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• Disassembly

  zakqwy • 08/03/2018 at 17:22 • 0 comments

  Last fall, I removed one of the stuck wheel assemblies and brought it home. The wheels are single piece plastic that fit tightly on an aluminum rod, secured by a cotter pin:

  I unscrewed the three aluminum posts, revealing the Acme screw:
  

  Notable in the picture above: the nut on the left is aluminum and is roll-pinned to the Acme screw. This nut bore the load of the dock itself via the largest square tube (also on the left); an identical pinned nut that broke during use was attached to the left end of the screw and was used for adjustment from above.
  

  Removing the Acme screw from the welded aluminum mount required fighting a small amount of rust:

  I tried a good soaking with penetrating oil but couldn't get the screw loose. I used a cut-off wheel to slice into the brass nut a bit, and then tried to split the nut using a punch. This did not work:
  

  Then I cut an access hole in the side wall of the square aluminum tube, which allowed me to slice the nut the rest of the way:
  

  I continued to use the punch to pry apart the brass nut (bronze? Might be bronze) and eventually got the far side to fracture. The nut was still frozen to the screw and didn't have much room to move, so I tried hitting the nut with a bunch of penetrating oil. Then I cut the Acme screw right above the nut using a cutoff wheel, and ground a slot into the remaining stub so I could loosen it with a screwdriver:

  Somehow, probably due to a combination of penetrating oil and extra clearance from the split (and using a box wrench to assist the hex-shafted screwdriver), this worked. I was so excited that I took another picture showing the screw at a different angle:

  I drove the remaining screw through the nut and pulled the nut out of the square aluminum tube. This allowed me to extend the Acme screw through the top of the housing, cut it, and remove it from below. Doing so revealed another pinned fastener that prevented me from pulling the lead screw out through the top:

  The blackened area above is where the brass nut used to live. As expected, the rust really just built up around it and didn't actually stick to the nut, which allowed me to remove it fairly easily once I'd increased the clearance by splitting the nut.
  

  Removing the Acme screw left me with a slightly modified but still hopefully serviceable leg post. My hope is that the hole won't cause any issues; once the new Acme screw is threaded into the new Acme nut, the screw itself should retain the nut side-to-side:

  More to come!

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