Supercharger Spinning Freely?

Hi Al, hope all is well with you and your family.
Interesting reading about superchargers and how to set them up properly.
One bright spark out here in Australia had one explode many years ago. The engine and bonnet ( hood ) were destroyed.

Thanks Guys! The issue is exactly what you are all saying. The impeller spins freely when not rubbing against the face plate.

There was no whine before so I was not overly concerned with the bearing, but the catching bothered me. Now that I understand I feel much better.

When pushing the floor plate back into place make sure the locating pins go in there appropriate hole; I have seen broken floor plates as a result of misalignment.

I second what EL said about the impeller rotation when the housing is removed.  With the housing removed the cast iron floor plate is pushed up by the springs that retain the upper thrust ring for the planetary drive.  If you want to rotate the impeller with the housing removed you can use clamps to force the cast iron base down thereby compressing the springs and creating the spacing between the base and the impeller that should occur when the housing is mounted.  This is a good test to do as you can measure the spacing to see how it looks and you can spin it to make sure that it does not rub the cast iron plate.  You have your supercharger close to apart so you can likely already see how it goes together but I have attached an sketch that shows how all of the pieces fit together.

I pulled my supercharger off my car about a year ago to address a very loud whining sound that it would make at all RPM.  The person that I bought the car from was a well known Cord person and he had not been concerned about the whine.  When Roger von Bergen heard my car running he recommended that I stop driving it and investigate the supercharger noise.  He was concerned that it was not getting enough oil and could have a catastrophic failure is I kept driving it.  Once I got the unit apart I found that the aluminum impeller had been rubbing on the cast iron floor plate.  The rubbing had been so severe that the bottom of the aluminum impeller and the top of the cast iron floor plate were both heavily scored.  The metal debris that had been generated had migrated into the planetary drive assembly and caused pitting and scoring of the rollers and races.  I was fortunate that I had gotten an extra, new planetary assembly with the car.  Upon working to reassemble the unit I found the source of the problem.  The issue was that the step in the top aluminum housing that captures the cast iron plate was about 0.025 inches deeper than the height of the corresponding step in the cast iron floor plate.  This meant that once assembled the cast iron plate was allowed to move upward 0.025 inches which seemed to have allowed it to rub on the impeller.  To address the issue I fabricated a 0.025 inch thick brass shim ring to take up the difference and insure that the cast iron plate was held in place.  I also used some very thin shim material to shim the impeller a small amount higher on its taper on the shaft.  I did the shimming to create safe clearances between both the bottom and top of the impeller.  So far I have been bench spinning the supercharger with an electric drill while supplying oil to it in order to break in the planetary assembly.  As an extra measure I added the supplemental oiling method shown in the attached article and drawing.

I hope to get the supercharger back on the car in the next few months and will follow up with an update on the results of the rebuild.

Bill

P.S.  It seems that the pictures that I have are too large to add.  I will see if I can find a way to get them posted.

 

The impeller is rubbing on the floor plate . .Impeller should not be turned without being mounted to the upper housing to compress the finger spring and therefore pushing the floor plate down. Also the planetary could be worn out as there should be an interference fit between the shaft and rollers.

Please check out this video and tell me if this is a problem?    The impeller spins with a catch in one spot.  It seems to me it should spin freely.   Thoughts?


youtube.com/shorts/Vko_8niUTTs?feature=share