OS50 Hyper rear bearing removal?

[Made2Fade]

Hi guys... how you guys removing the rear crankshaft bearings in your OS 50 Hyper engine? Im only replacing the rear bearing, the front is fine. Is there any special way to get it out? Cheers
Lee

[Sieze2]

Wasn't this discussed recently? I seem to remember needing to heat the engine in an oven for 10 mins ?

[robgt]

Strip the engine down to just the crank case and stick it in the oven for 15 minute - gas mark 5
Start listening for the clank at around 10 minutes... the bearing will just drop out.

Cheers,
Rob

[Made2Fade]

ah ha now i remember! Your right it was discussed Sieze2. Cheers guys... i think that next article is needed Rob lol. Got it down to just the 2 bearings and crankcase now so will try that. What about the front bearing though? Will that not get damaged? Can i just not heat it up with a blow torch? I only have the rear bearing as spare thats all.
Cheers
Lee

[robgt]

The bearing article will happen - it's on the waiting list
(Sorry )

You could use a blowtorch, just make sure you get the inside of the engine spotlessly clean again afterwards.

The top bearing shouldn't be harmed in the oven process, but if you're worried at all, once the back bearing has dropped out, tip the engine over and pop the top bearing out too, then once it's cooled you can re-grease it.

For fitting the bearings back into the crank case, heat the engine body up and stick the bearings in the freezer in the meantime - then get the bearings fitted fairly swiftly when you get to the re-assembly.

Cheers,
Rob

[Made2Fade]

Will try that, crankcase is in the oven as i speak. Thanks for the fitting tips.
Lee

[robgt]

One final fitting tip - make sure the back bearing goes all the way in - use the crank and drop it through the crank case in one swift movement. As soon as the cold bearing contacts the hot crank case, it will start expanding again, so you have to be quick, but that back bearing must be fully seated or you won;t get the engine back together again properly.

You will know when it's in fully as the journal (where the con rod connects to the crank) will rotate fully inside the cutaway in the crasnk case - look through the head end of the crank case for alignment.

Good luck!
Cheers,
Rob

[Made2Fade]

Seems all pretty straight forward and common sense really. I was thinking on the right tracks just wasnt sure about ruining the front bearing in the process. Cheers Rob will post how i get on.
Lee

[LipolyGone]

Incase anyone else here hasnt already done their engine in the oven thing.
I find the halogen hob method far easier as you can see whats going on
Just turn on your halogen hob place the engine stripped down sat on the rear of the crankcase & wait till the bearing drops out it's also slightly easier on the front bearing as it's not being heated to the same degree as stuffing the engine in the oven.
I have also heard of the toaster method but Ade or jamie are going to need to pipe in as I've yet to see it done.
Another tip is to place the new rear bearing on the crank & pop it in a freezer bag & put it in the freezer for an hour or two before your going to need the bearing replaced. The whole process can then be done in one hit. The crank & bearing shrink with the cold & the crankcase expands with the heat & it makes it realy easy to put the bearing back in with plenty of time to line it all up properly.
Martin
ps remember to do it when the wifes out as the fumes are quite nasty in the kitchen for a while.

[robgt]

I find the halogen hob method far easier as you can see whats going on

Good idea Martin... I'm on gas here so the thought hadn't occurred to me!
(Noted for future reference )

I have also heard of the toaster method

I think a metal mesh/gauze over the top of the toaster would be advisable?
You wouldn;t want to drop a bearing in there, surely?

Cheers,
Rob

[LipolyGone]

Good idea Martin... I'm on gas here so the thought hadn't occurred to me!
(Noted for future reference )

Ah yeh forgot to mention dont try it on a gas hob lol

I think a metal mesh/gauze over the top of the toaster would be advisable?
You wouldn;t want to drop a bearing in there, surely?

Cheers,
Rob

I would imagine a piece of tin foil would be better, would also stop the gooey magnum residue from spoiling your breakfast
Martin

[trvo]

I'd advise against the blow torch method, it deforms the crankcase and although the engine will prolly still work it'll have no guts whatsoever... Ideally you want something that'll heat the whole crankcase equally... Don't ask me how I found that out...

Trev

[Made2Fade]

Right easy bits now done... i used Robs method of baking in oven for 10 - 15 minutes. Bearing came out straight away. Think ill use Martins idea of freezing the bearing and crankshaft together and getting it in with the one hit hopefully. Thanks guys.
Lee

[SRH990]

I've just got this strange vision of toasted rear bearings, do you eat them like bagels

The oven method is pretty foolproof and using the freezer for the crank/rear bearing makes it a doddle. The piston liner in my OS50 is very tight in the crankcase and I have to use the same heat/freeze method to get it in and out. So far on the 3 engines I've worked on I've replaced both front and rear bearings but in all cases the front bearing has actually been fine and didn't need replacing.

[Ashley Davis]

Agree with Trev, idealy blow torches should not be used on anything on the heli as it will anneal the metal, it's just too hot. Blow torches are way up there in the hundreds of degrees where as an oven is temp controlled and nowhere near the temps required to start the annealing process. Plus you want to heat the engine evenly, not just heat up one spot (which causes crank case deformation).

The same advice goes for mainshafts, don't be tempted to blow torch them and try to straighten, they just anneal and go all bendy (usually inflight).