Driven mad by a defiant lawn mower!!

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Old 06-14-16, 07:45 PM
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Driven mad by a defiant lawn mower!!

My itsy-bitsy lawn mower (the Lawn Pup by GrassMasters, which I think is as small as electric mowers come) has been presenting me with bigger and bigger problems in recent seasons, but now I guess they've officially gone beyond "big" and reached "infinite", since I can't get the mower to function at all.

In previous years (and earlier this year), I'd always have to struggle to get it working-- I'd press the start button, I'd hear a noise as though the mower were "making an effort", but it wouldn't actually come whirring to life in the necessary and proper way. When I turned it over to check its innards and to test whether I could manually rotate the blade-apparatus (the circular piece of metal that the blade is attached to), I'd find that there'd be a point in the rotation where it was very hard to turn, even though there'd be nothing obviously blocking it. I would keep trying-- without ever doing anything that I thought would produce a beneficial effect-- and eventually, quite mysteriously, it would roar into normal operation. In May, 2016, the first and only time I used it this year, I encountered the difficulty I just described, but perhaps for a more prolonged time than usual.

Then, today, I must have labored for twenty minutes, perhaps thirty -- certainly longer than I ever have before-- and though the motor seemed to be making a heroic effort, it just wouldn't start. Using the same electrical cord and outlet, I was able to use an electric hedge trimmer, which functioned normally.

I still have the Lawn Pup's Instruction Manual (I purchased it around 2000), and it says explicitly that it needs no lubrication.

Because I know nothing about the details of a mower's normal operation, I have no idea if what I'm describing as difficulty in turning the blade-apparatus at one point in its rotation is pinpointing the specific problem we must solve or if that actually is normal for electric mowers.

Oh, one other, related question: is it possible for an outlet to supply enough electricity to operate a hedge-trimmer perfectly normally but to be falling short with the Lawn Pup, perhaps because the Lawn Pup's greater-than-normal difficulty in turning requires greater-than-normal current? The specifications for the Lawn Pup, as given in the Manual, are Model LP1000, Elektromotor 1.0 kW, 110 V.~ 60 Hz. The Hedge Trimmer is a Black and Decker, TR165, 268 W., 2.4 A, 120 V.~ 60 Hz.

So: Does anyone have any advice? Any penetrating insights? Any wild conjectures?... at this point I'd actually like nothing better than a magic word that will make my mower come roaring back to life and get me known in the neighborhood as the Lawn Pup Savior.
 
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Old 06-14-16, 07:50 PM
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Have you ever hit anything hard enough to bend the shaft? You need to bring it to an electrical expert to test it.
 
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Old 06-14-16, 08:00 PM
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There is not a whole lot to that thing. It's direct drive, so the blade attaches to the motor shaft without any gears or belts. And there is a capacitor.

The capacitor would be a suspect, although I'm not sure that would explain the intermittent nature of the problem.

The binding you describe sounds like a bent shaft binding (ever hit a rock?); that wouldn't be intermittent either.

One thing you could check for... it's not clear from the parts diagram if the capacitor is a start cap or a run cap or both. If it's a start cap, there is likely a switch inside the motor that connects the start capacitor when the motor isn't turning, and disconnects it when it comes up to speed. *If* there is such a switch, and *if* it is gummed up with grass or dirt, then the mower might act the way it is.

If you're up for it, take the cover off and blow the motor out really well with compressed air. You might get lucky.
 
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Old 06-14-16, 10:09 PM
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Oh, one other, related question: is it possible for an outlet to supply enough electricity to operate a hedge-trimmer perfectly normally but to be falling short with the Lawn Pup...
At the receptacle unlikely, at the end of a long extension cord VERY likely.

Your mower takes approximately FOUR TIMES more power than does the hedge clipper. Using an extension cord with too small a gauge number of conductors is not unlike trying to use a soda straw sized hose to put out a building fire. Most long extension cords are simply too small for the task in which they are used. Sometimes it seems to work but the long-term result is often burning up the motor.

Still, with what you have written about having a "hard" point in turning the shaft by hand leads me to the same conclusion as a bent shaft. I have a (battery) mower motor that when run slowly has a definite thump. I can feel it when turning the shaft by hand although I haven't absolutely determined why it has that hard spot. Motor brushes as well as foreign material stuck in the motor are also possibilities.
 
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Old 06-15-16, 04:21 AM
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Try this. Do as Paul says. Then take off the blade. Try turning the shaft by hand.
Then using a short extension cord turn it on. Does it start smooth or not at all? All signs still seem to indicate bent shaft.
 
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Old 06-15-16, 05:33 AM
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In addition to a bad start capacitor possibly causing your problem, it is possible a motor shaft bearing (blade end) has gone bad due to penetration of dust or a bent motor shaft,
The motor shaft can be checked for concentricity by placing a nail or similar pointer at a right angles to the shaft and at it's centerline (as near to the end of the shaft as possible) and rotating the shaft by hand. Make sure the motor and pointer are secure. If the gap between the pointer and the shaft changes, the shaft is bent and needs to be straightened or replaced. Good luck.
 
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