Re: [Amel Yacht Owners] Re: Toe pulley (headsail)


Mike Ondra
 

Hi Mark,

I am going to hold off on ordering the stainless sheaves for now since I already have Bernard’s PETP pulleys and his additional explanation below which I will test out and perhaps modify if necessary. In the event this doesn’t work do you think your machine shop would take orders at a later date?

For those who have ordered or are using Bernard’s PETP sheaves,  what have been the success or failure results? His updated installation instructions are attached.

Mike Ondra

Aletes SM#240

St. Augustine, FL

Home port: Rock Hall, MD

 

Hi Mike

I was away with a daughter to country skiing in mountains...

I had a phone call with Jean-Luc Mertz who installed first these pulleys with me and I looked at the message of Peter you join.

 

Peter used ropes with too small diameter 3/8" equals 9.52 mm, and according to Jean-Luc and I, did not pull enough on the rope (which is probably too soft and extensible). I would advice him to use a rope compatible with the wedge principle.

 

The principle of wedge contact of a cable or a rope is universally used in elevators, electric motors,..., and needs a minimum of pairing between the pulley and the rope.

 

A good pairing needs :

- a tight rope of aramid fibers with diameter of minimum 10 mm, never less,

- a rope with a maximum extension of 2% at half load and

- a rope tension above a few kN.

 

Due to the mechanical thinning of the rope when tensioned (Poisson

coefficient) the rope must be tight enough to not reduce its transversal dimension too much.

Outside these rules good working is only chance.

 

I have joined the updated manual.

 

Wish you an Happy New Year.

Bernard

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