Thread: Spindles
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Old 10-25-07, 08:02 AM
surly old man
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so-called "sealed" bearings are not really sealed. Not even close, in fact. They are "sealed" in the sense that they cannot be opened to adjust or regrease. Off the cuff, I would say that neither type of bearing will keep water out at all if submerged. Since that goal cannot be accomplished with bicycle bearings, the goal might as well be to limit the damage of running in water. Two thoughts on this: first, you could just accept that this aspect of the design is imperfect and expect to have to repack and replace the bearings frequently. Second, maybe an older style cup and cone bearing would allow more water movement OUT of the bearings when not submerged, so maybe it would last longer.

You asked about the terminology I was using above. So, let me try to explain a couple of terms I used. A bottom bracket is the entire axle assembly that connects the crank arm of one pedal to the crank arm of the other. I suppose it includes the spindle (the axle, really), the bearings that the spindle spins in, and the section of the frame that houses both. A cartridge type BB has the spindle and "sealed" bearings as one unit that cannot readily be opened up and re-greased. The older type of BB allowed the bearing races (the cups and cones) to be taken apart for adjustment and re-greasing.

Looking at your design, I might suggest thinking about just cutting the entire BB assembly out of a bicycle frame and welding it on. Also, note that in your design the spindles extend considerably farther outboard of the crank arms; bike spindles will not do this, so you do not need to account for this added width. Also, older crank arms typically did not have any outward bend to them, so they rode closer to the frame. As such, they would help reduce the overall width of the pedalling space.

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