stunthanger.com
Engine basics => Engine set up tips => Topic started by: Paul Smith on July 03, 2020, 05:57:27 PM
-
I'm in the process of taking apart an old OS 25 FS which I suspect has bad bearings. I got it used and it must be at least 30 years old.
I've tried everything and can't get the rear bearing out. Heat, cold, boiling in anti-freeze.
The bearing sets in the case flush so there's nothing to get a hold on.
Is there a tool or good technique?
-
Since you are not concerned with saving the bearing, heat the case up again and give it a tap on the inner race with a soft drift of some kind. A solid tap onto a piece of wood ought to do it also once you have the case heated enough. If old castor is glueing it to the case, it may take repeated heating and soaking with PB-Blaster until it soaks the castor oil soft again. I'm surprised the crock pot trick did not get it loose. Maybe try that again.
Type at you later,
Dan McEntee
-
Put it in the oven at 275 for 15 min. Tap the crankcase straight down on a 2x4 or something.
-
I hit it pretty good with a heat gun, but I don't know the temperature. As you said, I banged it on a wood block. I kept the backplate screwed-on to protect the back edge of the case.
I did the crock pot for two days. That's good for external dried oil, but maybe not a fused-in bearing.
I have it soaking a acetone overnight.
This engine seems to have vibration issue that can't be cured by prop balancing or bolt tightening. The front bearing came loose, but I had the back edge to press against.
-
I don't know if this will help but Value Models sells a really nice bearing remover.
It is cheap and will take out up to 14mm bearings. There is only one thing to realize. It is an RC site. Oh the horror of it!
http://www.valuehobby.com/accessories/tools-and-instruments/rc-bearing-remover.html
-
Use vise grips on a mounting lug.
This says it all n1 LL~ LL~ LL~
-
Pliers of any kind have no place among tools for working on small precision machines. If I heat an engine to remove bearings I have a threaded holder that screws into the case on F2D engines. On larger engines or one offs that I don't have a special tool for, I heat the engine on a wood block, then pick up the case with a welding glove and tap it on the block. Pliers don't belong on needle valve assemblies either; that's why they make six point sockets and box or open end wrenches. They don't belong on prop drives either, or prop nuts for that matter.
As for your smart ass genius comment.....Thanks I'll just consider the source and take that as a compliment
-
A monokote heat gun gets to 400 degrees, and is most definitely hot enough to heat the case to release a undamaged bearing. The aluminum isn't very thick, and has a lot of "structure" around it that will not allow it to expand very much, a few tenths at most, but that should be enough to release a normal bearing. There is no danger of over heating. Heating the case to anything near 300 degrees either in an oven or with a heat gun heats the whole case, and should not expand an outer race that is not damaged. Spot heating with a propane torch could over heat the case, which will be hard to tell, and then grabbing the mounting tab and hammering it against a block of wood raises the possibility of damaging the case. The aluminum adjacent to the mounts would bend in a heart beat. To handle hot cases, I use welding gloves or a thick rag. Tapping the back of the case against a smooth, wooden block should not damage anything at these temps. What might be going on here is a cracked out race. The spring effect of the race would really wedge the bearing in place. One thing else to try that may take two people. If there is any kind of seal or shield on the bearing, pick it off with an o-ring pick or something like that. See how much room between bearings to see it a sharp music wire hook can securely grab the bearing. Make the wire hook long enough so that you can securely grab it with a pair of vice grips. Test how it grabs several times before trying it with heat. When the case is hot enough, have some one hold it with some gloves, while you try pulling on the hook, and maybe even tapping on the jaws of the vice grips with a small hammer. You want to create a pulling motion. I have a home made slide hammer type puller like this in my work toolbox for such things on machinery. You just have to make up something similar in a scale to do what you need to do. After a number of repeated heating and cooling cycles I would think that it would eventually pop out, unless, like I mentioned, the out race is cracked. Beyond this, I would have to have the engine in my hand to figure out anything else.
Keep us posted,
Dan McEntee
-
Thanks a lot for the advice.
I devised a tool that worked. The ID is .470, so I ground down a 1/2" dowel to a press fit. I put in a 4-40 lag bolt and tightened it with the Allen wrench so as to expand it inside the bearing. Then I heated the case with the heat gun (paint stripper, not Monokote). I hit the tee wrench with the hammer and the dowel came out without pulling the bearing.
Then I repeated the process with some Prop Shop CA glue on the dowel. It pulled the bearing on the first light stroke of the hammer.
This engine, and another like it, have been giving me trouble no matter what I changed. One theory is that they were abused in their childhood and just wanted some TLC.
The next step is to local some new bearings.
-
It looks like I have three FS-R's which could be as old as 1977. I see that Boca has not just one, but FIVE levels of bearing to chose from.
Hopefully, a set of bearings will cure some of my problems with these otherwise fine engines.
This is the first time I've looked at Boca. I found the site, found the bearing, and ordered it in under 30 seconds. This is THE BEST sales web site I've ever used. Zero hassle. Other web jockeys need to copy them.
-
Put it in the oven on a cookie sheet type (metal) back plate side down. Start out at 350 or so. If that doesn't work in 15 minutes, kick the heat up to 500 and it will drop out! And NO that heat will not distort the CC.
You will hear it hit the cookie sheet.
Motorman; I hold "hot" items with a glove intended for such purposes. Like when removing a hot cookie sheet full of cookies! H^^
Jerry
PS: Put the new bearings in the same way.
-
Excellent tool Paul.
I agree with you on the Boca site. They are really easy to work with!
-
putting it in an oven lets the bearing heat up along with the caes
-
as a last resort on an engine that i couldn't get the rear bearing out of .i took a Dremmel with a 1/8 square burr.came through the front and made 2 small slots up against the bearing then using a small punch tapped the bearing and it came right out. cleaned any burs from the slots and good to go.
-
putting it in an oven lets the bearing heat up along with the case
The theory is that the aluminum expands more than the steel.
One of these engines had the aluminum head seized to the steel sleeve. I was able to FREEZE it apart in the ice compartment. The steel sleeve contracted more that the head and allowed it to separate.
If somebody made an assembly of two parts of the same material and used a heat/cool assembly technique, it would be near-impossible to get it apart.
-
When changing bearings in my OPS .40s the local machinists told me to set it in the oven at a higher temp than I normally would,,,, guess what? Mike Haverly was right it worked. It just fell out.
John L.
-
The theory is that the aluminum expands more than the steel.
One of these engines had the aluminum head seized to the steel sleeve. I was able to FREEZE it apart in the ice compartment. The steel sleeve contracted more that the head and allowed it to separate.
If somebody made an assembly of two parts of the same material and used a heat/cool assembly technique, it would be near-impossible to get it apart.
The aluminum will expand quite a bit more before the steel even gets close to getting hot enough, especially aluminum like an engine case that has been cast. If you have to do the same exercise on a bar stock engine you may see a difference in heat needed because the aluminum is more dense. You heat the whole case because that's easiest, but if you have a way to do it, just spot heating the case will be enough to get a good bearing to drop out. Doing it for the first time on an old engine, it can tend to get stuck from the aluminum oxidation of the case pinching the bearing tighter, or some one may have used a loctite type product on the outer race of the bearing when it was put in if it was a bit sloppy. Lots of reasons for an old bearing to get stuck in an old crank case.
Type at you later,
Dan McEntee