GlassyClass on tue 13 nov 01
Good Evening,
From a post awhile back, I took the MPH meter off my bike (kinda afraid to
ride, balance is not good). And put it on the kickwheel for grins.
I also put a motor on it over the last couple of days, found a half horse
that ran at 1785 RPM that was reversible for $70.00, the man at the store
showed me how to hook up a motor shaft arbor and a 1.5 inch rubber tube
sander arbor (just used the rubber, not the arbor) into a drive wheel for
the flywheel. So now my kickwheel has motor assist for about a hundred
dollars. Got a pretty good wheel going for $200.00.
What I am wondering, are there any math wizards on the list ?
The bike meter is calibrated for a 27.5 inch bike wheel, it reads out in
MPH, the motor spins the flywheel up to a top speed of 8 MPH.
What would that be in RPM ?
Math is something that does not work good for me, I trust people not to
cheat me in the stores, and most don't. Have only had it happen a couple of
times, and I just did not go back to that store anymore.
Thank You if anyone can figure this out for me, I have tried only come up
with outlandish numbers, so am not doing something right.
Sincerely,
Bud
Bill Aycock on wed 14 nov 01
Bud to figure that one out, I will need the wheel size, also.
Bill still doing arithmetic, on Persimmon Hill
At 06:31 PM 11/13/01 0800, you wrote:
>Good Evening,
>
>The bike meter is calibrated for a 27.5 inch bike wheel, it reads out in
>MPH, the motor spins the flywheel up to a top speed of 8 MPH.
>
>What would that be in RPM ?
>
>Sincerely,
>Bud
>

Bill Aycock  Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG  Grid EM64vr
baycock@HiWAAY.net
w4bsg@arrl.net
TRAVIS MAXWELL on wed 14 nov 01
I could be wrong on this one, but I think you have given enough information
to calculate RPM.
Assumptions:
1. 27.5 inch bike wheel means 27.5" diameter bike wheel
2. Bike MPH meter is electronic magnetic sensor trip type
A typical electronic bike mph meter works by measuring the time it takes a
wheel to make
a complete rotation and divides the programmed bike wheel circumference
by this number.
This works since in one revolution, the bike travels the circumference of
the wheel.
A mph meter that is calibrated for a 27.5" diameter
wheel assumes in one rotation, the bike has traveled 86.39 inches, or
.00136 miles (Pi*D=circumference) which is the circumference of the
bicycle wheel. If the meter is reading 8 MPH, it thinks there is a 27.5"
bicycle wheel turning
8/.00136 times per hour based on the time it takes the sensors to trip on a
revolution. Example, if the 27.5" wheel turned 1000 times in one hour, it
would have went 1.36 miles in one hour, or 1.36 MPH. For 8 mph, it made
8/.00136=+/5882 revolutions per hour. Which is 5882/60=+/98 revolutions
per minute.
Which sounds about right for a pottery wheel.
It does not matter what the diameter of your pottery wheel is since it will
take the same amount of time for a revolution if it were mounted 2 inches
from center of revolution or 30 inches. It only matters to the MPH meter
how long it takes the sensor to trip, which it does on each revolution. It
then relates this time to the programmed wheel diameter to figure out a
distance traveled in this time and the MPH.
I would put a piece of tape on the wheel and count the revolutions in 30
seconds, then multiply by two to check the math and the accuracy of the MPH
meter. My guess is the 98 RPM will be close, but not exact.
I hope this helps, though not sure if it is useful information.
Travis Maxwell
 Original Message 
From: "GlassyClass"
To:
Sent: Tuesday, November 13, 2001 9:31 PM
Subject: MPH to RPM for the Math Wizards.
> Good Evening,
>
> From a post awhile back, I took the MPH meter off my bike (kinda afraid to
> ride, balance is not good). And put it on the kickwheel for grins.
>
> I also put a motor on it over the last couple of days, found a half horse
> that ran at 1785 RPM that was reversible for $70.00, the man at the store
> showed me how to hook up a motor shaft arbor and a 1.5 inch rubber tube
> sander arbor (just used the rubber, not the arbor) into a drive wheel for
> the flywheel. So now my kickwheel has motor assist for about a hundred
> dollars. Got a pretty good wheel going for $200.00.
>
> What I am wondering, are there any math wizards on the list ?
>
> The bike meter is calibrated for a 27.5 inch bike wheel, it reads out in
> MPH, the motor spins the flywheel up to a top speed of 8 MPH.
>
> What would that be in RPM ?
>
> Math is something that does not work good for me, I trust people not to
> cheat me in the stores, and most don't. Have only had it happen a couple
of
> times, and I just did not go back to that store anymore.
>
> Thank You if anyone can figure this out for me, I have tried only come up
> with outlandish numbers, so am not doing something right.
>
> Sincerely,
> Bud
>
>
____________________________________________________________________________
__
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>
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melpots@pclink.com.
>
Michael Wendt on wed 14 nov 01
Bud,
Figure it this way : 1 mile = 5280 feet so 1 mph = 5280 ft/ hr / 60
minutes per hour = 88 ft/ minute. 27.5" / 12"/ ft gives 2.29 ft X PI (
3.14) gives the circuference of the wheel = 7.2 ft so... divide 88 ft by
7.2 ft to get 12.2 rpm per mile per hour on the speedometer IF it is hooked
up correctly.
Regards,
Michael Wendt wendtpot@lewiston.com
You wrote:
The bike meter is calibrated for a 27.5 inch bike wheel, it reads out in
MPH, the motor spins the flywheel up to a top speed of 8 MPH.
Jim Bob Salazar on wed 14 nov 01
man, i wish i were smart like that!!!
jim bob
Michael Wendt wrote:
> Bud,
> Figure it this way : 1 mile = 5280 feet so 1 mph = 5280 ft/ hr / 60
> minutes per hour = 88 ft/ minute. 27.5" / 12"/ ft gives 2.29 ft X PI (
> 3.14) gives the circuference of the wheel = 7.2 ft so... divide 88 ft by
> 7.2 ft to get 12.2 rpm per mile per hour on the speedometer IF it is hooked
> up correctly.
> Regards,
> Michael Wendt wendtpot@lewiston.com
> You wrote:
> The bike meter is calibrated for a 27.5 inch bike wheel, it reads out in
> MPH, the motor spins the flywheel up to a top speed of 8 MPH.
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
 
