More B & G MHU woes

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davidej

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I have a 496 MHU which needs the anemometer bearings replaced. I have looked at the oppedjik website and the pictures there and read the recent skipper stu thread on the subject but am still stumped.


I have taken off the bottom nut and the spinner but can't loosen the grub screw which is visbile thru a hole immediately above the spinner. I dont know what size it is but none of my metric or imperial allen keys fit well and I think I may have rounded off the hole.

I cant really see how to proceed now -should I drill the screw out? The oppedijk picture suggest this does not need to come apart and I should start dismantling higher up. How?

Any help would be appreciated.

Also can anyone tell me the number of these bearings.

I need to get on with this as the boat is setting off on the annual cruise soon.

thanks
 
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The bearing number is SFR2-5ZZ.

I have to do mine as well sometime soon.
As I have not yet removed from the mast I cannot help with a description of how to dismantle.
Looking at the picture on the oppedjik site, I was wondering if the shaft can be driven out after removal of the circlip.
Anyway best of luck
Cheers
Nigel
 
Skipper stu mentioned the circlip. Where is it?

Do I have to take the wind vane unit off the central staff to get to it?

OR does the middle part in the photo (a sort of aluminium tube wider at the bottom) unscrew downwards from the staff
 
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Thanks for the B&G link. that confirmed my suspicion the the ally casting (Anomometer Bearing Assy) is screwed on to the main Spar Assembly.

However, in our case the ally was well corroded and by applying a bit too much force we have sheared of the thread on the plastic part. I am hopeful that a bit of epoxy will get it all together when the time comes.

I have now got the axle out and assume that the two bearing push out from each other - ie the top one goes upwards and the bottom one down. I will PM Skipper Stu to find where he is getting his replacements.

One thing that still puzzles me is that the part I take to be the magnet (a very small black 'tube') was not attached to the axle -surely it is meant to rotate with the axle asembly.
 
FWIW - The picture of the label printed on the packet containing the bearings on the oppedijk website looks exactly like the label on the packet that was packed for me at SMB bearings...

Bearings packet on Oppedijk website

SMB bearings did next day delivery on mine (for a Raymarine MHU) at a very reasonable cost..

SMBbearings homepage

and a desciption of what SFR2-5ZZ means (thanks to Nigel1 for the bearing part number)

( No connection to supplier. Just happy customer.)
 
davidej said:
Thanks for the B&G link. that confirmed my suspicion the the ally casting (Anomometer Bearing Assy) is screwed on to the main Spar Assembly.

However, in our case the ally was well corroded and by applying a bit too much force we have sheared of the thread on the plastic part. I am hopeful that a bit of epoxy will get it all together when the time comes.

I have now got the axle out and assume that the two bearing push out from each other - ie the top one goes upwards and the bottom one down. I will PM Skipper Stu to find where he is getting his replacements.

One thing that still puzzles me is that the part I take to be the magnet (a very small black 'tube') was not attached to the axle -surely it is meant to rotate with the axle asembly.
Click to expand...
Its too late, if the plastic has crumbled, its cheque book time, you need a new wand, phone B&G up and sit down whilst they tell you how much!
Stu
 
nigel1 said:
The bearing number is SFR2-5ZZ.

I have to do mine as well sometime soon.
As I have not yet removed from the mast I cannot help with a description of how to dismantle.
Looking at the picture on the oppedjik site, I was wondering if the shaft can be driven out after removal of the circlip.
Anyway best of luck
Cheers
Nigel
Click to expand...
It can be driven out, I just gently tapped it down, I didnt notice the circlip! the magnet seemed to be gently glued on, it came off as I was tapping it down. The grub screw is 1.5mm across flats, I rounded mine! I have bought mm bearings, I will have to dress the shaft to suit. The shaft measures 3.3mm so the id of the bearing needs to be that BUT I could only find 3mm id bearings in SS and shielded. The bit about the plastic crumbling happened to me, I gave up on glueing that and picked the bits of plastic out of the alloy bearing housing to reuse it, (its actually on my mast head!) It seems the newer wands are made out of crumbly plastic!
Stu
 
davidej said:
Thanks for the B&G link. that confirmed my suspicion the the ally casting (Anomometer Bearing Assy) is screwed on to the main Spar Assembly.

However, in our case the ally was well corroded and by applying a bit too much force we have sheared of the thread on the plastic part. I am hopeful that a bit of epoxy will get it all together when the time comes.

I have now got the axle out and assume that the two bearing push out from each other - ie the top one goes upwards and the bottom one down. I will PM Skipper Stu to find where he is getting his replacements.

One thing that still puzzles me is that the part I take to be the magnet (a very small black 'tube') was not attached to the axle -surely it is meant to rotate with the axle asembly.
Click to expand...
my magnet was glued, not very well and slightly off centre.
Stu
 
nigel1 said:
In hindsight, is there a better way to unscrew the bearing housing so as to avoid breaking the plastic threads. Application of some hot water maybe??
Click to expand...

There must be but definitely NOT hot water.

I had intended to spray it with penetrating oil and leaving it overnight. However my co-owner came round and wanted some action. He suggested plunging it in boiling water for 30 seconds. This seemed a good idea but the effect was to soften the plastic and it sheared with very little effort - much less torque than I had originally applied.

At least, I now have it all apart and the bearings out. My local supplier says he can get replacements in 2-3 days. So I have high hopes of re-assembling the bearing assemble and then epoxying that back in the main staff.
 
Thanks David,

Take it that the bearings tapped out easily enough once the shaft was out, and as you suggested in the earlier post, top bearing pushes up, and the bottom one, down.
Were they a tight fit, or will finger pressure be enough to resit the new bearings
 
Yes one up one down.

They are absolutely tiny (about the diameter of a pencil) and I tapped them out using a nail with the point ground off.

I have not yet got the replacements but I imagime a light tap with the hammer will be needed again
 
Working again

Finally had a nice enough day to go up the mast and replace it. It works fine (thank god).

I ordered the bearings from my local supplier (SFR2-5ZZ) and they arrived within 24 hrs -about £5 each. Easy to reassemble. However where the ally housing had broke away from the plastic, I put it together with 10 min epoxy and when that was hard, I wrapped a 'bandage' of glass tape epoxied round. A coat of black paint and you would never know the difference.
 
Just done the bearings in the 496 mast head unit, no problems.
The assembly unscrewd from the main body with no problems. The grub screw which holds the threaded part of the assembly to the shaft also unscrewed with no problem.
The shaft then tapped out from the bottom, in the direction of the magnet, taking the upper bearing out at the same time. The lower bearing needed some small persausion to come out as there was light corrosion around it.
Re-assembled and refitted. Took about 20 mins to change bearings once the unit was off the mast
 
davidej said:
Well done!

Glad to hear your bearing housing unscrewed so easily. Do you know how old it was?

Mine was dated 2001 so it had done 11 years
Click to expand...

Must be about the same age, cannot see the date, but the B&G stuff was fitted to the boat at new build stage.
I did find that the plastic capped nuts which retain the vane and the cups were in very poor condition. The one for the vane was split in two places, and just pulled off.
I replaced both with washer and M5 Stainless Steel nylocs
 
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