the tufnol blocks on my genoa cars will not turn under load

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homa

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The headsail sheet block attached to each of my genoa tracks is made of tufnol and held in place by a stainless steel pin between 2 stainless cheek plates. It's not possible to dismantle the block to investigate further. But I'm sure there are no roller bearings.

I have noticed that with no load the roller is free and appears smooth running but when I sheet in the headsail under load the block does not turn. This gives tremendous amount of friction and is quite an effort to winch in even on low speed.

Any ideas other than renew ?

As I write this I realise I must have a similar problem with the masthead headsail halyard sheeves, I've been up the mast and they too appear smooth running with no load but a hell of a job to hoist the (roller) genoa. (it's a brand new foil this year so smooth running)

Cheers Homa
 
Maybe the pulleys have deformed. Check that the hole is concentric with the outer diameter of the pulley. I would also check the wear in the bearing hole to make sure that the pulley is unable to tilt under load and foul the housing. What happens if you lubricate the bearing (with water)?
 
I have seen plastic sheaves where the pivot holes became pear shaped instead of round. Presumably this occurred after they had been left in one position for a long time whilst loaded and the plastic deforms. Should be easy to check by just feeling the side play of the sheave at different positions.
 
The pulleys have not deformed, althought the pivot hole is probably a mill or so bigger but still round.
I am pretty certain its all original kit abt 37 yrs old but that is no reason to renew. Had hoped there was a simple solution.
It would certainly be cheaper to refurbish or even have new pulleys made - has anyone done this ?
 
Consider: why do we not use Tufnol now in general -reason :because we have better solutions IMHO.. I'd also suggest that a refurb could actually cost more than reasonable quality new ones and would not work as well.... /forums/images/graemlins/confused.gif
 
The tracks are pretty standard - just be sure you measuer the width properly. I have exactly the same problem and my boat is a lot newer than yours. I.m getting cars fitted with bearings this time.
 
Yes I've done this. The cars on my boat were Lewmar and about 25years old. they had flats worn on them made by the sheets. I disassembled with the help of an anglegrinder and had a local engineering shop make up new ones but a bigger diameter because I thought that this would let them roll easier under load. This was done last season and has worked very well, the cost was £30 and most of that was for the material I think.

ed.
 
It might be time to get out an angle grinder and remove the axle pin. It may then be possible to replace the sheave with perhaps nylon. You may also be able to fit in a bit of sstubing over the axle to give additional bearing parts which may or may not help.

I notice some sheet cars have a quite small diameter but wide sheave. This is presuambly to get the lead of the sheet as low as possible when approaching the winch base. Obviously larger diameter sheaves would be far better. You may have to extend the cheeks to cater for a larger diameter sheeve.

persevere and don't throw in the towel and buy new ones, no no no no no............ olewill
 
I'm certainly not going to buy new as the cost is prohibitive and it's rather low on my list as a priority. Was hoping for a simple solution, But these small jobs never seem to end up being that simple !

It looks like an angle grinder job and have new sheaves made up, ideally with some kind of bearing inside. I can then hold it all in place with new SS bolt and nylock nut.

Cheers
 
Have you looked at Barton fittings www.bartonmarine.com. They manufacture genoa cars to fit other makers' tracks and these are generally very much cheaper than the originals. Alternatively they might be a source of new nylon sheaves if you decide to do that.
 
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