Propeller "support"

[TomIre]

My poor brain needs a jog!  As I understand it, normally the propeller through the shaft "pushes" on the engine.  The engine is fixed to the boat with motor mounts and so the push is transferred to the hull and off we go!  

What I'm trying to find/remember is a slightly different way of accomplishing this.  There is a system/product and brand name that goes between the propeller and engine.  The shaft bears on an intermediate cross member.  This member is mounted to the boat and that is what provides thrust. Advantage is that the engine can me mounted on much softer mounts reducing noise and vibration.  Strangely I remember that the shaft, at he "break" has to be out of alignment by a few degrees.

 

Can anyone help me with the brand name of this device/installation?

[Tony Brooks]

Aquadrive, Pythondrive or a long Centaflex coupling.

[TomIre]

Ding Ding!  Thanks Tony.  Aquadrive it is.

[Ray T]

A "Plummer Block" may also fulfill this function.

 

The two grub screws screw down into indents in the prop shaft & help transfer the load.

 

Edited March 12, 2021 by Ray T

[OldGoat]

1 hour ago, TomIre said:

Ding Ding!  Thanks Tony.  Aquadrive it is.

The best / better fitting because it not only absorbs any thrust but also because it's designed to compensate for any some misalignment. 

I was advised by the experts at Beta not to have too soft engine mounts - as the engine needs to be constrained....

[Tracy D'arth]

20 minutes ago, OldGoat said:

The best / better fitting because it not only absorbs any thrust but also because it's designed to compensate for any some misalignment. 

I was advised by the experts at Beta not to have too soft engine mounts - as the engine needs to be constrained....

May become impossible to buy now that GKN have gone.

[IanD]

48 minutes ago, Ray T said:

A "Plummer Block" may also fulfill this function.

 

The two grub screws screw down into indents in the prop shaft & help transfer the load.

 

Plummer blocks are only intended to support the prop shaft radially, they're not designed to absorb thrust -- a couple of little grub screws has little chance against the full thrust of a propeller, and the bearings aren't designed for this either, nor are the fittings that hold them down.

 

To do this you need a proper thrust bearing like the ones that are part of the Aquadrive/Pythondrive/Centaflex AGM assemblies, and these usually have either a massive clamp onto the prop shaft tightened down by half a dozen big bolts, or a big collet clamp also tightened down by big bolts. This is the bearing at the right-hand side of this Centaflex AGM drawing.

 

 

Edited March 12, 2021 by IanD

[IanD]

45 minutes ago, OldGoat said:

The best / better fitting because it not only absorbs any thrust but also because it's designed to compensate for any some misalignment. 

I was advised by the experts at Beta not to have too soft engine mounts - as the engine needs to be constrained....

The Beta manual says "if a constant velocity drive shaft is being considered then it may be necessary to have the standard engine drive plate that is supplied replaced to avoid torsional noise problems. Please contact Beta Marine for technical guidance"

 

The Centaflex-AGM avoids this problem and is said to be quieter than the CV-joint couplings (thought you probably wouldn't notice the difference unless the engine is *very* well soundproofed), but isn't very common. It's also shorter in length so easier to retrofit.

Edited March 12, 2021 by IanD