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17499Re: [RoboMower] Re: "New" gearbox shot!

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  • Danny Miller
    Apr 1, 2011
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      No, the gear axles seem well-placed and rigidly mounted. The one
      exception being that the motors tended to sag with heat, especially in
      the earlier model gear frames, and that causes terrible meshing.

      Again, mine's got problems with the SECOND pinion, which rides on a big
      axle.

      The plastic wears easily in this extended-duty usage. They didn't seem
      to anticipate just how many hours the dedicated users would put them
      through. They wear, and mesh poorly as a result. They don't have
      anything like the designed trapezoidal shape anymore.

      Some people talked about lubing the gears with grease. I suspect it's a
      bad idea because of how much dust I've seen right there in the box when
      I take it apart. That may be specific to my environment, but I expect
      that lube would pick up dirt and turn into an abrasive paste after a
      short time.

      Danny

      On 4/1/2011 2:28 PM, bkelley9401 wrote:
      > It's not the gears that are at fault! You could use cast iron gears and they would fail too (not in are lifetime tough). You have gear mish-mash which is caused by the box that holds the gears.
      > bkelley
      >
      > --- In RoboMower@yahoogroups.com, Danny Miller<dannym@...> wrote:
      >> Oh wow, I DO have replacements- 2 of them!! Yay!
      >>
      >> The gear ratios are conveniently labeled on 2 of them:
      >> Pinion: 18T
      >> then 87/22
      >> then 18/82
      >> then 60 for final drive
      >>
      >> Total ratio is 1:60.0505...
      >>
      >> They're labeled POM, so that's polyoxymethlene plastic.
      >>
      >> Yeah for belt driving, we'd have a problem. If you used 3:1 drive,
      >> which is already pretty high- you'd need like 4 belts.
      >>
      >> There are RC gearboxes. I dunno- physically, they're much smaller and
      >> most still use a plastic gear, usually meshed to a metal pinion though.
      >> They're designed for less torque and much more speed. The question is,
      >> is it a tougher plastic, and/or would the exclusion of dust in a sealed
      >> box make enough difference?
      >>
      >> Danny
      >>
      >> On 3/31/2011 10:14 PM, Danny Miller wrote:
      >>> Hmmm, actually, I could see a small gearbox with a timing (toothed) belt
      >>> driving the output. There might be room for that!
      >>>
      >>> These motors are largely obsolete by now, brushless DC is more often
      >>> used for this sort of thing. They're much smaller. Unfortunately, they
      >>> require a controller that is not compatible with the motor drive of the
      >>> mower. I could make something work there, but it'd be "complicated".
      >>> The justification would be in the size savings if it allowed a gearbox.
      >>>
      >>> Awhile back we heard from someone who did take the pinions off. I
      >>> assume he used a bar between the pinion and motor to bear the force
      >>> (keep the force off the motor shaft) and a bearing press to punch the
      >>> shaft out. But, hard to say. They could be machined with a flat to
      >>> take a set screw on a replaceable set.
      >>>
      >>> My motor pinions are worn, but it's actually the second pinion that failed.
      >>>
      >>> Yeah I'm wondering if I can get a replacement. Actually, I might have
      >>> one of these pieces from the old gearbox, IIRC I ordered a replacement
      >>> on one of these with bearings, but later when the motor frame sagged and
      >>> ripped up the motor pinions I had to replace the whole shebang with the
      >>> "improved" version. Hope what I have is the right gear.
      >>>
      >>> Yeah
      >>>
      >>> Danny
      >>>
      >>> On 3/31/2011 9:38 PM, Dan Barclay wrote:
      >>>> Where do you get the $35 gear sets? Are other parts available at reasonable cost?
      >>>>
      >>>>
      >>>>
      >>>> Last time I looked, the mowing motors were far more expensive than they should have been. I tried to get bearings replaced but the shop couldn’t get the pinion off without breaking it apart.
      >>>>
      >>>>
      >>>>
      >>>> We need (reasonable!) parts. When it makes more sense to buy a working mower and use the old one for parts, something is wrong with their strategy. I’m hoping you can show me I’ve just been getting bad info on parts cost.
      >>>>
      >>>>
      >>>>
      >>>> Dan
      >>>>
      >>>>
      >>>>
      >>>
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