SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 21, 2013, 07:35 PM
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
2,435 Posts
had a .28FSR (think that was it) that would not let go of its rear bearing with a reasonable amount of heat. so out came the dremel with a carbide burr, first to take the cage apart and then to cut through the outer race. only took a minute or so. left a few marks on the bearing seat but not enough to hurt anything. new bearing went right in with no problems after heat soaking the case and freezing the bearing.
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 22, 2013, 12:57 AM
Registered User
DarZeelon's Avatar
Israel, Ramat HaSharon
Joined Nov 2003
1,164 Posts
Dave,


Aluminium expands nearly twice as much per K as steel.
22.2 (10^-6 mm K) Vs. 13.

Yes, it is possible to 'trick' the lower mass bearing, to heat-up and expand more than the higher mass crankshaft; thus making it slightly looser on it... But these techniques cannot be considered general practice and are not applicable for everyone...

Relying on the difference in CoTE is a sure-fire method, to extract a steel bearing from inside an aluminium crankcase.


The problem you encountered with your OS.28FSR (there were only a .28F and a .25FSR), was probably a result of a 'trampled burr' not noticed during build-up, in the seat of the rear bearing...
I had this problem with the carburettor mounting of an MVVS 26 cc engine...

It took me nearly an hour to pry it out...
DarZeelon is online now Find More Posts by DarZeelon
Last edited by DarZeelon; Feb 22, 2013 at 06:53 AM. Reason: Wording.
Reply With Quote
Old Feb 22, 2013, 02:43 AM
Registered User
DarZeelon's Avatar
Israel, Ramat HaSharon
Joined Nov 2003
1,164 Posts
The removal of the crankshaft is well illustrated in this no-nonsense video.

Please watch from about 6:30 minutes.
The engine is a four-stroke, but the procedure for crankshaft and bearing removal, is exactly the same as for an OS.55AX and virtually any other glow engine; in regards to when heat should be applied.

It is by Greg that we know from these pages.
DarZeelon is online now Find More Posts by DarZeelon
Reply With Quote
Old Feb 22, 2013, 06:58 AM
Registered User
Reginald's Avatar
Belgium
Joined Aug 2004
3,743 Posts
Quote:
Originally Posted by DarZeelon View Post
The removal of the crankshaft is well illustrated in this no-nonsense video.

Please watch from about 6:30 minutes.
The engine is a four-stroke, but the procedure for crankshaft and bearing removal, is exactly the same as for an OS.55AX and virtually any other glow engine; in regards to when heat should be applied.

It is by Greg that we know from these pages.
Regarding Greg's movie disassembling the OS engine, nice clear images and definetely of great help for the un-initiated. But a few comments. First, I am under the impression that the engine was brand new or hardly used for a long period. This can make all the difference when having to disassemble an engine, no bad gumming up f.e. I did like when he said "if you're lucky the bearing will fall out". With a good used engine these just do not fall out. Also, I did not see him remove those camshaft bearings ! His removal of the piston pin is the same method I have suggested here before on many occasions, only he uses a wood screw where I suggest a small round file, it is a matter of inserting an object that does have side-grip.
Reginald is offline Find More Posts by Reginald
Reply With Quote
Old Feb 22, 2013, 07:48 AM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,386 Posts
Yes, the FS-52 was new. The reality is that even gummy castor engines, when heated to the right temperature, only need a small tap on a block to remove main bearings. Front bearings can be tight but they can also be pushed out easily. I use a hotplate for crankcase bearings, because I just set it there and come back when I'm ready. Maybe I've been lucky not to have a stuck bearing. I've only had to cut one rod in an OS and that wrist pin was badly corroded. Cam bearings rarely need replacement because they are stainless. I've found cam bearing fit in OS to be pretty tight so I made a puller for cam bearings. I have intentions to make a video for Saito and YS, and other more mundane things like valve adjustments, cam timing, and split collet valve keepers.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old Feb 22, 2013, 09:16 AM
Registered User
earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
13,104 Posts
Greg that was a nice video, thanks for sharing.
earlwb is online now Find More Posts by earlwb
RCG Plus Member
Latest blog entry: My new Gaui X5 Rc Helicopter
Reply With Quote
Old Feb 22, 2013, 11:49 AM
Registered User
Joined Nov 2012
219 Posts
Quote:
Originally Posted by earlwb View Post
I have had to use a metal cutting tool a couple of times to get the bearing off of something before. That happened when the inner race comes out and the bearing comes apart, leaving the outer race in place. Of course with a Dremel tool it can take a while and use up a number of the cutoff discs. When the bearing itself is pretty small I had to fabricate a puller tool to get it out.

I think the most interesting way to remove a ball bearing race that was stuck inside a really expensive aluminum part one time, was when the machine shop used nitric Acid to dissolve it. Before then I would not have thought that nitric acid wouldn't dissolve aluminum. But since seeing that I have used it a few times to remove broken off taps, bolts or screws too.
That is neat
New one to me
I have welded outer bearing races like you describe just the race stuck and hard to get out
You weld around where the bearing runs inside and when it cools the race falls out
You could do that on a model engine too
Tig would be best there
Not everyone has access to that
But it is really painless way
Just me sharing
Machzx is offline Find More Posts by Machzx
Reply With Quote
Old Feb 22, 2013, 04:06 PM
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
2,435 Posts
Quote:
Originally Posted by DarZeelon View Post

Yes, it is possible to 'trick' the lower mass bearing, to heat-up and expand more than the higher mass crankshaft; thus making it slightly looser on it... But these techniques cannot be considered general practice and are not applicable for everyone...


outside the model engine world it is common practice as bearings are more often than not fit tightly on the shaft/spindle and relatively loose in the seat/bore. if a bearing needs to come off with no damage then the proper application of heat is often the only way to do it.
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Old Feb 22, 2013, 04:23 PM
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
2,435 Posts
Quote:
Originally Posted by Machzx View Post
That is neat
New one to me
I have welded outer bearing races like you describe just the race stuck and hard to get out
You weld around where the bearing runs inside and when it cools the race falls out
You could do that on a model engine too
Tig would be best there
Not everyone has access to that
But it is really painless way
Just me sharing
yep, no quicker way to add an extreme amount of heat very quickly without doing damage to other parts....same shrink method can be used to "restore" cox cylinders but with a torch instead of welding. cherry red then air cool and you're ready to hone....do just the top of the cylinder and you can even get some taper.
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Old Feb 22, 2013, 07:27 PM
Registered User
Joined Nov 2012
219 Posts
Wow ! Neat post thanks for that
It's the metal freezing that pulls the race under size in the weld
Heat is a great tool !
Machzx is offline Find More Posts by Machzx
Reply With Quote
Old Feb 23, 2013, 12:43 AM
Registered User
DarZeelon's Avatar
Israel, Ramat HaSharon
Joined Nov 2003
1,164 Posts
I am quite sure this thread was about 'normal' bearing removal...

A frozen-in-place outer race almost never happens in rear bearings... Even bearings that have shed the cage, or cracked a ball, come out as a unit.

I never had one disintegrate.


In front bearings this could be more common.
DarZeelon is online now Find More Posts by DarZeelon
Reply With Quote
Old Feb 23, 2013, 05:49 AM
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
2,435 Posts
Quote:
Originally Posted by DarZeelon View Post
I am quite sure this thread was about 'normal' bearing removal...

A frozen-in-place outer race almost never happens in rear bearings... Even bearings that have shed the cage, or cracked a ball, come out as a unit.

I never had one disintegrate.


In front bearings this could be more common.
but how boring would this forum be without a bit of drifting off topic once in a while?
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Old Feb 23, 2013, 06:09 AM
Registered User
earlwb's Avatar
USA, TX, Grapevine
Joined Dec 2008
13,104 Posts
I have only had the bearing races come apart on those little pesky cam bearings in the four stroke engines. But I would not be surprised if it hasn't happened to someone with a main rear or front bearing already. Somehow they got all the bearings in between the unit when they first assembled it at the factory. So it ought to come apart too.
earlwb is online now Find More Posts by earlwb
RCG Plus Member
Latest blog entry: My new Gaui X5 Rc Helicopter
Reply With Quote
Old Feb 23, 2013, 06:17 AM
Registered User
Joined Nov 2012
219 Posts
Well there are the guys that do stuff and guys that just type
Pretty easy to pick em out
Just sayin
Machzx is offline Find More Posts by Machzx
Reply With Quote
Old Feb 23, 2013, 06:22 AM
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
2,435 Posts
Quote:
Originally Posted by earlwb View Post
I have only had the bearing races come apart on those little pesky cam bearings in the four stroke engines. But I would not be surprised if it hasn't happened to someone with a main rear or front bearing already. Somehow they got all the bearings in between the unit when they first assembled it at the factory. So it ought to come apart too.
with a deep-groove bearing it's only going to happen if the cage is gone or there is some extreme wear...although with those tiny little ones i can see enough force being put on them that the races actually deform enough for the balls to pass through

with most angular contacts a bit of heat on the outer race is enough to pop them apart as that's how they put them together...the cages are usually solid plastic or metal and not installed after the balls like on the deep-grooves.
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold OS 55 AX bench ran only Bob Shultz Aircraft - Fuel - Engines and Accessories (FS/W) 1 Jan 29, 2013 05:43 AM
Found Os 55 ax nib barkleyb Aircraft - Fuel - Engines and Accessories (FS/W) 1 Jan 28, 2013 01:59 PM
Sold *** Price Reduced *** OS Power Box E-3010 Muffler for OS 46 AX, 55 AX and others modestmagi Aircraft - Fuel - Engines and Accessories (FS/W) 2 May 08, 2012 09:48 PM
Sold OS Power Box E-3010 Muffler for OS 46 AX, 55 AX and others modestmagi Aircraft - Fuel - Engines and Accessories (FS/W) 0 May 05, 2012 04:40 PM
Discussion What is the tolerence on the crank of an OS .46 AX ? SKromfols Engines 7 Dec 10, 2006 09:37 AM