Well I've worked on the cutting problem some more and I'm ready for a brief
report.
I've found a workable attachment system. It still needs some refinement
but is fairly good:
1) Get a part from the auto place called a wire stop. Its purpose is to
set a wire in place. It's brass, has a hole to pass the wire and a set
screw. ASCII:
S
-----------------------------S
| |S
| o |S
| |S
-----------------------------S
S
Unfortunately for some reason the item is threaded the same way all the way
through. Doen't make a whole lot of sense because once the wire is passed
though the hole the set screw can cross to the other side. Would have been
better to have two set screws on opposite sides.
2) I placed the disk on the shaft and mounted the wire stop over it. The
disk still wasn't attached. Went looking for a L bracket so I could attach
like this:
L
| LS
--------------|--------------LS
| | |LS
| | |LS
| | |LS
--------------|--------------LS
| LS SSS
| LLLLLLSLLLL
DDDDDDDDDDDDDDDDDDD|DDDDDDDDDDDDDDDDDDDDSDDDDDDDD
| BBSBB
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
3) The guy at the hardware didn't have an L small enough. Had an interesting
suggestion though: strap the disk to the wire stop across the top like this
sssssssssssssss
s------|------s
s | s
s | s
s | s
s------|------s
SSS s | s SSS
sSsssssssss | ssssssssssssssSs
DDDDDDDDDDDDDDDDDDD|DDDDDDDDDDDDDDDDDDDDSDDDDDDDD
BBSBB | BBSBB
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
MMMMMMMMM
I used a piece of picture hanging metal for the job. Works fairly well.
So now on to the experiment. I bought a pack of 5 Xacto knife blades
(curved heavy duty). For the experiment I attached 2 180 degrees on the disk.
I back stopped each blade by placing a second screw at the edge of the disk
on the trailing edge of the blade.
Some observations:
1) Screws spinning at several hundred RPM can hurt! I ripped up a knuckle
handling the test rig.
2) The blades cut fairly well.
3) The disk stops spinning at the slightest resistance.
4) Cut grass easily becomes caught in the assembly.
I think 4) is fairly easily solvable. I think that encasing the top on the
assembly with a plastic funnel that spins along with the blades will keep
the grass out.
Now I want to tackle 3). It seems that simply having a more powerful motor
with more torque would solve the problem. To verify that its the motor, I
attached the head to my drill and tried that out. Still had the grass
spinning onto the head but it cut very very well.
I think that attaching 4-5 blades will help in the process along with
with smoothing the top and bottom will help.
Any suggestions for more powerful DC motors. The Rat Shack motor isn't
going to cut it for this applications.
And best part: the whole head runs less than $10 US! At that cost I can
affort to put three or more heads on the bot.
BAJ