Does anyone know of a supplier that offers quad-thread worm & wheels that are larger (stronger) than a 6 diametral pitch? The required ratio is approximately 7.5:1.
Look for any supplier that offers you a 7.5:1 ratio and has a 5" or more distance between input shaft and output shaft those sure are larger than 4 DP (which should be around 3 to 3.5" between shafts).