OS50 Bearing replacement - part 1

[Dedcalm]

Finally found the time (been busy, then fixing mates Rx, then ill with flu, then looking after kids) to take a look at my OS50 bearings...

The engine (OS 50 Hyper) was one of the first engines in the UK (official import) back in 2004(ish) . It has been in my Raptor ever since and has been flown quite a lot on (and mostly) off throughout the past 6 odd years. When the heli was laid-up for rest it was fed some after run oil and when in use has always been run dry at the end of a session. That said finally my bearings had had enough of their smooth life and threw in the towel last weekend so I ordered up replacement front (just in case) and rear.

Took the engine out tonight and after something of a battle of wills I got the crankshaft out. Its amazing how stuck in place the liner can be, how much gunk can form on the gudgen pin thus resricting any lateral movement to get the big end of the con rod off the crank .

The front bearing is (as suspected) A-ok but the rear bearing is a nasty sight, very very rusty and corroded and notchy as hell (although all balls are rolling as it rotates). I will get a pic before chucking it in the oven tomorrow in what I suspect will be a vain attempt to loosen the bearing from its home.

Can anyone offer any advice on how to loosen up the bearing other than heating the crank case and giving it a heathy tap? Its not as if there is a lip available to wack it etc. and I dont really want to have to destroy the old one and take it out in pieces as I may damage the casting...

[Andy from Sandy]

Heat is your friend when for removing either bearing. If this is your first attempt then put the crankcase in the oven and set it to 230degrees C. It will not damage the case. With the crankshaft out put the new bearing on it first. Get something like an old fashion bread board. Have something to hold the crankcase with. After 15 minutes tke the case and gently tap it on the board and the rear bearing will drop out. It does not take huge forces or hefty hits to remove the bearing. If it does then the case hase not expanded enough. With the old bearing out and the case still hot you can drop the crankshaft in but be carefull not to push the front bearing out.

Search google for bearing replacement there is loads of threads and some videos of the whole procedure.

[Janek]

Wait until your missus is out.

Put the stripped down crankcase (everything out/off, except the 2 bearings) on a baking tray in your missus oven, at about 200, for 15-20 minutes. Put it the back plate end on the tray. i.e. stand it vertically.

After this time the rear bearing will usually drop out on it's own, if not tap the back plate end lightly on a waste piece of wood, or chopping board (NOT the kitchen worktop !), this will get it out. DO NOT use your missus's clean white oven gloves, but protect you hand with a waste piece of clothe, otherwise you'll get BBQ'ed fingers. . . . .

Clear up before your missus gets back.

No responsibility is accepted by me for you loosing your nuts if you mess up HER oven, oven gloves or worktop (or anything else) . . . . good luck, no pressure !

[richieclarkie]

To add to that.

Open the windows too, the fuel residue on the crankcase being cooked stinks

[GravityKills]

yes, just fry it
Usually it comes out by its own weight, or very easily. But I cannot imagine you could move it without damage when the motor is cold.

[jamiem]

It's worth putting the new bearing on the crank and putting them both in the freezer while baking the case, that way it will drop in really easily and expand out locking in place almost instantly.

[Dedcalm]

Great, I am hoping it will just drop out but given the amount of corrosion etc I feared the worst... we will see I guess.

Going to give the engine a good clean prior to baking it to reduce any smell (kids in the house etc) and prevent any burning on or staining (although I guess its unlikely with the synth oils).

I have already removed all other components of the engine so its just the crank case and the 2 bearings left.

Wouldnt dream of banging it on the worktop - the're wood and under a year old... I would have to kill myself if I marked them else the wife would do it!

Will wait for the kids to have their nap this afternoon and give it a go

thanks all

[Sesame]

I cant believe your bearings lasted 8 years, incredible

[Janek]

I cant believe your bearings lasted 8 years, incredible

He's obviously not trying hard enough

[Aidi]

Have a read of this. It will take you step by step on how to remove and replace bearings:

Links and Downloads Manager - Engines / Motors - RcHeliaddict

[Dedcalm]

He's obviously not trying hard enough

I pretty much flew on my own (at least with the heli) and I guess as a result I am too cautious - however since joining SCMHC back in April I have come on quite a bit (I hope).

Remember too the heli has spent much of its life stored away rather than being flown - thats why it looks mint

[Dedcalm]

10 mins at 200C and a tap on a piece of wood saw the old bearing out (phew!), let the casing cool and cleaned up the bearing seat ready for the new one. Checked the front bearing to be certain I was happy and I had a glimmer of doubt creep in so rather than mess about I decided I would replace this one to (lucky I had bought both!).

Re-heated engine and stuck the new bearings in the freezer, even cold the rear bearing went onto the crank without issue. Lifted out the front bearing from the hot crank case using a pair of long nose pliers opened to grip each side of the inner face. laid the new front bearing face down on the piece of wood and pushed the crank case onto it - slipped in nice and cleanly. Then popped the crank shaft with cold rear bearing installed through the crank case and everything ended up where it should be - superb!

Am just waiting on it to cool off so I can then put it all back together and get it back in the heli... might even get a Wednesday eve test flight in if work doesn't get in the way.

[gareth08]

Great video i used when doing my bearings in my 'now dead' OS37

[ame=http://www.youtube.com/watch?v=TuzEco3EDUM]YouTube - How to change model airplane engine bearings (part 1 of 2)[/ame]

Also

[ame=http://www.youtube.com/watch?v=OLSoXPLGzOI&feature=related]YouTube - How to change model airplane engine bearings (part 2 of 2)[/ame]

Incidentally if you follow the link to the website of the guy who made the video there is some interesting stuff there too!

[Dedcalm]

Got it all back together without any problems (well apart from forgetting to re-fit the governor hall effect sensor when putting the engine back on the mounting plate - doh!). The OS piston/con-rod locking tool (machined white plastic thing) is fantastic, had mine for ages, in fact when I got the engine and it only comes out to play rarely but what a simple solution to the need.

Checked the main and header tank clunk pipes and found (as I suspected) the main tank clunk pipe was shot, strangely though the header is fine. Replaced as necessary and fitted some day-glo green piping for muffler pressure and main to header feed. leaving header to carb clear so I can see fuel/bubbles etc...

[Dedcalm]

For those interested attached is a (rather poor) pic taken on my blackberry of the old bearings



Thanks all for the help and advice