29 votes
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Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

If I model this as a simply supported beam having load at mid span [...] I suspect that this is where your analysis went awry. First off, you should always model bridges with distributed loads, not a ...
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7 votes

Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Since this bridge is crossing over a waterway, besides aesthetics, the arch-shaped bridge provides several advantages: Less restrictive over the height of marine traffic due to more headroom in the ...
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  • 7,491
7 votes

On a car with all-wheel drive, how does the engine provide the angled front wheels with power?

You could also include front-wheel drive in your question. It would be enlightening for you to look at what radio control rock crawlers do. It has much of the excess of a full-sized car stripped away. ...
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5 votes

Direction of fluid flow

Heat the pipe at some point, and find the direction in which heat transfers. This will give you the direction of the flow. Caution: Don't do this for flammable fluids. Thanks to @Carl Witthoft for ...
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4 votes
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Torque Problems vs Motor Problem?

The motors have a rated speed of 2750rpm. It doesn't look like there's much of a gear ratio, so at the moment the motors spin at the same speed as the wheels. With 16" wheels, 2750rpm is about ...
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  • 156
4 votes

Direction of fluid flow

Yes, purchase an ultrasonic flow meter. Needs a straight length of pipe and very careful placing of the sensors. However, if done well one can get good results, if not then the results can be ...
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3 votes

Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Spreading the upward reaction load from the support pillars is one reason, the function of an arch translating vertical load to horizontal thrust is another. But there are already good answers saying ...
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3 votes

Why is Scotch-Yoke mechanism not used for internal combustion reciprocating piston engines?

Making an engine using scotch-yoke mechanisms for all pistons on a multi-cylinder engine will increase the cost and add a lot of needless complexity and mass, especially rotating mass that won't ...
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3 votes

Direction of fluid flow

If this is a pumped system, try measuring the reaction forces when you turn the system on. For example, if you're trying to measure the direction of fluid flow in a hermetically sealed "black box&...
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2 votes
Accepted

What is the definition of depth of cut in machining?

The maximum cutting depth is the deepest cut that can be made in one pass. Trying to cut too much will cause the cutter to dig in and achieve nothing usual. It can damage the machine. Consequently, ...
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2 votes

Will a (stainless steel) underwater gear, formed by a 1500 RPM pinion and a ring cogged wheel 20 time its diameter, work?

You want something like this, located above the surface and shafted to the underwater generator, presumably the two are connected with a torque tube. They are pricey and high maintenance. This is ...
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2 votes
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Could a hybrid system of mechanical levers and hydrostatic/hydraulic cylinders be able to lift 200+ kg with the force of an arm?

Levers and hydraulic cylinders are not typically used for the distribution of force, but are more frequently used to transmit and otherwise modify applied force. Per your reference to class one levers,...
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2 votes

Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Simply put, it is because the mass of the spans has to be supported and each pillar has to support 1/2 the mid span plus some of the end section.
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2 votes

How to calculate elastic deformation due to kinetic energy (impulse)?

When punching an indent into a piece of metal, the residual stress that is concomitant with the indentation implies yielding and so you have a non-linear interaction. If you still want to do the ...
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2 votes
Accepted

Airflow visible over the airplane wing

Specifically, what you are seeing here is a vortex which is basically a sideways tornado. Vortices occur when moving air forms a twisted stream when flowing over an object with a complicated shape. ...
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1 vote

Understanding physics principals behind machining

Your motivation is great. But you’re confusing the trees for the forest. An important part of engineering is understanding when you need to use complicated models or not. There is little point in ...
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1 vote

Understanding physics principals behind machining

Unfortunately, what @DKNguyen commented is still how the field mostly look like. We lack computer models for most machining tools we use. Unlike EE heavily built on electromagnetic axioms, machining ...
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1 vote

How to calculate the magnetic force for metal on magnets?

If you wish free and open-source software, i can recommend ONELAB, which is combination of Gmsh (mesher and GUI) and GetDP (general purpose solver). You will have an exciting dive into physics and ...
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1 vote

Why would you put covers in front of the output of the condenser fan on these mini-split units?

They are fragile and easily damaged, so it is common practice to protect them with shrouds. Those shrouds also serve to guide the airflow from the fans that blow air over the coils to maximize heat ...
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1 vote

What is the safe rpm limit for a solid steel wheel

For a start calculate per: Rotating Disk with hole But it is possible to vary cross-section as bell curve profile to increase speed and reduce weight.
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1 vote

Is there a way of "shortening" a mechanical lever, but keeping its mechanical advantage intact someway?

Although you need to move the ends of the lever through the correct distances to get the correct advantage -- work equals force times distance -- you don't need to have the same linear distance to do ...
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1 vote

Is there a way of "shortening" a mechanical lever, but keeping its mechanical advantage intact someway?

Yes. Assume the load and the force are in equilibrium condition initially. You can shift either the load, the force, or both, toward the fulcrum, so the resulting work done (mechanical advantage) by ...
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  • 7,491
1 vote

Torque Problems vs Motor Problem?

I would swap the gears between the motor and the shaft, as it looks like you are trying to drive the axle shaft faster than the motor. If you have a small gear on the motor and a larger (*3 or *4) ...
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1 vote
Accepted

Calculations of a sphere

First, consider a circle with same diameter as the sphere, with the distance $d_2$ being the projection of $D_2$ onto the plane and assuming $d_1=D_1$ relative to your figure: The radius of the circle ...
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1 vote

Could radial bearings with brackets hold the weight and load of a large cart

You will have a few problems. If only one wheel is driven the cart will turn as soon as the motor is energised. This may be unmanageable for the user and cause injury. The axle is fixed. It doesn't ...
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1 vote

Where can I buy industry quality ready prototype construction set?

First step if you find that your children's toy prototype is failing should be attempting to figure out the forces you are putting on it and seeing whether they can be distributed better. Sometimes ...
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1 vote

Flow of fluid in branched pipes

Why assume Q1(Mass flow rate through opening 1)=Q3(Mass flow rate through opening 3)? The tee pipe itself impedes at least some flow between points 1 and 3 (flow rate would be at least slightly faster ...
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1 vote
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How to design the thickness and diameter of a cantilever beam in bending for both composites and metals?

The equation for bending stress is $\sigma_b = \dfrac{My}{I}$ For a thin-walled circular shaft, $I = \dfrac{\pi d^3t}{8}$, $d = 2r$ (diameter) Rewrite the equation, with $y = d/2$: $\sigma_b = \dfrac{...
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  • 7,491
1 vote

What's the difference between a four jaw independent chuck and a faceplate chuck

If you mean something like this for 'faceplate chuck', then it can be viewed as a four-jaw chuck with a lower profile, designed to hold discs rather than round or square bars. There are also some ...
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1 vote
Accepted

portable humidifier (balancing a bucket of water on a bicycle)

Random idear. Use a gel blanket on top of the heated water reservoir. The gel will acquire water from below and transpire it into the air. The water can be heated normally. Sodium polyacrylate is used ...
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