Instructables

Indoor Bike Trainer

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Picture of Indoor Bike Trainer
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After moving from west Texas, with mild winters and roads with wide shoulders, to rural Southern Kentucky, with long winters and roads with steep ditches instead of shoulders, it was time to start riding inside. My search for bike trainers left me feeling poor as it was hard to find one for under $100. With more time and tools than money I decided to build my own trainer.

The total cost of this project was about $30 because I used scrap wood and found a free fan in a friend’s junk pile. If you go out and buy all the parts new you might as well buy the trainer it will save you time and headache. But if you are low on cash, have spare time and don't mind "recycling" old stuff this Instructables is for you.
 
This project could also be used to make a Bike Powered Generator. Simply substitute the fan for a pulley and v-belt connected to an electric motor or a car alternator.

 
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Step 1: Tools and Materials

Picture of Tools and Materials
This is pretty simple and only requires basic tools
1. Power drill
1/4" drill bit, square drive bit, Phillips bit, bit to match the OD of your bearings
2. Circular saw and straight edge
3. Grinder or file
4. Square
5. 2 clamps 6" or larger
6. Jig saw or coping saw
7. Kreg pocket hole jig
- Note- if you do any woodwork you NEED a Kreg jig it will drastically speed up assembly and simplify your projects. They can be had for $40 at Lowe's and it is the best $40 you will ever spend on a tool.
8. Pencil
9. Hammer
10. Tin Snips
11. Half round file
12. Wood Chisel

Materials
I built this out of scrap 3/4" oak ply wood
1. Squirrel cage fan from a junk car or a window air conditioner
2. 4- Sealed ball bearings I used 5/8" inside diameter, looking back I would have used bigger bearings 3/4" maybe larger
3. 2- Lengths of axle the same diameter as the inside of your bearings (the bigger the better)
- the length of the axle is determined by the width of the rear hub assembly on the bike. One length of axle will need to be about 2.5" longer than the other to fit into the fan
4. 1 - Box of 1 1/4" course thread Kreg screws
5. 1 - Box of 1 1/4" brad nails
6. 10 - 1/2" ring nails
7. About 1 sq. ft. of aluminum flashing 8" x 15" should be enough
8.1' threaded rod that will fit through your bike's rear hub I used 12x24 all thread
9. 2- Wing nuts to match the threaded rod
10. 2 flat washers

Cut List (all scrap I had lying around)
1. The bottom I used a 3/4" piece of "Advantech" flooring 24"x24"
2. The base is a 24"x24" 3/4" oak plywood
3. Spacers between the base and bottom 4 - 3"x24"x3/4" oak ply
4. Bearing supports 2- 4"x 24" x 3/4"oak ply
5. Axle keepers 1 -4"x24"x 3/4" oak ply 1- 7"x24"x3/4" oak ply (height determined by size of the fan)
6. Upright supports 2 - 6"x18"x3/4" oak ply (the size is determined by your bike wheel size)
7. Inner upright support 2 - 6"x 14"x3/4" oak ply (same as other upright minus the width of the bearing supports)
8. Fan shroud 8"x8"x3/4" (determined by the size of the fan you find)
9. Fan shroud front and back 2- 3"x6"x 3/4" oak ply
Haha, cool idea!
bgerlt2 years ago
Why not run some ducting off of that fan and use the airflow produced while pedaling to help keep you cool?
timnterra (author)  bgerlt2 years ago
Not a bad idea. The air is tunneled thru the base and out the front already, so really all that i'd have to do is add a piece to the front to deflect the stream of air upwards.
Would constricting the airflow increase the resistance felt when pedalling?
timnterra (author)  baz40962 years ago
I believe in theory reducing the ammount of air flow would increase the resistance but the resistence is very high as it is because the fan is quite large. The resistence increases proportionally with the speed of the fan so shifting into a higher gear increases the resistance. I would recommend increasing the axle diameter to decrease the fan speed because I have never been able to ride above the lowest gear.
jj.inc baz40962 years ago
It would, but you will want to restrict the inlet so air is thrown out creating your own little vacuum which makes it mad so it tries to stop you.
Aron3132 years ago
This is exactly what i need to set up in front of the tv and just pedal. Its way to expensive to buy one even with my store discount.
Broberg2 years ago
Very nice instructable. Gonna have to try this out. I love the extra block of wood you used to level out the bike. I don't think I would enjoy going "down hill" inside the house... It took me a little while to figure out what the fan is for but you pointed it out.

Thanks agin and good job.
rimar20003 years ago
I did one of these, too. But it holds the rear wheel an inch over the soil by the axis, and keep it in its central position by means of two little wood wheels. I made the mistake of underestimating the effect of friction on the axis of these wheels, which causes that after a few minutes of pedaling they overheat and I must stop. I have to replace the shafts with ball bearings, I will do it next winter.
Phil B3 years ago
You did a nice job. I did something similar quite a number of years ago, but used only the resistance of the tires on my roller and no fan. (I have two photos.) I used 1/2" steel shaft in bearings with 1/2" ID, but ganged up 5" squares of 3/4" pine. Each had a 1/2" hole at the center. I slid them onto the shaft and glued them together. I turned the ganged squares to make a round cylinder using a spinning circular saw blade set sideways. That part was easy because I have a radial arm saw and could push the whole assembly into the saw blade while manually advancing the rotation of the ganged squares until they were a nice round cylinder with a dip in the center. I had to pin the cylinder to the shaft so it did not turn on the shaft.

The rear axle is an inch or two over center to the rear of the cylinder's axle so the bike's rear wheel wants to go off of the cylinder to the rear. But, it cannot because there is a wheel chock behind the front wheel. To "ride" this trainer I position it in a doorway and use my shoulder to balance. (It was actually made for a different bike, so the rear wheel does not appear in the photo as "over center" as I described.)
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timnterra (author)  Phil B3 years ago
Nice, I bet yours is a lot quieter than mine. When that fan gets to spinning it really humms.
Mine is rather noisy. The pieces of wood I sandwiched together creak on the shaft somehow. I have not used this roller support for a bike in recent years. All of the parts were free. Some renter left a home quickly and I drove by when the owners were setting out all sorts of stuff on the curb for the next garbage day.
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