Rudder Bearings

[hquinn]

I need to replace the top and bottom rudder bearings on my Dehler 34 - does anyone know what the clearances should be and what sort of material they should be machined from.

Many thanks

Heather Quinn

 

[richardandtracy]

The wet bearing should probably be phosphor bronze. If the upper bearing is dry (due to glanding - I don't know your vessel I'm sorry), then I would tend to go for a roller bearing of any type otherwise another phosphor bronze. As for bearing clearance, well I would suggest the normal distance recommended by bearing manufacturers for PB journal bearings - E7 fit (BS4500) and is based on a known shaft diameter. This translates into between +0.050 and +0.032mm for shaft diameters between 10 & 18mm, +0.065mm to + 0.040mm for shafts 18mm to 30mm, then +0.080mm to +0.050mm shaft diameters 30 to 50mm.

Regards

Richard

 

[davidbains]

Dehler should be able to tell you which manufacturer produced the bearings.
Otherwise consult the catalogues of Edson and Whitlock, the bearings they supply for any shaft diam will have the correct clearances. I machined a long bearing out of a solid cylinder of tufnol allowing 1/32 inch oversize which turned out to be too much for a 1 1/2 inch stock which now rattles.
Get those catalogues which I think can be perused online.

 

[timevans2000]

dont under any circumctances use nylon. It expands horribly when emersed in water for a period of time. Acetel, similar in appearance to nylon, is the thing to use. I am just having some made at the moment by my local engineering shop.

 

[richardandtracy]

Sure, use plastic if you don't mind changing the bearing again in the next 10 years. Some people enjoy it. Personally, I don't. Depending on a reasonably high shaft hardness, a PB bearing should last you longer than a plastic one.

BTW 1/32" equates to 0.79mm, and it being too large a clearance accords with BS 4500.

Regards

Richard

 

[timevans2000]

I accept that you will get longer life out of your metal bearings but I personally would want to remove my rudder for inspection every 5 to 10 years any way.

If you have the rudder off you may as well change the bushes at the same time. This is just my personal view and I could imagine it is not so easy to remove the rudder on every boat as it is on mine. Whilst I have my rudders off at the moment I have dicovered that the bottom s/s rudder brackets are corroded. They have been on 21 years so have not done badly. It does emphisise the point though that you should inspect these things periodically evev if it means a strip down to do so. I will stick to my Acetel bushes.

 

[Guest]

I replaced my bearings this year using acetal, got a local machine shop to turn them up gave him the old bearings for o/d measurement and brought along the rudder for him to check the stock "70mm o/d" with a mic, the stock was worn as it's alloy and he made the bearings to suit, great job and very cheap cost 80 euro about 50 sterling.