Rear bearing wont stay in place
05-13-2007, 08:30 AM
#1
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Rear bearing wont stay in place
Hi,
Sorry for my english. I have bought a new sealed rear bearing for my OS-140RX engine from TH: http://www2.towerhobbies.com/cgi-bin...&I=LXWY09&P=ML.
I removed stock bearing without any troubles. Though i think i could slightly overheat crankcase in an owen because it has no temperature indicator. Maybe this could cause such a problem. So now.. new bearing won't stay tight in crankcase and cames out every time I pull out crankshaft. It stays in place only then I put crankcase with bearing in refrigerator for some time. But once it thaws out the story repeats. I have no idea how to fix that bearing in crankcase. I am afraid of heaving spun bearing if i will use engine. Help please..
Sorry for my english. I have bought a new sealed rear bearing for my OS-140RX engine from TH: http://www2.towerhobbies.com/cgi-bin...&I=LXWY09&P=ML.
I removed stock bearing without any troubles. Though i think i could slightly overheat crankcase in an owen because it has no temperature indicator. Maybe this could cause such a problem. So now.. new bearing won't stay tight in crankcase and cames out every time I pull out crankshaft. It stays in place only then I put crankcase with bearing in refrigerator for some time. But once it thaws out the story repeats. I have no idea how to fix that bearing in crankcase. I am afraid of heaving spun bearing if i will use engine. Help please..
05-13-2007, 10:38 AM
#2
RE: Rear bearing wont stay in place
Is it possible for you to obtain some bearing seater in your city?
In this country we have "Locktite" and to use some of the formula for differential metals would work great in this application.
In your case the bearing race is AISI 52100 steel and the crankcase is what we call in this country a "Zinc die casting" but the main ingredient is aluminum. It just has a lot of zinc mixed in with the aluminum so the metal will flow in the mold die without cold checking.
This Locktite chemical will have a reaction when applied to the outer race and inserted into the aluminum case and lock the bearing in place.
I've rebuilt a lot of model engines and have found that tolerences can stck up on you to the point where this happens. The original bearing was undoubtedly tight in the crankcase but the new bearing is slightly smaller and fits loose. I've found this phenomena to exist with relation to the fit of the bearing on the crankshaft also. I have obtained another bearing in this case.
The bearings from OS are not anything made just for OS. They are standard bearings you can obtain from a local bearing supplier. You could try another bearing?
The front bearing is 6000ZZ and the rear bearing is a 6904
There should be enough preload on the assembly when the prop is installed to prevent any movement?
In this country we have "Locktite" and to use some of the formula for differential metals would work great in this application.
In your case the bearing race is AISI 52100 steel and the crankcase is what we call in this country a "Zinc die casting" but the main ingredient is aluminum. It just has a lot of zinc mixed in with the aluminum so the metal will flow in the mold die without cold checking.
This Locktite chemical will have a reaction when applied to the outer race and inserted into the aluminum case and lock the bearing in place.
I've rebuilt a lot of model engines and have found that tolerences can stck up on you to the point where this happens. The original bearing was undoubtedly tight in the crankcase but the new bearing is slightly smaller and fits loose. I've found this phenomena to exist with relation to the fit of the bearing on the crankshaft also. I have obtained another bearing in this case.
The bearings from OS are not anything made just for OS. They are standard bearings you can obtain from a local bearing supplier. You could try another bearing?
The front bearing is 6000ZZ and the rear bearing is a 6904
There should be enough preload on the assembly when the prop is installed to prevent any movement?
05-13-2007, 11:01 AM
#3
RE: Rear bearing wont stay in place
I used green loctite for many years to retain loose fitting ball bearings in small engines.
The color was green. I used it on engines where the bearing had already spun, and
the fit was very loose. It works good.
Check here....
http://www.loctite.com/int_henkel/lo...id=19&layout=3
Click on:
Assembly products
Cylindrical assemblies (retaining)
Removable
Retaining compound 641
FBD.
The color was green. I used it on engines where the bearing had already spun, and
the fit was very loose. It works good.
Check here....
http://www.loctite.com/int_henkel/lo...id=19&layout=3
Click on:
Assembly products
Cylindrical assemblies (retaining)
Removable
Retaining compound 641
FBD.
05-14-2007, 02:43 PM
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RE: Rear bearing wont stay in place
I fixed the bearing in place with loctite 648. Thanks for the advice for all you guys. Now I observed that cylinder sleeve does not fit in case as tight as it was before. Does it means I will have serious troubles with engine running? Any suggestions...
05-14-2007, 03:37 PM
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RE: Rear bearing wont stay in place
Front bearing sealing (i removed other one) cooked out to black in just a half an hour. So I think it was really hot.. [sm=75_75.gif]
05-15-2007, 02:11 AM
#9
RE: Rear bearing wont stay in place
A loose fitting sleeve will leak past the case into the exhaust port and you will loose some crankcase pressure for the intake charge until it carbons or gums up and seals itself.
If you assemble it and use soapy water on the exhaust port you will see what I mean with gobs of air bubbles. Exhaust ports benifit from having a good seal between the crankcase casting and the sleeve. Makes for nice idle!
An easy fix that I have been using that works good is install the sleeve with a sheet of cigarette rolling paper (with the glue edge cut off) over the exhaust port on the sleeve. Slide it down without crunching, then take an exacto and cut open the port. It will stay sealed until it is carbon itself.
It is thin enough not to distort the sleeve and easy enough to work with, and sometimes can provide the perfect seal. Give it a try! If you have too much trouble installing the sleeve with the rolling paper, then the gap isn't enough to worry about.
If you assemble it and use soapy water on the exhaust port you will see what I mean with gobs of air bubbles. Exhaust ports benifit from having a good seal between the crankcase casting and the sleeve. Makes for nice idle!
An easy fix that I have been using that works good is install the sleeve with a sheet of cigarette rolling paper (with the glue edge cut off) over the exhaust port on the sleeve. Slide it down without crunching, then take an exacto and cut open the port. It will stay sealed until it is carbon itself.
It is thin enough not to distort the sleeve and easy enough to work with, and sometimes can provide the perfect seal. Give it a try! If you have too much trouble installing the sleeve with the rolling paper, then the gap isn't enough to worry about.
