RE: [mowbot] A Basic Platform

Raymond Skarratt (skarratt nospam at
Wed, 13 May 1998 13:21:34 -0400

> -----Original Message-----
> From: Doug Smith [SMTP:dsmith nospam at]
> Sent: Wednesday, May 13, 1998 12:22 PM
> To: mowbot nospam at
> Subject: Re: [mowbot] A Basic Platform
> >This message will detail the choices I made for my Mowbot platform. I
> hope
> >it will clarify many of the issues that come up during robot
> construction.
> Thanks for the great info. I'm glad to see some desire to focus on
> the
> platform because that's the stage I'm at. Here's a little of what I'm
> doing...
I think there are probably a lot of people on the list who are either at
the platform stage or they are at the "dreaming" stage. I'm sort of at
that dreaming stage as I don't really have any sort of platform even
started but I have a very good idea of what it will look like in my

> I'm trying not to think like I'm building a standard lawn mower. (I
> already have a self propelled gas mower rigged up with a cable winding
> on a
> spool to mow large circles.)
That is pretty funny. I'll bet the neighbors talk about you. :)

> Since I'm not pushing it, it can take longer
> to mow. In fact, I don't care if it mows continuously as long as it's
> not
> annoying and it can keep up with the lawn.
This is my thinking exactly. I basically have three areas of lawn that
I need to be cut, two small ones of less than 300 square feet and one
larger one of probably about 800-1000 square feet (those are total
areas, not perimeters). I think that if I could keep the cutting time
of the smaller areas to about an hour or less the larger one would take
3-4 hours for a total cutting time of about 6 hours I would be happy.

> So I'm going for small and light to keep the power requirements down
> which
> keeps the battery size and weight down, which keeps the power
> requirements
> down, and so on. And hopefully that will translate to reasonable run
> time
> between charges or low enough power drain to be supplemented by solar
> charging. (Yes, that's part of platform design considerations because
> that
> wouldn't even be a reasonable cost option for a larger unit.)
I totally agree with Doug here. Smaller is better and smaller removes a
lot of complications. Supplementing power with solar cells helps keep
the cut to charge ratio low which is good. Another benefit of smaller
platforms is that if some one has a larger lawn or wants their lawn cut
faster they can put together two or more of the smaller mowers while
keeping cost relatively low. Smaller platforms will also be easier to
move so the motors don't have to be as big and _maybe_ we can get away
with using motors on the larger end of the toy motor scale...

So my idea for a basic design (which is still a very rough idea and may
fall a little outside of my own definition of small) is something
similar to Dave's idea. A square made from angle irons (those extruded
aluminum or iron or whatever 'L' shaped bars in case some one doesn't
know what angle irons are) would make up the basic frame with bolts at
the corners holding the frame together. I was thinking that everything
should be able to fit in a one foot square (including the wheels). I
think it is Ken Reed that has a pretty good description of what
something like this would look like (including diagrams) on Dave
Everett's web site
This square frame would be just that, a frame that would have a body
that would fit over it. The body would basically be a protective cover
but would also house the solar panels and bump sensors. The body would
be circular and the axis of the drive wheels would be on the centre line
of the circle so that the 'bot would be able to get out of any tight
corners it might get itself into...

Anyway, its is just an idea. Comments? I guess the most important
thing from my standpoint would be keeping the size down so the power
consumption can be kept down so the batteries and motors can stay small
and the solar panel option is still there....

Ray Skarratt