Title page for ETD etd-06112010-193036


Document Type Doctoral Thesis
Author Marenya, Moses Okoth
Email moses.marenya@univen.ac.za
URN etd-06112010-193036
Document Title Performance characteristics of a deep tilling rotavator
Degree PhD
Department Civil and Biosystems Engineering
Supervisor
Advisor Name Title
Prof H L M du Plessis Supervisor
Keywords
  • tillage performance
  • soil shear strength
  • soil-metal friction
  • bite length
  • kinematic parameter
  • down-cut rotavator
  • power
  • specific energy
  • soil-failure modelling
  • deep-tilling
  • rotavator
Date 2010-04-16
Availability unrestricted
Abstract
This study was undertaken to develop an analytical model that is capable of predicting the torque requirements of a rotavator fitted with commercially available L-shaped blades. An analytical approach based on the limit equilibrium analysis was used to develop the proposed model. The proposed model was verified by comparing the model and measured torque requirements at predetermined rotavator blade angular positions from the horizontal for a down-cut rotavator.

The study findings indicated that there was an optimum set tillage depth for each rotavator configuration and operational conditions at which the resultant horizontal thrust generated was greatest. This unique depth was influenced by the bite length. The validation of the proposed model showed that the predicted and measured torque requirements, at different angular blade positions from the horizontal, correlated reasonably well for all the set tillage depths. As the depth of tillage increased, however, the curve for the measured torque requirements exhibited a cyclic behaviour after the peak torque requirements value had been recorded. The cyclic behaviour was probably due to the re-tilling and the instability of the tool-frame carrier, which increased with the set tillage depth.

The knowledge contributed by this research will afford the designers of active tillage tools a better understanding of the operations of the rotavator, particularly in deep tillage. The modelling approach, and instrumentation technique used in this research, can be extended to analyze the performance of rotavators fitted with other types of commercial blades.

2009, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Marenya, MO 2009, Performance characteristics of a deep tilling rotavator, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-06112010-193036/ >

D10/438/ag

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