Sinbad1
Well-Known Member
Many thanks everyone for help. Have just called into local motorbike breaker and he has the whole works, rust resistant calipers, pads and stainless steel cable....
Shaft lock mechanics...help plse.
- Thread starter Sinbad1
- Start date
Avocet
Well-Known Member
Re: Shaft lock mechanics...some thoughts
I'm not convinced about this!
I wouldn't mind betting that a slowly rotating prop carrying no appreaciable leoad keeps all the grease in the bearings evenly distributed. (guess?)
Also, if a rotating prop causes more drag than a stationery one, it must need more energy putting into it to make it turn -surely? If that's the case, why does it start to turn in the first place? Surely it would just do whatever was easiest for it? I mean, why hammer a screw into a piece of wood when you can twist it?
I'm not convinced about this!
I wouldn't mind betting that a slowly rotating prop carrying no appreaciable leoad keeps all the grease in the bearings evenly distributed. (guess?)
Also, if a rotating prop causes more drag than a stationery one, it must need more energy putting into it to make it turn -surely? If that's the case, why does it start to turn in the first place? Surely it would just do whatever was easiest for it? I mean, why hammer a screw into a piece of wood when you can twist it?
castaway
Well-Known Member
Re: Shaft lock mechanics...some thoughts
On a previous airing of this matter (to fix or free wheel yr prop) someone brought in the example of how an autogyro works. I found that this convinced me, finally that a spinning prop causes more drag(or lift) than a fixed one.
However having a hydraulic box on my boat I cant fix it without all the bother of brakes etc.
Interestingly enough I did just read in the manual that the engine should be started every 6 hrs to recircuate the fluid in the box, I hadnt ever realised that before.
Nick
On a previous airing of this matter (to fix or free wheel yr prop) someone brought in the example of how an autogyro works. I found that this convinced me, finally that a spinning prop causes more drag(or lift) than a fixed one.
However having a hydraulic box on my boat I cant fix it without all the bother of brakes etc.
Interestingly enough I did just read in the manual that the engine should be started every 6 hrs to recircuate the fluid in the box, I hadnt ever realised that before.
Nick
Plum
Well-Known Member
Re: Shaft lock mechanics...some thoughts
Thanks for the reminder abot the autogyro.
Regarding your comment about starting the engine every 6 hours, please note that more than 80% of the wear on an internal combustion engine, over its lifespan, happens during startup! What a dilemma......
Thanks for the reminder abot the autogyro.
Regarding your comment about starting the engine every 6 hours, please note that more than 80% of the wear on an internal combustion engine, over its lifespan, happens during startup! What a dilemma......
steve_cronin
N/A
Disadvantage of using an automotive disc brake
Ventilation.
Even though the pressure willbe off the pads they will stillbe contacting the disc which will generate heat. It the open air on a moving vehicle this is not much of a problem as heat will dissipate into the airflow. (even so try touching a brake disc that has been running a while - it is VERY hot. SO do you want this hot disc in the confines of an onder-bunk space/
Just a thought. It would be Ok if you could devise a mechanish to ensure that the pads made absolutely NO contact with the disc whilst the shaft was turning by pulling them off.
Steve Cronin
Ventilation.
Even though the pressure willbe off the pads they will stillbe contacting the disc which will generate heat. It the open air on a moving vehicle this is not much of a problem as heat will dissipate into the airflow. (even so try touching a brake disc that has been running a while - it is VERY hot. SO do you want this hot disc in the confines of an onder-bunk space/
Just a thought. It would be Ok if you could devise a mechanish to ensure that the pads made absolutely NO contact with the disc whilst the shaft was turning by pulling them off.
Steve Cronin
philmarks
Well-Known Member
Did you get this to work? I have a Borg Warner box with a disc fitted, and need to set up a shaft brake. The idea sounds good, particulalry as it's off the shelf.
<hr width=100% size=1>Rgds
Phil
<hr width=100% size=1>Rgds
Phil
trouville
N/A
Re: more drag from a rotating prop when sailing
am i the only one with a shaft break???mine is a simple clamp I have an open housing bolted to a frame the a screw which clamps the shaft via an asbestos pad(?)As i turn the screw the top and bottem pads grip the shaft. as i have a sail boat it stays quite if you have a fast motor boat the force of the water on the prop my turn the shaft??
Ive found that when i leave port if i clamp the prop (leaving a note its clamped on the start ) i sail even when my speed drops below 3knots! i just open it again to enter port or when the wind drops very ecological
<hr width=100% size=1>liveaboard
am i the only one with a shaft break???mine is a simple clamp I have an open housing bolted to a frame the a screw which clamps the shaft via an asbestos pad(?)As i turn the screw the top and bottem pads grip the shaft. as i have a sail boat it stays quite if you have a fast motor boat the force of the water on the prop my turn the shaft??
Ive found that when i leave port if i clamp the prop (leaving a note its clamped on the start ) i sail even when my speed drops below 3knots! i just open it again to enter port or when the wind drops very ecological
<hr width=100% size=1>liveaboard
andy_wilson
Well-Known Member
I would have thought that you don't need too strong a mechanism to hold it, which would be an advantage if you forgot to release it.
How about a modified cycle mechanism, they fit disc brakes now, then you just need some way of locking the lever down when applied.
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How about a modified cycle mechanism, they fit disc brakes now, then you just need some way of locking the lever down when applied.
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alahol2
Well-Known Member
I'd have thought an ordinary (not disc) cycle brake would be the best option. They can be opened wide to prevent rubbing and just pulled up using the cable and something like a T handle. It can't require much force to prevent a prop from turning.
<hr width=100% size=1><A target="_blank" HREF=http://www.troppo.co.uk> Follow the Tightwad Sailor</A>
<hr width=100% size=1><A target="_blank" HREF=http://www.troppo.co.uk> Follow the Tightwad Sailor</A>
chippie
Well-Known Member
I read of one fellow who just used to tie a piece of string to his propshaft. If he forgot about it he didnt have to worry as it would break with no damage to anything.
I belive he cut all the odd bits of string from his shaft every couple of months or so.
I guess it takes all sorts.
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I belive he cut all the odd bits of string from his shaft every couple of months or so.
I guess it takes all sorts.
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jollyjacktar
Well-Known Member
Re: Now you\'ve gone and done it!
Compare a hellicopter with spinning rotor in autorotate mode or perhaps an autogyro. Non spinning of rotor caft drops like a rock i.e. less drag. Auto gyro will not take off unless rotor rotating. That is why when a hellicopteer has an engine failure the action is to allow the prop to autorotate. Try this out for your self with a sycamore seed. Throw one up, it spins and slowly falls to thje ground [ignore wind effect for this arguement] Now prevent the rotation by feathering the wings on the seed, strip of the wing parts, it drops like a rock.... ergo quad est demonstrandum [QED]
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Compare a hellicopter with spinning rotor in autorotate mode or perhaps an autogyro. Non spinning of rotor caft drops like a rock i.e. less drag. Auto gyro will not take off unless rotor rotating. That is why when a hellicopteer has an engine failure the action is to allow the prop to autorotate. Try this out for your self with a sycamore seed. Throw one up, it spins and slowly falls to thje ground [ignore wind effect for this arguement] Now prevent the rotation by feathering the wings on the seed, strip of the wing parts, it drops like a rock.... ergo quad est demonstrandum [QED]
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Plum
Well-Known Member
Re: more drag from a rotating prop when sailing
Shaft brakes are rare as the majority of sailing Yachts have mechanical gearboxes which lock the shaft when you engage reverse gear with the engine stoped.
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Shaft brakes are rare as the majority of sailing Yachts have mechanical gearboxes which lock the shaft when you engage reverse gear with the engine stoped.
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