Kyrasis6

Ok guys, managed to get time during lunch today to do another scan. This time I didn't bother trying to get seal locations and all that good stuff. So here are the reports.



You can ignore all the nominals and tollerances, that report is exactly what the CMM measured. I do not have X,Y values on the bearing location because I was not able to setup a reliable origin with the time I had and having to setup a new probe and calibrate it. Here are the scans of the bearing:

Scan of the bearing closest to the oil webbing:



Scan of the bearing near the gear side:



Explainations in a few min in the next post.

Kyrasis6

What I forgot to mention in my last post was this was from an 87 RX-7 N/A with 158k miles on it. The entire rotor was hot tanked, dried, then cleaned in paint thinner dried again, then wiped down with a lint free cloth and blown off with compressed air. I wanted no dirt of any type to contaminate the measurement.

Measurements where taken with the rotor sitting on the gear side down on the granite table.

Ok, the top scan is the side of the bearing I.D farthest away from the stationary gear. The scan shows that it is less out of round and less worn than the side closer to the stationary gear.

The big notch is the puzzle seam of the bearing just like in my other scans. Just like before the protruding squiggly spots are where the bearing is badly worn which line up with the combustion chambers. I noticed one more thing during this scan which makes perfect sense, the wear is not lined up with the center of the combustion chamber nor accross the whole length of the chamber the highest points of wear are on the leading 1/4 length of the combustion chamber.

The second scan is the side of the bearing I.D. closest to the stationary gear. You can see the puzzle seam location. There is a locating tang pressed into the bearing, which is shown as the gap in the scan on the left as labeled. The tang location is in a location which does not see a lot of stress. The puzzle seam is closer to the combustion chamber which is a higher stress area but I do not see any evidence of it causing wear or load problems. The squiggly lines on the right are the same wear pattern as in the top scan. The chamber towards the bottom does not show much wear. The most obvious feature is the chamber on the left which is very badly worn. Copper babbit was showing through on this portion of the bearing.

So this leaves me to wonder, why is the side closest to the stationary gear the most badly worn? Is it because the side farther away free floats on the ecc journal while the side meshed with the stationary gear has the forces on the journal while also being in a bind with the stationary gear.

Going by the guidance of some of my engineering books I'm going to try to do another scan in the future just above and below the oil groove to see if the higher oil pressure and volume in that area affects the wear. I can definatly see where Mazda's decision and Aaron Cakes recommendation to increase the oil pressure would increase reliability. Speaking to one of our engineers at work his personal opinion was if no bearing errosion can be seen the benefits of increasing oil pressure far outweighs the small power drop due to pumping losses. The increased oil pressure will increase the load capacity of the bearing which would increase it's longevity, especially under high rpm or high power applications.

Turblown

iTrader: (12)

Nice update. I was pressing in some bearings today and the thought went through my head, damn I wish I could scan these. Increasing oil pressure is a bandaid fix, if you look way back into the early 60s piston cars did the same thing, and now they are completly different, running much lower oil pressure.

By the way the areas of most wear make perfect sense, same areas you see on con rod bearings.

How are those rotor housing scans coming

Kyrasis6

Oil pressure is a very important variable when considering bearing design and is like other things, you can manipulate the required oil pressure and volume with the bearing length, diameter, and materials to get the desired results. So raising the oil pressure is a perfectly acceptable fix from our end of building it is probably the easiest option considering we can't exactly make a new eccentric shaft or design new bearing materials to get the results we want.

My next couple of scans are going to be focused on the wear of the apex seal grooves and corner seal holes I want accurate measurements before ordering new ones.

iceblue

Absolutely fabulous!

Kyrasis6

I learned some stuff yesterday and today which should allow me to do some very complex scans and dimentions on other parts. When I do the rotor housing I should have some very detailed scans but I'll have to do them in sections because even a simple scan on the inside of a rotor may take an hour or two after the program is written.

I won't be able to get very detailed scans of the apex seal grooves because the probe I will have to use is about the size of small sowing needle and the stylus is about .015" in diameter. This would make it pretty much humanly impossable to get the stylus to read due to needing the part in an EXACT 90 deg angle to the probe and even slight wear will cause shaft deflection. But I should be able to measure the width and flatness near the edge with an accuracy to .0001"