RCV58CD

[Manish Chandrayan]

For the 58 RCV, the reason why I said remove shields on rear bearing and remove only one side (inside) on the front is because that is how they are installed from the factory.

If you haven't yet tossed out the original bearings you may compare.  

 

Graeme in my case I can not afford to experiment, modelling stuff is not cheap here.

I would rather emulate the manufacturer. So if one of Lasers require a bearing replacement and I see the original shielded or sealed I would rather copy that.

      

[Jon H]

A bearing with metal shields (2z designation) is not oil/grease tight and so will allow oil from the crankcase to make its way in for general lube. A rubber sealed bearing (2rs designation ) will be sealed and not allow oil in/out. 

 

On Lasers, we used to use 2z shielded bearings for the front of our engines but got loads of complaints as they would leak oil. We changed to 2rs sealed bearings about 10 years ago but we have to remove the rear seal to allow oil to make it into the bearing. 

 

You can remove the seals from 2rs and 2z bearings as long as you do not damage the cage that retains the balls. Some bearings have a riveted steel cage and these hang on even when the bearing is open race and has no shields. Some bearings have a plastic clip thing to hang on to the balls and while they may be safe to use in open race form i would not be confident suggesting you try that after yanking it out. It might be ok, but equally it might be damaged or need to have shields around it to keep everything togther. 

 

My general advice is to order an exact copy of what you had before as it prevents mistakes and confusion. Without seeing the bearing you have in hand its hard to say if you have damaged it. But given the cost of a new one vs the cost of rebuilding the engine after the balls fall out i would very much take the cautious route. 

[Andy J]

Before I ruin a second bearing Jon, pictured below is the original and new cylinder head bearing. Do you recommend I remove the outer rubber shield from the new bearing?

[Jon H]

Yea thats a rubber sealed bearing and you should easily be able to remove the rubber seals with a needle or very small flat blade screw driver. Just be sure not to catch the metal cage on the inside as any damage to that can cause it to fail. 

[Andy J]

Thanks Jon, rubber shield was easily removed.

 

Propose to install the new bearing by first freezing it whilst also applying heat to the engine cylinder then pushing the bearing in with a metal drift working against a washer placed over the bearing. The washer being just a little smaller than the bearing outer diameter. Hopefully that way I can avoid any damage to the bearing.

[Jon H]

if you are pressing a bearing in you need to press on its outer race. Pressing on the inner race will load the balls and you may end up damaging them. 

 

You could try fitting the bearing to the cylinder, cooling that lot as one piece, and then inserting the whole thing into the hot crankcase. The added mass of the cylinder will help keep the bearing cold longer and should allow hand fitting. A few gentle taps wont harm the balls, but dont go mad

[Martin Harris - Moderator]

+1 for fitting the bearing/cylinder as an assembly as suggested by Jon.  I normally do the same with conventional engine rear bearings and there's the added benefit that it's a lot less likely to gall as the bearing will be essentially in line as it's inserted.

 

I put the assembly in a plastic bag before popping it into the freezer for a few minutes.

[Manish Chandrayan]

Check!!!

The assembly order if I recall correct should be

1.Bearing

2. Bearing circlip 

3. The rotating cylinder

Because if you install the bearing on the cylinder the cylinder gear will obstruct the space for bearing circlip   

Essentially the reverse of the way it came out

1. Cylinder

2. Cicrlip

3. Bearing

Edited May 10, 2021 by Manish Chandrayan

[Andy J]

Engine now re-assembled with new bearings and it sounds even worse over 2 quadrants of rotation with what I think is gear meshing! Will start it up though just to see if the noise remains with heat but seem to recall last time the model was flying it sounded like a sewing machine so don't have much hope. Could not see any damage or wear on the gears so can only think the cam shaft is slightly bent. Strangely the noise only appeared when I tightened the bottom crank case shell fixings.

[Jon H]

RED ALERT!!

 

If it sounds bad, dont run it. Find out why!

[Martin Harris - Moderator]

Can you post a video with sound of it being turned over?

[Andy J]

Well after talking to Weston they had two recommendations. The first was to try tapping the shaft to push it further back and the second to try re-seating the cylinder head bearing by tapping it further down.  Tried both and it seemed to be little difference once I had tightened the lower case screws.

 

Then in desperation I applied a little locktight on the bottom casing to stick the two shaft bearings in place and also noting the order of tightening up the 6 screws on the lower casing ensuring both end screws were tight before tightening the 2 in the middle. This seems to have done the trick but why it has fixed the issue I have no idea.

Once I have made a new gasket for the head seal, will give the engine a quick run and see what happens when it warms up.

[Jon H]

i would suggest heating the parts before attempting to tap anything into place. It is likely something is not fully home but you will need some heat to get the ali to let go of the steel bearings. 

[Manish Chandrayan]

Here is a short video that I had done when I tested the engine after rebuild. Prop was a 12x6 APC . Could not locate the original muffler so pinched one from an OS 95V that was lying idle

Rebuilt RCV 58CD on test  

[Andy J]

Did a very short run of the engine this afternoon and all appears well so will do some extended running in of the new bearings tomorrow.

[Andy J]

Ran the engine again for about 3-4 mins and found the noise has returned. Tried slackening off the lower casing screws but the noise still remained over part of the rotation of the prop.  Thinking I will now have to live with this issue as at a loss what to try next or replace.

[Jon H]

Can you pop up a video of the noise?

[Engine Doctor]

When you first posted you had a picture of the conrod fitted round the wrong way. Was the engine run like that? Have you checked for any damage caused by rod being damaged ? An out of alignment con rod shows up as a tight spot on one half of the rotation and could explain the noise you describe. Check the rod for alignment using two  snug fitting drill shanks and check they are parallel.  If not parallel then fit new rod and try again. Its also possible that damage has been caused to the piston as rod in that position (over to one side) would effectively try to twist the piston in the bore.

[Andy J]

Video as requested.

 

Yes the engine was ran  with the con-rod in the incorrect position so will double check its alignment.

00007.MTS

[Gary Manuel]

Ouch. That sounds nasty.

[Jon H]

Oh my...

 

I think the gear mesh is not quite right. I would check the cylinder/crank are in their correct positions. 

[Andy J]

Must be related to the piston as without it fitted it sounded fine. Yet to remove and split the engine (yet again!) so will first check the con-rod as suggested.

[Martin Harris - Moderator]

Could that be the piston ring catching and releasing against the cylinder wall as it rotates?  Maybe a by product of a twisted con rod or a tiny defect on the cylinder wall?

 

If it is twisted, could a partial seizure have caused it? 

 

Either way, check the piston and bore for any witness marks.

[Mike T]

Sounds like a problem with the gears binding up part-way through a revolution.  Did you check the crankshaft for straightness/concentricity?  If the noise lessens or disappears without the bottom case on, then to me,  that would indicate the shaft and bearings are moving to accommodate any mis-alignment.

Check the gear teeth as well - there may be some damage, which you should be able to dress with a file, though this will compromise any hardening.

HTH

Mike (91CD user/rebuilder)

Edited May 14, 2021 by Mike T
punctuationally fussy...

[Martin Harris - Moderator]

I noticed that the first couple of rotations were quiet.  Does the noise still go away if oil is injected into the inlet port as mentioned in the original post?