Sorry, yeah the large gear has a sprag clutch between the gear an the shaft. and there's two sprockets on the clutch. The jack shaft is driven by the gear with the sprag until the clutch on the jackshaft is driven fast enough to engage, then it drives the jack shaft away from the sprag gear. Pretty simple really, but most of the parts are special. Somebody here did a special run of the parts, a little heavier duty than what you see here, but really good quality parts. You might try searching two speed and see if it comes up.