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1. ### Calculating constraint reactions

Thanks, it helped me a lot
2. ### 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. ### 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. ### I Time required to cool down a botte of wine

You can Open the link and have a look 👍
5. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### Is there something happening below 0°C in this daily temperature graph?

This is the link I used for the screenshot
15. ### 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. ### 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. ### 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. ### 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. ### 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. ### Solving a standard integral

Solving integrals is an art
21. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### Sensor for detecting piston axial position

I'm not native english, what do you mean for "inside the box"? Thinking like a robot?
29. ### 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. ### Sensor for detecting piston axial position

Thanks for suggestion. Can you be more clear here?
31. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### 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. ### Hydrostatic Dampening System

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

45. ### 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？
46. ### 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?
47. ### 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}##
48. ### 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...
49. ### 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
50. ### 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...