[QUOTE=87cr250r;88581]I haven’t seen any mention of Vigor’s possible involvement in this. So far this year incidents I have heard include, one partially capsized dry dock with a large tug inside, one rolled crane, one fatality after a fall from scaffolding, and now a destroyed propulsion motor?[/QUOTE]
I don’t like this bit about overspray all over the communtator on the propulsion motor. What’s so difficult about covering exposed openings? Lazy or what?
The shaft brake being left on must have been from the tow but with a motor disconnected from the switchgear why put a shaft brake on? It can’t regenerate if the breakers are opened. correct?
It’s more fuel efficient to tow with the shafts locked than it is to tow with the propeller freewheeling. That is my understanding.
[QUOTE=c.captain;88610]I don’t like this bit about overspray all over the communtator on the propulsion motor. What’s so difficult about covering exposed openings? Lazy or what?
The shaft brake being left on must have been from the tow but with a motor disconnected from the switchgear why put a shaft brake on? It can’t regenerate if the breakers are opened. correct?[/QUOTE]
Negative, towing with the shafts locked creates a ton of drag slowing you down. Sometimes they freewheel or clutch out. The reason they lock the shafts is when she goes dead ship and they don’t have the oil going to the shaft bearing I believe maybe an engineer can shed some light on that?
I don’t have any towing experience but I do have some engineering experience.
I guess it really boils down to the gearbox. Get on an old steam ship and the shaft must be locked or the gearbox and turbines will destroy themselves. On a smaller scale like a tug, Lufkin gearboxes drive the oil pump off the engine and do not make oil pressure while freewheeling. Falk and Haley boxes drive the oil pump off the output side of the box and only make oil pressure while the shaft is turning. Neither type of box requires pressurized lubrication and can operate at reduced power without damage. Hydraulic boxes like Twin Disc, ZF, etc… are sensitive to having propellers freewheel because they require a significant amount of oil flow to keep the clutches cool even when they are disengaged. The same is true for Rolls-Royce and Ulstein Z-drives.
Correct about the shaft brake. I’ve worked on boats that had shaft brakes that we could control and with it on you stop instantly, with it off you drift forever.
With the motor off there is no lubrication to the transmission if the lube pump is driven by the motor side. If it is driven by the turning of the shaft then there is no need for a brake but most pure motor boats never have that arrangement because they never move through the water with the motor off.