Effect of Feed Rate, Concave Clearance and Peripheral Speed on the Performance Evaluation of Pre Thresher for Onion Umbels (Allium cepa var. aggregatum L.)

Abstract

Freshly harvested, sun dried onion umbels consists of florets attached to the hard umbel heads. Conventional threshing method involves tractor treading, rubbing umbels using rubber slippers on hard surface and beating with sticks. This method resulted in seed damage and affected the germination and vigor index. High quality seeds can be produced through effective threshing and separation process. Threshing of onion umbels was carried out in a lab model thresher resulted in chocking of umbel heads in the threshing chamber and reduced the threshing efficiency of the thresher. Pre threshing is an important unit operation carried out before threshing of onion umbels. The main aim of the study was to develop a pre threshing unit to separate the florets from hard umbel heads. Hence, a pre thresher with peg tooth type threshing cylinder was designed and developed for separating the florets from onion umbels further florets are conveyed to the thresher for separation of seeds from the florets. The performance of the unit was evaluated in terms of florets threshing efficiency, floret separation efficiency, percentage floret loss and seed damage at different feed rate, concave clearance and peripheral speed. The peg tooth type pre thresher’s performance was good at 100 kg•h-1 feed rate 6 mm concave clearance and 7 m•s-1 peripheral speed.

Sveže požnjevene cvasti crnog luka, osušene na suncu, sastoje se od cvetova usađenih u glave cvasti. Konvencionalna vršidba uključuje gaženje traktorom, trenje cvasti gumenim papučama po tvrdoj podlozi i udaranje štapovima. Ovaj postupak dovodi do oštećenja semena i smanjenja klijavosti i indeksa vigora. Visoko kvalitetno seme se može proizvesti efikasnom vršidbom i odvajanjem semena. Vršidba semena iz cvasti crnog luka izvođena je laboratorijskim modelom vršalice, što je dovelo do zagušenja glava cvasti u vršidbenoj komori i smanjilo efikasnost vršidbe. Pred vršidba je važna operacija koja je izvedena pre vršidbe cvasti crnog luka. Glavni cilj ovog istraživanja bio je da razvije pred vršidbeni uređaj za odvajanje cvetova od tvrdih glava cvasti. Zato je konstruisana i razvijena pred vršalica sa vršidbenim cilindrom sa klinastim zubima za odvajanje cvetova iz cvasti luka i dalje odvođenje cvetova do vršalice za odvajanje semena iz cvetova. Karakteristike uređaja su ocenjivane prema efikasnosti izvršaja cvetova, efikasnosti odvajanja cvetova, procenta gubitka cvetova i oštećenja semena pri različitim normama punjenja, zazorima podbubnja i periferijskim brzinama. Pred vršalica sa klinastim zubima imala je najbolje rezultate pri normi punjenja od 100 kg•h-1, zazoru podbubnja od 6 mm i periferijskoj brzini od 7 m•s-1.