Velvet drive prop shaft brake

[JamesKoss]

Does anyone have a design, a comercial product, or plans for a prop shaft brake on this transmission? Ideally one that positions the prop behind the dead wood as well.

[FAST FRED]

Commercial prop brakes attach directly to the shaft , not usually the tranny.

When installing one it is EZ to index it to hie the prop.

However what "looks" good behind the deadwood, may not be lowest drag.

With a big wrench its best to slightly move the locked prop while sailing at your cruise speed.

Sometimes the drag is least with the blades in a position they prefer.

When you are holding the LEAST amount of force from the shaft , and the prop wants to not rotate very hard at all, lock it there!

FF

[JamesKoss]

Attached to the shaft it would spin. The brake assembly attaches to a stable site and clamps on to the shaft to keep it from spinning. Like brake calipers on a car, nothing attaches to the axle or shaft except the spinning disk. The caliper grips the disk when activated. It is the caliper attachment idea I need help with. I do not want to use a vice grip or wrench. I want to remote control it. Any ideas out there?

[marshmat]

Hi James,

Just curious, for what purpose do you need a shaft brake?

I've only ever seen shaft brakes in two types of applications. One is what Fred says- a simple fitting attached to the shaft, somewhere between transmission and stuffing box, so that you can lock the prop while under sail. I don't think you ever actuate this kind of brake while the shaft is powered.

The other is for gas-turbine engines driving jetpumps, in which case a car-like disc brake is often used at the reduction gear output so that power to the jet can be killed quickly. (These turbines take a long time to slow down, so putting a brake on the shaft is an easy way of controlling them without affecting the turbine itself- the turbine rotor from which power is extracted usually spins separately from the compressor and its power turbine, and so can be quickly brought to a halt while the engine spins down to idle.)

[FAST FRED]

A shaft brake is a great tool to keep the tranny from dieing , as many should not freewheel, to reduce the drag of the spinning prop, or best of all to hide the prop behind the deadwood on a cruiser for almost Zero drag.

Look in a copy of Sail , or Cruising World , if they still exist , and you should locate a few suppliers.

FF

[bntii]

I have one for sale.

It is the 'Shaft Lok' Produced by SHAFT LOK INC.

http://www.shaftlok.com/User_Inquiry_Letter3.htm

I have a type II. Pm if interested

http://www.shaftlok.com/cover.jpg

[FAST FRED]

That looks like it will work, but there are other styles that do not require the end coupling to be removed to install the unit.

FF