rzbill
Well Known Member
This post is not about general nose wheel pivot bearing maintenance but rather something I discovered yesterday on my craft while doing the standard maintenance that was honestly overdue.
Over the last 6 months, I had noticed more "stiction" in the nose pivot when pulling and pushing the plane in and out of the hangar. I could tell it during taxi too. Obviously the breakout force was going up.
I took the assembly apart, cleaned it well (Plenty of grease from prior maintenance remained) and found some undesirable wear in both top and bottom bronze thrust bearing surfaces. The majority of the bearing surfaces were pristine but adjacent to the bore, there was a groove and proud burr.
The groove on the bottom bearing is obviously caused by the Belleville washer geometry. While I did reassemble per plans, I may put a steel flat washer at that interface the next time I disassemble. Next Spruce order.
The groove on the top is more insidious. It was caused by a discrepancy in the geometry of the nosewheel swivel stop that forms the other half of the top thrust bearing. On my plane, the center tube was proud (sticking downward) of the stop plate that acts as the bearing surface. SO, 100% of the bearing loads and preloads were impinging on that small surface area and just digging right into the bronze.
The following is a couple of cell phone snap shots. Sorry but this is after some judicial hand filing to remove the burrs and flatten things out a bit. Did not think about sharing until I was done.
Note the bright ring from filing the tube down close to the flat plate.
Note the matching worn ring on the top bearing.
Same sort of thing on the bottom but less severe (from Belleville washer impingement)
Over the last 6 months, I had noticed more "stiction" in the nose pivot when pulling and pushing the plane in and out of the hangar. I could tell it during taxi too. Obviously the breakout force was going up.
I took the assembly apart, cleaned it well (Plenty of grease from prior maintenance remained) and found some undesirable wear in both top and bottom bronze thrust bearing surfaces. The majority of the bearing surfaces were pristine but adjacent to the bore, there was a groove and proud burr.
The groove on the bottom bearing is obviously caused by the Belleville washer geometry. While I did reassemble per plans, I may put a steel flat washer at that interface the next time I disassemble. Next Spruce order.
The groove on the top is more insidious. It was caused by a discrepancy in the geometry of the nosewheel swivel stop that forms the other half of the top thrust bearing. On my plane, the center tube was proud (sticking downward) of the stop plate that acts as the bearing surface. SO, 100% of the bearing loads and preloads were impinging on that small surface area and just digging right into the bronze.
The following is a couple of cell phone snap shots. Sorry but this is after some judicial hand filing to remove the burrs and flatten things out a bit. Did not think about sharing until I was done.
Note the bright ring from filing the tube down close to the flat plate.
Note the matching worn ring on the top bearing.
Same sort of thing on the bottom but less severe (from Belleville washer impingement)
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