New Rudder bearing is too tight. Now what?

[Neil_Y]

Just a comment on srp post.

Delrin and vesconite both swell due to moisture, less than nylon though. But the biggest problem is swell with heat/friction.

The horror stories and perception of moisture related swell came, I believe, from the incorrect use of nylon.

 

[Spyro]

You could try a flap wheel.

 

[AndrewB]

What I do is abrade the rudder post rather than the bearing. This is so much easier to do evenly and accurately. Use best quality coarse emery paper, dry. You may question how effective it can be at cutting steel, or be concerned at reducing the strength of the post, but you'll probably find that by the time you have it polished nicely, it will fit easily (NOT too easily!).

However, before tackling either the bearing or the post, do double check that you don't have an alignment problem, or a slighly bent rudder post.

 

[lenseman]

If you are still looking to ream out the bearing why not use an engine cylinder reamer? They are usually 3 or 4 stones spinning inside the bore on a drill press using the centrifugal force of the stones as the only cuting force.

I think you just might be referring to a cylinder bore honing tool, not a reamer as such. Whether or not it might be suitable is another matter? They are readily available depending on size. See here in e-Bay:

http://www.ebay.co.uk/itm/NEW-Cylin...t=UK_Hand_Tools_Equipment&hash=item2a0fc7aa15

 

[Iliade]

You really should avoid any form of abrasive cutting as the bearing is designed to be soft enough to incorporate any hard debris, such as particles spalling off the shaft. Consequently the bearing will incorporate particles of the abrasive, aging it significantly.

If you wish to simply rebore it, ideally you need a guided adjustable line reamer such as would be used to ream camshaft bearings in a straight line. As someone here suggested, a fair approximation could be made with a dowel with an inserted electric planer blade. The idea is you have the reamer passed through both bushes so that the lower bush is bored in-line with the top one.

Some possible causes of the problem:

- The o/d of the bearing being too large such that on pressing into the rudder tube the bearing was compressed.
- Oval rudder tube (see above)
- debris in the rudder tube
- bent rudder tube (why?)
- Rudder tube detached at top
- Rudder tube broken
- bearing machined undersize i/d (checked on shaft prior to fitment so probably not this, though was it checked on the right part of the shaft?)
- Water absorbtion, though as it was stiff before launch that can be largely discounted.
- Flexion in the hull when launched. (This and water absorbtion probably account for it getting stiffer after launch)
- bearing not fully inserted
- thrust bearings too tight

 

[wotayottie]

I am worried this might be the case, as the man who made the bearing said it was 'free' when he tried it on the shaft

If this is the case then dont open it out any more. If there is no play at alkl in the shoe I would be amazed. First thing is to loosen that off and see if that allows the tiller to move easily.

 

[srp]

Just a comment on srp post.

Delrin and vesconite both swell due to moisture, less than nylon though. But the biggest problem is swell with heat/friction.

The horror stories and perception of moisture related swell came, I believe, from the incorrect use of nylon.

I don't know about Delrin as I don't use it. Vesconite is around 0.7% (which they say is for an extended soak) , which looking at your data is about the same as Maritex, as you say much less than nylon and many others. I don't think heat should be an issue for a rudder bearing assuming a proper fit.

I'd like to have a play with Maritex - do you sell small pieces (say 40 od x 100 long)?

ps I wonder if the OP is in the water yet, and if the problem is solved, as the thread is a few weeks old now.

 

[Neil_Y]

Rudders often have heat expansion related failure as they are either grease or dry in the upper bearings. Grease is a poor conductor of heat.

Our clearance allowances for thermal change are around 1.5 x that for moisture, still small but significant when you may be running 0.30mm clearance on an 80.00mm shaft.
.08 min running
.09 moisture swell allowance
.14 thermal swell

Allowing for the fact that Maritex has thermal expansion around half that of many other materials you can see how it might add up.

Yes we do supply everything from small rods to half metre tubes, but it comes in a variety of grades, what are you looking for in terms of its use? Load, speed, duty cycle, environment, lubricants, sliding surface material/finish?

 

[srp]

Yes we do supply everything from small rods to half metre tubes, but it comes in a variety of grades, what are you looking for in terms of its use? Load, speed, duty cycle, environment, lubricants, sliding surface material/finish?

Prop shaft bearing for 1" stainless shaft. Max speed is probably around 1200rpm, obviously fully immersed, lubricated and cooled by seawater. 45 hp engine running an 18x14 prop.