why it is necessary to use gear box for speed reduction?

Question

can we directly fed output of engine to the axle by controoling r.p.m of engine through throttle or by using simple pulley for reducing r.p.mor ssspur gears? why to reduce r.p.m in fact?

Answer 1

If you used pulley's or spur gears wouldn't you be infact making a type of transmission. You would be going back almost to the beginning of automotive technology.

Why reduce RPM? well imagine an engine, crankshaft, turning at 4000 RPM, a direct 1:1 with the read axle would mean the rear axle would have to be spinning at 4000 RPM also.

Another thing is the physics of vehicles. The weight of a vehicle and trying to get it moving would require so much torque. To make that much would also bring considerable weight with it, then you would need more torque.
Hence gear ratio;s that allow and engine to turn the wheels and as the engine revs (crankshaft begins to spin) faster you reduce the overall ratio allowing the engine to rev slower and the wheels to spin faster.

Here is a neat site to help explain technology
http://science.howstuffworks.com/gear-ratio.htm

Happy holidays

Answer 2

Gearing is used as a mechanical advantage. It allows the engine to stay in the RPM range where it makes the best torque and horsepower.

There is more than one place where gearing exists too. There is gearing in the transmission AND in the axle (final drive) are you refering to both?

If you just had one speed going directly into the final drive/axle then you'd have a car that would either have a top speed of about 30 mph, where it would redline, or you'd have a car that was very hard to get rolling and could maybe top out at 50 mph, but it would take forever to get there.

It just makes no sense. Gearing gives us a mechanical advantage and allows the engine to stay near it's sweet spot where the most power is made at a variety of different speed.

Your suggestion does make more sense with an electric motor though, which is totally different because it can spin up to much higher RPM and it makes full power and torque immediately.

Continuously Variable Tranmissions or CVT do use a system of pulleys to work and while they were less durable in the past, the designs have gotten much much better now and they have equivalent durability to regular transmissions. Audi uses an excellent chain-driven one on some of their cars, Toyota uses the CVT on the Prius and Honda uses it on a their hybrid and offered it on the Civic HX. Nissan is also big on CVT's and offers them in a few models now, including some Infiniti models. The CVT offers the fuel economy advantage and responsiveness of a manual transmission with the convenience and ease of use of a traditional automatic.

Answer 3

An internal combustion engine can not rev below its own idle speed without stalling.

Granted, a CVT uses two variable size pulleys and a belt to replace gear changes, but they're usually of poor reliability.

Answer 4

hi sorry yet lots greater engineering is in touch right here the gearbox does not be the undertaking or slowing down the motor as a floor polisher has this type of low powered motor. to bend metallic demands fairly some torque especially chilly and what style of thickness is in touch. subsequently why 2 issues are frequently performed whilst bending metallic a warmth it up till finally it quite is cherry study warm makes it greater handy to shape and the 2nd is finished via hand as a blacksmith might do it. in commercial tactics a hydraulic ram is used so it could administration the quantity of bend and enhance in rigidity may be performed with a beer Ram. the help in motor velocity with electric powered automobiles additionally has a tendency to shrink the potential interior the torque of the motor. the main undemanding technique used with Ac automobiles is area administration which reduces velocity and potential and decreases potential ate up besides.