A lot has changed in the agricultural industry in the last 50 years, but a constant has been the rubber seed drop tube. It is found on machinery from almost every manufacturer and works for planting a wide variety of crops. However, for as similar as the application of the parts is, the sizes and materials can be quite different.
If there is one key characteristic, it would be that the tubes need to stretch to accommodate the undulations in the field and movement of the equipment. Some designs want a firmer tube that will move, but not too much. For this, a higher durometer and/or a thicker wall are recommended. Other designs require a great deal of stretch, up to 4:1 ratio, and use lower durometer (softer) material and thinner wall thickness to allow for more convolutions.
In terms of material types that are best to accommodate such applications, EPDM rubber has long been the choice of manufacturers for it’s ability to resist UV and O-zone degradation as well as staying flexible through years of freeze-thaw cycles. A newer material option is synthetic natural rubber, which has great elongation characteristics and additives that help it handle weathering better than natural rubber can.
Sizing is fairly standard with typical diameters between 1.25” to 1.75”, but sometimes larger sizes are required. It is common to have a tube with a 1.25” ID with larger cuff diameters to help with connections. Tube lengths in the shortest state range from 6” on the short end to over 20” on the long end, demonstrating the vast difference between the distance between the hopper and the drills on different models. Any way you go, custom size options are available to meet your needs.