2006 * XVII * 2

M. Heinloo,T. Leola.    
  Multiparametric of synthesis the manipulator of the scraper of the press manure removal 88
This paper presents the results of solving the following problem of multiparametric synthesis: determining 4 parameters of the manipulator of the scraper of press manure removal and finding out their values as the manipulator takes the prescribed positions and has equal angular velocities at the beginning and end of its turning. The solution to this multiparametric synthesis problem is based on the methods of the Machine and Mechanism Theory. The results of this paper can be useful for the designers of manipulators for press manure removals.

Keywords: agriculture, machinery, manure, technology, simulation, computer graphics, Mathcad, synthesis, manipulator, pressurer.

J. Olt, L. Käis.  
  Kinematics of the working unit of the blueberry harvester 101
The height of the plant of lowbush blueberry is in the range 10–60 cm and berries ripen more or less at the same time (Starast et al., 2005). It is appropriate to harvest blueberries with machines. The functional working unit of the machine is a picking-reel and the working elements are four picking rakes. A picking rake consists of rake teeth fixed on a rotating shaft. In this case we study the rough blueberry harvester. The task of the blueberry harvester is to pick berries undamaged and to transport them into a container. The harvester is without a sorting line and because of that the berries and additives are not separated. The apparatus parameters of the picking reel are: reel radius r, reel height H, number of rakes z, teeth length of the picking rake lp and angle of inclination γ.

Keywords: blueberry harvester, picking reel, picking rake, rake teeth, kinematics parameter.

V. Palge, M. Pennar.  
  The determination of strawberry plant temperature in spring frost conditions 110
Measuring the surface temperature of the strawberry flower in spring frost conditions gives new information that helps to explain the damages caused by spring frost. The traditional way of measuring spring frost temperatures does not reflect the actual nature of the process. This paper presents data recorded during spring frost. We have measured air temperature in the traditional way of recording spring frost temperatures. We have also recorded the temperature of the strawberry flower – the part of the plant that is damaged by spring frost. Measurements were made at night in the spring of 2006. Measurements were made with IR thermometer UT-02S, temperature sensor TMCx-HA and data logger HOBO U12-006. The data was retrieved by the programme Greenline. 5 K to 9 K lower temperatures were observed on the surface of the flower and the air temperature sensor. –4.5 °C was the lowest temperature of flower surface that was recorded.

Keywords: strawberry, plant, spring, frost, temperature, measuring.

J. Priekulis, V. Zujs, U. Iljins.  
  Ensuring of milking equipment washing liquid operation temperature 113
The article presents mathematical substantiation of heat leak from the washing liquid circulating in the milking equipment. In addition, the possibilities of reducing this leak have been investigated by covering the milk and washing liquid pipes with heat insulation material.

It has been stated that in a barn where milking equipment for milking 100 cows in milk pipe is installed, the washing liquid loses approximately 60% of heat flowing through the milk and washing liquid pipes.

If the milk and washing liquid pipes are covered with heat insulation material the heat leak through these units will only be in the amount of 26% calculating from the total leak.

Methods and appropriate software have been developed for determination of the final temperature of the milking equipment washing liquid.

Keywords: milking equipment, washing liquid, heat leak, ensuring of liquid temperature, heat insulation, mathematical substantiation.

B. Reppo, E. Mikson.  
  Relation between the indoor and outdoor climate in uninsulated cowsheds 126
In Estonia, there are about fifty farms with uninsulated and loose housing cowsheds where the outdoor climate has big impact on the indoor climate of the cowsheds. It is known that cows can put up with lower temperatures much better than with higher ones, so we can say that these buildings are well suited for animals, although there are problems with workers and working environment in uninsulated cowsheds in extreme cases, during very low and high outside temperatures.

The goal of this study was to find out the outdoor climate impact on indoor climate in cowsheds with 500, 420 and 250 cow places during winter and summertime. For that, indoor temperature, relative humidity and ammonia content were measured, using measuring device ALMEMO Data Logger 2690-8 with respective sensors and computer programme AMR WinControl. At the same time, outdoor temperature and relative humidity were measured, using measuring device HygroLog with sensor HygroClip S.

The data about empiric dependence of indoor temperature, relative humidity and ammonia content upon outdoor climate are given. The processed results are well applicable when designing new cattle housing or improving the indoor climate of already existing uninsulated cowsheds.

Keywords: uninsulated cowshed with cubicles, outdoor climate, indoor climate, air temperature, relative humidity, ammonia content, Data Logger, computer programme.

T. Sõõro.  
  Traffic safety of a slow vehicle 139
Slow vehicles (tractor, farm or forest machine, etc.) which go on the roads significantly slower than the traffic flow, obstruct road traffic and become a source of hazard. This fact must be taken into consideration both by the drivers of slow vehicles and drivers of fast vehicles. For ensuring traffic safety, it is essential that the drivers be able to estimate the speed of vehicles and distances, when approaching a slow vehicle. In practice, drivers estimate separation distance and speed of vehicles "by feeling", intuitively. It is necessary for the drivers to cognize safe separation distance and know the influencing factors.

The minimal distance from a slow vehicle (safe separation distance), at which the driver, approaching the slow vehicle, has to decide if it is possible to pass the slow vehicle at once or if he should start slowing down, has been studied in this paper.

Dependence of safe separation distance upon the speeds of vehicles, on road adhesion factor and on the reaction time of the driver have also been studied. Dependence of safe separation distance on the speeds of vehicles and on road surface adhesion factor is non-linear. Safe separation distance is 66–52 m in case of real speeds of vehicles (5–40 km/h for slow vehicles and 90 km/h for fast vehicles). As it is very difficult for the driver of a fast vehicle to estimate the exact speed of the slow vehicle, the driver of the fast vehicle must become observant with regard to the slow vehicle at the distance of 70 m and estimate the possibility of passing the slow vehicle.

The speed of the fast vehicle has greater impact than the speed of the slow vehicle on safe separation distance. In case of varying the speed of the fast vehicle in range 50–120 km/h, safe separation distance varies in range 20–100 m (speed of slow vehicle is equal to 20 km/h).

Road surface adhesion factor has as essential influence on safe separation distance as the speed of the fast vehicle. If on clean dry asphalt surface of the highway (speed of fast vehicle is 90 km/h and speed of slow vehicle is 20 km/h) safe separation distance is 64 m, then on wet surface of the highway, safe separation distance is 6–10 m longer, on muddy or slimy surface, safe separation distance is 15 m longer and on slippery road surface (adhesion factor φ ≤ 0.4), safe separation distance is over 100 m at the given speeds (Figure 4).

Dependence of safe separation distance on the reaction time of the driver is linear. Safe separation distance is equal to 64 m when driving on the highway at given speeds and the reaction time of the driver is 0.8 s. Safe separation distance varies in range 55–72 m, if reaction time of driver varies in range 0.5–1.2 s. For a drunken or drugged driver whose reaction time is 2–3 s or more, safe separation distance is 100–120 m or more (Figure 5).

Approaching a slow vehicle, the driver of a fast vehicle must decrease the speed proportionally to the decrease of separation distance for ensuring traffic safety (Figure 6). At separation distance of 60 m, the safe speed is equal to 75–90 km/h, at distance of 40 m the safe speed is equal to 55–70 km/h and at the distance of 20 m the safe speed is 25–45 km/h, when the speed of a slow vehicle is 7–40 km/h.

The driver of a slow vehicle ought to indicate at least 6–10 s before left turn and changing to the left lanes.

Keywords: slow vehicle, fast vehicle, separation distance, stopping distance, adhesion factor, reaction time of driver.

K. Tamul, J. Olt.  
  The programming peculiarities of benches in contemporary agricultural mechanical engineering business 150
Businesses producing and repairing agricultural technology still largely use NC-led benches – mostly lathes. Benches with technically outdated NC control system are still being used for the simple and CNC-led benches for handling the complicated surface geometry. Such a work division provides a more economic usage of the CNC-led bench resource. Programming NC-led benches is far more complicated when compared to that of CNC-led benches – even for handling the simplest surface geometry (phases, cones), a blueprint needs to be compiled with the CAD programme. According to the change in the measurements of the detail, a new blueprint needs to be compiled each time. Compiling the blueprint could be renounced when a mathematical model would be compiled for the corresponding surface element – it would help to find the coordinates of certain points required for programming. The present article describes the mathematical model for calculating the coordinates necessary for programming phases and cones with different measurements. The model has been compiled on the basis of MS Excel, as this programme (or analogues) are used in most of the mechanical engineering businesses.

Keywords: cutting treatment, phase, cone, main measurements of the instrument, insert nose radius, mathematical model.

I. Tomson, V. Viljasoo, N. Bajeva, A. Bajeva.  
  Factors influencing the indoor climate of a cowshed and the reliability of indoor climate parameters of a milking parlour 165
During various technological processes, inevitable changes in the chemical content and electrical characteristics of air occur. Thus, it is essential to research the influence of materials used in production and proceeding sideproducts upon micro-, para- and electroclimate in a cowshed.

This article studies data regarding the provided norms of indoorclimate parameters, the indices of reliability of specific parameters and their subordinance to distribution laws.

Keywords: indoor climate, microclimate, electroclimate, paraclimate, environment, technological processes, materials, reliability

Ü. Traat, M. Padar, K. Kaljuvee.  
  The maintenance of tractors and the developments in Estonia in 2006 187
The problems connected to the maintenance of tractors in agricultural enterprises have not been studied in recent years. In this article an overview of what is the current situation with the diagnostics of tractors, repairs and maintenance works in reality is given. How they are actually organized, what are the future prospects and expenses in this field and how satisfied the workers are with the situation. As a separate part are discussed at the characteristics of the western tractors, their expenses connected to repair works and maintenance. The fuel consumption of Valmet, John Deere and New Holland tractors is compared. All the statistics are also compared to those of the Russian tractors.

Keywords: tractor, repairs, maintenance, diagnostics, maintenance costs.