# Tag Info

### Why are two wires used in railway overhead equipment?

Overhead line worker here. It's about speed. To answer your question, the purpose of the catenary wire is to get the contact wire to lay flat, so it isn't catenary itself. In your second photo, there ...
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### Transmitting power over long distances what is better AC or DC?

It is more efficient to transmit DC using about the same infrastructure. This is because of several effects: Skin effect experienced with AC. There is no skin effect with DC. Higher voltage ...
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### Transmitting power over long distances what is better AC or DC?

I actually worked on HVDC schemes, back in the mid-to-late 90s. Olin Lathrop's answer is partially right, but not quite. I'll try not to repeat too much of his answer, but I'll clear up a few things....
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### Why are two wires used in railway overhead equipment?

It isn't to do with current-carrying capacity; it is to maintain good contact between the current-carrying wire and the pantograph pickup on the locomotive, as it allows the contact wire to be ...
• 341

• 11.7k

### How does my automatic car shift without complete temporary loss of acceleration

Multiple Clutches Many manual transmissions feature just a single clutch between the engine and the transmission. This requires that the clutch be disengaged before switching gears, during the switch,...
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### Is transmitting windmills' mechanical power to ground level that complex?

TL;DR:IMHO, the driver for keeping the electrical generation closer to the hub is for primarily for eliminating -as much as possible- moving parts for safety concerns. The secondary benefit is the ...
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### Why in the construction of power transmission towers , the rods are hinged oblique?

If you imagine a square or rectangular shape made from rods joined with points at the corners. If those pins act as hinges then the whole shape can easily deform, effectively acting as a 4 bar link. ...
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### What is meant by "shock load" in gears?

a shock load on gearing is imposed when the gear train is forced to start or stop turning very suddenly, or when a heavy load is suddenly applied to a set of rotating gears. A good example of this is ...
• 11.7k

### Transmitting power over long distances what is better AC or DC?

All else being equal DC transmission is more efficient than AC transmission at the same nominal voltage due to the elimination of reactive losses. However all else is rarely equal. At a given voltage ...
• 179

### What's the history of the 345 kV voltage level in power transmission?

With the high voltage AC power lines, there are trade offs between losses due to resistance in the wires, where the higher voltages are better and losses due to capacitance to the air, etc. where ...
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### Torque and RPM calc

The transmission ratio is related to the number of teeth on the worm gear, and the number of starts on the worm. In your case, $$i=\frac{z_{worm\ gear}}{z_{worm}}=\frac{25}{1}=25$$. This means that ...
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### Attaching Gear onto Motor

What are the respective tolerances on the “6mm”? Either it will be a press fit which will be sufficient to handle the torque and shock loading or it will not. If not, then you have to fit set screws ...
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### Attaching Gear onto Motor

Boston Gear or McMaster-Carr might have suitable off the shelf gears. You could also press the gear onto a hub that has a set screw. I would avoid pressing anything directly onto a motor shaft, you ...
• 2,402
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### How to connect a motor shaft to a plate

That might be overkill in your application (but I don't know). Figure 1. A random rigid flange coupling from an image search. A rigid flange coupling may be a more economic choice if it suits. From ...
• 7,499
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### Delivering RPM from a fixed wheel to a moving wheel

you can use a pantograph belt. They use them in large machines to transfer rotation to a moving drill to cut squares and what not. Basically they are several pullies assembled on a pantograph with ...
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### How does my automatic car shift without complete temporary loss of acceleration

I don't know why the other answers are talking about CVTs. Maybe I'm missing something? But the basic way how automatic gearboxes achieve smooth switches is that they use multiple clutches, instead of ...
• 1,835