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15073Re: Click of death.........RM Gear-case failure

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  • Bill
    Jul 1 6:34 PM
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      > The gear frame that holds all the gears and motors and axle together
      had trouble where the motor- mounted only on one side, so it hangs-
      would get hot, soften the plastic, and sag permanently. That leaves
      the motor's pinion only halfway touching, it caused the gears to skip
      and grind and both wore out. I had this happen twice. In fact, this
      MAY be what happened to you.>
      ------------------------------
      That was NOT what happened to me.........
      although, it was the mode of failure I expected with the experiences
      I've observed here on this list.

      As I said in my original post, I made a 'motor shade'/'heat sink'
      which also serves as a 'spreader' between each inside surface of the
      plastic boss onto which the drive motors are mounted.
      Even if the plastic becomes hot enough to sag.....
      (and w/o support, it WILL sag toward the interior and lifting the
      drive motor and pinion off the first set of gears.)
      My mod completely eliminates that possibility because the
      'shade'heat-sink/spreader' will prevent any movement (sagging) toward
      the center.
      Think of it as an add-on brace cut to a tolerance in length
      (side-to-side) to prevent any movement.
      BTW I also considered that heat from this 'motor
      shade/heat-sink/spreader' possibly could ADD enough heat to the area
      where it touches the inside of the frame and cause a failure...
      This is another area where I used fish-paper....this time to serve as
      both a thermal barrier and shim.
      I don't believe the motors will EVER sag with this modification.
      If the motor mount on one side tries to move toward the interior,
      (lifting the pinion off its gear-mate) the 'spreader' will apply the
      force on the other side in the opposite direction, and pressing the
      pinion on that opposite side AGAINST it's mating gear preventing a sag.
      It can not move! (at least not side-to side)


      Speaking of bearings.....
      all the OTHER rotating parts of my RL-800's gear-case (& I believe the
      500) HAVE sealed ball bearings.
      It's just that ONE set of gears that don't......
      and THAT'S WHAT FAILED.
      I want to buy JUST that shaft/bearing and gear set.

      What's my cost?

      WB

      --- In RoboMower@yahoogroups.com, <dannym@...> wrote:
      >
      > The "white plastic bushings" were replaced with proper sealed ball
      bearings on all gears. These will never give you trouble.
      >
      > The gear frame that holds all the gears and motors and axle together
      had trouble where the motor- mounted only on one side, so it hangs-
      would get hot, soften the plastic, and sag permanently. That leaves
      the motor's pinion only halfway touching, it caused the gears to skip
      and grind and both wore out. I had this happen twice. In fact, this
      MAY be what happened to you. They fixed this with a higher temp
      plastic gear frame.
      >
      > The motor pinion- the little gear on the output shaft- was not made
      of a sufficiently durable plastic and could wear out even without gear
      frame sagging or the plastic bushings getting sloppy. They fixed that
      by switching to a tougher plastic.
      >
      > Don't try to just fix the one problem you have, get the whole gear case.
      >
      > Arrg... I don't remember who I did the gear case replacement with.
      He's on the list, at least he WAS, I'm surprised he didn't respond
      yet. Maybe he's off the list now, in which case I'll have to look up
      his email.
      >
      > Danny
      >
      > ---- Bill <wild_bill_howell@...> wrote:
      > > < Yeah I know you're gonna complain>
      > > --------------------------
      > > Has my reputation preceed me? ;-)
      > > ============================
      > > > Swapping the gear case is relatively easy- pull the wheels,>
      > > ---------------------------------------
      > > Not ~THAT~ easy because I have 'dualy-wheels', two knobby wheels
      > > bolted together which eliminated the stuck-on-stupid behavior in my
      > > sandy soil.
      > > First the wheels must be unbolted before I can get to the snap ring.
      > >
      > > Maybe I wasn't clear, but my RL-800 now has the gear-case robbed from
      > > my low-hours RL-500.
      > > The only original RL800 parts are one drive-motor shroud with the
      > > thermistor attaced.
      > >
      > > Now...........
      > > about the new gear-case.....
      > > I just want to get it clear in my mind.....
      > > the new gear-case has replaced the white plastic bearings with
      > > ball bearings?
      > > If not ball bearings, then what is it?
      > > I understand the plastic composition has changed for the frame,
      > > pinion/motor assy and the gears, but I need a clear explanation of
      > > what has replaced the white 'bearings' before I plunk my money down on
      > > a frame/new gear-case/ drive-motor assy.
      > >
      > > BTW, I'm an engineer and this stuff interests me...........
      > > especially now that I have a NEED. :-)
      > >
      > > TIA
      > >
      > > WB
      > >
      > >
      > >
      > >
      > > --- In RoboMower@yahoogroups.com, <dannym@> wrote:
      > > >
      > > > Ah yes, the click of death.
      > > >
      > > > Those plastic bushings were recognized as a problem and fixed in
      > > later designs. They changed out the plastic bushings with proper
      > > bearings, changed the plastic the whole case is made of so the motors
      > > don't soften it and sag, and changed the type of plastic the motor
      > > pinion is made out of.
      > > >
      > > > You'd think you could just get the plastic gear frame and side gears
      > > cheap, but really the other problem was motor pinion wear and heat
      > > tolerance. Unfortunately the motor pinions are not removable; you
      > > need new motors there. So it comes down to just swapping the whole
      > > thing out, otherwise the old worn pinions will eat into your brand new
      > > gears anyways.
      > > >
      > > > Yeah I know you're gonna complain about how much the mower cost
      > > initially, this is a sort of defect, how somebody should fix it for
      > > free, blah blah. I *do* feel your pain. But the mower was a
      > > completely innovative design when it came out (actually there's a LOT
      > > in here which is innovative), so it's not surprising that it's not
      > > going to be a completely maintenance-free deal in the first 5 yrs.
      > > Gas mowers break too and taking one back to the dealer to get fixed
      > > would probably run you more than this gear case will cost. The good
      > > news is the new gear case WILL be a long term fix. There's enough
      > > benefit there to justify the $ to buy a new drive train (gear case).
      > > It's not a cheap fix but not monumentally expensive either and it's
      > > really good.
      > > >
      > > > Swapping the gear case is relatively easy- pull the wheels, take off
      > > the tach board, unplug the motor wires, IIRC move some wires going to
      > > the rear out of the way, pull the gear case out, reverse steps with
      > > new one. Test to see if you have the motors hooked up the right way
      > > before putting the top back on (hook up controller and drive forward,
      > > if it reverses or turns them obviously you need to fix that).
      > > >
      > > > I don't think lubing the plastic is gonna help. In fact it may
      > > attract dirt which acts as an abrasive and accelerates the problem.
      > > But really the problems are inevitable no matter what you do. Getting
      > > the improved gear case is essential.
      > > >
      > > > Danny
      > > >
      > > > ---- Bill <wild_bill_howell@> wrote:
      > > > > Well, it finally happened.....
      > > > > part of the gear-case failed after 328 hrs on my RL-800.
      > > > >
      > > > > It did NOT fail at the drive-motor pinion, although it shows some
      > > > > wear, there was still plenty of teeth engagement to work.
      > > > >
      > > > > The failure occured in the gears which are 'supported' by two
      white
      > > > > 'bushings'/bearings'.........
      > > > > two 'bearings' on each wheel or a total of four on the same shaft.
      > > > > what a junky POS, crappy-assed design.....
      > > > > designed as though it was INTENDED to fail!!!
      > > > >
      > > > > The 'clicking' came from only one side where the part of the
      gear that
      > > > > receives the 'bearing' had worn so badly that it formed a
      cone-shaped
      > > > > hole so the gear wobled on the shaft...
      > > > > the other side was on the verge of failing in the same manner.
      > > > >
      > > > > So...
      > > > > I cannabalized my $200 Woot RL-500 and swapped out the gearcase.
      > > > > I, of course had to remove the drive-motor shroud with the
      thermistor
      > > > > pop-rivited to it from the original 800 and put it on the
      replacement
      > > > > gear-case and resolder the thermistor leads.
      > > > >
      > > > > Just for drill, I lubed up those white bearings with
      "Break-Free" oil
      > > > > and put it all back together.
      > > > >
      > > > > While I was already into the job, I decided to make an additional
      > > > > heat-sink "shade" for the two motors with two pieces of 1/6" alum
      > > > > angle.
      > > > > I cut them so that they will also serve as a 'spreader' to
      prevent the
      > > > > drive motors from ever sagging inward from over-heating.
      > > > > One angle required cut corners to provide relief for the part
      of the
      > > > > plastic frame which have molded gussets.
      > > > > I also put TWO layers of heat-shrink tubing over both
      thermistor leads
      > > > > to keep them from shorting out...
      > > > > In addition, as a further precaution, I glued some 'fish-paper'
      > > > > (phenolic impregnated fiver paper) on the 'shade' in the area that
      > > > > might come in contact with the thermistor as an additional
      electrical
      > > > > insulation precaution.
      > > > >
      > > > > I oriented the drive-motor shroud containing the thermistor in the
      > > > > 'valley' of the alum angle, then clamped each end of the angles to
      > > > > the ends of the two drive motors with hose clamps.
      > > > >
      > > > > Here is my question....
      > > > > Why did Friendly use those two crappy-assed white 'bearings'
      instead
      > > > > of something more substantial?
      > > > > I swear, it looks to me like it was designed to fail in order to
      > > > > generate after-sales repair income.
      > > > >
      > > > > What is REALLY new with the new generation RMs to eliminate this
      > > > > failure mode?
      > > > > If the answer is 'a better plastic formulation', then it's
      still not
      > > > > very satisfactory.
      > > > >
      > > > > Those white plastic 'bearings' are gonna require periodic PM
      lube to
      > > > > keep them from failing....
      > > > > and considering what must be done to just get to them for that
      > > purpose ...
      > > > > really is an unnecessary time-waster and it pisses me off that
      I'll
      > > > > have to disassemble the mower just to keep an eye on it.
      > > > >
      > > > > Grrrrr.
      > > > >
      > > > > WB
      > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > > >
      > > > > ------------------------------------
      > > > >
      > > > > Yahoo! Groups Links
      > > > >
      > > > >
      > > > >
      > > >
      > >
      > >
      > >
      > > ------------------------------------
      > >
      > > Yahoo! Groups Links
      > >
      > >
      > >
      >
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