Renewable energy exercise bike

hi every one

here I am back with a new project

as Mary is a keep fit freak and is turning our conservatory into a gym

with treadmill and weight machine I thought I would make use of that energy that she's just wasting and turn it into power

after all that's what Renewable energy is all about

recycling it so its not wasted :)

I have seen exercise bikes on the Internet using dc motors running off the bike tire

which is noisy and and creates friction tiring you out more quickly

so I decided to design one of my own on my cad.

Cad drawings are here to download at the bottom of the page for more detailed but you will need a cad or DWG viewer to see them

parts needed are:

old bike


copper wire

40 mm box steel (1-1/2" )

2 steel plates 480 mm 4mm thick

fiberglass resign

fiberglass matting


nuts and bolts


the 2 plates I used was 2 old saw blades but they are very hard to cut and cannot be drilled

I had to use a plasma cutter to do all the work on them.

Here is the cad layout of the coils not a clear pic but you can just make it out.

The first thing to do is make the coils I used 14 AWG (1.60mm) copper wire Polyester 200 Dual Coat

Temperature Class - 212 Degrees Celsius

52 turns per coil this was the max size of the coil I could fit in the size of the stator

the center of the coil is the same size of the magnets I am using to max the magnetic field to the center of the coil

as this is a 12volt unit 52 turns will be plenty but if you need to make a 24volt the min of

72 turns will be needed or 48 volt 144 turns

but thinner wire can be used as the amps will be lower for the same watts output

watts are watts no matter what the volts are

its the amps that get bigger on lower volts that's why you need thicker wire for 12volts

eg: 12v divided by 100watts = 8.33amps

24v divided by 100watts =4.16 amps

as you see the amps have halved

as I am going to wire this into the 12v wind turbine system I already have I am staying with 12v

I will need 18 coils for the 3 phase stator

6 coils on each phase

there you are 18 coils

this took 1 night to wind watching TV :)

I made a winding former to make them all the same size


now the coils are made

the cast for the stator is to be made

3 sheets of mdf or ply can be used 30"inch square

mark out the center of each board

to draw out the circles I used a aluminum rule and drilled holes in it

at the size I needed to make it perfectly round.

On one sheet of board draw 2 circles 580mm and 280mm

cut out the 580mm hole first

this board is the center board of the mold place it on top of one of the other boards and screw it down

now cut out the the 280mm out of the part you just cut out of the part above

this is the center part of the mold put it in the center and screw it down

the coils will fit in like above 20 degree's apart

in this pic you will see 2 more lines !

these mark where the coils fit 512mm and 329mm .

the last board will fit on top after the cast has been pored

before casting paint the mold first to stop it being porous and the wax it to stop the cast sticking to the mold.

Now your mold is ready

lay in the coils as above

before casting the coils need to be connected to each other

cut the ends of the coils to length and burn off the coating with a blow torch

and sand it after cooling as above.

It is important that the center of one coil connects the the next outside coil

on every third coil as there are 3 phases do one phase at a time that's every third coil

solder the 2 ends together like above

remember the outside of the coil must connect to the center of the next coil in that phase

insulate the joint using electrical tape or heat shrink

when all the connection have been made you will have 6 ends left

3 ends for the start of each phase A B C

and 3 for the end of each phase D E F

it will be a good thing to mark them to help you later

lay the ends outside the mold

now it is ready for casting

cut out 2 circles of fiberglass matting to fit inside the cast

one under the coils mix the resign and pore over the coils

place the second matting over the top pore a little more resign over the matting

now screw down the top of the mold tight

and let it dry.

Sorry had no pic of this as it needs to be done quickly

no one to do pic (Mary was in farmville ) lol

now the magnet rotors

here is the cad pic of the rotor


here are the 2 saws I used

I use saws because as they run true better that plate

but they are very hard to cut.

I did all the work on the saws with a plasma cutter

cuts like a hot knife through butter :)

here's one I did earlier :)

cutting a 36mm hole out the middle for the spindle to fit in

the spindle is the center from the back wheel of the bike

after removing the rim and spokes.

On the opposite side from the sprocket (cog) where the spokes fit

will have to be removed so it will fit through the hole in the plate.

The other side of the spindle sprocket side this welded to the plate

as above

mark out were the magnets will fit

I printed out a part of the cad drawing at 1:1

and use it as a template the magnets are 15 degree's

here are the magnets all 100 of them

size 25mm x50mm 3mm thick (1" x 2" 1/8 thick)

on each plate there are 24 magnets

so I will need 48 magnets doubled up to make a 6mm thick magnet stronger magnet

now I can hear you asking what not buy a 6 mm magnet?

these was on offer :)

they worked out cheaper :)

this is a magnet pole finder

very handy to have

stick the magnets on with super glue

with the poles north south north south and so on

be very careful with strong magnets

this one flew out my hand and shattered

good job I go a spare

here they are all stuck on

now you can see the spindle on the other side as well

here is the second rotor all fin

after bonding it in the same way as the stator

to help keep the magnets in place

both rotors need bonding

here is the rotor overlay over the stator

to show how the magnets react with the coils

over 5 degree's rotation the magnet is over the next phases coil

now the rotors are done

to the stand for the bike

here is the stand after fabricating the parts

out of 40mm thin wall box steel

here is the stand slotted together

the arch is were the stator and rotor fits

here it is after a coat of paint

now to put it all together


putting in the rotor and stator

after fitting the stator housing the bike frame

the bike frame was a little shabby so I spoofed it up with green spray paint :)

now for the connections

the 6 wires coming out of the stator

need to be trimmed and cleaned bear

drill a hole next the each wire that comes out of the stator

as above

the three wires that was marked up as A B C

are the ones that will be connected to the control panel

as above

the other 3 will be wired together

as above

they will need to be covered before uses

as it is possible to produce high AC voltage

crimping the ends on the 6mm cable

here is my spaghetti box lol :)

this is my homemade bridge reflector 30AMP

the blue yellow and red wire are the ones that come from the stator AC power.

The 2 connection at the bottom are the DC power output

here is the cad layout of the bridge reflector

also a homemade 1 amp 12 volt regulator

for powering the 2 digital volt and amp meter

and cooling fan

here is the panel closed up and mounted on the front of the bike

a amp meter on the left volt meter on the right

a cooling fan in the middle

1amp fuse for the power regulator

30amp fuse for the main power cable

here I am giving it a test run

I hit 21AMPs peek

didn't last long at that speed lol

I averaged at 7- 8amps

at normal biking speed

after a coat of paint it's all finished



here are the cad drawings to down load