Monday, November 28, 2011

Axle post build processing results

    Both the end up and diameter down axles were post processed using a hand file and Dremel tool sanding wheel.  Both were improved in diameter smoothness and consistency.  The end up version raft end bulge was reduced from an oversize condition of 0.045" to 0.021".  It was hard to judge when the axle was uniform, however, it should be possible to improve it more by making measurements during the effort.  The top end was not processed and remained oversize by 0.010".
    The diameter down axle version initially was oversize by 0.0265" and 0.0207".  The raft attachment area was very rough due to removal using a side cutter pliers.  The file was used to make the attach point smoother and more uniform.  This was followed by use of the Dremel tool sanding wheel to improve roundness along the attachment area.  The final result was 0.0131" and 0.0142", considerably a better match than was obtained with the end down axle.
    In recap, the axle holes in the two driver wheels were 0.0173" and 0.0187" undersized.  The combination results in an interference of approximately 0.04" using the end down axle and 0.033" using the diameter down method.  Since the diameter down axle results in better uniformity between the ends, it appears that the Wheel-Axle Kit would benefit by reducing the axle diameter about 0.0176" and increasing the wheel axle holes by 0.022".  This should result in an axle diameter closer to target of 0.0412" with a clearance between the wheel hole and axle diameter of a few thousandths of an inch.  Careful post processing should result in a reasonable slide fit suited for bonding using glue.
    The driver bearing parts will also need to have their axle hole adjusted to clear the axle sufficiently to permit easy rotation without binding.   However, due to the extensive amount of support required, it would be better to build the bearings using the ABS raft and support which is more easily removed using needle nose pliers or fingers.

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