the rear bearing could be pitted and when pressed into the case the outer housing is not able to expand .dose it feel bad in the case without the crank installed

Possibilities:

1. The bearings are contaminated:
(a). They still have hardened oil in them and need to be soaked and cleaned. (Not really damage, but poor maintenance.)
(b). They were clean and oiled, but got dirt in them from a crash over grass, or grit blew into things while the plane sat on the pavement during a wind gust

2. The bearings are damaged:
(a). They have rusted and balls and/or races are pitted, and should be replaced.
(b). They have Brinelled balls or spalled balls due to impact overload or fatigue. This can happen if the crank hits the ground in a crash, or, if the fits aren’t right and the bearing is drawn into the case with the threads, etc.  Or a lot of cycles under high load, like the main bearing in a diesel that has been run hard. Replace the bearings.

3. The assembly is poor:
(a) If it was gummed up, was it solvent soaked and flushed to check for free running before tearing it down? Solvent flushing never changes fits or alignment and should be your first choice.
(b) If all of these same parts were once free-running and now they are not, did it hit the ground? Are there vise marks on the case? (I have come across several of these….)
(c) During assembly, if the parts did not fully seat when you dropped them in using differential thermal expansion, and you “pull up” the assembly with the prop nut you are changing the contact angle of the bearing. As Bob said, check the freedom and noise of the bearing in the case with the crank removed. If it now feels very smooth, then something is not aligned. If they still feel rough, then the bearings are damaged, improperly installed, or do not have the correct internal clearance for the case fit that you actually have.
(d) There is still contamination on the bearing shoulder(s) and the bearings are not seating. For example, if the rear bearing is going in cocked, and it scrapes the case, pushing a burr or flake of metal in front of the outer race, you now have a problem with the symptoms you describe. If you look inside the case bore and see scrape marks, well….
(e) Overloaded bearings will “feel rough.”  What you are feeling is the lack of proper internal clearance and high spots hitting on high spots which periodically deform the balls/races. Do not use a bearing with tighter internal clearance than the press-fit was designed for. Paying big bucks for tighter tolerances and tighter internal clearances does not achieve what you want here….
(f) Don’t spin the bearings with the balls dry! This makes them prone to skidding, generating flat spots and making them noisy. Clean them with solvent, flush them, but oil them right away! Arguably the best bearings for our purposes are made from 52100 steel—not stainless. Rust ruins bearings quickly.

4. The parts are not to tolerance:
(a) Wrong bearing internal clearance
(b) Case fit is too tight. This would take up too much of the bearing internal clearance after shrink-fitting. If the bearing drops in at 300F or so, then this is not problem.
(c) The case is damaged--dinged or ovaled or the nose of the case bent out of line.
(d) The crank fit is too tight. This would take up too much of the bearing internal clearance after shrink-fitting. If the crank slid in with less than a couple hundred degrees F differential, this is not the problem
(e) The crank is bent. Engines are set up with back-to-back bearing preload. It is unforgiving of misalignment due to the higher moment stiffness. A slightly cocked bearing pair will cause ball noise.
(f) The crank journal is too short for the case. This can happen with poor tolerances. For example, it may have been fine before, but if you swapped some parts around (case and crank) and maybe the manufacturer really didn’t achieve full interchangeability. Things feel fine until you tighten the prop nut and now you feel the balls, and if you keep going, you Brinell the balls. You now need new bearings and you also need to shim the front of the crank.

     Hello All:

      Thanks for all of the prompt replies!

       You all gave me a large amount of information to ponder.  Some comments are in order:

I can not see any reason why the bearing will not seat in the case.  There are no scrapes, burrs or foreign material to be seen on the bearing or its seat.

The bearing has been cleaned very well!  There is no foreign material in the bearing.

The bearing seat is the tightest that I have ever encountered!   

Yes, the bearing is rough sans the crankshaft when the bearing is installed in the case.

     I will purchase a new bearing today to determine if it is a bad bearing.  What else could it be? If the new bearing does not solve the problem, this engine will be relegated to the junk drawer.  Since finding a new p&c for this engine may be difficult, it is time to cut the losses!

     Thanks again for the replies!

     Frank

  One thing to keep in mind here is that we are talking about a possibly 30 year old bearing. How long have the Fox.15 Schnurles been out of production, and this is the original bearing?? All bearings have an engineered "fit" and clearance in them. Depending on brand and type of use, there may be several different clearance fits for one size bearing. C-3 is typical, run on the mill bearing clearance and what is seen most often. On some machinery I used to work on, the rollers needed a much looser bearing so that they would spin very easy and any oil or grease would just slow them down, so they had more clearance and were called "free running" bearings I think. The bearing in question here is probably a C-3 but just has some pitting or rust still in it. When you install a bearing like this, the outer race does close up and takes up some of the clearance, because it is the largest diameter. That is why it is rough with out the crank shaft installed. The inner race does expand just ever so slightly, but not as much as the outer race collapses. Try putting the bearing on the crank and see how it rolls. If you have another engine, try the bearings out of that engine, or just bite the bullet (or the bearing!!) and pop for a new read bearing.
  Type at you later,
  Dan McEntee

The young chap should have sold you a bearing without shields or seals.  I don't know if or how you can remove them yourself without damaging the bearing, so if no one answers the question in this thread you may want to ask.

I was going to say earlier -- Boca bearing specializes in bearings for model engines.  It's been a long long time since I looked, but the last time I did you could tell them the make & model of the engine and they'd tell you what bearing to get.

Good advice from the MM. This is the wrong application for grease-packed bearings. Too high a DN value (higher rpm) and high temp enough to degrade common greases before the engine lifetime is used up. And since you have a good bearing oiling system already built in to the engine...why negate all those benefits? Greased bearings are useful mostly in applications where you do not have a good oiling system, and want to avoid the expense and complexity of adding an oiling system. Greased bearing systems are not better just because everyone has seen them on car axles....

Bearing seals and bearing shields are two different things. A shield is a stamped metal piece that snaps into recesses machined into the bearing race. It is non-contacting so it has no drag. But while it prevents free flow of oil lubrication (and that's why you don't want it in your rear engine bearing) it does let grease slowly migrate out in a grease-packed application. So that's not "greased for life" in our application, either. A seal is a rubber/plastic closure in contact with both races of the bearing. It will keep in the grease, but it also has drag. Most commercial bearings will be way over-greased for a high-speed, low drag application like this. So the balls can't fully plow the grease out of the ball track, which is what is needed. The grease is there to weep the base oil out over a long period of time, thereby lubricating the contact zone. If the bearing is packed so full that the bearing can't clear the ball track it causes a lot of self-heating of the grease. Something else you don't want. Power loss and putting unnecessary heat into the lubricant. Hopefully that gives some idea of the "whys."

To pop the shield out, I use a short tool that looks like an ice pick. Put the point into the shield, but biased toward the outer race. You don't want to hit the race, and you don't want to hit the cage. Gently tap the tool handle until it just punctures. Then pry it out. The shield material is quite soft and will puncture easily. Make sure you remove both shields if they are installed.

If you have a bearing with seals, you can use the same technique, but it may be a bit more difficult.

I believe BOCA will remove shields from their stock bearings for you before shipping if you ask?

Good luck with your (noisy) bearings.

Dave

     Hi All:

     The problem was solved when I took a walk on the Wild Side and spent $13.25 for @ new bearing. Lol

     Thanks for all of the great replies!

      Frank