Time to accelerate the learning curve 1

skygoat327

Newbie
Joined
Nov 26, 2009
Messages
17
Location
Columbus, ohio
:peace:

I need to know what is the purpose of a reduction drive?

I keep running into this term as I research different gyrocopter models.

Merry Christmas everyone!
 
David,

It's simple. Some engines are designed to develop their ideal Horse Power at an RPM range that is simply too fast to be turning a propeller. To keep the propeller tips from going super-sonic and still allow the engine to develop the max Horse Power, you sometimes have to use a reduction drive. Most engines designed specifiaclly for aircraft are designed to make their HP at lower speeds by using more displacement, so they don't need to add the weight and complexity of a reduction drive, but many of the lighter aircraft engines or conversion engines will need to use a reduction drive as they may be running at 5,000 to 8,000 rpms at max power. Depending on the size of your propeller you will probably want to be turning at 2,500 to 2,800 rpms.
 
The purpose of a reduction drive is...

The purpose of a reduction drive is...

to allow you to turn a larger diameter prop, at a lower RPM. The tip speed of a propellor is a function of RPM and diameter. A larger diameter prop turning slower is more efficient because the tip speed is lower. Some prop engine set-ups (without reduction) are turning the tips at near sonic speeds, and this makes for increased drag as the tips approach 700 mph. The air simply can't get out of the way fast enough, and becomes compressed, creating more drag. And it creates a lot of noise as well. Very in-efficient. Also, with a reduction drive, you can tailor the speed of the prop specifically to the engine horsepower output range (or RPM) to allow you to get the most out of your engine. This explanation is very over simplified, but is what I think the purpose of a reduction drive is for......:):help:
 
Eureka moment!

Eureka moment!

Thanks. Your explanation is completely understandable. Now i can investigate motors for my "ideal gyro" with an understanding of HP and RPM's.

:yo:
 
Top