Wobbling in Pneumatic Systems for Transporting Seedlings

Abstract

When a containerized seedling is pneumatically transported through a pipe or hose it occasionally undergoes oscillating movements, referred to as “wobbling“, with the container being flung from one side of the hose to the other. Data on this phenomenon obtained in a previous feed-time study were further analyzed. In addition, a laboratory study was carried out in which the behaviours of seedling-container dummies of different sizes and shapes were studied at different air velocities in Plexiglas pipes of various diameters. Both the analyses of the frequencies of wobbling from the previous feed-time study and the results from the laboratory test confirmed that there is covariation between the wobbling tendency of a seedling and the shape of its container. Containers with a large butt-end area tend to wobble more. This leads to differentiation of the seedlings into two groups, seedlings with butt-ended and less butt-ended containers. This differentiation was the same whether it was based on feed times from the previous study, frequencies of wobbling from the previous study, or the wobbling behaviour in the recent laboratory test with dummies.