Minimizing Thruster Shear Pin Breakage

[johnmurray]

I just replaced (for the second time) a broken shear pin in my 55KGF Vetus bow thruster. While it is not technically difficult to do a replacement, I find it to be a very awkward job that I would like to avoid to the extent possible.
I noticed in the installation part of the Vetus manual that it is possible to install "grid bars" in the thruster tunnel, presumably to keep out bits of debris that might lead to pin brekage. The manual warns however that the installation of grid bars will reduce thruster effectiveness. As an alternative I also wonder if some kind of very wide mesh strainers might be installed on the entrances to the thruster tunnel.
Does anyone have such grids or found an alternative way to reduce pin breakage?

[StockHR]

John, something to keep in mind. The last time I sheared off the thruster pin I found that it wasn't so much that something was in the tube but that I wasn't giving the thruster prop enough time to come to a stop before changing direction. If you switch directions too quickly, that will cause the pin to shear off just from the force of switching back and forth. So you may not need bars or mesh over the tube. One last thing, the thrusters that have bars are more work to clean out when you have the bottom power washed.

Mike

[JackK]

Mike hit it on the head. The shear pins wear quickly if you reverse direction on the thruster too quickly. Vetus even offers a new controller that has an automatic delay built in. It won't let you reverse directions until safe to do so.

It's not a bad idea to verify that there is no growth in the tunnel which may be shortening the life as well. An easy (dry) method of checking is to spin the hub by hand while the motor off the unit. It should spin freely.

Jack

[Yearwood]

Vetus makes a time delay unit which I installed after breaking two pins. Have not broken a pin since the installation and the time delay is not excessive simply allows the unit to stop turning.

[johnmurray]

I appreciate the comments that have been made. I am probably guilty of switching the thruster direction too quickly.
Is there any more information available of the delay device? Where does it connect in?

[Yearwood]

As I recall the delay unit connects between the control stick and the control box on the thruster. It is a simple installation. Vetus provides info with the time delay. Vetus seems to have a solution for everything ... if you ask. Of course, when I did it I reversed the connections and one hot day when I was getting ready to correct my mistake and not looking forward to getting under the vee-berth, in a stoke of marine electrical engineering brilliance I simply reverese the connections on the joy stick.

[fairtide]

What number of seconds is needed for the thruster prop to stop so that a reverse direction can be made with it? There is no clue in the Vetus literature, of course.
Fair Tide

[Pitou]

What number of seconds is needed for the thruster prop to stop so that a reverse direction can be made with it? Fair Tide

I think the idea is just not to toggle immediately back and forth. These props seem to stop fairly quickly and do not free wheel. I have been running mine since my 1st season (2004) and many times wait only a second or two before reversing direction when need be, but I do wait. No problems with shear pins yet. I probably just jinxed myself.

[JackK]

Like Pitou, I wait just a second or two. Besides, much more than that and I might need a gel coat repair kit and a whole lot of beer to soothe the nerves of my dockmate.

The idea is to not "shift-through" from one direction to the other. Just a momentary pause should prevent breakage.

Having experienced my first shear pin breakage on a windy day with no-one around to help guide her back into the slip, I have been trying to practice using the thruster sparingly. RicM described the process of Back and filling in the rudder discussion. I've been practicing that maneuver a whole lot since the nerve wracking day. The sound of the motor whirring with no thrust made my stomach knot like a bad burrito.

Jack

[Mariner]

I'm trying to think of a situation where it would be necessary to go immediately from running the thruster in one direction, to running it in the other direction, and I can't think of one.

I think it's safe to say that if you have to suddenly switch directions, you were probably running it too long in the first direction and need to work on your technique a little bit.

The thruster is really something you should only use when your plan goes down the toilet and you need a rescue net. Or for steering in reverse. I do that sometimes.