The Gearing Assembly v1.0

Contents of this tutorial:

How to use this tutorial
Step by step instructions
Finalizing and tuning

What does it do?

The Gearing allows The Wheel to turn the Main Collector, and attaches both to The Frame.

How does it do it?

The Gearing is basically a worm drive, which gears the rotation down about 90 times, so that a one turn of The Wheel results in a roughly 4 degree turn of the collector, greatly decreasing the amount of force required. It's also one-directional, so The Wheel can turn The Collector, but not visa versa. This means the SolarFlower is unaffected by wind or other interference.

How to use this tutorial

To view the animation to the left you will need to install Quicktime
There is also a YouTube based version, if needed, but the Quicktime version is recommended for better playback and control.

The best way to view the animation is to click and hold the time slider at the bottom and move it left and right to view whichever part of the animation you like, at your own speed.

You can download the animation here (right click, 'save link as'):
High quality (25.5 Mb)
Low quality (1.8 Mb)

If you are using a netbook or other small monitor, you may need to press F11 in your browser to view the page full screen.


Bench vice
Power drill
(Corded is best, battery will do)
4mm, 6mm, 10mm metal drill bits
Adjustable grips, also called Pipe wrench pliers, or Adjustable pliers
Hacksaw or Angle grinder

Allen key, also called Hex key
Sized No.8, 9/64, or 3.5mm, or to fit the long bolt in the bike stem as listed below.

Metal file
Circular or Half round is best
M6 Spanner or Pliers


Bicycle handlebar assembly

First get yourself an old bike you don't mind destroying. With a hacksaw or preferably an angle grinder, make the cuts illustrated in red in the image above. The forks and frame can be cut anywhere in that general vicinity, but it's important that the handlebars be cut flat across the stem, ie at as close to 90 degrees as possible. Every bike is different, but most should work ok.

With an Allen key, remove and keep the long bolt that runs down the inside of the stem (if your bike uses that system, which it probably does), so as not to damage it. Remove and discard any cables, gear shifters, brakes etc.

You'll be taking this to pieces during the tutorial anyway, so it might be a good idea before you start to strip it all down and clean everything with some paper tissue, which will also let you see what it looks like on the inside.


Bicycle large front sprocket (gear)

The sprocket pictured on the left is ideal, and fairly common on older European style bikes. There's a proper way to remove it, but the easiest is just cut free it and the pedal to which it's attached, then pop it off the pedal shaft with a hammer. Again, all bikes are different, so you'll need to figure the best way with what you have.

The sprocket set pictured right is more common on newer bikes and trickier to work with. Try to get the other type.

1 Spring

This needs to fit your sprocket, be at least 5cm long, 2 - 2.5cm diameter, and be as smooth as possible. Best to buy it new, unless you can find one just the right size without any rust.
Pretty much every bike sprocket in the world has a tooth spacing of half an inch (12.7mm), and you want two spring windings per tooth, so a quarter inch (6.35mm) spring would be ideal.
It's easy to check, just hold your spring against your sprocket and make sure that it lines up like so:

It needs to be fairly precise, but if the spring is slightly too widely spaced it can be compressed down to fit.

Bike wheel axle

Actually any threaded shaft at least 12cm long should work.
Best if the axle is threaded its entire length, but most have a flat section in the middle, which is fine if that's what you've got.

2 nuts to fit the axle above

Must be larger diameter than the spring.


2 cones or other small nuts to fit the axle

Must be smaller diameter than the spring, ie be able to fit inside it.
Most cone nuts (pictured on the left, part of all bike wheels) have a little round metal skirt which can usually be popped off.

2 M6 bolts, at least 70mm long

Get ones that are threaded all the way to the head.

10 M6 nuts

Square section metal

Roughly 3 - 4cm square by 8cm long.

2 pieces Flat metal

Roughly 3 - 4cm wide by roughly 30cm long,
roughly 3 - 4cm wide by at least 16cm long.

2 cable ties, also called zip ties

You can also use twisting wire.

Gaffer tape, also called duct tape, cloth tape

Step by step build instructions

These relate to the animation to the left.

Step 1:
Remove the stem (straight pipe that the handlebars were attached to) from the head tube. It should just slide out after you've removed the long bolt that was holding it in place. Also remove the short metal cylinder cut at an angle (called a wedge) which the bolt screws into.
Your bike probably uses this system, if not; adapt.

Using adjustable grips or an appropriately sized spanner, remove the top nut from the head tube.

Place the large sprocket over the head tube's thread. The sprocket hole will probably be slightly too small, in which case use a metal file to enlarge it until it fits. It's important that the sprocket be centred as accurately as possible.

Replace and tighten the top nut. Check that the sprocket is centred by spinning it. If it describes a perfect circle then it's centred, if it seems to be wobbling in and out even a little tap with a hammer until it's centred. You may need to file part of the hole larger.
(To avoid damaging the sprocket teeth with the hammer place something thin, such as a piece of flat metal, between two teeth and hit that instead.)

It's important to get this reasonably accurate. Once in place tighten the top nut as much as possible, to ensure the sprocket doesn't slip. Recheck that it's still centred.

Check that the top nuts aren't too tight against the head tube, and that everything can rotate freely If there's any friction wind the nuts back slightly. Too loose is better than too tight.

Take the square section steel and cut so that it's about the same length as the cut top of the bike stem.

Drill a 6mm hole through the top and bottom walls, about a centimeter from one side.

Drill a 6mm hole about a centimeter from the other side, through the top wall only

Drill a 4mm hole through the bottom wall only, so that it lines up with the previous hole.

Place the square steel over the top of the stem, so that the 4mm hole is in the center of the pipe.

Insert the long bolt and screw partially into the wedge. The head of the bolt should be able to pass through the top 6mm hole (if it doesn't, make it larger), but not the 4mm one.

Drill a 6mm hole in the bit of metal sticking out the side of the stem, so that it lines up with the other holes in the square steel.

Reinsert the stem into the head tube, just enough that it's stable.

Tighten the long bolt with an Allen key until it's all locked in place.

Drill 10mm holes in each of the two bits of remaining bike frame, so that they're about 1.5cm past the edge of the sprocket, vertically.

Take the 30cm length of flat metal and bend it with a vice and hammer, more or less like so:

Drill two 6mm holes in the flat metal so that they line up with the 10mm holes in the bike frame, with the top of the flat metal sitting about 3cm above the level of the sprocket.

Insert a 6mm bolts through each of the two holes in the flat metal.

Place two nuts on each bolt, one tight against the metal, the other with about a 1.5cm gap.

Insert the two bolts through the two 10mm holes in the bike frame.

Place another nut on each bolt on the other side of the frame and tighten. You want the bolts sitting more or less in the center of the larger holes so that you can adjust their position later.

Take the bike wheel axle and wind on the two cone nuts or other small nuts so they sit more or less in the middle, about 2cm apart. If the axle has a flat section you may need to force the nuts onto it by placing the flat section tight in a bench vice and turning the nuts with a spanner or similar, so that they cut their own threads into the axle.
Whatever works.

If necessary, wrap the nuts in gaffer tape or similar, so that when you place the spring over them it fits tightly, without rattling or shifting.

Place the spring.

Place the two larger nuts so that the spring is immobilised. Make sure not to compress the spring, unless it's too widely spaced for the sprocket, in which case use the nuts to squeeze it til it matches.

Cut one end of the axle so that about 1.5cm is left after the nut.

Perhaps the most important part of the whole SolarFlower is the interface between the spring worm gear and the sprocket. If the teeth of the sprocket mesh too tightly with the spring they'll rub, but too loose and it may detach and slip. They need to be flat on the same plane, and meet halfway up the spring, like this:

So you need to drill a hole in the bent piece of flat metal very slightly larger than the axle diameter (probably 10mm, but check) so that the axle can sit in this sweet spot. However, you will be able to tune this later by shifting the metal, so it doesn't need to be millimeter accurate at this stage.
But get it as close as you can.

Place the axle in the hole and check that it and the sprocket can turn without friction while meshed.

Place a nut on each of the M6 bolts, about 1.5cm away from the bike frame.

Take the other piece of flat metal. The width isn't greatly important, but it needs to be long enough that it can be attached to the two M6 bolts with enough space above to drill a hole for the axle.

Drill two holes that line up with the M6 bolts.
Drill a hole for the axle (probably 10mm) in such a place that it will sit in the sweet spot with the sprocket.

Place the flat metal on the M6 bolts and axle, and secure with nuts.

Drill 6mm holes near the ends of the two pieces of bike frame, through both sides. This is where you'll attach the gearing to the wooden frame later.

Finalizing and tuning

There should be only a couple of millimeter gap between the nuts holding the spring and the two pieces of metal holding the axle. Adjust by shifting the nuts on the M6 bolts which hold the metal.

The spring worm gear needs to sit on the same plane as the sprocket:


And they need to mesh well, not too tight, not too loose:


To achieve this, tap the two pieces of flat metal with a hammer until aligned correctly. Tighten all the nuts firmly, then recheck. The spring should be able to turn the sprocket practically without friction, the sprocket should not be able to slip against the spring.
This is something you will want to check periodically while the SolarFlower is running.


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