toys made with handheld fans
This is a toy car made from a hand-held electric fan
The bottle top is attached to the spinner with sticky fixers, will only work on a smooth floor. Link to movie
This is another example but with rubber-band gearing
This is a toy boat made along similar lines
You need two drinking straws, a thin one to make the prop shaft and a wider one for the bearing. Make the propellor by sticking two bits of plastic together at an angle with araldite. Don't make it too big. Link to movie
This is a more elaborate car
This is another one
This is a fan taped to an LED wall light
It is suspended from a wire bearing so that when the fan is switched on the light spins round & round. It can be hung from a light fitting.
Link to movie of one going round inside a big lampshade
This is an electric fan driving a cardboard flywheel by a connecting rod
I had to fiddle with it for ages to get it to start turning, but once it started it was surprisingly smooth and you can twist the conrod through a right angle and it will go on working; you can also make it work tipping the flywheel towards the fan by as much as a right angle.
Link to movie the movie makes the fan & the flywheel appear to turn much slower than they really do.
It turns the flywheel either forwards or backwards depending on which way it starts.
This is a detail of the driving end
This is a detail of the driven end
A more conventional way of getting a turning force to go round a corner is to use a universal joint.
This is a universal joint made from four sellotape hinges, each one at a right-angle to the last. Notice it is constrained by two bits of straw joined by a paperclip; one end of the constraining structure has been sellotaped to a lump of wood.
The straw can be rotated by taping it to the hub of a hand-held fan
Here I am holding one end of the constraining structure; in this movie I twiddle the constraint so that the rotating straw points in different directions.
In this slightly modified version I have added an extra drinking-straw sleeve which I am holding
This allows the constraining structure to spin freely, which it does of its own accord.
When turning forces go round corners
like this they behave in quite a mysterious way. Any braking force exerted on the central spinning drinking straws will tend to make the universal joint lock up, this causes it to start behaving like a solid right-angled structure which drives the constraining structure round & round. In the same way any braking torque applied to the constraining structure directs more of the fan's power to the central spinning shaft. These braking forces can be applied aerodynamically
The propellor acts as a brake on the central shaft and the large vane acts as a brake on the constraining structure. By changing the size of the large vane it is possible to make the braking forces roughly equal. Because the fan is now suspended from a bit of string the whole thing is free to rotate. Because the direction of the propellor is slowly rotating around the axis of the fan the mobile keeps changing direction.
If the fan is held steady rather than allowing it to swing round
the way the fan's rotation is divided into two separate elements can be more clearly seen.
This is the same toy made with much more efficient universal joints
It works with a single AA battery, the wires are bent & hooked into the motor terminals which means it can be made without soldering.
The 'tail' is angled so that it rotates near the axis of suspension; when the toy spins round this axis the slipstream over the tail is minimised. This is quite an important factor in allowing the direction of spin to alternate at regular intervals: if the slipstream over the tail is too great it tends to remain in a horizontal orientation.
The propshaft is made from paperclips, it is supported by a bearing made from a paperclip bent into a hook, the weight of the toy is enough to stop the shaft jumping out.
The friction-free universal joints are made by bending the ends of two paperclips at right angles and passing them through holes made in a short bit of drinking straw. The holes should be big enough to allow free rotation of the wire.
The central linkage is quite long, it's made of a whole paperclip, I found that this seemed to help get the positioning of the two universal joints right: the input & output shafts run in barings made from narrow bits of drinking straw which are held in place by a wider bit of straw that cuts the corner. The tail unit is also taped to this straw.
Link to much simpler universal joint toy
Another universal joint toy
Link to cable car made with electric fan
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