48
votes
Accepted
Why do hydraulic systems use special fluid - what's wrong with water?
Water meets the low compressibility requirement, but there are many other considerations in the design of a hydraulic system:
Boiling point/vapor pressure: If the system warms up during operation, ...
- 812
19
votes
Why do hydroelectric plants use turbines instead of an efficient 'water wheel' configuration?
Actually the turbine method is very efficient. The Turgo turbine is up to 90% efficient at extracting the energy from the water. Large-scale hydro plants using Francis Turbines can be as high as 95% ...
- 5,930
14
votes
Why do hydroelectric plants use turbines instead of an efficient 'water wheel' configuration?
There are two different ways for the water flow to transmit energy. One is the pressure difference between the water entering and leaving the turbine. The other the kinetic energy change of fast ...
- 12.5k
13
votes
How to calculate flow rate of water through a pipe?
Laminar Flow:
If the flow in the pipe is laminar, you can use the Poiseuille Equation to calculate the flow rate:
$$
Q=\frac{\pi D^4 \Delta P}{128 \mu \Delta x}
$$
Where $Q$ is the flow rate, $D$ ...
- 2,989
10
votes
Accepted
How do I calculate the weight needed on a press board to deliver a certain amount of pressure?
The obvious place to start is "what does psi mean?" It's an abbreviation for "pounds per square inch".
If we have a 24" x 24" board, then we have
$$24~in\times24~in=576~in²$$
To get 40psi, i.e. 40 ...
- 3,135
10
votes
Does a motor suffer damage when resistance to the intended motion is met?
The answer depends on the specific type of motor you intend to use, but in general: when a motor is loaded down, it draws more current, which means its windings get hotter at the same time that the ...
- 12.1k
7
votes
Accepted
How do I add a resistance to mechanical movement in both directions, apart from friction?
The two basic mechanical options are either a viscous damper or inertia or indeed a combination or both.
Of the two a damper is probably the closest to what you want as it will provide a force which ...
- 15k
7
votes
Does a motor suffer damage when resistance to the intended motion is met?
It depends on the specific type of motor, as @nielsnelson mentions, but it also depends on what you use to drive the motor.
In general, a motor that's designed to run continuously isn't going to take ...
- 2,218
6
votes
Accepted
Motor for a hydraulic pump in a hydraulic system
You are correct, getting oil pressure will require an electric motor as your source of rotation, potentially a gear box to slow that rotation down, and the pump itself. You'll also need a reservoir to ...
- 4,501
6
votes
How do I add a resistance to mechanical movement in both directions, apart from friction?
Elaborating on CarlWitthoft's comment, magnetic damping, sometimes called eddy-current damping, is a standard way of introducing damping in metallic systems. The principle is fairly simple; as a ...
- 6,306
6
votes
Why are hydraulic systems widely used to multiply force ? won't a couple of gears do the job?
Power density. Modern hydraulic systems are way better compared to ropes and pulleys, gears, electromagnetic systems or levers.
Freedom of geometry. Put a cylinder somewhere, get a rubber hose to it, ...
- 231
5
votes
Help with hydraulic design
Siphoning works when water goes from a higher point to a lower point, such as from an aquarium on a stand into a bucket on the floor next to the stand. Siphoning only works when the start point is ...
- 3,971
5
votes
What is the best way to dry something that is quite thick?
Solar heating would not "elevate" moisture in the object, but instead evaporates whatever is on the sunny side, allowing moisture from the bottom to soak back up by capillary action.
Your best bet (...
- 151
5
votes
Accepted
Hydraulic power source
Pretty much all electric motors demand a lot more power for starting from a dead stop than for generating motion in a steady state. There are a whole lot of schemes for smoothing out this 'inrush ...
- 4,501
5
votes
Accepted
Why no hydraulic piston gas compressors?
There are two aspects to this. First is that the main advantage of hydraulics is that is provides a compact means of greatly multiplying force but in compressing gasses you have to a huge amount of ...
- 15k
5
votes
Why actuators are mounted in inverted position?
The cylinder will be mounted where it is easiest to get the hydraulic lines to it.
- 4,668
4
votes
Recoil of hydraulic lift/elevator
When an elevator stops it will set a brake to immobilize the elevator cabin. This way a sudden leak doesn't drop the cabin while the door is open.
When the controller prepares to move the elevator ...
- 5,666
4
votes
Why do hydraulic systems use special fluid - what's wrong with water?
In addition to the other answers, water is commonly used as a primary working fluid in industrial hydraulic systems with additives to prevent the issues mentioned above. Typical applications include ...
- 371
4
votes
Force required to crop/cut a mild steel bar
This is a simple shear force problem. However there are a few considerations.
You don't need 2 hydraulic cylinders. One should be mobile, the other should be stationary. Below is a simple and quick ...
- 692
4
votes
Hydraulic Symbols
I worked in a hydraulics design field for two years and found that unfortunately there isn't a standard way to draw many components. Each manufacturer seems to choose their own route. Designers are ...
- 7,469
4
votes
Calculating piston force for pneumatic vs hydraulic
The formula is valid independant of the fluid.
The force in an hydraulic system is based on pressure and area - a height difference between pistons is usually small compared to the acting pressure ...
- 13.9k
4
votes
Managing water supply pressure to a building
The best method is to pressurize your tank on the upper floor, then regulate the flow as it goes down. This is because pressurizing will require active components (i.e. pumps, and other devices that ...
- 5,303
4
votes
What kind of pressure switch can I use for pressures up to 5-10 tons/cm^2?
You do this by monitoring the hydraulic pressure rather than the press tonnage.
Since force = pressure x area we can rearrange so that pressure = force / area.
Using your quaint units of measure, 5 ...
- 8,229
4
votes
Accepted
How to make sure a pipe does not take all of the water from a stream?
You can put a valve on your pipe to control the flow.
Or partition the stream by means of a short concrete wall which looks like an indented grout trowel upside-down . Say two opening for the stream ...
- 21k
4
votes
How to lift an antenna tower into position?
The forces to lift a 100 ft tower from horizontal are going to be enormous. So you will have to build the tower stronger, which will make the forces even larger.
For a 100 ft tower erect it once, and ...
- 4,668
3
votes
Hydraulic cylinders
Hydraulic (or pneumatic) cylinders are merely a means to provide a linear force between two points. You select the cylinder based on how much force, how much distance and how much speed you need for ...
- 6,749
3
votes
Why do hydraulic systems use special fluid - what's wrong with water?
In terms of historical interest, water was used in the first hydraulic brakes and very soon the obvious problems of freezing (due to ambient temperature) and boiling (due to lots of brake use) became ...
- 13.9k
3
votes
How to calculate flow rate of water through a pipe?
General case
The basic tools for this kind of questions would be Bernoulli's equation, in the case of water, for an incompressible fluid.
$\frac{p}{\rho} + gz + \frac{c^2}{2} = const$
As you stated ...
- 1,704
3
votes
Accepted
Where exactly will a hydraulic jump occur?
First a hydraulic jump is where fluid will transition from supercritical (having a Froude Number greater than one, to subcritical (having a Froude Number less than one). When the Froude number is near ...
- 1,295
3
votes
Accepted
Hydraulic Arm - Handbrake
It is a gas spring. They are rated in units of pounds and travel in inches. Typically ranges are 10 to 200 pounds, and 6 to 24 inches. Here is one example :
https://www.amazon.com/JR-Products-GSNI-...
- 446
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