| Subject: |
|
Shaft brake |
| Name: |
|
Guillermo Gefaell |
| Date Posted: |
|
Feb 27, 05 - 8:50 AM |
| Email: |
|
bmccommodore@banjer37.net |
| Website: |
|
http://www.banjer37.net |
| Message: |
|
I have been crossing some messages about whether it is good or not to install a propeller's shaft brake, with Colin and Dees. Here you have some excerpts:
Guillermo:
"...It is confirmed now that Paragons can be let to freewheel when sailing with engine off, without suffering damage to the gear. Good! On the side of braking the shaft, generally speaking it should be better not to allow the shaft turning: As a matter of fact noise is much less, wear and tear is also less on bearings, etc., possibility of tangling ropes around the shaft is lessened and resistance (draft) will probably be less, although very much discussion has been done about this last point. In my opinion and experience, resistance is less if the propeller is stopped than if it is freewheeling in most of the cases, mainly with two bladed propellers fixed as to the blades remaining vertical. With three bladed propellers, and depending on underwater forms of the hull , propeller size and boat speed, things may be more tricky.
In my opinion, and talking about Banjers, I think it's better to brake the shaft when in long passages, unless you want to add a shaft generator to take advantage of the available energy, of course. But if the sailing scheme is mainly based on relatively short trips, it probably doesn't worth while to mount a brake. I have owned MARIE for 14 years now and, as I only go for short trips, I have not felt the necessity of a shaft brake up to this moment."
Dees:
"...I once red in the 'practical boat owner' that a simple brake from a renault-car was installed on a shaft. I intended to do the same, but did not dare.(the mainreason was that I was afraid that the shaft was pulled or pushed out of the center of the bearings, the same problems I had the first year of owning the banjer. The result by then was that the shaft leaned on a bearing and was overheated. Since then I have simply installed a temperature device on the bearing (Price 3 Euro at Halfords), changed the lubricating from grease to waterlubrication and had a new shaft installed).
But I have seen brakes on Banjers. I do not know whether it was the Chapeau, the Sprot, the Elskerinde but I have twice seen a break.
Is it possible to ask this on the site?
Colin,I have red an article in the PBO some time ago about propellers and I was also surprised to read that a propeller that did not rotate made less drag than a propeller that rotates.I had to do with the rotating, meaning that it merely started pulling instead of being an obstacle."
Guillermo:
"I don't think a brake, even a simple made one, may overimpose excessive loads on the shaft as to desalign it. These brakes are supposed just not to allow the propeller to freewheel, not to stop the boat, as a car's brake does. I think (I have no experience, I recognize!) it's only a matter of careful workmanship, most of mechanical people in professional workshops are supposed to be able to provide."
Colin:
"I had a shaft brake on a previous boat - one with a perkins 4108 diesel in. If I remember - it was 25 years ago - it was just a disc - as on a car brake - mounted on the shaft. There was then a standard disc brake mounted to grip it. The brake pulled on like a hand brake.
It was fine but the big worry was how to remember when the brake was on or off when the engine had to be started quickly. It also went very rusty.
I think I shall put one on Sulasgeir when she comes back to Scotland in 2006. But with the aft cabin - as for Dees - it may be a bit tight to find the room." |
|
Replies:
|
|
|
|
|
Hey Webmasters! New Photo Album Service Launched - Check it out!
Reply
Forum
bravenet.com