http://www.tech.mtu.edu/~jwfrana/strtbike.html http://www.uidaho.edu/engr/ME/sr_des/bps/pict http://members.aol.com/zetabike/zetabike.htmSunstrike Solar Cycle Team
Subject: Drive train
I've used two methods for transferring the drive to the rear wheel. For the first I drilled and tapped six holes in the left side of the rear hub and bolted on an aluminium disk that had a large sprocket mounted on it. A chain ran from the motor to this sprocket. The hub had a fairly substantial flange on it - it was a Sachs 3x7 hub. I wouldn't recommend this for a smaller, lighter hub.
The second method was to use an intermediate shaft that had sprockets on it for chains from both the pedals and motor. A third chain ran from the intermediate shaft to the rear wheel. This has the advantage that the motor is driving through the bike's gears so you can keep the motor spinning at its optimum speed. By having two freewheels on the intermediate shaft you can ensure that the motor does not turn the pedals and the pedals don't turn the motor.
I haven't had problems with torque from the motor damaging the hub with either of these methods.
I think that the motor that Currie Technologies sells has a sprocket that attaches to the spokes of the rear wheel - perhaps someone who has actually seen one can verify this. The spokes would be much more likely to suffer from torque damage but perhaps if you spread the force over enough spokes it is OK.
From: Daryl Gaspero
Subject: MECI Motors
Date: Thu, 25 May 2000
I have been a quiet onlooker to this top list for several years now. In that time I have built an electric and ICE assist using some of the information available from this broad range of knowledge.
The electric was made using two old computer tape back up motors coupled together at there shafts with a nylon friction roller that drove a rear tyre. Even though they were PM motors they were less than 50% efficient. (24V 8.5A and 1/8HP. ie:93W not 24V * 8.5A = 204W) Using a PWM circuit built at Monash and two 12V 10Ah SLA batteries a range and speed of only 12Km @ 25Km/Hr was achieved. PRETTY AVERAGE!
The ICE has just finished some vigorous testing on my mountain bike around backblocks and dirt roads. The motor WAS a Honda Mini 4 Stroke GX31 motor from a brushcutter which could develop 1.5HP. The 7mm rotary shaft was shortened to mate with a 9" angle grinder assembly which provided a gear reduction and right angle. This also allowed me to use the centrifugal clutch provided on the brushcutter. The output from the grinder was coupled to a freewheel clutch mounted on the opposite side to the cluster on my rear hub using a left hand thread, via a chain and sprocket. Mounting the motor rearward of the seat and just above the rear wheel was rather difficult. A bracket fixed to the rear stays and also to the point where a pack rack usually attaches provided a very solid mount. A range and speed of 50Km on a 650ml tank @ 30 - 40 Km/Hr max was achieved. Unfortunately the 7mm rotary shaft sheared in two I gather from too much vibration. A BIT NOISY BUT PRETTY GOOD!
***NOTE: I will try to post pictures and details of these assists on a web page shortly.
BACK TO THE DRAWING BOARD............................................!!!
Seeing now that I have a freewheel clutch mounted on the rear wheel I would like to revert back to an electric assist. I recently rode a USPD and found it to be well engineered and quite exhilarating. I hope to use the following motor coupled to the freewheel with a very short chain using a similar setup to the USPD. I have emailed MECI who were unable to provide specifications on these motors of which I would obviously like before making a purchase.
From: Jim Sealy Jr
Subject: Re: timing belt primary reduction
Date: Sun, 16 Jul 2000
I've used the gearhead out of an old Milwaukee 9" angle grinder with a lovejoy connector between the motor and the gearhead where it originally had a splined connection on the grinder. Looks like a windshield wiper motor on steroids with my 1/2 HP GE PMDC motor attached. It came completely sealed and is dead quiet, 15:1 gear reduction, rated at 3 HP, light (about 3 lb?)and apparently very efficient since it spins seemingly forever if given a quick turn by hand. I've seem some industrial drillheads, bandsaws, and milling machines with similarly quiet/efficient reduction boxes.. Something to look for if you're around a repair shop where they work on that sort of equipment.
Subject: Re: Pullies and belts
Date: Fri, 14 Jul 2000
Reply-To: power-assist@topica.com
... It's not too hard to drill the rear hub so a sprocket can be attached. Greenspeed has an adapter kit that allows the installation of a disk brake on a Sachs 3x7 - this is what encouraged me to drill the flange on mine and install an aluminum plate. Seens to work pretty well so far with no signs of fatigue on the flange.
From: Colin Dedman
Subject: timing belt primary reduction
Date: Thu, 03 Aug 2000
Qn - I am trying to decide what type of primary reduction drive to use on my Honda mini project. Hugh Currin used 2 1/5 3/8" belts. Would a ribbed v-belt be a better choice for 1.5 hp @ 7000 rpm ?
I would lean towards a toothed belt because they have the thinnest section, and therefore lowest loss at high RPM. ... it would appear that a 9mm wide, 5mm pitch Powergrip GT profile toothed belt would easily handle your requirements. Minimum recommended pulley size would be about 22 groove, or 35mm diameter.
Hi again, I incorrectly thought that the "ribbed V-belt" you were considering was a standard single-section V-belt with ribs running along the length of the belt. These are known as "cogged belts", and offer slightly higher efficiency with small pulleys than a standard V-velt because they flex more easily.
In fact you were referring to what I know as "Poly-V" belts, and I agreee that they would be a suitable choice for you application of high speed (7000RPM) and a small motor pulley. If absolute maximum efficiency is important to you then the toothed belt suggested above is the better choice but, for practical purposes, a Poly-V belt would be just fine.
You mention the possibility of a 16 rib J section belt. According to my design manual that would be overkill. The variables are power rating, service factor, and arc of contact.
Service factor for an ICE with less than 4 cylinders, operating for under 10 hours per day, is 1.1, and that should be extremely conservative for your situation where I doubt the average service would be even 1 hour per day. I'll guess your contact arc on smaller pulley could be 145 degrees, for a correction factor of 0.9 There is another factor for belt length, but is negligible except for very short belts.
Drive Design Power = 1500x1.1/0.9 = 1800W (approx)
Next comes the tricky part - how small in diameter are you you prepared to go, remembering that belt life, efficiency and power rating-per-rib all drop with decreasing pulley diameter. Personally I would regard 32mm diameter as the minimum, and would prefer 40mm if possible.
At 7000RPM, a 32mm dia J pulley is good for 300W per rib, so you would need 6 ribs, or14mm wide. At 7000RPM, a 40mm dia J pulley is good for 520W per rib, so you would need 4 ribs, or 9.5mm wide.
Out of interest, the 9mm wide, 35mm dia toothed belt that I originally suggested has a power rating of 1750W, which is a slightly higher rating per mm of belt width compared to Poly-V, which is what might be expected given that the toothed belt has no slippage.
So, on the basis of my design manual, a 16 rib J-section PolyV belt would be overkill.
From: Colin Dedman
Subject: I want to make an electric bike
Date: Tue, 01 Aug 2000
.... The simplest arrangement is generally to use a direct roller drive from the motor to the wheel. The required roller diameter depends on the rated motor speed, but I'd guess you need about the smallest diameter possible, maybe something around 25mm. A really simple idea is to find a short length of fabric reinforced industrial hose that is a tight press fit on the motor shaft - that's what I did for my first e-bike at around 11 years of age ... You know a bit of maths, right? Well, if you know how fast the roller spins (how many times per minute) and the distance around the roller (circumference), then you could figure out how fast the outside of the roller must be moving , and therefore, the expected speed of the electric bike. An example. You measure that it is 8cm around the roller, and it rotates at 3000 revs per minute. Therefore, the outside of the roller must be travelling at a speed of 3000x8 =24,000 cm per minute. Of course, that is 240 meters per minute, or 0.24 km per minute. But there are 60 minutes in a hour, so that is the same as 0.24x60 = 14.4 km per hour.
You will find that roller drive is not perfect. It sometimes slips, and some of the motor power is lost as friction and heat. Maybe your first attempt will not travel far, or fast. It doesn't really matter though. You WILL get that bike to move under electric power, you WILL do it by using your own brains and hands, and you WILL gain a fantastic amount of fun and learning by doing it.
From: Sam
Subject: I want to make an electric bike
Date: Tue, 01 Aug 2000
Another thing that may be of help is to search "electric bicycle" in the various search engines. There are many photos of various ways of connecting a motor to one of the bike wheels (front or rear--you choose.) A tire pressure roller is certainly the easiest, and safer than a chain or a belt that must have a guard to keep fingers from being munched.
If you decide to try something fancier, you can attach a "V" pulley to the motor and connect an automobile "fan belt" to it and another pulley you attach to the wheel's axil (on the opposite side of the chain if you're using the rear wheel). You have to have a way to put tension on the belt by moving the motor up and down...and locking it in place. Some bike racks come with a spring-loaded, hinged, holder--which can be used as the belt tensioner (if you wedge and lock something beneath it). Again, you must instal a belt guard to protect fingers!! The guard could be off an old saw or other belt driven device. But you'd probably be better off if you found a plastic tray of sorts that is deep enough when inverted to cover the motor (for protection from rain)...and you may find some lengths of plastic "U" channel extrusions (or two "L's" you connect together),that could help complete the belt guard. I've seen some "computer cable management" extrusions that might work.
If you can find a cogged belt and cogged pulleys, you will have a better drive system that won't slip as easily.
From: John Bryan
Subject: Re: I want to make an electric bike
Sender: owner-ev@listproc.sjsu.edu
Although a chain drive would be more efficient, there should not be any abnormal wear with the Zap system compared to unpowered riding. The roller should never slip under ordinary conditions. If the front brake is locked and power is applied, the motors should stall. Slipping can be caused by an improper tire or incorrect adjustment of the system. I've learned though experimentation how to optimize the system and I'm very pleased with the results.
The Continental Goliath is a perfect tire for Zap use. Also, Zap switched to a new longitudinal-cut roller design several years ago that works even better than the original diamond cut roller that was used. I wore out the original roller in one ride while trying to over-optimize the adjustments. Now after 500 miles on the system, the tire still looks like new even after taking out that roller, and smoking the tire at a NEDRA drag race. The only condition that I've found will cause slippage is snow, which causes icing of the roller with no resultant wear. In rain, the motor needs to be locked into regen position to prevent slippage.
The critical adjustments are the distance that the roller rests off-tire while unpowered, and the amount of tension on the pivot screws where the motors rotate, which should be lubricated. The type of tire is the most important thing though, as is proper tire pressure.
Date: Tue, 1 Aug 2000
Subject: I want to make an electric bike
Sender: owner-ev@listproc.sjsu.edu
Hello Mica, you and your dad might find some of the information at http://www.econogics.com/ev/evbikes.htm to be helpful.
You need at least four more things. 1) a charger for the batteries 2) a way to connect the motor to a wheel 3) a way to control the power 4) at least one fuse Personally, I would also recommend an ammeter and a voltmeter, but it is possible to work without them. Chargers are pretty easy to find. An automotive type will work if you have a 12-volt battery system (which would match your motor). Otherwise, some surplus stores carry chargers.
You have to decide if you want to power the front or rear wheel. Both have been done. The simplest system is to put a roller sleeve over the shaft of the motor, then mount this on the front forks so that the roller sleeve is horizontal and pressing down on the tire. Maximum speed is controlled by the diameter of the roller sleeve. Bigger roller gives higher speed, and uses up the battery faster. Smaller roller means lower top speed, but the battery will last longer.
It is also a good idea to have this unit on some kind of lever so that it can be lifted off the tire when you want to pedal the bike normally.
Personally, this is the approach I would go with. Some have tried driving the chain to the rear wheel, but this is more complex, and not much better in terms of efficiency.
Now you need some way to control the speed. There are several approaches. The simplest is an on/off switch. If the maximum speed is low enough, and the switch is strong enough, this can work. The switch can also be used to control a relay, (like the relays used for fog lamps on cars). You can also use a multi-position switch, with some resistors, to control speed in steps. In some electric devices, 3 speeds is common - 1st speed (slowest) has 2 resistors in series in the power circuit. 2nd speed (medium speed), shorts out one of the resistors, leaving one in series with the power circuit. 3rd speed shorts out both resistors, and puts the full battery voltage to the motor. The resistors reduce the voltage from the battery to the motor, and thus the power to the motor. Caution: use very robust resistors, or they will burn up. Warning: the resistors get very hot, so they should be inside a cage where you cannot touch them. The system should be designed so that the resistors are used mostly for starting out from a stop, and not for running the bike continuously. This is because you want to use the electricity in the battery to move the bike, not to heat up the resistors, so you can go farther.
You can also buy a small electronic controller. These are a little expensive to very expensive. Some people have tried to build their own, but I don't know of anyone who has done this successfully and cheaper than just buying one. I think someone else is writing to you about electronic controllers.
The fuse(s) should be installed near the batteries. Automotive fuses should work well for your project. Start with lower power fuses (perhaps around 10 amps). These should be good for testing. Fuses are meant to protect the batteries, other electrical equipment and YOU if there is a problem. Please make the fuse the first part of your project. When you start riding, and if the 10 amp fuse blows (but is still ok for testing), then you can move up to 15, 20, 25 or 30 amp fuses until you find one that does not blow easily or quickly. It will still blow if it needs to protect you.
For wiring, I recommend you go with about 10 gauge wire, flexible, stranded, insulated, copper wire. You should be able to get this at an automotive supply store, as well as crimp-on connectors that will work with it. The 10 gauge wire will be big enough for the kind of power you should be using that it will not get hot.
Subject: Re: Left side sprocket mounting
Date: Thu, 31 Aug 2000
Reply-To: power-assist@topica.com
Re: mounting freewheels on left side of hubs
The bodies of most BMX frewheels seem to be quite deeply case-hardened rather than a solid piece of hardened steel. This keeps them tough, and cheaper to manufacture. I've discovered that (after dissassembly) a carbide bit and lathe will clean off the threads leaving a smooth bore. Believe it or not, it's then possible to cut three transverse grooves with a hand file into this bore, about 2mm deep. The freewheel can then be mounted on a suitable carrier. Lots of work, but strong and compact. I have mounted two separate freewheels this way on the input side of a Sachs 3 X 7 hub (internal 3-speed hub). This allows for separate motor/pedal input to the hub, with independant freewheeling of either system. (Three "keys" engage the slots in the casette carrier, and the slots in the inner bore of the modified freewheels. A larger sprocket is mounted on one of the freewheels for the motor drive) Another approach to your dilemma of mounting a right-hand threaded BMX freewheel on the left hand side of a standard hub is to find the type of freewheel which has four really beefy notches in the threaded body, designed for the remover tool. Positioned on the left hand side of a wheel these notches can engage projections on a suitable carrier. Anyway you look at it, there's a bit of custom machining involved. The strongest and most elegant carriers will bolt to the spoke flange of the hub, with the spokes attaching to a slightly large flange on the carrier. Custom spokework, but bulletproof. Depends how much torque and service life you're designing into the system. Maybe the quickest, strongest, and dirtiest way to set up your freewheel is to have a carrier made up with a right hand thread, spin your freewheel onto it, and have a keeper ring skillfully welded onto that part of the carrier which projects through the middle of the freewheel. (quick shots with a TIG or MIG welder and cool the piece frequently to avoid destroying the temper in the critical bearing lands and pawls). "Dirtiest" because you cannot dissasemble or remove the freewheel in this case. Yet another approach is to have a hub made which accepts two unmodified BMX freewheels on the right hand side, allowing for independant input. Not what you had in mind though. I hope this is helpful.
Mailing-List: list power-assist@yahoogroups.com
Date: Wed, 27 Jun 2001
The current Jun/July issue of HomePower magazine has a report on 20yearold lead-acid batteries used in a solar- electric power system (page50) as well as How to Build a Voltage Monitor (page56) and a report about a trike powered by an electric-drill motor (page84)... the entire table of contents can be viewed at: http://www.homepower.com/contents.htm
and/or goto:
http://www.homepower.com/download.htm
in order to download .pdf files of the entire issue or any of 3 section as follows:
Entire HP #83 (June / July '01), in Acrobat format. (9± megabytes) or HP #83 broken into segments:
Pages 1-43 (3.2± megabytes)
Pages 44-89 (2.0± megabytes)
Pages 90 to end (3.8± megabytes)
From: "Matt Strobl"
Mailing-List: list power-assist@yahoogroups.com
Date: Tue, 29 May 2001
Subject 35MPH 46cc Chainsaw scooter
I finally finished my 40MPH 46cc Chainsaw engine powered Go-Ped scooter and got the website updated. It ended up being a 35MPH Go- Ped, the higher gearing was just too slow on takeoff and hills. I expected to build this in a couple weeks, but it took me 4 months with the sheet metal and everything! It was a lot more work than I expected to get everything right. Pictures and drawings are all here: http://www.geocities.com/ResearchTriangle/Forum/5450/goped
The unique thing about this machine is that it uses gear drive. A special cut gear attached to the rear wheel meshes with a chainsaw clutch sprocket. It makes for a very compact efficient design. So far I only have about 30 miles on it and it shows no signs of wear.
Date: Tue, 15 May 2001
From: David Rodenhiser
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.
Mailing list power-assist@yahoogroups.com
Date: Thu, 08 Mar 2001
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.
From: Frank Sant'Agata
Promise
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
http://TimelessMiracles.com/projects/right.jpg
Mailing list power-assist@yahoogroups.com
Date: Tue, 27 Mar 2001
Subject: Help identify motor
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.
Mailing list power-assist@yahoogroups.com
Date: Fri, 02 Mar 2001
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
http://www.geocities.com/ResearchTriangle/Forum/5450/goped/
From: power-assist-owner@yahoogroups.com
Date: Fri, 9 Mar 2001
Check out my HondaGX31 recumbent. The drive system could work on a mnt bike. Mount the motor on a heavy duty bike rack with custom supports. Bolt on a freehub based mid drive below saddle. MAKE CHAIN GAURDS ! Run chain from BB up to mid drive, using only granny gear. Have four gears in the mid drive with a chain angling down to rear dearailer (which would probably need to be ratated about 30 deg counterclockwise). http://mars.ark.com/~rossjudy/page2.html
From: :power-assist-unsubscribe@yahoogroups.com
Date: Mon, 21 May 2001
My left hand drive solution,
using a chunk of a coaster brake hub brazed to a steel
hub: http://www.outsideconnection.com/gallant/hpv/powerassist/5_16_2001/hub1.jpg
From:: Power-assist@yahoogroups.com
From: "Andy Johnson" ajohn@oneimage.com
Subject: [power-assist] Zeta 111
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
easily switchable.
From: "Matt Strobl" matt_strobl@yahoo.com
Subject: [power-assist] The Best Hub Motor.
From what
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.
Date: Thu, 28 Jun 2001
Subject: [power-assist] Ecycle motor and serious performance
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 -----------------------------
----------------------------- LOW-SPEED/HILCLIMBING
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 -----------------------------
Comments.
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 ...
From: denbecr@aol.comDate: Sat, 13 Oct 2001
Subject: ICE power trailer description
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.
From:
"Allen, Todd" todd.allen@midwaygames.comDate: Sun, 18 Nov 2001
Subject: How many watts do you need?
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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