Rudder plain bearings

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Ülari
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Rudder plain bearings

Post by Ülari »

I need to replace my rudder plain bearings, since old ones are getting too large and rudder stock can move too much. However it seems that they are glued inside helmsport pipe. Is there a good way to get old ones out, or I just need to brute force it?
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asalovuo
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Re: Rudder plain bearings

Post by asalovuo »

I used wooden stick and hammer to get the bearings out (brute force) but I guess you could also try to saw them in half.
It may also happen that the helmsport pipe would get loose during the removal but that can be easily laminated back to the boat. In my case the bearings came out without breaking anything but I have seen one boat where the aluminium pipe got loose from the laminate and started to move out together with the bearing.
The upper bearing should come out pretty easy but the lower one is really tight fit.

If you haven't noticed there is ready made pictures for the bearings in the gallery. So measure the old ones and compare the measurements to the values in the picture (https://www.fe83.org/gallery/index.php/ ... akerihelat)

I changed the bearings couple of years ago and I needed to sand the bearings a bit before I could get the rudder back to the boat.
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Re: Rudder plain bearings

Post by Panu »

Ülari wrote: Sat Dec 12, 2020 16:45 pm I need to replace my rudder plain bearings, since old ones are getting too large and rudder stock can move too much. However it seems that they are glued inside helmsport pipe. Is there a good way to get old ones out, or I just need to brute force it?
Hi There

The rudder stock bearing's outside diameter is usually larger than the hole's diameter that it is put into (seat). In mechanical engineerin this is called compression fit. Like wise car wheel bearing is also compressed into it's place by using hydraulic press. Rudder bearings are not clued. Small compression, sea water and time makes it stuck quite hard.

I used dia ~30mm steel pipe to hit the bearings out. So my way can be called a brut force method. Hitting the bearing out is much better than using constant force. The impact that hitting generates makes the bearing loose easier than by pulling (constat force). Constant force could cause damage into construction (delamination).

I suggest you to measure dia of rudder stock and bearing seat's inside dia. Use those measurements to fine tune the actual mearures of the new baearings. Just keep in mind that compression between bearing and it's seat should be roughly -0.02mm - 0.1mm/dia and that the play between rudder stock and bearing's inside dia roughly 0.05 - 0.1mm.

Be sure that new bearing are made of proper material. Nylon is not suitable, because it absorbs water and expands... POM or so called Delrin plastic should be a good choice.

You must have noticed that there are drawings of bearing in Fe83.org's wiki : https://www.fe83.org/wiki/index.php/Per%C3%A4sinlaakeri
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Ülari
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Re: Rudder plain bearings

Post by Ülari »

Today I decided to go for it and took metal saw sheet and made a longitudinal cut in bearing and then used chisel to break bearing longitudinally. After that, some poking with a wooden stich and came out really easy (hammer was not even needed for stick). Bearings are ofcourse semi-destroyed, but thats not a problem. New bearings are probably going to be Derlin or maybe bronze. Need to figure this out, since preferably rudder must go in with first try, since I need to lift boat for that, digging a hole is not an option.

No glue was inside, however if i remember correctly, for my previous boat, when I got new rudder and bearings with it, manufacturer adviced to use a putty for bearings, however outer diameter were large enough for pretty serious compression fit, that I had to sand them a bit, because after fitting the bearings at first, rudder did not go in anymore
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