Introduction: Friction Drive Build for Bikes

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Friction drive build for bikes

Hello to all,

I decided to build this friction drive system for my hybrid mountain bike(Carrera Vulcan disc spec) earlier this year to essentially aid me up a hill(average grade 4%) on the journey home from work.

I had looked at many other electric and non-electric drive systems, but most were too costly ranging from £600-£2,000+, heavy and bulky looking. I was looking for something small, cheaper and not too attention grabbing.

After browsing the web for a few weeks I came across a website called www.endless-sphere.com and found a post with a nice looking friction drive system titled Commuter Booster made by user adrian_sm, please take a moment to check out Adrian's website. After reading through his posts and other comments I found that this friction drive system ticked all the boxes, small, cost me <£300 and wasn't too obvious and would be best suited to assist my travels too and from work. I built my own version and that's what I'm sharing with you today.

PLEASE NOTE: This type of drive only works on rigid bikes with enough space to mount it.
(It won't work on full suspension bikes or rear suspension bikes).
Please see Friction Drive Template pdf below.

The youtube clip below shows me testing the friction drive system on my bike.

Disclaimer.
I will not be held responsible for any injuries incurred or damage caused whilst building or using a friction drive. Anyone building or using a friction drive should take personal accountability for their own actions.

Attachments

Step 1: Materials, Tools, Machinery and Parts

MATERIALS

Metals and plastics:

  • Motor Mount = Aluminium (75mm x 100mm x 12.7mm - stock sizes)
  • Bracket = Nylon 66 (30mm x 70mm x 75mm - finished sizes)
  • Spring Tension Bush = Stainless steel (19mm dia x 14mm long - finished sizes)
  • Spring Wire/ piano wire = (1.5mm dia x 400mm long)
  • Pivot Shaft = Silver steel or Stainless steel (10mm dia x 100mm long - stock sizes)

Safety wear:

    • Safety glasses
    • Safety footwear

MECHANICAL TOOLS

Cutting tools:

  • Centre BS2 (all drilled parts)
  • 3.3mm drill (spring tension bush)
  • M4 x 0.7 tap (spring tension bush)
  • 10mm drill (spring tension bush)
  • 2mm drill (spring tension bush and nylon bracket)
  • 4mm drill (pivot shaft)
  • 5mm drill (pivot shaft)
  • 4.2mm drill (aluminium motor mount and nylon bracket)
  • M5 x 0.8 tap (aluminium motor mount and nylon bracket)
  • 9.5mm drill (aluminium motor mount and nylon bracket)
  • 10mm reamer (aluminium motor mount and nylon bracket)
  • 5.5mm drill (aluminium motor mount)
  • 6mm reamer (aluminium motor mount)
  • 11mm drill (aluminium motor mount)
  • 20mm end mill / slot drill (aluminium motor mount)
  • 10mm end mill / slot drill (aluminium motor mount)
  • 6.8mm drill (nylon bracket)
  • M8 x 1.25 tap (nylon bracket)
  • 8.1mm drill (nylon bracket)
  • 15mm end mill / slot drill (nylon bracket)
  • 30mm drill (nylon bracket hole for tube size may vary)
  • Boring head / boring bar (nylon bracket)
  • Fly cutter (aluminium motor mount)
  • Tap wrench (aluminium motor mount, nylon bracket and spring tension bush)
  • Facing tool (spring tension bush)
  • Parting off tool (spring tension bush)
  • Boring bar (spring tension bush)

Hand tools:

  • Mallet (aluminium motor mount and nylon bracket)
  • Hand file (All parts)
  • Pin punch (aluminium motor mount)
  • Nail/carpenters pincers (spring)
  • Hacksaw (nylon bracket)
  • Spring mandrel (spring)
  • Square flat end bar (spring)

Machinery:

  • Hurco Hawk CNC Milling Machine (or any CNC milling machine)
    (Profiling the aluminium motor mount)
  • Bridgeport Milling Machine(or any manual milling machine)
    (All other milling and drilling operations for the aluminium motor mount, Nylon bracket and spring tension bush)
  • Harrison Centre Lathe (or any manual lathe)
    (Turned the pivot shaft, spring tension bush and spring)
  • Fly Press
    (Pressing in the pivot shaft into the aluminium motor mount)
  • Oven
    (Heat treating)


ELECTRICAL PARTS

Motor, batteries, speed controller, charger etc:


WIRING TOOLS

Wiring:

    • Weller WHS40 Soldering Station
    • Solder wire 60/40 1mm
    • Wire strippers
    • Insulation tape
    • Wire cutters
    • Soldering jig
    • Heat gun
    • Multimeter


    ASSEMBLY FASTENERS and TOOLS

    Allen key / Hex key = metric: (preferabley long series ball end)

    • 2mm (for m4 grub screw spring tension bush)
    • 2.5mm (for m5 grub screw pivot shaft locking, motor swing adjustment)
    • 3mm (for m4 socket head cap screw aluminium motor mount)
    • 6mm (for m8 socket head cap screw Nylon bracket to frame)

    Spanner:

    • 8mm open ended spanner (m5 nut, motor swing adjustment)

    Screws:

    • M8 x 40 Socket head cap screws (x2)
    • M4 x 20 Socket head cap screws (x4)
    • M5 x 20 Socket set grub screws (x2)
    • M5 x 10 Socket set grub screw (x1)
    • M4 x 8 Socket set grub screws (x2)
    • M5 full nut (x2)
    • Dowel 6mm x 20 (x1)

    Step 2: Aluminium Motor Mount

    Materials and Tools used:

    • Aluminium (75mm x 100mm x 12.7mm - stock sizes)
    • Tap wrench
    • Fly cutter
    • 10mm end mill / slot drill
    • 20mm end mill / slot drill
    • 11mm drill
    • 6mm reamer
    • 5.5mm drill
    • 10mm reamer
    • 9.5mm drill
    • M5 x 0.8 tap
    • 4.2mm drill
    • Hand file
    • Centre drill BS2 (all drilled parts)
    • Safety glasses/ Safety footwear

    SAFETY
    Safety glasses and Safety footwear should be worn in a workshop and when using machinery.

    Using a Bridgeport Milling Machine (or any manual milling machine):
    Working to the DWG, DXF and PDF drawing files :-
    Square up the aluminium plate using a 20mm end mill / slot drill, leave about a minimum of 1mm on width and length to allow for profiling later.
    Fly cut the top and bottom faces to 12.1mm thickness.**
    Drill holes using centre drill, 4.2mm***, 5.5mm, 9.5mm and 11mm drills and 6mm, 10mm reamers and counter bore with 20mm end mill / slot drill on top face.

    Using a Hurco CNC Milling Machine (or any CNC milling machine):
    Clamp part to a sacraficial piece of steel in a machine vice using M4 screws and bolt through 10 dia hole.
    Mill profile using a 10mm end mill / slot drill.(see video)

    Using a Bridgeport Milling Machine (or any manual milling machine):
    Centre drill, drill 4.2mm and tap M5 hole.

    (Remove all burrs, sharp edges etc after each operation).

    NOTE **
    Deviation from 12.1mm thickness will affect hole positions of PIVOT SHAFT

    NOTE***
    The motor used in this build had M4 bolt holes and position dimensions as the drawings above.
    Check YOUR motor mounting holes for size and position and drill accordingly as they may differ.

    Attachments

    Step 3: Pivot Shaft

    Materials and Tools used:

    • Pivot Shaft = Silver steel or Stainless steel (10mm dia x 100mm long - stock sizes)
    • Facing tool
    • Parting off tool
    • Hand file
    • Emery cloth/ paper
    • BS2 centre drill
    • 4mm drill
    • 5mm drill
    • Safety glasses/ Safety footwear

    SAFETY
    Safety glasses and Safety footwear should be worn in a workshop and when using machinery.

    Using a Harrison Centre Lathe (or any manual lathe):
    Working to the DWG and PDF drawing files :-
    Face Pivot Shaft to 98mm long and knurl one end 12mm long.
    Chamfer each end using parting off tool or a hand file.

    Using a Bridgeport Milling Machine (or any manual milling machine):
    Use the pivot shaft jig (see .DWG file and photo)
    Align end of pivot shaft jig with end of machine vice,(see photo) this ensures all 4 holes are the same distance when rotating the jig.
    Drill a 5mm hole 1.5mm deep at the knurled end and a 4mm hole 1.5mm deep at the opposite end,
    rotating the pivot shaft jig at 90 degree intervals drill a further three 4mm holes 1.5mm deep.(see .DWG file and photos)
    It is advisable at this stage(before pressing into the aluminium motor mount) to emery the pivot shaft down to about 9.98mm so that it will slide freely into the nylon 66 frame bracket.
    Note
    Hole positions may need adjusting if you deviate from DWG dimensions of Nylon 66 frame bracket(70mm) and Aluminium motor mount(12.1mm)

    Attachments

    Step 4: Aluminium Motor Mount and Pivot Shaft Sub Assembly

    Materials and Tools used:

    • Pivot shaft
    • Aluminium Motor Mount
    • 6mm Dowel
    • Pin Punch
    • Hammer
    • Bench vice
    • Flypress
    • Marker pen
    • M5x10 Socket set grub screw
    • 2.5mm Hex/Allen key
    • Safety footwear

    Using a Flypress
    using a marker pen, mark the centre of grub screw hole on the Motor Mount and pivot shaft at knurled end.(see photo)
    Push pivot shaft through 10 dia hole aligning markings, ensure the shaft protrudes on the 20dia conterbore side.(see photo)
    Use the Pivot shaft drill jig to assist with Flypressing the pivot shaft home(see photos)

    Using a bench vice
    Locate the 6mm x 19.5 long dowel in 6mm reamed hole (see photo), hammer all the way home using pin punch and hammer.(see photos)
    Ensure the dowel protrusion is max distance of 8mm.
    Finally screw in and tighten the M5x10 grub screw using a 2.5mm Hex/Allen key

    Step 5: Nylon 66 Frame Bracket

    Materials and Tools used:

    • Nylon 66 (30mm x 70mm x 75mm - finished sizes)
    • 2mm drill
    • 4.2mm drill
    • M5 x 0.8 tap
    • 9.5mm drill
    • 10mm reamer
    • 6.8mm drill
    • M8 x 1.25 tap
    • 8.1mm drill
    • 15mm end mill / slot drill
    • 30mm drill
    • Boring head / boring bar
    • Tap wrench
    • Centre drill BS2 (all drilled parts)
    • Mallet
    • Hacksaw
    • Bridgeport Milling Machine (or any manual milling machine)
    • Safety glasses/ Safety footwear

    SAFETY
    Safety glasses and Safety footwear should be worn in a workshop and when using machinery.

    Using a Bridgeport Milling Machine (or any manual milling machine):
    Mill to dimensions 70** x 75 x 30mm flat and square with 20mm end mill and fly cutter.
    Working to the DWG, DXF and PDF drawing files:-
    Drill 6.5dia x 50 deep, drill 8.1dia x 29 deep, counter bore 14 dia x 8 deep, start M8 tap hole by hand in chuck to make sure its square.
    Sit on parallels and Drill 9.5dia and Ream 10dia through, counter bore 15.80dia x 13 deep, drill 2dia hole 10 deep.
    Sit on parallels and drill and bore tube size hole, next use centre drill to mark a guide line for cutting apart later(see photo).
    On opposite side of part drill 4.2dia x 11 deep (start tap M5 hole by hand in chuck to make sure its square finish later)
    On end drill 4.2dia x 11 deep (start tap M5 hole by hand in chuck to make sure its square finish later).
    Chamfer all corners where part allows 1.5mm or 0.75mm

    Using a Hurco CNC Milling Machine (or any CNC milling machine):
    Setup in vice and mill segment pocket 8 deep(see photo .DXF file)

    Using a bench vice
    Finish Tap M8 holes and M5 holes.
    Nylon 66 tends to leave drilled, reamed holes a little smaller than in steel or aluminium so, check that the pivot shaft slides freely through the nylon 66 bracket, if not free then you may need to make a
    polishing stick from either steel:-
    8mm dia and hacksaw slit down as far as the width of some emery and use a drill to polish the hole
    or
    wood:-
    wrap some emery around a piece if doweling or similar and polish it out by hand.
    Hacksaw through part, carefully following the guide line marked earlier.

    Using a Bridgeport Milling Machine (or any manual milling machine):
    Mill a minimum cut across sawn edges to flatten and square it up.

    Deburr as needed

    NOTE**
    Deviation from 70mm dimension will affect the PIVOT SHAFT hole positions

    Attachments

    Step 6: Spring Tension Bush

    Materials and Tools used:

    • Stainless steel (19mm dia x 14mm long - finished sizes)
    • Tap wrench
    • Centre BS2 (all drilled parts)
    • 3.3mm drill
    • M4 x 0.7 tap
    • 10mm drill
    • 2mm drill
    • Facing tool
    • Parting off tool
    • Boring bar
    • M4x8 socket set grub screws(x2)
    • 2mm Hex/Allen key
    • Safety glasses/ Safety footwear

    SAFETY
    Safety glasses and Safety footwear should be worn in a workshop and when using machinery.

    Harrison Centre Lathe (or any manual lathe):
    Working to the modified PDF drawing file
    Face up part with facing tool then using a centre drill, drill 10mm hole.

    EDITED
    The spring has been modified (See modified spring details) and you will NOT need to use the boring bar to turn 16mm diameter x 1.6mm deep recess.
    Part off to14mm long.

    Bridgeport Milling Machine (or any manual milling machine):
    Setup job in vice, grip across 14mm length to centre drill and drill a 3.3mm hole through.
    Setup job in vice with veeblock and centre drill and drill a 2mm hole through.(see photo)
    EDITED
    Added another 2mm hole at 22.5 Deg to existing hole to allow more fine tuning of the spring (see photo, PDF)

    Using a bench vice:
    Tap the M4 grub screw holes.
    Loosely fit both of the M4 grub screws.

    Deburr as needed

    Attachments

    Step 7: Spring

    Materials and Tools used:

    • Spring Wire or Piano Wire = (1.5mm dia x 260mm long) Edited
    • Spring mandrel
    • Nail/carpenters pincers
    • Square flat end bar
    • Safety glasses/ Safety footwear

    SAFETY
    Safety glasses and Safety footwear should be worn in a workshop and when using machinery.

    Using a bench vice:

    EDITED
    After making several more springs and assemblies, I found the spring performed better coiled in the opposite direction tothe original. Also I discovered a better way was to form both of the legs first.
    All photos and PDF's now show the Modified Spring.

    Bend one end of the wire to form a 10mm long leg at 90 degrees.
    Bend other end of wire to form a 15mm long leg at 90 degrees but in the opposite direction to the first.

    Using a Harrison Centre Lathe (or any manual lathe):
    Working to the PDF drawing file:-
    Place spring mandrel in lathe chuck insert 10mm bent end of wire into the mandrel hole so that the wire is pointing upwards (see photo), using the square bar with a flat end in the tool post, move towards the wire leaving a little clearance so as not to trap the wire against the mandrel.
    EDITED

    Rotate the lathe chuck towards yourself (see photo), approximately 6 full rotations should take you to the end of the wire.
    As you approach the final turns use the pliers to ensure the legs are opposing each other.

    CAREFULLY (be aware of the wire springing back) move the bar away from the spring so you can remove it from the mandrel.
    If you forgot to form both legs first then you can always bend the other leg later by making yourself a bush 25 dia x13 long with a drilled hole 14mm to enable you to bend the other leg(see photos)

    Using a bench vice:
    Bend the other end of wire in vice 15mm long 90 degrees.(see photos)
    Using Nail/carpenters pincers cut leg 15mm long

    Using an oven:
    To heat treat the spring place it on a metal tray in an oven for 30mins at 250C.
    Remove from oven and leave to cool naturally.

    NOTE
    Don't worry if your spring is not perfectly coiled or the legs are not quite inline with each other.
    As long as the spring will fit over the pivot shaft and you have made the Modified Spring Tension Bush with 2 holes, then you should have enough adjustment to suit your motor

    Attachments

    Step 8: Parallel Lipo Battery Leads

    Materials and Tools used:

    • Weller WHS40 Soldering Station
    • Solder wire 60/40 1mm
    • Soldering jig
    • 10 awg Silicone Wire (1metre Black)
    • 4mm Bullet connectors (male x6, female x4)
    • Wire strippers
    • Wire cutters
    • Heat shrink 5mm x 150mm, 15mm x 80mm (Red and Black)
    • Heat gun
    • Copper olive 15mm (x2)
    • Insulation tape
    • Pliers/pipe pliers
    • Multimeter

    Preparing the wire
    I used black wire as you can see in the photo, but you may want to use 500mm of red and 500mm of black for clarity when connecting up later.
    Cut 10awg silicone wire into 100mm lengths(x5).
    Remove 4mm of insulation at one end and 15mm at the other end.
    Twist together 4 wires (all same colour) at the 15mm bare end, and lay ontop of the twisted end another piece going out the opposite direction.
    Slide the copper olive along over to the twisted area and crimp the olive tight over the wires using the pliers.
    Using a multimeter check for continuity of the crimped parallel leads, set the dial to the musical note(see photo) and then keep one probe on the single wire end and then touch the other probe to each of the four other wires and if you hear a tone then all is well, if not then crimp tighter or add some solder to the joint until you have a good connection.
    Wrap some insulation tape around the crimped joint.
    Cut a piece of heat shrink 15mm x 40 long (RED for positive,or BLACK for negative), slide over the crimped joint and use heat gun to shrink in place to secure and insulate the joint.

    Repeat the above for the second lead.

    Soldering Positive lead(Red)
    Twist the wire at the single end of the lead and slide into a MALE bullet connector
    Using the soldering jig(see photo), grip the bullet connector with the tiny solder hole upwards and wire in a horizontal position.
    Set the soldering station to a high temperature as the wire and bullet connector need to become hot enough to melt the solder.
    Place soldering iron tip in contact with and under the bullet connector near where the 10awg wire enters and allow a few minutes for the iron to heat up the parts to be soldered(DO NOT TOUCH PARTS VERY HOT),still keeping the soldering iron in contact apply the solder to the bullet connector through the tiny soldering hole; the solder should melt so keep feeding the solder in until you see it escaping near the 10 awg wire now remove the soldering iron from the parts and allow the soldered parts to cool down for a few minutes as they will be VERY HOT.

    Repeat the above with the other 4 wires using all MALE bullet connectors.

    Use the multimeter to check the integrety of the soldered connector.
    Cut 5 pieces of 5mm x 30mm long RED heatshrink, slide part way over bullet connector and over the 10 awg wire and use heat gun to shrink in place to secure and insulate all the joints.

    Soldering Negative lead(Black)
    Twist the wire at the single end of the lead and slide into a MALE bullet connector
    Using the soldering jig(see photo), grip the bullet connector with the tiny solder hole upwards and wire in a horizontal position. Set the soldering station to a high temperature as the wire and bullet connector need to become hot enough to melt the solder.
    Place soldering iron tip in contact with and under the bullet connector near where the 10awg wire enters and allow a few minutes for the iron to heat up the parts to be soldered(DO NOT TOUCH PARTS VERY HOT),still keeping the soldering iron in contact apply the solder to the bullet connector through the tiny soldering hole; the solder should melt so keep feeding the solder in until you see it escaping near the 10 awg wire now remove the soldering iron from the parts and allow the soldered parts to cool down for a few minutes as they will be VERY HOT.

    Repeat the above with the other 4 wires using all FEMALE bullet connectors.

    Use the multimeter to check the integrety of the soldered connector.
    Cut 5 pieces of 5mm x 30mm long BLACK heatshrink, slide part way over bullet connector and over the 10 awg wire and use heat gun to shrink in place to secure and insulate all the joints.

    NOTE
    Use 10mm heat shrink to shield any exposed bullet connectors to eliminate shorting out when connecting and disconnecting for charging the Lipo's

    Step 9: Power/Kill Switch Lead, Motor Lead

    Materials and Tools used:

    • Weller WHS40 Soldering Station
    • Solder wire 60/40 1mm
    • Soldering jig
    • 10 awg Silicone Wire (2 metres Black)
    • 4mm Bullet connectors (male x4, female x4)
    • 6.35 spade crimp terminal female(x2)
    • Heat shrink Black (5mm x 30mm, 15mm x 600mm)
    • Heat shrink Red (5mm x 200mm, 15mm x 40mm)
    • Rocker switch
    • Wire strippers
    • Wire cutters
    • Heat gun
    • Insulation tape
    • Multimeter

    IMPORTANT
    I strongly advise that you fit some form of a Power/Kill Switch, which will disconnect the battery power from the circuit.
    The Power/Kill Switch should be situated in an easily reachable/accessible position.
    (If the throttle connection to the servo tester was to become disconnected, the motor could be active continuously)

    Power/KillSwitch Lead
    Cut 2 pieces of 10awg silicone wire 500mm long and bare each end of both wires about 4mm long.
    Crimp a 6.35 female spade terminal to one end of each wire.
    Use the soldering jig to solder a MALE 4mm bullet connecter to one wire and a FEMALE 4mm bullet connector to the other wire.
    Check continuity and integrety of the joint using the multimeter.
    Cut 2 pieces of Red heat shrink 5mm x 30mm, slide onto the bullet connector end and use the heat gun to shrink in place.
    Connect each of the spade end terminals to the rocker switch, and test with the multimeter by holding one probe to the female bullet connector and one probe to the male bullet connector, when the switch is operated it should complete the continuity circuit and you will here a beep.
    If no beep is heard check connections are tight, you may also need to check the switch directly to seeeif this is ok.
    If all is well then you can insulate the connection at the switch end with tape and also use a piece of Red heat shrink 15mm x 40mm.
    Finally cut a piece of Black heat shrink 15mm x 400mm and slide over both the wires and use the heat gun to shrink the wires neatly together.

    Motor Lead
    You could substitute one length of wire here for Red 10awg silicone wire, for clarity when connecting up later.

    Cut 3 pieces of 10awg silicone wire 260mm long and bare each end of all wires about 4mm long.
    Use the soldering jig to solder 1 MALE 4mm bullet connector and 1 FEMALE 4mm bullet connector to each wire.
    Cut 2 pieces of Black heat shrink 5mm x 30mm and shrink fit these to each end of one piece of wire (black)
    Cut 2 pieces of Red heat shrink 5mm x 30mm and shrink fit these to each end of one piece of wire (Yellow)
    Cut 2 longer pieces of Red heat shrink 5mm x 40mm and shrink fit these to each end of one piece of wire (Red)
    Finally cut a piece of Black heat shrink 15mm x 200mm and slide over all three wires and use the heat gun to shrink the wires neatly together.

    NOTE
    Once the motor lead is connected, the motor may be rotating in the wrong direction; if so all you have to do is swap over the 2 red heat shrunk wires.
    You may want to mark the wire going to yellow with some yellow tape or something so you can disconnect and reconnect without worrying about the motor rotation direction.

    Use 10mm heat shrink to shield any exposed bullet connectors to eliminate shorting out when connecting and disconnecting.

    Step 10: Speed Controller, Servo Tester Modification, Thumb Throttle

    Materials and Tools used:

    • HobbyKing 85A Blue Series Brushless Speed Controller 5A SBEC
    • Etronix 3 Mode Servo and ESC Tester
    • Thumb twist throttle
    • Weller WHS40 Soldering Station
    • Solder wire 60/40 1mm
    • Soldering jig
    • 4mm Bullet connectors ( female x5)
    • Heat shrink Black (5mm x 60mm)
    • Heat shrink Red (5mm x 90mm)
    • Wire strippers
    • Wire cutters
    • Heat gun
    • Insulation tape

    Speed Controller battery side
    Using the soldering jig, solder 2 female 4mm bullet connectors to the battery side (red wire, black wire) of Speed controller.
    Cut 1 piece black heat shrink 5mm x 30mm and 1 piece red heat shrink 5mm x 30mm, use heat gun to shrink 1 piece each wire.

    Speed Controller motor side
    Using the soldering jig, solder 3 female 4mm bullet connectors to the motor side (3 black wires) of Speed controller.
    Cut 1 piece black heat shrink 5mm x 30mm and 2 piece red heat shrink 5mm x 30mm.

    NOTE
    You might want to be sure of motor rotation at this point before shrinking the 3 black wires to match the motor colours.
    When satisfied use heat gun to shrink one piece to each wire.
    Use 10mm heat shrink to shield any exposed bullet connectors to eliminate shorting out when connecting and disconnecting.

    Servo tester modification
    When using a motor and a speed controller we need some way to regulate the amount of throttle used, which in most cases comes by the way of a transmitter and reciever as used with radio controlled models.
    We are not planning to control the Friction Drive unit wirelessly so we are going to use a servo tester connected to a Thumb throttle.

    Remove potentiometer thumb screw, separate at the join the flimsy outer covering of the servo tester and proceed to
    remove, desolder the potentiometer and solder a jump wire across the 2 terminals of the servo tester.(see photo)
    Refit outer covering, at this point i wrapped it with insulation tape just leaving access to the two sets of 3 pin connectors, one for the throttle and the other for the speed controller to attach.(see photos)

    Thumb throttle
    Take note of the order of the wires and the type of the connector fitted.
    You need to make sure they are in this order Black, Red, colour(see photo) they might be blue as shown in picture or white or other.
    Solder as shown for a permanent connection, or obtain and solder a female 3 pin JR plug(see photo) and have the ability to disconnect and reconnect as desired.

    IMPORTANT
    If you choose to fit a 3 pin JR plug to the throttle wire, then you MUST ensure that this connection to the modified servo tester is secured with electrical tape or similar so that it cannot accidently loose connection.
    This could result with the motor being activated continuously, hence the reason for a Power/Kill Switch.

    Step 11: Friction Drive Assembly

    Materials and Tools used:

    • C6374/08 KV200 Brushless Motor
    • Motor mount sub assembly
    • Nylon 66 frame bracket
    • Spring
    • Spring tension bush
    • 8mm spanner
    • M4 x 20 long Socket head cap screws (x4)
    • M5 x 20 long Socket set grub screws (x2)
    • M5 full nut (x2)
    • M8 x 40 Socket head cap screws (x2)
    • M4 x 8 Socket set grub screws (x2)
    • Dry Teflon bike lube
    • Hex /Allen keys 2mm, 2.5mm, 3mm and 6mm (preferabley long series ball end)

    Assembly
    Starting with the nylon 66 bracket screw in the 2 m5 x 20 grub screws so that the inner end is level with the edge of the segmented pocket, loosely screw on the M5 full nuts. Insert the spring short leg first into the other end of the nylon 66 bracket (see photos).
    Slightly raise the nylon 66 bracket above the aluminium motor mount so that the spring leg protrudes above the pivot shaft, this will allow you line up the leg with the 2mm hole of the spring tension bush fitted counter bore side first, as you now slide that all the way home (see photos).

    EDITED

    Depending on which direction you form the spring, the the tension applied could be CLOCKWISE or ANTICLOCKWISE. (See spring section).
    The spring should be set so as to lift the motor towards the wheel, but only enough tension to allow the motor to drop away from the wheel when the drive is disengaged.
    To set the tension; rotate the Spring tension bush 1/4 to 1/2 turn CLOCKWISE / ANTICLOCKWISE until you find a corresponding hole in the pivot shaft, use the 2mm Hex/Allen key to assist and then finally tighten the M4 grub screws
    Using the M4 x 20 Socket head cap screws and the outer 4 holes on the motor mount to secure the C6374/08 KV200 Brushless Motor, taking note of where the wires are located(see photo)
    Although not neccessary at this stage you can attach the other half of the nylon 66 bracket with the M8 socket head cap screws.

    NOTE
    Do not over tension the spring as this could leave to the legs getting bent and loose its location in the 2mm hole.

    Step 12: Fitting Friction Drive to Bike

    Materials and tools used:

    • Friction drive assembly
    • Straight edge (steel rule or length of wood)
    • 8mm spanner
    • Hex/Allen key 2.5mm and 6mm
    • Tape

    Fittingthe drive unit
    Offer the friction drive unit to the seat post frame so that the motor is about 10mm away from the tyre in its lowest retracted position and lightly tighten the M8 socket head cap screws, so you can align in parallel the edge of the drive with cross bar(see photos).
    Tighten the M8 screws evenly a little more about 1/2 turn until you cannot rotate the assembly about the frame.
    Extend the motor outwards and with a little force you should be able to wedge it against the tyre. Using a straight edge (steel rule) from the centre of the rear wheel hub to the centre of the pivot shaft, see where the centre of the motor lies (seee photo).
    It probably lies above the straight edge, so you need to use the 2.5mm Hex/Allen key and tighten the lower adjusting screw so the centre of the motor is directly on or slightly below the straight edge.
    I found that when correctly adjusted the motor would just about stay engaged against the tyre, with minimal force to disengage it.
    When happy with the adjustment then lock up the adjusting grub screw with the nut using an 8mm spanner.You may find it easier to tighten that nut from the other side of the cycle and with the motor engaged with the tyre, its a little tricky to get the spanner on. (I will maybe have to mill a cut out on the aluminium motor mount on the next version).

    Next is to set the distance of the motor from the tyre when it is disengaged in it lowest position.
    Using the upper adjusting grub screw tighten it until the motor raises itself towards the tyre and leaves about 5mm clearance, tighten the locking nut when happy (see photos).

    NOTE
    After fitting the friction drive in position you may want to wrap some tape around the cycle frame above and below the nylon 66 frame bracket as a guide for refitting to the cycle if you remove it.

    Step 13: Friction Drive Wiring

    Materials and tools used:

    • Cable ties
    • pliers/wire cutters
    • Hex /Allen keys
    • Thumb throttle
    • Motor lead
    • On/Off switch lead
    • Parallel leads
    • Servo tester (modified)
    • Battery bag (Topeak Aero Wedge Pack - Large)
    • ESC (HobbyKing 85A Blue Series Brushless Speed Controller 5A SBEC)
    • Lipo's (Turnigy 5000mAh 5S 20C Lipo Pack) x 2

    Connecting the wires

    Fit the thumb throttle in a suitable position on your cycle handlebars and route the wire along the crossbar and to the underside of the cycle saddle/seat, securing in place with cable ties (see photo).
    Connect Motor lead to ESC and fit it to the underside of battery bag (see photo) and fit bag to cycle (see photo).
    Connect the Motor lead to the motor(see photo).
    Route the On/Off switch lead to the underside front of the saddle/seat and secure wire with cable tie, then connect one end of it to the positive(red) wire on the power supply side of the ESC (see photo).
    Connect Thumb throttle to the servo tester which is situated under the saddle/seat and connect the thin ESC wire to the otherside of the servo tester (see photos).
    Connect 2 lipo's with parallel leads and insert into the battery bag as far in as you can get them (see photo)
    Connect up the Red parallel lead to the On/Off switch lead and the Black parallel lead to the negative (black) wire on the power supply side of the ESC.
    Finally zip up the battery bag and your all done.

    Basic throttle calibration with the ESC (1st time use)

    Read the instructions that came with your ESC and calibrate the throttle, you must do this for the Thumb throttle to function correctly.

    For this particular ESC the first thing to do is to put the Thumb throttle to full maximum position and hold there, now power up the system with the on/off switch, then you will hear some fast beeps, at which point you fully release the throttle to minimum then you will hear another beep which indicates the calibration is complete, power off the system with the on/off switch. Thats all there is to it.

    Note
    Do NOT operate the throttle at power up whilst the ESC is beeping, unless you are configuring the ESC.

    Step 14: Using the Friction Drive

    Thumb Twist Throttle use
    (Please note that this friction drive system is designed for assistance only and should not be activated from a stand still as this is likely to damage the motor)

    I activate the twist thumb throttle when I'm cycling at a minimum speed of 14mph(22.5km/h), I then hold it either on half power or go straight to full for about 3-4 seconds then release.

    Li-po Battery usage

    I currently use only two Turnigy 5000mAh 5S 20C Lipo Packs of the four listed in this build of which I find ample for the 12 miles(19.3km) round trip I travel.