Re: [mowbot] Re: Gotta have gas to cut ??

KEN_REED nospam at
Thu, 6 Mar 97 15:12:53 -0700

> ken wrote:
> Pardon me for saying so, but I'm not sure that is true.
> My experiments have shown that small dc motors will cut the grass just fine.
> My test cuts were done using a single dc motor, 12v nospam at 0.6 amps while cutting,
> will turn a 5" aluminum disk approximately 2000 RPM. The aluminum disk has 4
> X-acto knife blades sticking out 1/2" that do the cutting. The cuts were
> clean,
> and seemed easy enough. Now bear in mind that I didn't cut overgrown grass,
> but
> cutting off < 1" was easy enough.

BAJ wrote:

Now see? This is the kind of information I've been waiting to see. This is
an experiment I can perform this weekend. A couple of questions:

1) Is there actually a need for a disk? Would not two cross-members in a
propeller type arrangement do the same job?

>>>I believe the disk is important since it would stir the air less
>>>than some form of a cross. The air would be churned up by a cross
>>>always pushing air out of the way, and it moving right back in.
>>>It's interesting you used the phrase "propeller type arrangement",
>>>since it would be a zero pitch propeller.

>>>Note: I haven't experimented with anything but a disk, and I'm
>>>satisfied enough with it that it is designed into my LawnBot.
>>>To me it seems intuitive that a disk would cause the least air
>>>friction losses.

2) What was you power source and how long did it last?

>>>I used the alternator/battery from my Lawn Tractor to power
>>>my test and measured the power drain with my Fluke. To be
>>>totally accurate, the voltage was more like 12.5 at the dc motor
>>>I used, not 12v. The important part here is the 0.6 amps while
>>>cutting. The 600ma is not that much power. Recall some mowbot
>>>discussions that I've read show over an amp per drive motor
>>>w/no load, but that's another discussion.