Using a Bike Speedo as a Mill Tach
Posted by
vrsculptor <vrsculptor@h...
on 2003-01-05 08:19:59 UTC
I saw this on the cnc_mini_mill group and thought it was too cool
not to pass along. Note, prior message instructed setting the speedo
to KM, I didn't see that here.
Roger
From: Chris Difani <cdifani@p...>
Date: Wed Jan 1, 2003
Subject: RE: New Moderator
Jim and Daryl:
Finally found the bicycle speedometer setup information.
First of all these are now called "bicycle computers", since that
name sounds so much better to the marketing types. Also these little
gizmos display a lot more than the simple speed that we need. If you
go to a bike shop and ask for an electronic speedometer, the kids
may just look at you blankly.
Okay, now you know the correct label for our digital RPM display,
it's a bicycle computer. And don't tell that to the bike store
people, that will REALLY confuse them. I have used the "Sigma Sport"
brand, Model BC 1200. Actually just look for whatever is on
the "After Christmas Sale" table, and then have the clerk look at it
to make sure that you can set the wheel diameter to 1.667 meters. If
you can do that, and display the speed in KPH, you've got all you
need. Remember 1.667 meters, this is CRITICAL.
After getting the bike speedo, stop by a Radio Shack on your way
home, and get a couple of rare earth magnets. These are about $2.00,
and come in a bubble pack of two. Tiny little things, and you can
use both of them, one stuck on top of the other.
When you get home, go to whichever tool your going to add this
digital RPM display to, and decide where or how, you are going to
install the magnet carrier. Fancy name. All this is, is a piece of
acrylic plastic that is a rough circle, and about 3/16" or 1/4"
thick. Just thick enough to have a hole drilled in it (number 9, if
my memory isn't totally defunct), near the edge, about 1/16" or so
from the edge, that you can press-fit the two Radio Shack rare earth
magnets into. The plastic disc needs to be big enough to be attached
in any way, to the rotating part that you want to measure. On my
minimill I used three 4-40 SHCS to screw it to the nut on top of the
quill/shaft. On my drill press, I drilled a 1" hole in the disc, and
slipped it over the top of the quill shaft, and held it on with the
nut. On my minilathe, I drilled a 1.35" hole and slipped it over the
end of the headstock shaft, between the two jam nuts that are on the
end of the hollow headstock shaft. Just get it secured to the
rotating part. Any way, as long as it's pretty solid. But remember
all it is doing is rotating, it isn't driving anything, or touching
anything. Its just spinning.
The other thing you need to do is mount the pickup sensor. This is
the little gizmo that senses the magnet as it spins past. The
sensor, at least with the "old fashioned" bike speedos that I have,
is connected with two wires to the digital display unit. The sensor
needs to be within an 1/8" or so of the disc's edge, as the disc
rotates, and the magnet passes the sensor. I have used small nylon
wire ties to attach the sensor to a SHCS that I installed next to
the edge of the disc. Then I was able to twist the sensor to vary
it's distance from the disc's rotating edge. This isn't rocket
science. If you don't get any display, you have the sensor too far
from the magnet that is in the edge of the acrylic disc. To fix the
problem, just move it/twist it closer to the rotating disc.
Now that you have the magnet rotating, and the sensor sensing, you
should (if you got the bicycle computer correctly setup) have a
digital display that is showing you how fast your machine is
turning. Remember that it will show you in units of 10 (1 equals 10
RPM, 17 equals 170 RPM, and so forth).
If anyone has any questions, I'll try to give you the necessary
help. It's been a while since I did this, so I know that I am kind
of "detail challenged".
Chris Difani
cdifani@...
not to pass along. Note, prior message instructed setting the speedo
to KM, I didn't see that here.
Roger
From: Chris Difani <cdifani@p...>
Date: Wed Jan 1, 2003
Subject: RE: New Moderator
Jim and Daryl:
Finally found the bicycle speedometer setup information.
First of all these are now called "bicycle computers", since that
name sounds so much better to the marketing types. Also these little
gizmos display a lot more than the simple speed that we need. If you
go to a bike shop and ask for an electronic speedometer, the kids
may just look at you blankly.
Okay, now you know the correct label for our digital RPM display,
it's a bicycle computer. And don't tell that to the bike store
people, that will REALLY confuse them. I have used the "Sigma Sport"
brand, Model BC 1200. Actually just look for whatever is on
the "After Christmas Sale" table, and then have the clerk look at it
to make sure that you can set the wheel diameter to 1.667 meters. If
you can do that, and display the speed in KPH, you've got all you
need. Remember 1.667 meters, this is CRITICAL.
After getting the bike speedo, stop by a Radio Shack on your way
home, and get a couple of rare earth magnets. These are about $2.00,
and come in a bubble pack of two. Tiny little things, and you can
use both of them, one stuck on top of the other.
When you get home, go to whichever tool your going to add this
digital RPM display to, and decide where or how, you are going to
install the magnet carrier. Fancy name. All this is, is a piece of
acrylic plastic that is a rough circle, and about 3/16" or 1/4"
thick. Just thick enough to have a hole drilled in it (number 9, if
my memory isn't totally defunct), near the edge, about 1/16" or so
from the edge, that you can press-fit the two Radio Shack rare earth
magnets into. The plastic disc needs to be big enough to be attached
in any way, to the rotating part that you want to measure. On my
minimill I used three 4-40 SHCS to screw it to the nut on top of the
quill/shaft. On my drill press, I drilled a 1" hole in the disc, and
slipped it over the top of the quill shaft, and held it on with the
nut. On my minilathe, I drilled a 1.35" hole and slipped it over the
end of the headstock shaft, between the two jam nuts that are on the
end of the hollow headstock shaft. Just get it secured to the
rotating part. Any way, as long as it's pretty solid. But remember
all it is doing is rotating, it isn't driving anything, or touching
anything. Its just spinning.
The other thing you need to do is mount the pickup sensor. This is
the little gizmo that senses the magnet as it spins past. The
sensor, at least with the "old fashioned" bike speedos that I have,
is connected with two wires to the digital display unit. The sensor
needs to be within an 1/8" or so of the disc's edge, as the disc
rotates, and the magnet passes the sensor. I have used small nylon
wire ties to attach the sensor to a SHCS that I installed next to
the edge of the disc. Then I was able to twist the sensor to vary
it's distance from the disc's rotating edge. This isn't rocket
science. If you don't get any display, you have the sensor too far
from the magnet that is in the edge of the acrylic disc. To fix the
problem, just move it/twist it closer to the rotating disc.
Now that you have the magnet rotating, and the sensor sensing, you
should (if you got the bicycle computer correctly setup) have a
digital display that is showing you how fast your machine is
turning. Remember that it will show you in units of 10 (1 equals 10
RPM, 17 equals 170 RPM, and so forth).
If anyone has any questions, I'll try to give you the necessary
help. It's been a while since I did this, so I know that I am kind
of "detail challenged".
Chris Difani
cdifani@...