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Cruising America's Great Loop and other inland routes
View all threadsHow do I stop rotation on a 2.5 inch shaft
Once I needed to motor a long distance with only one engine. I had no good idea how to stop the idled shaft from turning while I idled my way back to port. Can anyone provide clear instructions on how to tied a shaft down, or is there a mechanical device available to do this?
I would appreciate all suggestions,
Joe
Large pipe wrench or large vice grips. Clamp on the shaft and let the wrench
handle rest on the hull to counter the rotation. It WILL gouge up the
shaft....but so what?
They sell elaborate devices that look like a car brake system with a caliper
and clamp on the caliper but I don't think its worth it unless you are doing
it often.
R.
-----Original Message-----
From: Great-Loop [mailto:great-loop-bounces@lists.trawlering.com] On Behalf
Of Joseph Roy
Sent: Thursday, February 09, 2017 9:44 PM
To: great-loop@lists.trawlering.com
Subject: GL: How do I stop rotation on a 2.5 inch shaft
Once I needed to motor a long distance with only one engine. I had no good
idea how to stop the idled shaft from turning while I idled my way back to
port. Can anyone provide clear instructions on how to tied a shaft down, or
is there a mechanical device available to do this?
I would appreciate all suggestions,
Joe
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On 02/09/2017 08:43 PM, Joseph Roy wrote:
Once I needed to motor a long distance with only one engine. I had no good idea how to stop the idled shaft from turning while I idled my way back to port. Can anyone provide clear instructions on how to tied a shaft down, or is there a mechanical device available to do this?
Yes, there are shaft lock or shaft brake devices. However, first I would
ask whether it is even necessary.
When we were boat shopping, any time we looked at a twin I researched
the make and model of transmission to see if it could be freewheeled. A
surprising number of them can be freewheeled without issue; some can be
freewheeled for short periods or below certain speeds, and some can be
freewheeled if the fluid is circulated with a pump. Stuffing boxes are
another issue of course; some dripless seals will require an external
water supply, at least above certain speeds.
Unless your transmission is not permitted to freewheel at all, you can
likely come up with a strategy to operate without locking the shaft. And
on some transmission/engine combinations, stopping the rotation may be
as simple as putting it in gear.
Quick story: While we were very careful to do this research for
twin-engine boats (on the theory that we'd cross oceans on a single
engine, alternating periodically), when we ended up with a single screw
boat, we neglected to check. And so it was that one day in the middle of
the night we awoke in panic to the sound of the propeller windmilling in
Winyah Bay, as perhaps as much as three knots of current passed under us
after a tide change. We started the engine to circulate fluid until we
could figure it out; after about an hour of research we learned there
were no restrictions on freewheeling our ZF transmission.
-Sean
m/y Vector
lying New Orleans, LA
http://OurOdyssey.BlogSpot.com
While doing the Loop I stopped the shaft a few times with a rope tied to
the engine mount on one end and the other eye spliced end looped a few
time around the shaft and over a coupling bolt. Some other people used a
piece of wire the same way. Once i spun the shaft by hand to tighten up
the line it stayed in place.
John Esch
Fet-Esch, currently lying Port St Lucie, FL
On 2/9/2017 9:43 PM, Joseph Roy wrote:
Once I needed to motor a long distance with only one engine. I had no good idea how to stop the idled shaft from turning while I idled my way back to port. Can anyone provide clear instructions on how to tied a shaft down, or is there a mechanical device available to do this?
I would appreciate all suggestions,
Joe
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And then there is the pre-GPS story of the guy who needed to economize of
fuel to make it and who removed one of his propellers and set off for Hawaii
from the west coast keeping an eye on the jetliner contrails, and when he
got halfway there dove to replace the prop and remove the original to even
out engine wear.
One thing that was discussed here long time back was the difference in
resistance between a freewheeling prop and a locked-in-position prop. That
was interesting.
Rich Gano
FROLIC 2005 Mainship 30 Pilot II
Panama City, FL
From: Ralph Yost <ralph@alphacompservices.com>
To: 'Joseph Roy' joroy40@hotmail.com; great-loop@lists.trawlering.com
Sent: Friday, February 10, 2017 6:33 AM
Subject: Re: GL: How do I stop rotation on a 2.5 inch shaft
"Large pipe wrench or large vice grips. Clamp on the shaft and let the wrench
handle rest on the hull to counter the rotation. It WILL gouge up the
shaft....but so what? " Snip.
Not a good idea. A stress concentration will be introduced which can lead to low-cycle fatigue failure depending on torque level. And yes, it will fall off as soon as the shaft momentarily reverses itself, such as while rolling in the troughs while stationary.
I think the easiest solution would be to affix one or more eyes to the shaft coupling bolts, and a short chain with a hook, attached to the hull, could just be hooked in, or be quickly attached if the shaft is jerking around while away from the dock.
FWIW, most modern marine gears drive the hydraulic pump, for lube and clutch application, off the input shaft, so no lube flow with a stopped engine, The frictional heat generated by windage and clutch plates rubbing, and lack of cooler flow, can cause the lube temperature to rise. 220 deg. F, is the point at which most gear lubes lose film strength, and metal-to-metal contact ensues. Death! $$!
Since the lube oil temperature sensor is probably in a flow path, it will not correctly indicate lube bulk temperature, and certainly not elevated temperatures at teeth-mesh surfaces and bearing races.
I've seen a common problem on 4- and 5-engine GOM crew boats, losing an engine underway, certain (unnamed mfg.) equipped boats actually had a wheelhouse plaque stating DO NOT FREEWHEEL. Then the crew had to somehow secure the shaft, whipping back and forth while possibly rolling violently in a beam sea. This impossible situation led to a lot of ruined transmissions. Lose the gear, not an arm!
In summary, after working at a marine gear manufacturer, especially on a project to develop a portable QD-attached auxiliary lube pump for freewheeling use, my advice would be not to freewheel if avoidable.
Phil Little