John Kent was the first black police officer in the UK. He joined the Carlisle police in 1837. As a notable character from Cumbria’s past he is a perfect subject for the Archive Project. Dawn and I have planned out a model featuring John Kent arresting a criminal. They will struggle back and forth then PC Kent will blow his police whistle. In theory we could probably run a pipe up his body and out of his mouth, then blow air through his mouth and into an actual police whistle. There are all sorts of technical difficulties to this solution so instead we are making the sound separately using a set of bellows and a pair of wooden whistles. These will be mounted in the mechanism part of the model user the baseboard.
Here’s how I put together the prototype whistles. Click on the top image to see and hear the whistle in action.
The whistles are made from six pieces of laser cut plywood and a strip of thick (280gsm) card. Police whistles use two tone for their distinctive sound, I’ve made two pipe, one longer than the other to make the two tone sound.
The cross piece is glued into place forming the bottom of the air hole.
Then the spacer is glued under the cross piece
The parts are clamped up whilst the glue dries.
Whistles work by blowing directed air across a sharp edge. The whistle top is sanded down to make the edge sharp.
Finally a strip of card is glued into place leaving an air hole at the front. Air blows up through the hole behind the spacer and out through the air hole. The whistle is glued down onto the top of board making the bottom of the whistle.
The top plate above the bellows has two small holes in to allow air out. The completed whistle are glued to the top plate so that the air comes up through the hole in the whistle and is blown out across the sharp edge making the whistling sound.
It works really well, the whistle sounds like a police whistle and is loud! Next step is to connect it up to cam or crank and check that the mechanism can make it sound effectively