Help: Mechanical Odometer

I have a bicycle trailer that I use for groceries and such, and hope to use for extended bicycle trips. I would like to get or construct an odometer for the back of the trailer, to advertise how far I've traveled. I've looked around a lot, but have had difficulty finding an non-electric or large-display DIY odometers (ideally, I would like the numbers to be 2 to 3 inches tall, and would like to keep it below ten pounds).

I would prefer it to be mechanical only, requiring no batteries or electrical power, but am willing to give on that point for the sake of simplicity of design, weight and cost.

If you have any advice where I could find advice or instructions on how I might set something up, I'd greatly appreciate it.

A mechanical odometer needs a very good adjustment so you get accurate readings.

Basically every number display out there can be substituted if you know your tools.

I have seen the displays of old petrol pumps used for it as one example.

But I think an electronic one would be easier to construct and calibrate.

Problem is that most bicycle odometers only have a tiny display.

I think it would be possible to use the LCD connections on a simple odometer to drive a bigger display or, with transistors even LED's but it is a lot of work.

Maybe a good sized odometer behind a fresnel lens could work for your project?