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

Byron A Jeff (byron nospam at
Thu, 6 Mar 1997 21:59:31 -0500 (EST)

> > 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.

OK. Mind telling some specifics?

1) Exactly what kind ot motor. Would something like the heavy duty motor
at Rat Shack be feasible? What about maybe a 12V DC fan motor?

2) What is the thickness and mounting method for the disk?

3) Any idea how to handle cutting on an incline? Will the cutting disk
simply always be perpendicular to the body of the Mowbot or does it have
some type of movement relative to the body.

> 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.

Thanks for the info. I'm grateful.