Ideas please for clamp to use as a shaft brake
- Thread starter pcatterall
- Start date
pcatterall
Well-Known Member
Thanks Fishy; I note that Gaelforce do a nice line! I think they are too big for my 30mm shaft
RobbieW
Well-Known Member
+1 My prop freewheels in reverse so forgetting the string is fine so long as you engage forward - and access is fairly easy underway, its just under a hatch above the coupling. NB I have a Technodrive box and found the oil got hot before I found an effective way to stop the prop - presumably because the oil cooler doesnt work when the engine isnt running
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testmonkey
Well-Known Member
get a 12vdc solenoid, fit a rubber end of a walking stick to the pointy end of the solenoid, mount so that this rests against propeller axle coupling stopping the axle, connect solenoid to to alternator B+ output. Whenever motor runs solenoid pulls the rubber bit away from the coupling and propeller axle can rotate freely. When motor stops, alternator B+ delivers no current and solenoid releases and axle cannot rotate. No power consumption when engine is not running and minimal when it does.
paul-essex
Well-Known Member
Beautiful beautiful ��
Rum Run
Well-Known Member
Lakesailor
Well-Known Member
Or how about trained Harakiri hamsters which will, on command, fling themselves around the prop shaft and jam it solid.
pcatterall
Well-Known Member
Yes sounds neat. ( A+!) My coupling is not the round type but similar to a vehicle joint, nothing to push against, so that might be a problem
charles_reed
Well-Known Member
Your understanding is only partially true it depends on the speed of the boat, the type of prop and its underwater configuration.
However he only want to stop the prop shaft rotating to prevent damage to his hydraulic gearbox.
paul-essex
Well-Known Member
I am a bit new to sail boat and I am wondering why if the gearbox should not turn when the engine is not running why don't they fit a dog clutch to let it free wheel or a lock to stop it in the gear box itself ?
theoldsalt
Well-Known Member
I think there is little market demand and it would make the gearboxes even more complicated and increase the price.
There are lots of different gearboxes with differing characteristics. Some are OK to put into astern gear when sailing - some not. Some are OK to "free wheel" some not. Some owners who sail a lot more than motor wish to stop the prop turning to reduce the wear on their shaft seal and cutlass bearing. So it is a complicated subject.
Daydream believer
Well-Known Member
Fix a metal bar ( say 25mm X 8mm) across the boat under the shaft so it misses by about 2mm
Above the shaft fix another bar about 100 mm long. This os basically just laying loose until required
In the bottom bar an 8mm stud sticking up goes through the short bar then a nut. & washer
The hole in the short bar needs to be 10mm so the bar has slack on the stud
The other side of the shaft is another 8mm stud this time going through the other end of the short bar & finishing off with a butterfly nut
Adjust the fixed stud to a set length & put on a locking nut . You need to experiment with the length
Then to stop the shaft tighten the butterfly nut which clamps the shaft between the 2 bars
Mark the shaft so you know what angle the prop is at ie in line with keel, or whatever
Then to stop prop you turn the butterfly nut & watch the shaft slip until it reaches the correct point & give the butterfly another half turn
To do the job properly a couple of strips of tuffnol on the bars where they rub the prop would be good
Above the shaft fix another bar about 100 mm long. This os basically just laying loose until required
In the bottom bar an 8mm stud sticking up goes through the short bar then a nut. & washer
The hole in the short bar needs to be 10mm so the bar has slack on the stud
The other side of the shaft is another 8mm stud this time going through the other end of the short bar & finishing off with a butterfly nut
Adjust the fixed stud to a set length & put on a locking nut . You need to experiment with the length
Then to stop the shaft tighten the butterfly nut which clamps the shaft between the 2 bars
Mark the shaft so you know what angle the prop is at ie in line with keel, or whatever
Then to stop prop you turn the butterfly nut & watch the shaft slip until it reaches the correct point & give the butterfly another half turn
To do the job properly a couple of strips of tuffnol on the bars where they rub the prop would be good
Lakesailor
Well-Known Member
Or save yourself the bother and get the clamp I suggested. It has a spigot mounting hole with clamp or 1/4" or 3/8" threaded inserts to use for mounting, rubber lined jaws and a rachet handle.
Daydream believer
Well-Known Member
But on its own it will spin round with the shaft giving the knuckles a good tap
To do the job properly the clamp needs to be fixed in an accessible location ( as i think you are suggesting)so that the user can operate with one hand
If the clamp you propose can be fixed ( say to a bar fitted across the boat under the shaft) so that the clamp sits ready to use then ok
But having the need to fix the bar then it seems hardly worth paying for anything other than a simple clamp that will not rust etc fitted to the bar
& if you try your other suggestion of hamsters-- where does one keep them, cleaning outcage regularly is also a pain
Then there is the ships cat to consider
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Lakesailor
Well-Known Member
That is possibly why I mentioned the various threads and mountings available on the clamp. I didn't actually think anyone would just stick a clamp on the shaft and leave it to thrash about (although having read some replies I am not so sure now). The Rolls Royce version I evidenced early in the thread had a very nice mounting platform welded in place.
You can get them for £17 new. http://www.ebay.co.uk/itm/MANFROTTO...56?pt=UK_Tripods_Monopods&hash=item3ce5e25e20
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djc
Well-Known Member
A friend installed this shaft brake to his yacht similar type/ set up to yours, Had the Mercedes OM636 42hp engine and TMP hydraulic type gear box so prop was spinning all the time when sailing.
That's If you have space between the coupling and shaft seal area I guess .
That's If you have space between the coupling and shaft seal area I guess .
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macnorton
Well-Known Member
Mountain bike disc brake, done it and it works!
TimBennet
Well-Known Member
I know. See post #7.
pcatterall
Well-Known Member
Yes that set up would fit is that shaft brake readily available? I will try another search.
The disc brake peals also but how to et the disc on the shaft?
Thanks all
D
Deleted member 36384
Guest
Next time you get the chance mark the prop shaft where either one blade of a 3 blade propellor is vertically in line with the back of the keel or the position where the 2 blade is vertically in line with the keel. For day sails or weekend jaunts it wont make any difference but over a long voyage it will help.
I use mole grips and a length of leather from an old belt. With the shaft spinning the leather is wrapped around the shaft saddle fashion with the two ends pinched together in my fingers. The mole grips are placed over the leather and squeezed shut, the position of the shaft is easily controllable by varying the pressure before the mole grips lock in place. The purpose of the leather is to not damage the shaft by the mole grips.
This is quite easy on my yacht as the prop shaft is accessible below the companionway sole into the aft cabin with lots of room. Also, if I start the engine with the mole grips engaged it is no big deal although I will knock the sole lid up and off it's support.
I use mole grips and a length of leather from an old belt. With the shaft spinning the leather is wrapped around the shaft saddle fashion with the two ends pinched together in my fingers. The mole grips are placed over the leather and squeezed shut, the position of the shaft is easily controllable by varying the pressure before the mole grips lock in place. The purpose of the leather is to not damage the shaft by the mole grips.
This is quite easy on my yacht as the prop shaft is accessible below the companionway sole into the aft cabin with lots of room. Also, if I start the engine with the mole grips engaged it is no big deal although I will knock the sole lid up and off it's support.
