One good way to mount a pulley or
sprocket to the rear wheel is to use a disk brake
compatable hub. You build an adaptor plate to mount your
sprocket on there. The standard hole spacing for disk
brakes is 6 holes, on a 44mm diameter circle.
Since most motors spin at 3000rpm or so, you will need a good deal of reduction. At 25MPH, a 26" wheel is spinning at about 340RPM so you will need a reduction of nearly 9:1. The easiest way to get that is to use go-kart sprockets. They come as small as 9 teeth and as big as 120. www.azusa.com is a good source for these. The bolt spacing is 6 holes, on 4 9/16 " circle for most of them.
Building the adaptor plate is something that can be done using a drill and a jigsaw. A drill press is best for this (and a small one sufficient for the job can be bought for $100) but it can certainly be done by hand if you are careful. After marking the holes, use a punch to put a dimple in the exact spot, and be careful to hold the drill perpendicular to the sheet. Aluminum is the best material to use as it is light and relatively soft and easy to drill.
One problem with chain drives is that they can be quite noisy. You may want to build some sort of chainguard to go over it and insulate for sound deadening. Other than that, chains are a good solution since parts are readily available in the necessary sizes, and they are the most efficient as well.
Another option is to go belt driven using V-belts. The
major problems with this are slippage (which reduce
efficiency) and the availability of pulleys that are
large enough. You would need to fabricate your own wheel
pulley, which can be made using plywood. If you want some
ideas about how to do that, let me know. It is relatively
simple to do.
The advantage to belts is simplicity and quietness. Chain drives need very good alignment, or the chain will constantly be derailing. Belt drives are far less finicky.
Two of my favorite sites for electric bikes are Eric Peltzer's at http://www.peltzer.net/ebike/ebike.htm
and Rob Cameron's at http://www.geocities.com/Yosemite/Gorge/9546/bikev/bikev.htm
Both of these guys are on this list. You may hear from them.
In particular, Version 1.0 of Eric's bike, seen at http://www.peltzer.net/ebike/ebike3.htm is a good simple design that works relatively well.
The orange colored V-belt that is used on this bike is called a PowerTwist belt. They're unique because the length can be adjusted by removing "links". They are also supposed to be more efficient and quieter than a standard V-belt. www.smallparts.com has them (and many other things useful for projects like this) as does Amazon.com. http://www.amazon.com/exec/obidos/ASIN/B00002240R/o/qid=989945360/sr=8-1/ref=aps_sr_th_1_1/102-8565962-3176938 has more info.
Try down loading this link to
calculate ground hp based on your speed: http://www.xsystems.co.uk/machinehead/powercal.html
The conversion is 1 hp is 550 ft-lb/sec. If you and bike weight 275 lbs, and it goes up one foot of elevation in one second, then you can say it has 1 ground horse power. However, that does not take into consideration for wind drag which becomes significant at 15mph. The above program let you take into account wind resistance I think. I have not used it yet, but I think I know what it does.
not to laught too much. I know it's rough, but I didn't
want to invest too much time or expense until I knew
whether or not the motor would work. It did! It jumped
right up to 21.4 MPH on flat ground. Scarry! I took it
for a four mile jaunt, and decided it is not what I want.
Too much power--too fast--too noisy--too much vibration--too
conspicuous to the cops, etc. Maybe I should go electric
instead. Has anyone ever used a boat trolling motor? I
have a battery powered weedeater, but I don't think it
would be gutsy enough. Maybe I should just buy what I
need. Anyway, here are the pics. The bike is one I built
about two years ago, and I love it. http://TimelessMiracles.com/projects/left.jpg
Grant Sellek wrote: Can anyone identify an electric motor I have located near my home? It is large but the price is right and it may be useful to me for experimenting. It is made in France by Polico Model number 96C 60 B1 Marked 48V It is at least 150mm diameter and appears to be brush type, but not certain. I presume it is PMDC. I would value any knowledge or estimates of wattage and rpm.
Some rough rules of thumb to go
by when dealing with a completely unknown motor: First
measure its resistance R. You may need a low-range ohm-meter
for this. Then: Stall current = V/R Max power = V^2/2R at
50% efficiency, the current will be V/2R, and the speed
will be half the no-load speed.
If you can get hold of a tacho, measure its RPM on the bench, and the current drawn. It should be low (1 amp or less). The peak efficiency should be 80-85%, at that fraction of the no-load speed, and at (1 - that fraction) of the stall current. At light loads the no-load current will be significant, due to motor friction.
Example: a 48V motor with a resistance of 0.5 ohm. Stall current = 96 amps Max power = (48*48)/1.0 = 2304W
Suppose the measured RPM = 3000, Assuming best efficiency of 85%, best speed = (3000 * 0.85) = 2550 RPM current = (96 * 0.15) = 14.4A power = (48 * 14.4) = 691W
Date: 27th March 2001
Sorry, I screwed up fundamentally:
Power IN = V^2/2R Power OUT = V^2/4R (50% eff.) at 50% of the no-load speed and half the stall current. This is the point at which power out is at a maximum. In my example power in = 691 W, out = 345W.
Some of you guys out looking for junk used grinders, don't do that. Get something that you can buy replacement parts for. I knew this before I started my project, but I learned it the hard way anyway. When I built my first chain saw powered Go-PED, I was excited about the idea, so without thinking I just grabbed the chainsaw I had. It was a fairly new chain saw, but even though it was new, I couldn't get parts for it. I melted the plastic rear wheel rim and crashed it into a flower pot and broke the $10 fly wheel on the first ride. The second time I got a metal rim rear tire and a Sears chain saw. Now I can order parts online. I had to redesign and rebuild the whole frame assembly to fit the Sears Chain saw. It was a good solid 3 days work. I crashed it again on the third test ride. The choke holds the throttle open about 1/4 throttle. When I was testing out the low gearing, I started it and it took off down the road without me. Sheared all the cooling fins off the flywheel. But this time it was no problem. I ordered a new flywheel for $10, and was back running again in a week. The regretfull thing is, I wasted about 3 days, and a $150 chain saw. Live and learn.
I'm thinking that I may be able to save money by
ordering the parts for the grinder head. I plan to go to
a local Sears, find the grinder I want, take the manual
out of the box and copy the part numbers. Then go to
their website, www.sears.com and order the parts. It may
cost less since I am not buying the motor and handle.
This is what I plan to try when I get to this project.
Most important is when I wear the gears out, I can buy
new gears for $20 and replace them in a day rather than
buying a new grinder and taking 4 days to build new
mounts and sprocket and everything. Regards, Matt
My left hand drive solution,
using a chunk of a coaster brake hub brazed to a steel
Their design criteria
is based on a 140lb rider, for optimal performance, which
is somewhat limited at best. By "most affordable"
the best pricing I see for "new" is at http://store.yahoo.com/jandr/ecr-z3.html.
If you like to tinker, there are other options available
at or about the same cost, see http://gwinfo.dhs.org/ebike01/
, using just the switch, batteries in a back pack etc. As
for the Zeta, they are limited to 6 to 10 mph. The
battery is a small 12volt 7 AH. You could add an external
battery as Timothy Smith on this list has done to an
earlier Zeta unit. Do they work? Well, sorta, kinda.
Mine does well on the flat, for maintaining momentum,
resting up for the inclines, where it's useless. It works
best on my road bike, but also works on the MTB, and is
I have found, the best hub motor available today is the
470 rpm, 1000W motor here: http://www.electricbikessys.com/motor.htm
These are more powerful than the Heizman's, and more
reliable because they are direct driven, no noisy
planetary gear system to wear out inside. This will also
make them less noisy. I am very impressed by what I heard
about these motors and I am going to the factory in
Camarillo CA. to look at them soon. I will report back.
Does anyone know of anything better in the high power
catagory? Switching from Currie to some kind of hub motor
because Currie has run dry of their kits. Heizman is too
much dollar too little power, 850Watts peak, same as
Currie for 4X the money is the best they offer.
As promised, this posting attempts to show the performance that should be attainable from the Ecycle motor. Not a single math equation, but a real-world description. I have assumed a 5:1 fixed reduction from motor to wheel, using the MG24 motor with a 48V battery, and the Ecycle FET controller. Gross vehicle mass assumed to be 110kg (70kg rider + 40kg bike). I have chosen the gearing to give a top speed around 47 km/hr (29mph), which should be enough for an occasional dose of fun, but still permit respectable acceleration and hillclimbing.
I have tabulated performance for three typical operating conditions - full speed at 47 km/hr, cruising at 33 km/hr, and low-speed/hillclimbing/acceleration performance at around 16 km/hr. The gradient capability, in percent, doest not include friction or wind drag. Let's go ...
----------------------------- FULL SPEED CHARACTERISTICS
SPEED POWER EFFIC SLOPE km/hr Watt (%) (%) 47.3 100 60 47.1 198 68 1.4 46.8 394 85 2.8 46.1 775 90 5.5 44.8 1506 91 11 42.1 2833 87 22 -----------------------------
----------------------------- CRUISING CHARACTERISTICS
SPEED POWER EFFIC SLOPE km/hr Watt (%) (%) 33.4 70 64 33.2 140 78 1.4 32.9 277 86 2.8 32.2 542 90 5.5 30.9 1040 89 11 28.2 1901 83 22 -----------------------------
SPEED POWER EFFIC SLOPE km/hr Watt (%) (%) 17.6 37 69 17.4 73 81 1.4 17.1 144 87 2.8 16.4 276 88 5.5 15.1 507 83 11 12.4 835 69 22 -----------------------------
At full speed, the motor has more than enough power - in fact the motor is capable of climbing 10% or more at 45 km/hr. However, this is pretty academic, as the relatively small battery that most of us carry (say, less than 15kg) will not be able to provide more than about 1kW anyway. In addition, those of us who adhere to a true "power-assist" philosophy dont need or want more than around 500W of assist. So, for the vast majority of the time, we are only interested in the range of powers from 200W to 800W or so, and the efficiency in this range very good. At full speed, the efficiency does drop off at 200W or less. However this is of no concern because, if you are knackering along at 47km/hr, I'll bet you are using 400W or more of assist anyway, where the efficiency is 85% or better. Overall, the motor power and efficiency at full speed is entirely satisfactory.
At a "cruising speed" of 33km/hr, you still have more than enough power, and the efficiency has improved under light load, namely 86% at 277W, and a quite useable 78% at only 140W. If your battery pack can supply the required amps, the motor will effortlessly and efficiently (89%) haul you up a 10% grade at 30 km/hr. Basically does everthing you could want at cruising speed.
At a "low" speed of 16km/hr or so, the available power has dropped considerably, but is still entirely adequate. You can chug up a 5% incline at 16 km/hr, with an impressive 88% efficiency, or an 11% inline at 83% efficiency. Ultimate climbing ability is an impressive 22%, corresponding to the recommended maximum motor current of 70 amps. I'd say the hillclimbing is entirely satisfactory, particularly when you consider that this is a fixed gear ratio that can also wind you up to 47 km/hr. Note also that at these low speeds you can reduce assist power down to a tiny 70W or so, and still get 81% efficiency.
Acceleration is good too - something around 0 to 40 km/hr in 5 seconds should be possible. Range should be as good or better than the vast majority of ebikes, if ridden at the same speed, but you clearly have the potential here to reduce the range almost without limit. Overall, I reckon the predicted performance is very impressive. Well, that's another lunch-hour gone. If I have time I will make a comparison with the Scott 1HP motor, or is this topic exhausted ...
Many years ago I
built several ICE bicycles. The first one was a front
wheel drive unit that bolted on to the front fork. It was
made from bed frame "angle-iron" and replaced
the bike's front wheel. The 3.5 HP horizontal shaft
Briggs engine (with a centrifugal clutch) was ahead of
the fork & right over a minibike rear wheel. The
minibike wheel had the same contact point on the ground
as the original bicycle tire. The mass of the engine was
unnoticed after 2-3 mph was reached. Vibration to the
handle bars prevented use of a rearview mirror. Headlight
bulbs didn't last long either, probably due to the
vibration. I glued leather to the constantly rotating
part of the clutch and mounted a bike generator to rub on
it (through a rubber grommet on the generator's wheel to
lower the rpms of the generator). Pedaling was useful
only for the first few feet off the line. I utilized the
minibike wheel's brake and had the bike's coaster brake
available as well. The best way I found to motorize a
bike was to put the engine on a one-wheel trailer (built
in one evening from scrounged parts without welding).
Very simple. I used angle bed frame material to attach
the Briggs 3.5 HP to a common minibike wheel. It had a
Max- Torq centrifugal clutch and #35 chain to the wheel.
The sprocket on the wheel was nearly as large as the tire
and gave a good ratio for acceleration & hill
climbing. I used 3/4 in. electrical conduit for the
tongue. Two pieces were bolted to the angle iron (one
piece on each side) and were bent with a conduit bender
to curve over the back bike wheel and join with each
other where they attached to the seat post. I took a 3-speed
bicycle twist-grip gear changer apart, tossed the detent
ball and spring and filed the stop for more range of
motion to make the throttle control. The long throttle
cable was made from 2 bike brake cables by drilling a
hole through a bolt near the head and crushing two bike
cable ends in the hole with a nut. At first the trailer
had a tendency to sway too much so I made the angle iron
pieces longer between the engine and wheel to get more of
the unit's weight under the line between the seatpost
attachment point and the tire contact point, hoping to
cure the problem with more pendulum effect. That helped,
but I could eliminate the swaying problem only by making
a simple u-joint at the seatpost. I split one tang on
each of two gate hinges, bent the split tangs in opposite
directions and bolted the split tangs of the two hinges
together so the hinge pins were at right angles to each
other to make this u-joint. Now the trailer could still
turn left & right, go up & down over bumps, but
leaned only when the bike leaned. I found that the little
mini-bike tire had such stiff sidewalls that it required
no air pressure to support the weight of the engine.
Actually, it absorbed bumps better without air pressure.
Never saw any indication of tire wear and it had plenty
of traction. I got a 35 MPH top speed & 120 mpg at
about 25 mph with a ratio that could have been higher. I
liked the simple construction, that it was quickly
removeable from the bike and did not put the vibration,
torque or weight of the engine on the bike itself. The
bends in the conduit absorbed vibration from the engine.
The bicycle's handling was not affected in any way I
could detect and the one driven wheel gave me a narrow,
single track to ride. I considered making a high- volume
quiet muffler from an empty propane bottle or small fire
extinguisher and concealing the engine; disguising it to
look like I was towing a toolbox, camping gear or
similar, but I never got that far. I recently retired and
decided I would like to make a more efficient one with a
4-stroke string trimmer engine and 3 speeds. I bought a
Ryobi 825R on sale at Menard's. Now I wish I had chosen
the Honda GX31 because a double bearing clutch housing is
available for it and the Ryobi is the first generation (half-crank)
engine with the recoil starter on the clutch side. I'm
offering to answer any questions about my pusher-trailer
and am asking for advice on how to get around the
limitations of the shaft & clutch & single
bearing of the Ryobi. I have laced a 16 in. bicycle rim
to a Shimano 3-speed gear hub and need to make a
reduction drive from the clutch to the 3- spd. hub. I'm
planning a reduction to the hub (with 75%, 100% and 133%
ratios) that will give me about 15, 20 & 27 mph. Is
this reasonable for 1.2 HP? This one wheel trailer design
cannot use a bump start so I must retain the clutch and
recoil starter. At this time I feel the only help I need
is in getting a gearbox or timimg belt pulley onto that
little clutch and supporting the PTO bearing if necessary.
Any ideas? Frank, did you ever use any of those first
generation Ryobi 4-strokes? I would far prefer to use the
Ryobi, but if I can't I'll use a 2HP Briggs I already
have and put a Max-Torq or Comet clutch on it, and a
reduction drive by jackshaft, and hope the small diameter
(16 in. ) wheel will reduce the torque enough to spare
the integrity of the 3-spd hub internal gears. Any
comments, questions or suggestions are welcome.
Here's a fairly easy to follow guide to calculating power requirements. While I won't vouch for its correctness it appears good to me. I found this on a kick-scooter website mentioned at the bottom. BTW, I have one of their kick scooters and it is excellent for dog walking. With my 18lb Jack Russel, Bella, I can hit near 20 mph when in pursuit of a squirrel on good pavement. She's got a power to weight ratio that puts most electrics to shame. ---- CLASS IS IN SESSION - DR. BEETZWAKEN ANSWERS: HOW MUCH POWER DOES IT TAKE TO MOVE A PERSON AROUND ON A SCOOTER OR CYCLE? I've seen scooters and cycles claiming 200 Watts and 18 mph top speed and others claiming 400 Watts and 12 mph top speed. How much power does it actually take to move a person around on a scooter or cycle? Bicycles, scooters, and even automobiles are all governed by the same fundamental power requirements. At constant speed, the power required to move the vehicle and the passenger goes to three places: 1. The power required to overcome the rolling resistance of the wheels on the pavement. 2. The power required to overcome the wind resistance associated with moving the vehicle/passenger through the air. 3. The power required/provided to move the vehicle and passenger up/down any incline (if not traveling on flat pavement). (NOTE: Stop here if you didn't like high-school physics.) We can write this as an equation: Total-Power = Power-rolling-resistance + Power-wind-resistance + Power-hill-climbing (Note that Total-power is the power delivered to the driving wheel of the vehicle net of any friction in the transmission and inefficiencies in the power system.) To a first approximation, power-rolling-resistance is in turn determined by the weight of the vehicle/passenger (W), the speed of the vehicle (S), and a coefficient that characterizes the rolling resistance of the wheel (a). Power-rolling-resistance = aWS To a first approximation, Power-wind-resistance is determined by the "frontal area" (F) of the vehicle/passenger (the area of the outline of the vehicle/passenger when viewed from the front), a coefficient (b) that characterizes the shape of the vehicle/passenger, and the CUBE of the speed (S x S x S). Power-wind-resistance = bFS^3 Power-hill-climbing is determined by the grade of the hill (G), the weight of the vehicle/passenger (W), the speed (S) of the vehicle/passenger. Power-hill-climbing = GWS So, the entire equation is: Total-Power = aWS + bFS^3 + GWS = (a+G)WS + bFS^3 Before we do some calculations, we can make some interesting observations: 1. Total power required is strongly influenced by speed. 2. At high speeds, the effect of wind resistance will be very large (because it depends on S cubed). 3. Light vehicles/passengers have an overall advantage. In fact, although W does not appear in the expression for wind resistance, frontal area (F) is highly correlated with W, so overall size/weight pretty much influences all three categories of power consumption. Now, some approximate numbers. (I use metric units, but provide some examples and conversion factors for those of you who think in English units.) a = coefficient of rolling resistance 0.008 for high-pressure 700mm road bike tire 0.020 for a mountain bike tire 0.040 for a typical (e.g., 9 inch) pneumatic scooter tire W is weight in Newtons (1 pound = 4.45 Newtons) S is speed in Meters/Second (1 mph = 0.45 meters/second) b = drag factor in kg/m^3 (This includes air density factor for sea-level air. Picky engineers: see note below.) 0.6 for a square-edged box 0.4 for most human-like shapes 0.2 for a egg-shaped object F = frontal area in square meters 0.4 for a crouched racing cyclist and bicycle 0.6 for an upright cyclist and bicycle 0.8 for a standing scooter rider G = height of climb/distance of climb (e.g., % grade) Typical maximum railroad grade = 0.02 Typical maximum bike path grade = 0.05 Typical maximum overpass grade = 0.08 Maximum grade on Pike's Peak mountain road = 0.10 Powell St. in San Francisco (cable cars) = 0.17 Examples: 1. How much power is consumed to propel a medium-sized (165 lb.) adult standing on a scooter with 9 inch pneumatic tires traveling at 12 mph? W = 165 lb. = 734 Newtons S = 12 mph = 5.4 Meters/second a = 0.040 b = 0.4 F = 0.8 square meters G = 0 Total-Power = (a+G)WS + bFS^3 = (0.04+0)734 x 5.4 + 0.4 x 0.8 x 5.4 x 5.4 x 5.4 = 159 + 49 = 208 watts 2. How much power is consumed in the same situation except traveling up a 2% grade at 12 mph? now G = 0.02 Total-Power = (a+G)WS + bFS^3 = (0.04+0.02)734 x 5.4 + 0.4 x 0.8 x 5.4 x 5.4 x 5.4 = 238 + 49 = 287 watts 3. What happens if the scooter is going 20 mph on the flat? now S = 20 mph = 9 meters/second Total-Power = (a+G)WS + bFS^3 = (0.04+0)734 x 9 + 0.4 x 0.8 x 9 x 9 x 9 = 264 + 233 = 497 watts Some notes: Note that climbing a 2% grade (G=0.02) consumes the same power as rolling on tires with a rolling resistance of 2% (a=0.02). Note that the power required to propel a vehicle does not depend on the power source. In other words, a scooter powered by kicking requires the same power for the same speed, weight, etc. as a scooter powered by an electric motor. Finally, let me note that the vast majority of small electric vehicle manufacturers do not appear to know these basic laws of physics. I see a lot of scooters with advertised top speeds of 15-17 mph, yet with 9 inch pneumatic tires, and with motors and transmissions that can deliver only about 150 watts to the wheels. You can calculate for yourself that the specs must be highly exaggerated (or the manufacturers must assume that a small child is riding the scooter down a big hill...). Caveat emptor. NOTE TO THE PICKY ENGINEERS (you know who you are): The expression for wind resistance is actually rho/2 * Cd * F * S^3, where rho is the density of air and Cd is a non-dimensional drag coefficient. Since rho is around 1.2 kg/m^3, the rho/2 term is around 0.6. To simplify these calculations, I included this factor of 0.6 in computing the "coefficient" b.
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Thursday, 29 January 2009