Sunday, October 25, 2009

Rainy day project

We are at the Wal-Mart in Pittsfield, Massachusetts (map). Other than the Berkshires as a backdrop and the handful of fall color scattered around the parking lot, we could be anywhere. Around us are Home Depot, Applebees, Barnes & Noble, Fashion Bug, and other various and sundry national chains.

We actually tried to stay much closer to downtown, which has a distinct local flavor, at the Elks lodge. Unfortunately, the lodge does not open until 3pm, and their parking lot is gated; we arrived there just after 1pm, having made a mad dash from Cranwell at the first break in the rain. Even so, we ended up driving through a light drizzle, and depending on the Rain-X to be able to see at all. There was no place to safely wait for the lodge to open; in addition to the disappointment of not staying in town, we also had to drive another four miles in the rain.

Being stuck here in a shopping center parking lot in the rain at least gave me time to work on the wiper motor situation. The steel spindle that comes out of the gearbox rests in a pair of copper alloy sleeve bearings. After studying my broken housing, with its smaller diameter spindle and thus bearings, alongside the intact housing sent to us by our good friend Bryce with its larger spindle, it appeared to me that the outer diameter of our existing bearings were actually very close to the inner diameter of the new bearings.

Having nothing to lose with my irreparable gearbox, I found a ¼"-drive deep socket of about that diameter to use as a drift, and a large 3/8" drive deep socket to support under the housing, and was able to drift the bearings out of the old housing using my trusty engineer hammer. With a few more taps of the hammer I was able to press those bearings inside the larger bearings on the replacement housing, and thus was able to insert my old spindle and ring gear assembly into the newer gearbox. The spindle also required some coaxing from the hammer -- I think the soft bearings deformed slightly when I pressed them in.

Once I had the whole thing reassembled, I hooked it up to a 24-volt circuit with some clip leads, and the spindle is turning as it should. The spindle had to re-seat in the relocated bearings, so I let it run for a good half hour or so; it sped up a bit in the process, which is a good sign that the bearings have seated. While it was spinning around, I walked over to Home Depot for some new mounting bolts -- two of the three that came on it were stripped.

This is still a temporary fix -- since we are reusing the plastic ring gear, which definitely has some abnormal wear near the park position, we can expect the worm gear to start jumping the teeth at some point in the future, especially under the heavy load imposed by sweeping a pair of 28" wipers through more than 90 degrees of arc. Also, the helix of the replacement worm gear is slightly thinner than the old one, so the worm-to-ring mating is not an exact match. Lastly, with nothing staking them in place, the "inner" bearings may move enough in or out to cause excessive shaft wear. But if it holds up under testing, it should be enough to get us somewhere where we can have a new actuator arm machined to fit the larger diameter spindle. I can then either reinstall the proper spindle into this unit (if I can pull those inner bearings without damaging the outer ones), or buy a new assembly from Setra.

This morning the rain has stopped. It rained so much here yesterday that the alarm on the weather radio sounded last night -- there was flooding in nearby Williamstown. Now that I can work outside, it's tempting to get the kludged-together wiper motor installed, but we have plans to visit family in Argyle, NY this afternoon, so we'd rather get an early start. Today is forecast to be dry, so we'll get underway, and try to get the motor in tomorrow sometime.

Photo by Sidereal, used under a Creative Commons license.

1 comment:

  1. That's some impressive shade tree engineering. Hope you get this one finished, soon. I have to imagine that it is becoming less than interesting after all of this time.


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