Hi, I am not following what you mean with with the thrust bearing, and
what would be the advantage of the reduction gear? thanks Bill

On 30 Oct 2005 13:20:29 -0800, "rvbilly" wrote:

Hi, I am not following what you mean with with the thrust bearing, and
what would be the advantage of the reduction gear? thanks Bill

It is a strange thing when you first hear of it: but the same HP can
give a few pounds of thrust at high boat speeds and hundreds of pounds
of thrust at slow speeds.
The latter place is where marine transmissions live - so they need
buff thrust bearings if they are to last any time at all.
Water props get inefficient at high speeds.

Brian Whatcott Altus OK

Horsepower is the rate of doing work. Why is it surprising that a small
force at high speed is different than a large force at low speed? It's how
the small displacement car engines at 9,000 rpm are able to compete.

Roger

http://home.earthlink.net/~derbyrm

"Brian Whatcott" wrote in message
...
On 30 Oct 2005 13:20:29 -0800, "rvbilly" wrote:

Hi, I am not following what you mean with with the thrust bearing, and
what would be the advantage of the reduction gear? thanks Bill

It is a strange thing when you first hear of it: but the same HP can
give a few pounds of thrust at high boat speeds and hundreds of pounds
of thrust at slow speeds.
The latter place is where marine transmissions live - so they need
buff thrust bearings if they are to last any time at all.
Water props get inefficient at high speeds.

Brian Whatcott Altus OK

"rvbilly" wrote in message
ups.com...
Hi, I am not following what you mean with with the thrust bearing, and
what would be the advantage of the reduction gear? thanks Bill

When you turn the prop (pushing water aft) the shaft is forced forward. This
forward thrust must be transmitted to the boat through a thrust bearing:
http://science.howstuffworks.com/bearing3.htm

The reduction gear takes the higher input rpm of the engine and reduces it
down to a usable rpm so the prop does not cavitate. It also allows F N R.