Re: [mowbot] test

adamdb nospam at
Mon, 3 May 1999 10:25:40 -0500


On Fri, 30 Apr 1999 19:43:53 -0400 (EDT) byron nospam at (Byron A
Jeff) writes:
> > Drivetrain: Two car power window motors with worm gear.
> Same. Center mounted so that the circular body can spin on its axis.
> I did most of my drivetrain work last spring. Learned quite a few
> things:
> BTW I'm using a couple of Hyundai WW motors....

What kind of RPM do these generate? The ones I saw at
operated at 100RPM. Figuring for 6 inch wheels (approximately 18 inches
in diameter) that would give a speed of 2.5 feet per second
(approximately). This seems way too fast to me, so I am thinking that I
need to look for a motor putting out 10-20RPM instead. Seem reasonable?

> > Cutting blade: Nylon blade adapter intended for use on string
> trimmers.
> Tried it. Not much success. My current blade is a 7 in circular saw
> blade.

Using a metal blade isn't feasible for me. I have small kids. What were
the principal problems with the nylon blades?

> I used a radiator fan motor. It has the heft to carry the saw blade,
> which is
> smaller and flat. So the saw blade actually spins faster than the
> original
> fan blade.

Any idea of the current draw for the radiator fan motor?

> > Grass cutting pattern: Random
> This is actually a real problem. By necessity the cut path is much
> smaller than
> Again I haven't gotten this far, but I'm pretty sure I'm going to
> implement
> a real grass height detector and cut uncut grass.

Did you see my earlier post on using an IR LED emitter/detector pair for
uncut grass detection? I realize there are issues with the
emitter/detector getting blocked by dirt or cut grass, but does this idea
seem feasible?

> a completely bounded area and bump sensors. Somthing like the very
> popular
> railroad ties. Anything I wish to protect will be bounded also.

Eminently reasonable. I also have been thinking along the lines of
keeping it simple for the initial implementation just so I can get
SOMETHING working, rather than never finishing anything due to an overy
complex design.

> Also I'm an advocate of dropping core knowledge here. Many of us a
> software
> or firmware folks. However trying to figure out how to attach an
> axel to
> the driveshaft of a motor is a completly different skillset. I'd
> like to

Speaking of which, how did you attach axles to the power window motors?
The specs on the ones I have been looking at say that the output shaft is
only 5/8 of an inch long.

Thanks for the informative post,

Adam Bryant (age 0x23)
abryant nospam at (work)
adamdb nospam at (home)
Parker, CO, USA
Robotics, RC Airplanes, anything using a PIC

You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at
or call Juno at (800) 654-JUNO [654-5866]