in an RL circuit does the voltage anticipate the current?

    In my idea the tension change after connecting the circuit to a battery is immediate, while the current takes some time before moving. That should be sufficient to prove my question but, so why in a RC circuit the opposite happens?
  46. Andrea Vironda

    Entropy increase of solid vs liquid

    Since randomness is described by entropy, i think you're asking something like: ##\text{this much change in quantity of water in air gives rise to this much change in humidity}##
  47. Andrea Vironda

    Modeling Hydraulic Brake Behavior

    Summary: Relation between deformed foil and friction force Good morning everyone, i have a small leaf or steel that is bent from one side by a Pressure of many bars. in front of the leaf there's a rotating disk, separated by the leaf by a small gap. this leaf, as it deforms, wins the gaps and...
  48. Andrea Vironda

    Friction to transmit a couple

    Why do the width is not important? if i have a 1 km cylinder i think i have to put a lot of effort more
  49. Andrea Vironda

    Friction to transmit a couple

    Good morning sirs, let's imagine a cylinder, surrounded on 360° by a coating of the same shape. I can close the 2 half using 2 bolt screws. what's the maximun transmittable torque? here's a scheme: i would to consider the sum of forces as a normal force on the top of the cylinder, producing a...
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