Materials
Trainer Assembly :
Bicycle trainer
One 6" x 14" piece ¼" aluminum plate 12-volt DC motor/generator (Dayton 3XE20)
Two ¼" x 1½" #20 bolts
Two ¼" #20 nylon locking nuts
Four ¼" x 2" #20 bolts with eight nuts
One jaw coupling with I.D. (inner diameter) to match generator shaft O.D. (outer diameter)
One jaw coupling with I.D. to match friction roller shaft O.D. (the body size of both jaw couplings must be the same)
One jaw coupling insert sized to match both jaw couplings
Electrical: Generator to Battery :
One ¼" spade-type crimp connector for 12 AWG wire (for diode anode lug)
Two 2" lengths of ¼"-diameter heat-shrink insulation tubing
One ring-type crimp connector for 12 AWG wire with ¼" hole (for diode cathode stud)
One 1N1190A diode
One 16" length 12 AWG wire
One wire nut (sized for two 12 AWG wires)
One automotive-type fuse holder 20-amp automotive fuse
Two battery clips to attach 12 AWG wire to battery (one clip should be red, the other black)
One 8" length of 1"-diameter protective wire loom
Two wire ties
Electrical: Battery to Inverter :
(see Facts below)
Two 12" lengths and one 24" length of 4 AWG wire
Six ring-type crimp connectors with ¼" hole (for 4 AWG wire )
Eight 2" lengths of ½" heat-shrink insulation tubing DC-rated fuse or circuit breaker (sized per inverter manufacturer specs)
Two battery clips (for 4 AWG wire; one clip should be red, the other black)
One 12-volt to 120-volt inverter Battery
DC voltmeter
A Few Essential Facts :
Notes on the electrical parts used to connect the battery to the inverter:
Connectors: The type and size of connectors and cables you use, as well as the kinds of connections you make, will be determined by your specific setup and size of fuses, cables, battery clips, and inverter connection. The wiring harness described here is sized for a 600- watt inverter and incorporates a resettable circuit breaker. Use smaller wire and connectors for a smaller inverter.
Heavy-gauge wire: For greater flexibility, use fine-strand welding cable instead of standard battery cable.
Inverter: Size the inverter according to the needs of the appliance you hope to operate. Anywhere from 200 to 600 watts would be an appropriate size for this project. True sine wave inverters will offer better performance than “modified” sine wave models, but the former are more expensive.
DC-rated fuse or circuit breaker: Size this according to the inverter manufacturer’s specifications. I used an 80-amp resettable DC-rated circuit breaker for a 600-watt inverter. The DC rating is critical, since DC-rated devices are electrically different from AC devices.`
1. Disassemble the trainer roller assembly.
The friction roller shaft will likely have a housing for the resistance mechanism on one end and a counterweight on the other end. Remove any screws as needed to get inside the housing, then disconnect the resistance mechanism from the end of the shaft. Remove the counterweight from the other end of the shaft; the weight is likely to be threaded onto the shaft. Remove any bolts or screws as needed to separate the roller assembly from the mount on the trainer frame.
2. Modify the friction roller.
You will connect the generator to the end of the roller shaft that had the counterbalance (which may have a screw thread) using a jaw-type coupling. The coupling won’t hold well on threads, so you have to cut off the threaded portion, using a grinder with a metal cut-off disc or a hacksaw or reciprocating saw. Secure the roller shaft in a bench vise to hold it while you make the cut.
3. Cut and install the generator mounting plate.
The generator mounting plate supports the weight of the generator and connects it to the roller mount on the trainer, while the entire assembly remains adjustable to fit various sizes of bike wheels.
Using a 6" x 14" piece of 1/4" aluminum, cut a notch to create a tab that slides underneath the roller mount. For my trainer, the notch measured 31/2" x 23/4". Cut the plate with a jigsaw and fine metal blade. Drill two 1/4" holes in the roller mount for attaching the generator plate. Slide the aluminum plate underneath the mount, and align the plate so it’s square with the roller mount, then clamp it in place. Poke a center punch through the holes in the mount to transfer their locations to the aluminum plate. Remove the plate and drill two 1/4" holes through the plate. Clean up the holes and metal shavings, then attach the generator plate to the roller mount with two 1/4" x 11/2" #20 bolts and locking nuts. Note: You may need to cut a notch in the plate to provide clearance for the trainer’s adjusting screw.
4. Fit the generator to its mounting plate.
Reinstall the friction roller onto its mount. Carefully measure where the centerline of the roller shaft extends over the generator mounting plate. Use a straightedge or small square to mark the centerline across the mounting plate; this line will serve as a guide for locating the holes for the generator mounting bolts.
Place the generator on the mounting plate and align the center of the generator shaft with the roller shaft, keeping their ends precisely 1/2" apart (this space is required for the shaft couplings). Using the centerline on the mounting plate as a reference, carefully measure and mark the locations for the generator mounting holes. Note: It may be easier to complete the assembly by removing the mounting plate. Drill four 1/4" holes through the plate for the 1/4" x 2" #20 generator mounting bolts. The bolts will thread directly into the generator housing. To adjust the height between the generator and its mounting plate (for aligning with the roller shaft), add a nut on each side of the mounting plate, and thread the bolts into the generator housing. Later, you can adjust the nuts as needed to move the generator up or down, then tighten them to secure the generator in the correct position. Leave the nuts loose for now so you’ll be able to move the generator for fitting the couplings.
5. Complete the mechanical assembly.
Slip a jaw coupling onto the end of the generator shaft, using the appropriate size coupling; do the same with the roller shaft. Install the rubber jaw coupling insert. Reinstall the mounting plate with the generator onto the roller mount while aligning the shaft couplings.
Use the double-nut system to adjust the generator height to align the two couplings. Once the shafts are perfectly aligned, slide the jaw couplings together and tighten all hardware, including the setscrews, to secure the couplings to the shafts. Test-fit the bike on the trainer.
Note: The mounting plate may need additional support so the generator’s weight does not bend the plate and cause misalignment; a simple wood block custom-cut to size and tucked under the free end of the mounting plate will suffice.
6. Prepare the generator wiring.
Strip 2" of sheathing from the loose end of the generator output cable to expose the three insulated conductors inside. The green wire is intended for equipment grounding, but it is not required in this case; you will be working with only the black and white wires, both of which will carry electrical current.
Operate the generator with the bicycle mounted on the trainer by pushing a pedal down with one hand, causing the back tire to spin. Use a voltmeter to identify which of the conductors is positive and which is negative. Polarity depends upon the direction of rotation. Mark the positive conductor with a piece of red tape. Strip 1/4" of insulation from the positive wire, and strip about 1/2" from the negative wire.
Attach a spade terminal to the positive wire of the generator and crimp it using a crimping tool. Slide a piece of heat-shrink insulation tubing over the terminal and apply heat with a hair dryer so that the insulating tube shrinks tightly over the wire and connector.
7. Attach the diode.
The diode has two ends: the anode and the cathode. The anode is the end marked + (plus) and connects to the positive conductor of the generator. The cathode is the end marked – (minus) and connects to the battery’s positive terminal. Look for this represented by a schematic diagram printed on the body of the diode. Attach the spade terminal of the positive generator wire to the anode of the diode. Slide a piece of heat-shrink tubing over one end of the fuse holder wire, attach the ring terminal to the fuse holder wire and crimp it. Apply heat to the heat-shrink tubing. Bend the terminal at a 90-degree angle and attach it to the threaded stud on the cathode side of the diode, using the nut supplied with the diode.
8. Complete the generator output wiring.
Strip about 1/2" from each end of the 12 AWG wire. Use a wire nut to connect the negative side of the generator to one end of the 12 AWG wire.
Prepare the other end of the fuse holder wire by stripping back about 1/2"of insulation. Attach each of these two wires to its corresponding battery connector (the fuse holder wire is the positive wire, and so is connected to the red battery clip) by crimping and soldering the connections, or use a terminal connector and screw. The type of connection you make depends on the type of battery connector you have, but avoid wrapping bare wire around a screw, as this is not a secure connection.
Make sure all exposed electrical connections are covered and protected to prevent exposure and physical stress. Slide the wire loom over the diode and its connectors, and secure it in place with wire ties. This will help to protect the connections and parts both physically and electrically. You can dress up the entire wiring harness by covering all of it with wire loom. If the bike generator is likely to be moved around a lot or otherwise abused, you can increase the durability of the wiring harness by using a piece of PVC tubing in place of the loom. In any case, be sure to leave access to replace the fuse if needed.
9. Connect the battery to the inverter.
Be sure to read A Few Essential Facts on page 30. To complete the wiring connections, strip about 1/2" from each end of all three 4 AWG wires. Slide a crimp connector onto each end and crimp the lug securely onto the wire. Slide a piece of 1/2" heat-shrink tubing over each lug, leaving the hole exposed, and apply heat.
Connect one end of each of the two short wires to the fuse or circuit breaker. This is the “positive” side cable. Attach a red battery clip to the cable coming from the fuse or circuit breaker connection point marked “line.” Attach the free end of the positive cable connected to the other side of the fuse or circuit breaker marked “load” to the inverter’s positive terminal.
Connect one end of the long wire to the negative battery clip, and connect the other end to the negative side of the inverter. Follow the manufacturer’s instructions to connect the inverter to the battery. Typically, you would attach the negative side to the battery first, then make the positive connection. Observe polarity carefully, as electronic equipment can be destroyed if hooked up backward.
Using Your Battery Charger
Once you’re all hooked up, you can start pedaling to charge the battery. But you won’t know when the battery is full, when to stop pedaling, or how hard you need to pedal to keep the battery full of juice. The only way to know is to hook up a voltmeter to the battery and watch the numbers. You can find inexpensive voltmeters at electronic supply stores, or devise a scheme to hook up a panel-mounted automotivetype meter to the battery.
Try not to let the battery charge level drop below 11.5 volts or rise above about 14.5 volts. Pedal faster or slower to vary the charging rate. Higher and lower voltages can damage batteries. Higher voltages may damage the inverter. There’s no need to have everything connected all the time; the inverter needs to be connected only when power is being used, and the charger must be connected only when you’re pedaling to charge.
Please be aware that incredible amounts of energy are stored in a battery, and its acid electrolyte will burn through skin, clothing, and lots of other things. If a tool or other piece of metal creates a short circuit across the battery terminals, the result could be a melted tool and an exploded battery with splattered acid. Insulate the battery terminals and consider enclosing the battery in a protective box to keep the young and uninitiated away.
example:
Trainer Assembly :
Bicycle trainer
One 6" x 14" piece ¼" aluminum plate 12-volt DC motor/generator (Dayton 3XE20)
Two ¼" x 1½" #20 bolts
Two ¼" #20 nylon locking nuts
Four ¼" x 2" #20 bolts with eight nuts
One jaw coupling with I.D. (inner diameter) to match generator shaft O.D. (outer diameter)
One jaw coupling with I.D. to match friction roller shaft O.D. (the body size of both jaw couplings must be the same)
One jaw coupling insert sized to match both jaw couplings
Electrical: Generator to Battery :
One ¼" spade-type crimp connector for 12 AWG wire (for diode anode lug)
Two 2" lengths of ¼"-diameter heat-shrink insulation tubing
One ring-type crimp connector for 12 AWG wire with ¼" hole (for diode cathode stud)
One 1N1190A diode
One 16" length 12 AWG wire
One wire nut (sized for two 12 AWG wires)
One automotive-type fuse holder 20-amp automotive fuse
Two battery clips to attach 12 AWG wire to battery (one clip should be red, the other black)
One 8" length of 1"-diameter protective wire loom
Two wire ties
Electrical: Battery to Inverter :
(see Facts below)
Two 12" lengths and one 24" length of 4 AWG wire
Six ring-type crimp connectors with ¼" hole (for 4 AWG wire )
Eight 2" lengths of ½" heat-shrink insulation tubing DC-rated fuse or circuit breaker (sized per inverter manufacturer specs)
Two battery clips (for 4 AWG wire; one clip should be red, the other black)
One 12-volt to 120-volt inverter Battery
DC voltmeter
A Few Essential Facts :
Notes on the electrical parts used to connect the battery to the inverter:
Connectors: The type and size of connectors and cables you use, as well as the kinds of connections you make, will be determined by your specific setup and size of fuses, cables, battery clips, and inverter connection. The wiring harness described here is sized for a 600- watt inverter and incorporates a resettable circuit breaker. Use smaller wire and connectors for a smaller inverter.
Heavy-gauge wire: For greater flexibility, use fine-strand welding cable instead of standard battery cable.
Inverter: Size the inverter according to the needs of the appliance you hope to operate. Anywhere from 200 to 600 watts would be an appropriate size for this project. True sine wave inverters will offer better performance than “modified” sine wave models, but the former are more expensive.
DC-rated fuse or circuit breaker: Size this according to the inverter manufacturer’s specifications. I used an 80-amp resettable DC-rated circuit breaker for a 600-watt inverter. The DC rating is critical, since DC-rated devices are electrically different from AC devices.`
1. Disassemble the trainer roller assembly.
The friction roller shaft will likely have a housing for the resistance mechanism on one end and a counterweight on the other end. Remove any screws as needed to get inside the housing, then disconnect the resistance mechanism from the end of the shaft. Remove the counterweight from the other end of the shaft; the weight is likely to be threaded onto the shaft. Remove any bolts or screws as needed to separate the roller assembly from the mount on the trainer frame.
2. Modify the friction roller.
You will connect the generator to the end of the roller shaft that had the counterbalance (which may have a screw thread) using a jaw-type coupling. The coupling won’t hold well on threads, so you have to cut off the threaded portion, using a grinder with a metal cut-off disc or a hacksaw or reciprocating saw. Secure the roller shaft in a bench vise to hold it while you make the cut.
3. Cut and install the generator mounting plate.
The generator mounting plate supports the weight of the generator and connects it to the roller mount on the trainer, while the entire assembly remains adjustable to fit various sizes of bike wheels.
Using a 6" x 14" piece of 1/4" aluminum, cut a notch to create a tab that slides underneath the roller mount. For my trainer, the notch measured 31/2" x 23/4". Cut the plate with a jigsaw and fine metal blade. Drill two 1/4" holes in the roller mount for attaching the generator plate. Slide the aluminum plate underneath the mount, and align the plate so it’s square with the roller mount, then clamp it in place. Poke a center punch through the holes in the mount to transfer their locations to the aluminum plate. Remove the plate and drill two 1/4" holes through the plate. Clean up the holes and metal shavings, then attach the generator plate to the roller mount with two 1/4" x 11/2" #20 bolts and locking nuts. Note: You may need to cut a notch in the plate to provide clearance for the trainer’s adjusting screw.
4. Fit the generator to its mounting plate.
Reinstall the friction roller onto its mount. Carefully measure where the centerline of the roller shaft extends over the generator mounting plate. Use a straightedge or small square to mark the centerline across the mounting plate; this line will serve as a guide for locating the holes for the generator mounting bolts.
Place the generator on the mounting plate and align the center of the generator shaft with the roller shaft, keeping their ends precisely 1/2" apart (this space is required for the shaft couplings). Using the centerline on the mounting plate as a reference, carefully measure and mark the locations for the generator mounting holes. Note: It may be easier to complete the assembly by removing the mounting plate. Drill four 1/4" holes through the plate for the 1/4" x 2" #20 generator mounting bolts. The bolts will thread directly into the generator housing. To adjust the height between the generator and its mounting plate (for aligning with the roller shaft), add a nut on each side of the mounting plate, and thread the bolts into the generator housing. Later, you can adjust the nuts as needed to move the generator up or down, then tighten them to secure the generator in the correct position. Leave the nuts loose for now so you’ll be able to move the generator for fitting the couplings.
5. Complete the mechanical assembly.
Slip a jaw coupling onto the end of the generator shaft, using the appropriate size coupling; do the same with the roller shaft. Install the rubber jaw coupling insert. Reinstall the mounting plate with the generator onto the roller mount while aligning the shaft couplings.
Use the double-nut system to adjust the generator height to align the two couplings. Once the shafts are perfectly aligned, slide the jaw couplings together and tighten all hardware, including the setscrews, to secure the couplings to the shafts. Test-fit the bike on the trainer.
Note: The mounting plate may need additional support so the generator’s weight does not bend the plate and cause misalignment; a simple wood block custom-cut to size and tucked under the free end of the mounting plate will suffice.
6. Prepare the generator wiring.
Strip 2" of sheathing from the loose end of the generator output cable to expose the three insulated conductors inside. The green wire is intended for equipment grounding, but it is not required in this case; you will be working with only the black and white wires, both of which will carry electrical current.
Operate the generator with the bicycle mounted on the trainer by pushing a pedal down with one hand, causing the back tire to spin. Use a voltmeter to identify which of the conductors is positive and which is negative. Polarity depends upon the direction of rotation. Mark the positive conductor with a piece of red tape. Strip 1/4" of insulation from the positive wire, and strip about 1/2" from the negative wire.
Attach a spade terminal to the positive wire of the generator and crimp it using a crimping tool. Slide a piece of heat-shrink insulation tubing over the terminal and apply heat with a hair dryer so that the insulating tube shrinks tightly over the wire and connector.
7. Attach the diode.
The diode has two ends: the anode and the cathode. The anode is the end marked + (plus) and connects to the positive conductor of the generator. The cathode is the end marked – (minus) and connects to the battery’s positive terminal. Look for this represented by a schematic diagram printed on the body of the diode. Attach the spade terminal of the positive generator wire to the anode of the diode. Slide a piece of heat-shrink tubing over one end of the fuse holder wire, attach the ring terminal to the fuse holder wire and crimp it. Apply heat to the heat-shrink tubing. Bend the terminal at a 90-degree angle and attach it to the threaded stud on the cathode side of the diode, using the nut supplied with the diode.
8. Complete the generator output wiring.
Strip about 1/2" from each end of the 12 AWG wire. Use a wire nut to connect the negative side of the generator to one end of the 12 AWG wire.
Prepare the other end of the fuse holder wire by stripping back about 1/2"of insulation. Attach each of these two wires to its corresponding battery connector (the fuse holder wire is the positive wire, and so is connected to the red battery clip) by crimping and soldering the connections, or use a terminal connector and screw. The type of connection you make depends on the type of battery connector you have, but avoid wrapping bare wire around a screw, as this is not a secure connection.
Make sure all exposed electrical connections are covered and protected to prevent exposure and physical stress. Slide the wire loom over the diode and its connectors, and secure it in place with wire ties. This will help to protect the connections and parts both physically and electrically. You can dress up the entire wiring harness by covering all of it with wire loom. If the bike generator is likely to be moved around a lot or otherwise abused, you can increase the durability of the wiring harness by using a piece of PVC tubing in place of the loom. In any case, be sure to leave access to replace the fuse if needed.
9. Connect the battery to the inverter.
Be sure to read A Few Essential Facts on page 30. To complete the wiring connections, strip about 1/2" from each end of all three 4 AWG wires. Slide a crimp connector onto each end and crimp the lug securely onto the wire. Slide a piece of 1/2" heat-shrink tubing over each lug, leaving the hole exposed, and apply heat.
Connect one end of each of the two short wires to the fuse or circuit breaker. This is the “positive” side cable. Attach a red battery clip to the cable coming from the fuse or circuit breaker connection point marked “line.” Attach the free end of the positive cable connected to the other side of the fuse or circuit breaker marked “load” to the inverter’s positive terminal.
Connect one end of the long wire to the negative battery clip, and connect the other end to the negative side of the inverter. Follow the manufacturer’s instructions to connect the inverter to the battery. Typically, you would attach the negative side to the battery first, then make the positive connection. Observe polarity carefully, as electronic equipment can be destroyed if hooked up backward.
Using Your Battery Charger
Once you’re all hooked up, you can start pedaling to charge the battery. But you won’t know when the battery is full, when to stop pedaling, or how hard you need to pedal to keep the battery full of juice. The only way to know is to hook up a voltmeter to the battery and watch the numbers. You can find inexpensive voltmeters at electronic supply stores, or devise a scheme to hook up a panel-mounted automotivetype meter to the battery.
Try not to let the battery charge level drop below 11.5 volts or rise above about 14.5 volts. Pedal faster or slower to vary the charging rate. Higher and lower voltages can damage batteries. Higher voltages may damage the inverter. There’s no need to have everything connected all the time; the inverter needs to be connected only when power is being used, and the charger must be connected only when you’re pedaling to charge.
Please be aware that incredible amounts of energy are stored in a battery, and its acid electrolyte will burn through skin, clothing, and lots of other things. If a tool or other piece of metal creates a short circuit across the battery terminals, the result could be a melted tool and an exploded battery with splattered acid. Insulate the battery terminals and consider enclosing the battery in a protective box to keep the young and uninitiated away.
example:
