Subject: Bicycle generator Part 1
sent: 10 oct 98

Doug Macintyre wrote:
> 
> http://www.zetatalk.com/energy/tengy05d.htm
> 2) if so, how exactly would you go about it?

More thoughts on how to make an effective bicycle generator: Put an amp meter 
(from a car or another source) in series with the alternator.  This allows the 
person pedaling to see how much output is produced.  

Take the front wheel (tire, rim and spokes assembly) off and mount the remaining 
yoke on a stable platform made of wood.  Use the same bolt holes that held the 
wheel on. 

Raise the rear wheel about 1"-2" above the platform so that the rear wheel turns 
freely.  Bolt this to the frame of the bike about 3"-6" in front of the back 
axle.  This allows 2 support pipes on each side to bolt or strap it to.  Could 
use 2" x 4" wood for the front and back supports.  Use triangle supports cut 
from plywood or any other wood to make it stable (side to side motion).  If 
needed carefully cut a notch in the back right wood support, so that the chain, 
and cables have plenty of clearance. 

Purchase a V-belt or V-ribbed belt big enough to go over the alternator and back 
rim.  I have found it easier to find the Serpentine or 5, 6, or 8 V-ribbed flat 
belts in the lengths needed.  A 5 ribbed belt is 45/64" wide. A 6 ribbed belt is 
27/32" wide.  A 8 ribbed belt is 1" and 1/8" wide.  These are more expensive and 
cost about twice as much as the 11MM or 15MM wide single V-belts.  However, they 
should last longer and will transfer more power.  Also the alternators that use 
these have smaller diameter pulleys.  Which is an advantage.  Flat belts should 
work better on the bare bicycle rim. They would be less likely to turn over. 

The alternators that use flat belts are more expensive, deliver more amperage 
and typically have an internal voltage regulator.  The older alternators have 
the voltage regulator separate and are a lot less to purchase.  Typically local 
rebuilt prices are estimated to be $20-$40 for the older 60 amp (Ford, GM in the 
1970's) type and $110 to $170 for the newer 70 amp and higher amperage.  All of 
these types from time to time can be picked up at yard or garage sales.

Mount the alternator on a peace of wood that is hinged (door hinge) to the 
platform (plywood, plank, etc).  This would be behind the back wheel.  The 
weight of the alternator helps to give it belt tension. A spring could be 
attached to add more belt tension if needed. 

The result would take no welding, and no great modification of the bicycle, so 
that if you wanted to unbolt it and put the back tire and front wheel back on 
you could still ride the bike.  It does take wood and a long enough belt. 

The only thing that is a question in my mind is - will this give the proper 
rotational speed for the alternator.  

Analysis: I have measured alternators that have a single V-belt pulley with 
diameter between 2.5" and 2.8".  Wide 6 ribbed belt alternators I have seen use 
pulley sizes between 2.2" and 2.5" diameter. 

Taking my car as an example the diameter of the alternator is 2.6" the engine 
pulley is 7.25" diameter.  Assume a minimum idle engine speed of 800 RPM is 
enough to generate reasonable current to maintain some amount of minimum 
charging to keep the alternator light off. 

The perimeter of a pulley is proportional to the diameter (Pie times the 
diameter).  Thus the minimum rotational speed of an alternator in 
revolutions/min (RPM) will be (7.25"/2.6")*(800 RPM) = 2230 RPM as a targeted 
minimum speed.  

To get full rated charging amperage one would need to run the engine at 2000 
RPM.  See: "Generator Output Testing" under the link 
http://www.acdelco.com/parts/l1145_00.htm.  To do this the Alternator in my case 
would need to run (7.25"/2.6")*(2000 RPM) = 5,577 RPM for full charging 
amperage.  Other alternators may be designed to run optimally at other speeds.

More measurements/assumptions: A typical kids bike with 20" tires has a rim of 
about 16" diameter and a 2.5:1 ratio between the back wheel and the pedal 
rotation of one turn.  A typical adult 10 speed bike with 26" tires has a rim of 
about 23.5" diameter and a 3.75:1 to 1.37:1 ratio between the back wheel and the 
pedal rotation of one turn. A typical exercise bicycle with 19.5" tires has a 
rim of about 17" diameter and a 2.5:1 ratio between the back wheel and the pedal 
rotation of one turn. 

Pedaling speed: My test show an optimum pedal rotational speed in the range of 
about 60 RPM.  Note: One can do a maximum of 110-120 RPM for short bursts but it 
is a strain.
 ----------------------- 
Subject: Bicycle generator Part 2
sent: 10 oct 98

Exercise bicycle: Now if one mounts the alternator with a 6 to 8 ribbed pulley 
directly against the hard rubber tire of the exercise bicycle. This could be 
spring loaded. May need to remove the fan on the alternator to miss the tire. 
May need to slightly grind the edge of the tire down to fit the grove if a 6 
ribbed pulley is used. An 8 ribbed pulley should work with out modification in 
most cases.  Grind the sharp edge of the ridges of the pulley down so it doesn't 
cut the tire.  This will also make it a bit smaller in diameter.  For a 2.2" 
diameter multi-ribbed pulley modified in this way the diameter of where the belt 
travels is about 2.0".  The rotational speed of the generator will be about 
(19.5"/2.0")*2.5*60RPM = 1,462 RPM.  This a little low to expect much output 
power.

Most alternator shafts are .5" or .625" diameter.  As a second test one could 
try the bare shaft on the hard rubber tire.  Assuming a .625" shaft this would 
give the rotational speed of the generator to be about (19.5"/.625")*2.5*60RPM = 
4,680 RPM.  This is more like it, however it probably will ware the tire too 
quickly. 

As a third test one could then start building up the shaft by epoxying or 
bolting (with the nut that held the pulley) a pipe to the shaft to make it 
bigger until the optimum diameter is reached.  What you are doing is balancing 
power output capability of the individual to maximize charging rate and charging 
time, while minimizing ware on the tire.  My best educated guess at a possible 
end point optimum pulley size for this approach is a diameter between 1" and 
1.5".  The above approach should work well with alternators that have internal 
voltage regulation. 

If an older type alternator is used with a external voltage regulator, fine 
tuning would then be done with a resistor in series with the field circuit and 
the battery.  The lower the resistance the stronger the field will be and the 
harder to turn the alternator and the more current it will produce at low 
speeds.  Note that once the alternator is not turning the battery will drain 
back through the field coil unless disconnected.  You can get around this by 
putting a diode between the battery and output of the alternator.  This diode 
would allow flow from the alternator to the battery, but not back from the 
battery through the field coil.  The output of the alternator is also connected 
through a variable resistor to the field coil.  Note, the field coil is in 
reality the rotating armature. 

Now if one uses a 10 speed 26" tire bike what can be expected:  Assume we are 
going to use a belt to drive it and the rear tire will be removed.  Rim diameter 
is about 23.5".  Assuming a multi-ribbed pulley (5,6,8 ribs) diameter of about 
2.2" is used on the alternator.  Assume the bike is running in 3.75:1 gear ratio 
(in high gear).  Assume we will be pedaling at 60 RPM. Then, the rotational 
speed of the generator will be about (23.5"/2.2")*3.75*60RPM = 2,403 RPM.  If 
the pulley is 2.8", then the rotational speed of the generator will be about 
(23.5"/2.8")*3.75*60RPM = 1,888 RPM. Smaller pulley sizes are desirable.  This 
arrangement should work fairly well, especially since you have the other gears 
of the bike to adjust the speed for the strength of the pedaler.  This 
arrangement should work well with internal and external voltage regulated 
alternators.

Now what if all you have is a 20" kids bicycle:  Using the belt over the rim, 
the rotational speed of the generator will be about (16"/2.2")*2.5*60RPM = 1,091 
RPM.  Putting the tire in contact with a 2.2" diameter pulley would give about 
(20"/2.2")*2.5*60RPM = 1,363 RPM.  Taking off the pulley and using a 5/8" bare 
shaft against a 20" tire then (20"/.625")*2.5*60RPM = 4,800 RPM.  Highly likely 
to ware out the tire quickly.  None of the above options are optimum but any may 
work in a pinch.  Especially if the pedaler is the size of the bike.

Summary: If you plan to use the pulley, get it as small as you can. A small 
change in pulley size can make a significant difference in final speed of the 
alternator.  An old 10 speed 26" bicycle and a small diameter multi-ribbed V-
belt over the back wheel rim, looks like the best approach.  Next most workable 
solution, the exercise cycle with a small pulley put in direct contact with the 
hard rubber tire.

If I haven't made any faulty assumptions or mathematical errors, the above notes 
should give one a starting point. The links that follow should help in 
understanding alternators.

Alternators & Starters - Introduction to Electricity
http://www.hotrodsworldwide.com/pgs/pgs-info.htm
See "Is It an Alternator or a Generator?" under the following link
See "Generator Operation" under the following link
http://www.acdelco.com/parts/l1145_00.htm
Understanding the functions:
http://www.ibm2.com/charging.htm#ALTERNATOR
The ABCs and 123s of Stinger Alternators
http://www.stinger-aamp.com/articles/stinger-alternators.htm


------------------- 
Subject: Bicycle generator
Sent: 9 Oct 98

Doug Macintyre wrote:
> 
> http://www.zetatalk.com/energy/tengy05d.htm
> 
> I've been reading the subject of bike/alternators from car parts. It's
> amazing, but I have some questions:
> 1) Is there a specific car alternator that is preferable, power-wise
> or
> make and model?

I will give you my opinion for what it is worth. I think any size above
30 amps should work. The reason being, the pedaler is going to have
trouble sustaining the pedaling on any kind of medium to high amperage. 
Your biggest concern should be getting the right ratio of pedal
rotations to alternator shaft rotation.  If this is off then it will be
too hard or too easy to pedal.  Now that I think about it. It might be
smart to feed back some of the output through the field coil in series
with a rheostat.  This rheostat could be adjusted to determine the
amount of charging rate and thus determine the ultimate rotational push
on the pedals.  One would not use the 12V regulator in this case.  

> 2) Can this be used to re-charge dead 12v batteries?

Yes and no.  If the battery is freshly dead then yes. If it is a
Lead-Acid battery and if it sat for a while discharged, say for 6 months
to a year (I am not sure of the exact time frame), then I doubt you will
get much charge in it. This is because the sulfation is crystallized
(hard) and will not go back into solution.  This is where a radio
frequency pulser would come into play to help un-sulfate the battery. 
 
> And if so, how
> exactly would you go about it?  

Hook the output of the alternator and the case of the alternator
(ground) to the battery.  Pay attention to proper polarity.  Attach the
field to a rheostat (size yet to be determined) and then to the battery.
Sometimes the other side of the field will need to be grounded. 

I like the idea presented: Take the tire off the rim and use the grove
of the rim as a pulley. Use the pulley already on the generator and
install a long belt around these pulleys. Because of the size difference
the generator will turn many times to that of the bicycle rim. Use the
muli-speed bike gear shift and the rheostat (described above) to adjust
for the proper peddling resistance. 
 
> 3) Even though there is a description on how to convert an ordinary
> bike
> to generate electricity I was wondering if someone could draw up some
> diagrams to better illustrate the process. Does anyone want to take
> this
> on?

Lots of different types of bicycles, and exercising devices. Becomes
difficult to cover all possibilities. I think as we make them - we will
take a picture of the result and write up lessons learned. 


