Re: Re electric rotary lawn mowers

[Andrew Gabriel]

Further to our recent discussion, I checked out eight different mowers

> at Payless today. All had geared reduction drives plus some form of > soft coupling between the motor and blades. The only exception was a > non-grass collecting Flymow which was direct coupled, ie cutter on > motor shaft. > The grass collecting Flymows had gearoxes (or it may have been a > toothed belt). A speed reduction device anyway. > I was getting funny looks, I couldn't dismantle them of course. > So, as I suspected, the Naturist Philosopher was right.

I don't know what thread you're looking at.

Universal motors (i.e. with brushes) have to be geared down to driver mower blades - they spin too fast otherwise. Universal motors are used in cheaper low grade mowers of the type you'll find in the sheds. Universal motors are dirt cheap but are completely wrong torque profile for grass cutting, which is why they slow down under load just when you need more cutting power, and deliver much less.

Induction motors drive mower blades directly. You'll find these on higher spec mowers, but you may have to go to a mower specialist. The torque profile of an induction motor is much more ideal for grass cutting - max torque at nearly full speed (so it will maintain speed and cutting power under load), rather than at locked rotor. Expect to pay more, but also expect longer motor life. Also, the induction motor is significantly more efficient, and unlike the cheap universal mower motors, IME induction motors in mowers don't waste power heating themselves up way too hot to touch. As a result of this, don't be surprised to find they are lower power rating for same width cut, because they manage to use more of the power for cutting and less wasted in the motor. No motor brushes to wear out either.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember harry saying something like:

lawnmowers. Not all lawnmower motors are geared, contrary to what TNP was insisting in his usual dogmatic fashion.

[The Natural Philosopher]

Well if not they will have to have a massive multipole motor, especially if its induction.

Which is a waste of iron and copper.

[John]

In my sample 7 out of 8 were. The one that wasn't was a unique type. So I imagine it's the only one that has no gearbox. Or belt. They are geared for the reasons above. All perfectly logical.

I have only had Flymos and these did not have any reduction in the drive.

[Andrew Gabriel]

I don't agree with much of what TNP said in his two articles in this thread, but ICBA to go through and correct every point, and I'd just be repeating what I already said. I didn't read all of the other thread, but I was referring to mains mowers here, not battery ones.

I would have guessed an even higher ratio overall, because most people who buy electric, buy cheap universal motor mowers.

I've repaired a number of other peoples' flymos, and they have all been geared, but admittedly cheap models. (Actually, they often aren't repairable because the plastic brush mounting melts when the brushes wear out - they seem to be designed as disposable consumables, I guess so you go and buy another one.)

My own two mowers are induction - one almost 20 years old (now with a relative), and the other is 10 years old.