nbTanya Louise Drive Failure

As I have posted about before, the main propulsion system onboard the boat is all hydraulic. To get the drive from the flywheel of the engine to the hydraulic pump stack, a custom drive plate was machined by Centa Transmissions over in Yorkshire, and a Centaflex A coupling was fitted to this.

Centaflex A Coupling
Centaflex A Coupling

This coupling is a big rubber doughnut, bolted to a centre hub of steel. The steel hub is splined onto the input shaft of the hydraulic pump stack.

Pump Stack
Pump Stack

The problem we’ve had is that to prevent the coupling from riding along the splines in operation, a pair of giant grub screws are provided in the side of the centre steel boss, that compress the splines to lock the device in place. These screws are a nightmare to get tightened down (the engineer from Centa who originally came to survey the system said we’d probably shear some tools off trying).

Because of this, the grub screws have loosened over the last 350-odd hours of running & this has had the effect of totally destroying the splines in the hub.

Spline Remains
Spline Remains

Here’s the backside of the centre boss, with what remains of the splines, the figure-8 shaped gap on the right is where the securing grub screws deform the steel to lock the coupling into place.

No More Splines
No More Splines

Here’s the other side of the coupling, showing the damage. The splines have effectively been totally removed, as if I’d gone in there with a boring bar on the lathe. Luckily this part isn’t too expensive to replace, and no damage was done to the input shaft of the hydraulic pump stack (Mega ££££). Quite luckily, this damage got to the point of failure while running the engine on the mooring, so it didn’t leave us stranded somewhere without motive power.

More to come when the new coupling arrives!

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.