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http://www.instructables.com/id/transparent-gearbox-on-a-homemade-bicycle/?ALLSTEPS

transparent gearbox on a homemade bicycle by champx

I wanted create a for a long time bike with gear box in the bottom bracket

as I Expanded a rim rear hub and built a custom coaster,
I could not have gear .... and I missed it!

I'm inspired by old bikes (1900), and tractor mower gearbox!

I used bike gears, plexiglass and machined parts


I put two weeks to get the idea and create plans
and about 2 months to realize the gearbox!

there are three speeds and axis drive and output are the same
the selection system is brass


plexiglass box is to see the mechanism



Step 1:

First I made plans and gear ratio

Plans were made to the scale to facilitate manufacturing and various tests of setting up

Step 2:

the system consists of a shaft on which a gear is driven all the time and the two other turn in the blank

when you change the speed which was led starts to rotate in the air and it is another that takes over

brass washers avoids usury

for machining gears supports, a special machine (mortiser) was used

I had to disassemble a lot of speed freewheel bike in order to make this arrangement

I then just solder the sprockets on their support

Step 3:

then, and still brass, I machined "sliding"

it slides on the shaft and causes a finger, which thanks to a spring, causes the pinion that is desired, while leaving the others free

just as a system of tractor mower!

Step 4:

Then I set up a temporary Chassis mechanism to try ...

- Bottom 4 sprockets rotate at the same time
- Right there the output gear (the piece with the red lines allows to see the rotation)
- Top left, the three sprockets rotate independently of each other (the brass Shifting used to lock the one you want)


here you can see in works

Step 5:

manufacture of the box to receive the mechanism

I asked a friends to machine the bearing location

for the rest I did everything by hand, with a hole saw and a jig saw .... not easy!

can perceive the selector and bearing housings

space that I shows with my fingers used to place the gearbox on the bike

to assemble the pieces of plexiglass, I used a special glue planned for this

Step 6:

tedious but important step, polishing!

I used several grade sand paper:

100, 240, 400, 800, 1000, 2500 and 4000

then polish has is sufficient vehicle body


This is the same method to renovate the plastic headlights;-)


someone told me it looks like a sprockets aquarium......lol

Step 7:

I was missing 6 mm in order to close the box properly ....
So I used orange plexiglass to fill this gap

orange ... why?
because I love orange
because according to the angle of view, reflections gives the impression that the entire gearbox is colored so that there is very few orange

Step 8:

Show All 8 Images

for the selector, I used pieces of brass I brazed silver

a small plexiglass cover can make a little more sealed all


here is general aspect

Step 9:

the spring of the cable not being effective, I made another system better finish to tighten the cable

here is the new system

Step 10:

remains only to mount the gearbox on my bike homemade

I do no more details than that the bike because for me the main subject is the gearbox!
a bike custom is simple to do for someone who used to do it

even when I put some pictures of the bike as I have also spent time on it

on the pictures it is a friend who drives the bike
on the video is me