Borgwarner does it really need a shaft break

rogersimms

rogersimms

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Hi

I am getting conflicting reports and need some advise if it is really necassary for a Borgwarner Velvet Drive to have the prop shaft stationary when sailing. I lose at least a knot when sailing with the shaft break on and am playing with idea of increasing prop size. for some reason I cannot find contact details to directly contact Borgwarner. Do they use a different name

Thanks
 
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I lose at least a knot when sailing with the shaft break on and am playing with idea of increasing prop size.

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Its counter intuitive but a locked prop has less resistance than a turning prop and you will sail faster. This has been discussed many times on here
 
FYI: If you decide to use some sort of shaft brake, give me a shout as I took a shaftlok off my boat last week and was planning to fleabay it.
 
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its a hydraulic box & need a brake with a fixed prop y not go folding / feathering

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I have a PRM Hydraulic box and it says clearly in the manual that shaft can freely rotate without problem. It is not necessary to lock it.
As I understand it - it becomes more important on a mechanical geared box where constant freewheeling is in effect wearing out the box as if you were motoring.

To OP - it's generally accepted in prop circles (forgive the wee joke !) that a freewheeling prop produces a greater drag through it creating a disc of resistance instead of a static area.
 
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on the TMP box the shaft can only be run for very short periods due to lack of lube if free wheeling

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Which goes to show that each box has it's own situation. I just posted in reply to the comment that being a hydraulic box you assumed all must be shaft locked. As to the BW box .. without manual ? I don't know - do you ?

/forums/images/graemlins/wink.gif
 
This is directly from Perkins Handbook. This is for a Borg Warner Velvet Drive gearbox.

" When oil operated reverse gears are used on auxillary yacht installations care must be exercised when trailing the propeller with the engine or engines out of use.
With the Borg Warner gearbox it is permissable to trail for 8 hours providing the following shaft speeds are not exceeded:-
Direct Drive 1,500 rev/min
1.5 1,000 rev/min
1.9 790 rev/min
2.1 715 rev/min
2.5 600 rev/min
2.9 520 rev/min

Transmisssions incorporating reduction gear must have means of stopping the transmission output shaft from prolonged or continuous freewheeling. This is because the engine, being stopped, does not drive the oil pump in the gearbox. The box therefore is not being properly lubricated."


Hope this answers your question.
 
My Perkins has a PRM box (reduction as well) page 17 of the Workshop manual of PRM Newage Marine Gearbox ... series 140 & 265's says >

<span style="color:blue"> PRM gearboxes are designed and tested to ensure that prolonged periods of trailing (free-wheeling) the propellor are permissable without any detrimental effect to the transmission. It is not therefore necessary to provide any shaft locking device. </span>

Non of my Perkins manuals ( I have 3 versions ... marine, land and general ) have any mention about gearbox's at all. But they are the old 4-99 ... 4-107 ... 4-108 series jobs.
 
Thought we were interested in Borg Warner /forums/images/graemlins/confused.gif
Who is PRM?
The workshop manual I'm quoting verbatum from is probably 30+ years old.
Over to you........................... /forums/images/graemlins/frown.gif
BTW this is for a Perkins 4.236!
 
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To OP - it's generally accepted in prop circles (forgive the wee joke !) that a freewheeling prop produces a greater drag through it creating a disc of resistance instead of a static area

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I can't subscribe to that theory at all! It could be also argued that it creates a disc of less resistance (the spaces between blades). Whatever, it remains a fact, that when you lock the prop. the speed through the water decays. I believe Peter Mckenzie's paper quotes figures as high as 100% additional drag with the prop stationary.

My Hurth box manual clearly states that the shaft must not be allowed to turn when the engine is stopped and the boat is under sail.
 
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