Ages ago I looked at the idea of making a Dynamo for the Lamp Post Engine, that would in turn power a lamp. I then left it some time before I got the urge to make the lantern and hence needed to consider the dynamo again.
I tried a motor that I had lying around, hooked it up to an LED and drove it with a small wheel on the motor shaft that I rested on the flywheel. However, I thought I could do better. So I bought a selection of motors on ebay.
I tried each motor in turn by placing an o-ring on the gear and once again resting them on the flywheel. A bit of trial and error showed me that the larger diameter motors worked better.
However, there are motors that are suitable all around us. The motors in the snow Christmas cards are large diameter, low power and perfect.
A post sticks out of the lamp post just above the edge of the flywheel and acts as the axle a simple swing arm. The brass swing arm is just 25mm between pivot point and the centre of the motor. The motor was bolted to the brass swing arm, luckily I keep a tin of nuts and bolts that I remove from old electrical, electronics and computers. Here I found two tiny bolts that fitted the threaded holes in the front face of the motor.
A small wheel 8mm diameter, machined from mild steel with a 2mm diameter hole to fit the motor spindle. No space for a fixing to the spindle and so a spot of superglue would have to suffice. This then has an o-ring tyre giving an overall outside diameter of 10mm. This runs against the 77.5mm diameter flywheel so giving a gearing of nearly 8:1.
The weight of the motor on the swing arm maintains contact and hence I have a dynamo for the lamp post engine.
The wires from the motor are then just simply connected to an LED.