Building a 55 MPH Bike

 

 

 

 

 

 

 

 

 

 

 

 

1. Introduction ………………………………………………….. 5
Why build an electric bike? ………………………………………….. 6
Safety ……………………………………………………………………. 7
2. Choosing a Bike ……………………………………………… 8
Frame ……………………………………………………………………. 8
Fork …………………………………………………………………….. 11
Handlebars and Stem ………………………………………………… 12
Pedal Drive train ……………………………………………………… 12
Brakes ………………………………………………………………….. 13
Rims …………………………………………………………………….. 15
Tires …………………………………………………………………….. 16
Kickstand ………………………………………………………………. 18
Accessories …………………………………………………………….. 18
3. Choosing Electrical Components ……………………… 20
Motor ……………………………………………………………………. 20
Controller ………………………………………………………………. 21
Batteries ……………………………………………………………….. 24
BMS …………………………………………………………………….. 31
Throttle …………………………………………………………………. 35
Cycle Analyst ………………………………………………………….. 36
Wire and Connectors …………………………………………………. 37
DC/DC Converter ……………………………………………………… 40
Charger ………………………………………………………………… 40
Auxiliary 12 volt output ……………………………………………… 43
Accessories …………………………………………………………….. 43
4.Building the Bike …………………………………………… 44
Fitting the Motor ……………………………………………………… 44
Motor Cooling …………………………………………………………. 53
Making a Torque Arm ………………………………………………… 58
Building Battery Boxes ………………………………………………. 62
Assembling the Bike …………………………………………………. 78
Installing Drivetrain ………………………………………………….. 93
Installing the Controller ……………………………………………… 96
Riding Tips …………………………………………………………… 105

How to build a 50MPH electric bike Greg Davey
-Page 4-

"How "Build a 50MPH Electric Bike"

1. Introduction
First of all I would like to say congratulations on your decision to
build an electric bicycle that will free you from oil dependency, save
you money every time you ride, and reduce your carbon footprint. I
have been commuting to work for several years now on an electric
bike and no longer have to deal with increasing gas prices, parking,
vehicle insurance, vehicle break-ins or traffic and I’m doing my part to
fight global warming.
My goal in building this bike was to make a fast electric vehicle that
would get me to work and back in the same time or less than driving.
Actually the bike is faster during rush hour traffic because I can pass
all the backed up vehicles by riding in the bike lane and I get away
from the stress of sitting in traffic. I had no intention of pedaling the
bike when I built it as I have another mountain bike I use for
recreational riding. My commute is 15km (9 miles) each way and I do
not charge the batteries while I am at work so I needed to have a
range of at least 30km (18 miles). I usually cruise at around 65kph
(40mph) but occasionally reach speeds over 80kph (50mph). The oneway
trip that used to take me up to 1 hour in my car during rush hour
now takes me around 15 to 20 minutes on the electric bike regardless
of the traffic situation.
I have no engineering or electrical background and didn’t know
anything about electric bikes when I set out to build mine. I decided I
wanted to build a better form of transportation for my commute to
work and started doing research. After several years of trial and error
building bikes, lots of broken parts, blown controllers and melted
connectors I now have a reliable electric vehicle. It easily keeps up
with traffic, can be ridden rain or shine, and should last for many years
requiring very little maintenance.
With a few basic skills and tools I will show you how to build a high
performance electric bike that costs pennies a day to operate and has
motorcycle like performance for about the cost of a quality downhill
mountain bike. You don’t have to be a rocket scientist to build one. If
you can follow directions and use some basic tools you shouldn’t have
any problems.

How to build a 50MPH electric bike Greg Davey
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Why build an electric bike?
You may be wondering why you should build your own bike when
you can go buy an off the shelf electric bike or scooter at your local
Wal-Mart or Canadian Tire for a reasonable price. The main reason is
these bikes just plain suck. They are underpowered with small motors,
low amperage controllers, and weak batteries. This is fine if you just
want to cruise slowly at 30kph (18 mph) on a flat road down to the
local corner store and back and don’t mind pedaling to make it up any
hill, but I don’t see them as a replacement for a car. I fly past people
on these bikes like they are standing still. You see them pedaling like
mad to make it up a small hill or sometimes pushing them because
their battery died. Traffic gets backed up behind them on narrow roads
because they are moving so slowly and cars cannot pass them.
There are a few companies that do make very nice high quality
electric bikes but only if you are willing to spend up to $10000 and
most of them are still not as fast as a bike you can build yourself for a
fraction of the cost. If you are serious about replacing your car and
cutting the umbilical cord to the oil companies you need to build the
bike yourself, hand pick good quality components and modify some
parts to increase performance and reliability. This way you can build a
bike that perfectly matches your specific needs and will last for many
years.
You may be thinking why not just build an electric motorcycle
instead of using a bicycle as a platform. Well the bicycle has several
advantages. In most places you do not have to license or insure an
electric bicycle, which can save you thousands of dollars a year alone.
You can also ride an electric bicycle on designated bike routes and
paths. On a motorcycle you are obligated to obey the same rules as a
car so you are stuck waiting in traffic with every other vehicle. A
bicycle weighs much less than a motorcycle chassis, which means it
will require less power to move it. This translates to a more efficient
vehicle that can use a smaller (therefore cheaper) battery pack to
travel the same distance. One final advantage of a bicycle is it can be
locked up to a bike rack instead of parking in a stall saving you even
more money by not purchasing a parking pass.

How to build a 50MPH electric bike Greg Davey
-Page 6-

 

Safety
If you plan on building a high-speed electric bike I recommend
wearing a helmet approved for motorcycle use as well as appropriate
protection for the rest of your body including motorcycle gloves and
boots. Bicycles are not designed for high-speed use and a failure of
any bicycle component could result in a crash causing serious injury.
That being said I have been commuting on my bike for several years
now and have not had any catastrophic component failures that
resulted in a crash. It’s a good idea to check your bike over before
each ride for any cracks, damaged parts or loose bolts.
How to build a 50MPH electric bike Greg Davey
-Page 7-

2. Choosing a Bike

Heavy duty doner bike

Greg’s Doner Bike. Notice the large & heavy duty frame. A must for just about any powered bicycle.

When most people decide to build an electric bike they usually go
down to the local department store and purchase a really cheap
bicycle. This is fine for an average electric bike because they are low
cost and come as a complete bicycle ready to convert. On the other
hand if you are building a high performance 50mph bike the thought of
nothing more than $150 worth of low quality bicycle between you and
the road is not very reassuring. They also have poor geometry for high
speed cruising. That’s why I strongly suggest you purchase a better
quality bike designed to take severe abuse that has a slacker
geometry giving you a more stable platform at high speed. Making the
wrong choice here and you will end up with a bike that is difficult to
control at speed, as well as not being strong enough to handle the
added stress of carrying heavy batteries and motor, hitting potholes
and bumps at high speed and the demands of heavy braking.
You could go purchase a new bike from a reputable bike shop (not a
department store) that meets these requirements but it will be
expensive and eat into you’re ebike budget (we haven’t talked about
the price of batteries yet). I recommend looking at a good condition
used bike or bike components on eBay, pinkbike, or craigslist. This
way you can buy or build up a really good quality bike for only a bit
more money than a cheap Wal-Mart bike. I will discuss the major bike
components separately if you choose to build up your own bicycle
piece by piece but you should be able to find a complete bike that
meets all these recommendations quite easily.
Frame
The best type of frame to start with is a mountain bike frame as
they are available in a freeride and downhill configuration. Crosscountry
type mountain bikes are built with lightness as a priority and
they do not have the best geometry for high speed riding.
Freeride and downhill mountain bikes are designed for strength.
These bikes are not used for very much uphill riding so the extra
weight that comes from beefing up the frame with additional bracing
and thick welds is not a concern. They are usually made from high
quality aluminum and are designed to withstand massive abuse from
huge jumps and drops without breaking and they also have a nice
slack geometry (lower head angle) which helps keep the bike stable at
high speed.

How to build a 50MPH electric bike Greg Davey
-Page 8-

The head angle or angle at which the fork comes out of the frame
affects how the bike handles. The steeper the head angle (closer to 90
degrees) the twitchier or unstable the bike will be at high speed. A
slacker head angle (closer to 0 degrees) will be more stable at high
speed but lose some stability making slow tight turns. A slack head
angle also lengthens the wheelbase of the bike, which further improves
high-speed handling. The head angle on freeride/DH frames varies
from about 64 to 69 degrees depending on the intended use of the
bike but I think 66 to 68 is a good number to aim for. Bicycle
manufacturers will list this info on their website under frame
geometry.
There are other factors of frame geometry that can affect bike
handling and it can get very complicated but as long as you start with
a downhill or freeride type frame you should end up but a good
handling bike. A freeride frame will handle a bit better than the
downhill frame at low speed and vice-versa at high speed.
These types of frames are available in a full suspension
configuration or as a hard tail, which only has a front suspension fork.
The advantages of full suspension frames are obvious giving you a nice
smooth ride as the fork and shock absorb the bumps on the road but
they also have a few disadvantages. The rear suspension system takes
up a lot of space inside the frame that could be used for locating more
batteries and they cost a lot more than a hard tail frame. If you don’t
need very long range from your bike, hence you do not need a large
capacity battery; the full suspension frame may be a better choice. I
chose a hard tail because I wanted to maximize battery storage space
inside the frame giving me the highest capacity battery possible. I ride
mostly on smooth paved roads so can I live without the rear
suspension. If you use a wide, high-volume tire on the rear wheel it
will help absorb small bumps making a full suspension bike
unnecessary.
When selecting the frame you want the biggest frame possible to
give you the largest battery storage area inside the triangle of the
frame. I tested bikes by lowering the seat to its lowest possible
position and making sure I was only an inch or two away from resting
my feet flat on the ground while sitting on the bike.

How to build a 50MPH electric bike Greg Davey
-Page 9-
This is important because when the bike is built it will be fairly heavy and trying to
remain balanced on the bike while stopped at a red light can be
difficult if your feet are not flat on the ground. If you decide to use
smaller diameter rims, which will be discussed later, it will help to
lower the height of the bike allowing you to use a bigger frame. I
normally would ride a small or medium size mountain bike frame but
for my electric bike I upsized to an XL frame. This gives me ample
storage space in the center of the bike for batteries, yet with some
minor frame modifications and smaller rims I am still able to rest my
feet flat on the ground when seated.

3. Choosing Electrical Components
Motor
There are basically two types of motors available for electric bikes.
One type uses a small motor that is mounted to the frame of the bike
and drives the rear wheel via a chain system. These types of motors
are commonly found on lower end department store electric bikes and
one of the more popular after market conversion kit systems is called
the Currie Electro Drive conversion kit. The other type of motor system
is a hub motor that is an integral part of the wheel and has the rim
laced directly to the outside flange of the motor. This system takes up
less space on the bike than the Currie system, has less moving parts,
is more reliable and virtually maintenance free. There is also a wide
variety of hub motors available with varying power ratings so you
should be able to find one that meets your needs.Battery Pack
There are two types of hub motors, geared or non-geared. The
geared hub motors have internal planetary gears and are usually
smaller in diameter than a non-geared motor. The gears help to
increase the torque of the motor, which improves acceleration and hill
climbing ability, especially when used with lower voltage (24-36volt)
set ups that would normally struggle with a non-geared motor. Some
brands of geared motors include BMC and eZee motors.
The largest of the non-geared hub motors are able to handle much
higher voltages and power output compared to the geared motors.
They have no internal plastic gears to wear out or break and they have
physically more mass to help deal with the extra heat generated from
running at high wattage. If you want a very fast electric bike you
should look at the big Crystalyte series of hub motors, sometimes
called the Crystalyte Phoenix series or H series motors. These heavy
hub motors (23lbs) are able to handle up to 100 volts and 150 amps
while still being reliable as long as you monitor the internal
temperature closely.

How to build a 50MPH electric bike Greg Davey
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The Crystalyte motors come in several different windings. The two
most popular are the HS 3540 (higher top speed, lower torque), and
the HT 3525 (lower top speed than the HS 3540 but more torque).
The diameter of the rim you choose to lace to the hub motor and the
amount of voltage and amperage you run to the motor will also affect
the torque and top speed of the bike. If you go to www.ebikes.ca they
have a fantastic simulator on their website where you can input
various motor models, rim sizes, and voltages and it will give you a
graph showing you the top speed and torque. This is very useful when
planning your ebike build to ensure it will meet your expectations.
For this build I choose the Crystalyte 5304 motor pictured below
which is the older version of the HS 3540 motor. It wasn’t disk brake
compatible and has since been replaced by the HS 3540 motor but
they are basically the same.
This motor has a high top speed and enough torque to tackle any hill
when built into a 24” rim and powered by a 100-volt battery pack. This
set up will have a top speed of just over 50MPH and lots of low-end
torque.
If you intend on building a bike for towing a heavy trailer or are a
larger person and need to climb a lot of long steep hills the HT 3525
would probably be a better option for you because of the increased
torque.

How to build a 50MPH electric bike Greg Davey
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Batteries
Choosing batteries is probably the most important and difficult
decision when building an electric vehicle. This is definitely where you
get what you pay for. If you try to cut costs here you will end up with
a bike that underperforms and doesn’t meet your speed and distance
requirements.
Battery capacity or how long a battery will last on a single charge is
measured by how many amp-hours (Ah) it can discharge before it is
empty. If a battery can discharge 1 amp continuously for 1 hour it has
a capacity of 1 Ah. The more Ah of capacity a battery has the larger its
physical size will be if you are comparing the same chemistries. A
10Ah battery will be twice the size of a 5Ah battery if they are the
same type. Multiple batteries can be connected in parallel (all the
positive terminals connected together and all the negative terminals
connected together) to increase the capacity or Ah to your desired
level.
Watt Hours (Wh) is a more important measurement when
determining how much battery capacity you require to travel a
specified distance. It represents the total energy available in a given
battery pack. It is calculated by multiplying the Ah of a battery pack by
the total voltage of the pack. A 36-volt 20Ah pack and a 72-volt 10Ah
pack both contain 720 watt-hrs; therefore they should both be able to
get you the same distance provided you ride at the same speed. With
the 72v pack you can accelerate faster and have a much higher top
speed than the 36v pack. If you take advantage of this (it’s really hard
not to use all that extra power) and ride at a higher speed you will
encounter more wind resistance using up more power. This will result
in your distance traveled prior to the batteries running out being less
than that of the 36v pack traveling at a lower speed but you will reach
your destination faster. With a Crystalyte hub motor in a 24-inch rim
and my controller set to 90 amps I usually average around 35 to 45
watt-hrs per km (58-75 watt-hrs per mile). This is at a cruising speed
of around 65KPH (40MPH) and no pedaling. How fast you accelerate
and your top speed will influence your power consumption. It will also
vary depending on how flat or hilly the terrain is and how much weight
you are carrying. I can use less than 25 watt-hrs per KM if I ride really
slowly on flat terrain or use over 65 watt-hrs per KM riding full throttle
up hills.
When calculating how much battery capacity you need for the
distance you want to travel on your bike you should only plan onbattery cycle life (how many times it can be recharged) specifications
are based on 80% DOD. If you discharge more than this each time the
cycle life can be reduced. The batteries will also slowly lose capacity
over time so the extra 20% capacity gives you an added buffer zone
before you need to replace them. Don’t forget to add any electrical
loads from accessories that are powered from your battery pack such
as lights and a heated jacket if you intend on using one. Something
else to consider is your battery capacity will decrease as the
temperature gets colder. I notice approximately 15% decrease in
capacity when riding in temperatures close to or below freezing so you
may need a larger capacity pack if you intend on riding in cold
weather. On my daily commute I only use about 70 to 75 percent of
my battery pack with all accessories running which gives me extra
capacity if I decide to take a detour and run some errands on my way
home. If you need to use close to 100 percent of your battery pack to
reach your destination you will be constantly worried about using too
much power accelerating or fighting a headwind which could leave you
stranded with a dead battery. That’s why you need a good buffer zone
of power so you can ride stress free.
The ‘C’ rating of a battery is a number that represents the safe
continuous discharge rate (in amps) of the cell. A battery rated at 1C
can discharge its rated Ah capacity in current without damage. A 2C
rated battery can put out twice the number of its Ah rating in amps. If
a 10Ah battery is rated at 1C, its maximum discharge rate is 10 amps,
if the same 10Ah battery has a rating of 3C, it can safely discharge 30
amps. Likewise if that 10Ah battery is rated at .5C it can only put out 5
amps safely.
As you increase the discharge current from a battery the voltage
drops or sags lower as the battery struggles to crank out the increased
amperage. Good quality batteries have low voltage sag at their ‘C’
rating while poor quality batteries start to sag heavily even before
reaching their maximum ‘C’ rating. If you discharge batteries beyond
their ‘C’ rating the voltage drop increases and the batteries heat up as
they fight internal resistance which can shorten their cycle life. This is
also happen if you are just under the max C rating. The more you
abuse the batteries by pushing them to their limit, the more you
shorten their cycle life. That’s why it’s good to have some headroom
keeping your batteries happily in their comfort zone. Comparing
discharge graphs at varying loads for different batteries is the best
way to tell the good from the bad.

How to build a 50MPH electric bike Greg Davey
-Page 25-