I'm working on a GBC module and want to turn a wheel made from four of the yellow quarter-rack things from the Bucket Wheel Excavator (https://brickset.com/parts/6151167/1-4-circle-gear-rack-11x11
) exactly one eighth of the speed of another wheel.
So, I need some gearing. Trouble is, the yellow wheel has 140 teeth so 1/8th is 17.5 and of course there are no 17.5 teeth gear wheels so it can't be done simply.
I suspect I'm out of luck but thought I'd ask here in case anyone better at maths than I can work out how to do it with a combination of 8, 12, 16, 20, 24, 36 and 40 tooth gears.
Driving it by a wheel or pulley is also possible. Its diameter is 166mm so circumference is 521.5mm which thus would need a wheel of 20.75mm diameter to drive it at 1/8th of the speed.