ON THE SCHOOL – “CRAYON”

AT SCHOOL - With a minimum of welding operations, avoiding difficulties of manufacturing in more modest circumstances than the school shops complex assemblies and precision parts to make your tractor versatile — such a task put before him a young technology under the guidance of teacher work secondary school number 3 g. Vyatskie Polyany N. Dulova. Developed original design I. golovizin, S. Karaulov, A. Martynov, Yu. a. Nagovitsyn and other school craftsmen began amicably “to translate into metal”. And now deservedly reaping the results of their work.

Mini-tractor “Dwarf” turned out to be extremely successful, unpretentious and easy to operate. A large trailer, plough, and cultivator, of the site and other mounted agricultural implements has made this machine a reliable helper when performing various works on the school grounds.
 
Design made by students of the school of the tractor was determined, in General, the selection of basic units of transmission and chassis parts. The engine used from scooter “Vyatka-150 M”. Suitable from equally popular among homebrew “Tourist”. Its capacity is 7 HP As shown, this is sufficient for universal mini-car, main purpose of which — the mechanization of various works on the school grounds, and clearing snow and transporting goods (also homemade) trailer. Reliable cooling of the motor provides forced air cooling.
Running removable kick starter type car. On the output shaft of the motor, a coupling sleeve (compound EV. 32х1,5 × 20). The other end of the clutch transmits a torque (splined connection 8х32х38) is not so scarce the gearbox from the car GAZ-69.
 
The output shaft of the CP are connected by a rigid u-joint with main gear rear axle. As a last used the block from charged electric vehicle. This block transmits the torque (due to chetyrehkantnomu the worm) from I=12:1 to the drive wheels.
 
In the end, the whole design has 12 gears: 3 of them — back, and all the rest — forward, allowing you to select the optimal mode of operation of the engine at the designed speed range, “Dwarf”, is from 0.5 to 15 km/h.
 
To ensure the tractor, sharp turns, and hold it up at stops, rises and slopes is the band brake. Moreover, the design of this brake has much in common with similar devices, widely used in agricultural machinery industrial manufacturing. A feature that is used from decommissioned harvester “Niva” steel tape with riveted thereto a friction lining homemade covers (St. 45) the brake drum. The diameter of its working surface 200 mm, width 60 mm When pressing on the brake pedal lever tightens the band around the drum, carrying out braking of the tractor. For setting the initial gap between the brake drum and the belt adjusting device is provided.
 
Frame — welded, rectangular shape. Made from strips of steel channel number 8. The cross-beams are simultaneously and brackets for mounting engine, gearbox, other equally critical components of the design of the tractor. On ladders attached to it (illustrations not shown) and the rear axle of the already mentioned electric vehicle. And in front, welded on the cheeks-kerchiefs of steel sheet (St. 45 thickness of 15-20 mm) in which holes with a diameter of 30 mm (figure missing), the axis of swing of the front axle.
 
Latest — homemade. The design is also welded. Made from strips of thick-walled steel water-gas supply pipes of appropriate diameter and looks like the front axle of the tractor “Belarus”. The vertical sleeve is provided with a bronze sleeve — bearings.
 
The steering gear used from decommissioned Polish car “beetle” – providing plenty of maneuverability, ease of operation, so necessary for the school mini-tractor. The machine is able without any difficulty to turn around even “patch” with a radius of slightly more than two meters.
 
Kinematic scheme of transmission
Kinematic scheme of transmission:
1 — front (driven) wheels with tyre size 9,00х16″ 2 — engine “Vyatka-150 M”, a 3 – stub coupler (double splines: EV 32х1,5 × 20 and 8х32х38), 4 — gearbox GAZ-69, 5 — universal joint, 6 — band brake, 7 — rear axle (from the electric vehicle, the worm gear I=12:1), 8 — rear (drive) wheels with tyre size of 9.00 x 16″.
 
Frame mini-tractor.
Frame mini-tractor.
 
Front axle
Front axle:
1 — front (driven) wheel, 2 — wheel axle that is welded to the rotary axle, 3 — bronze sleeve bearings, 4 — bushing, 5 — swivel arm, 6 — tube front axle 7 and the tube axis of the swing.
Coupling sleeve (double spline connection)
Coupling sleeve (double spline connection):
1 — sprocket hub from a “basic” scooter, 2 — cut water gas pipes, the 3 — hub of the slave drive GAZ-69.
 
The band brake mini-tractor.
The band brake mini-tractor:
1 — base 2 — brake lever 3 — adjustment fixture, 4 — steel tape with friction linings, 5 — brake drum, 6 — shaft.
 
Manual and foot throttle
Manual and foot throttle:
1 — the gas pedal (the image is a simplified, schematic), 2 — steel cord, 3 — sleeve (sleeve), 4 — protective sheath, 5 mounting surface 6 — operating lever arm of gas, 7 — cheeks 2 (used discs steering damper “base” of the motorcycle), 8 — a screw with wing nut M8.
 
Speed switch
Speed switch:
1 — rope control 2 — coupling, 3 — steel cord, 4 — body (arm of gas from a sports motorcycle “Java”), 5 — sheave (pulley gear for a basic scooter, with completion), 6 — axis (the screw head diameter 16 mm — M14), 7 — grooves with circular cutouts for the filling of the ends of the steel cord.

 
Front wheels with hubs taken from a disused tractor rake. Tire size 5,00х9″. You can use other wheels. For example, motorized wheelchairs, SZA, having tires 5,00х10″. The rear — driven wheels of the tractor T-16 with subsequent cutting of the tread. Quite acceptable as the leading and the driven wheels from other vehicles in the sizes of tyres 6. 5×16″ up to 9,00х16″. For example, the harvester SK-4, a tractor T-28, T-40.
 
The fuel tank is homemade. You can also use prepared from commercially available furnace “Smoke”, appropriately adapting it. Capacity is 6.7 litres, which allows mini-tractor without additional charging continuously to work (depending on the type of work performed) for 3-4 hours.
 
Cladding of steel sheet of thickness 1,5 mm. Covered with a protective enamel bright, pleasing to the eye and satisfying to the requirement of technical aesthetics colors. Looks good, for example, the combination of yellow with orange or red. Especially if applied to protective coloration Polish the enamel.
 
Used seat from a decommissioned “Fields”. Adjustment is provided on all ergonomic parameters, in order to provide convenience to the driver.
 
The front frame of the tractor is opposed to the sawn in half two ballast blocks from the DT-20. Dimensions each half: 140x50x220 mm. Mount — M12 bolt, with the inner side of the frame.
 
Design school mini-tractor is such that practically eliminates accidental touching of rotating and others representing while working high-risk detail. Where necessary, additional covers and flaps of the fence.
 
Other design features drew the attention of the technical solution to implement the manual and foot control switch with a single cable. Attached to the lever the outer shell serves for the manual control (lever gas) and passed through a hole in the steel cord coupler performs the function of the flexible rod from the pedal.
 
Is not a template, according to experts, the implementation of the switch lever speed. The case is here the throttle stick from a sports motorcycle “Java”. And as a pulley on which is wound a steel cord ropes used ground down to the appropriate dimensions (external diameter 45 mm, groove depth 6 mm) roller shift from the “Vyatka” any modifications. Spitz from the roller removed. Instead, the hole for the axle diameter 14 mm. In the cheek holes, ending with a hole diameter of 6 mm under clamped inside (bobbin-coil sound tape) the ends of the cord.
 
As for the trailer, a plow, and other attachments, they for the readers of “M-K”, we can say, traditional. The frame of the trailer, in particular, made from strips of thick-walled steel water-gas supply pipes. Suspension — shortened to 650 mm springs from GAZ-69. Wheel chains greater harmonization of the structure is taken again from a decommissioned tractor rake.
 
The plow is a little different from the drawing and which is described, for example, in No. 7 of the journal in 1981. The basis for the design can be from the old Coulter of the plow attachment with blade is welded to the reflector is provided with a support plate of high quality structural steel. Chisel and mouldboard recommend you to use prefabrication. For example, from written-off cultivator.
 
The site, which can be equipped with a mini-tractor is essentially mounted on a special rigid rods shovel mini-bulldozer. Made from 8-mm slightly curved in the vertical plane of steel sheet (St. 3) size 550х1100 mm, reinforced bottom plate-a knife with a width of 75 mm (silovsky, dilapidated spring).
There is a possibility of the use of harrows, other implements. And for decompression of the upper layer of the soil and the cultivator. On the frame there are for this (and other purposes) towing site.
 
It is taken from a written off truck (brand in this case is not important). Reinforced rear on the crossmember.
 
Mini-tractor “Dwarf” is heavily used in the school the first year. Breakdowns, and other malfunctions in all that time it did not occur.
 
The main characteristics of the mini-tractor “Dwarf”
 
Dimensions, mm: 1000х1965х1300
 
Base, mm: 1300
 
Track width, mm: 850
 
Minimum turning radius, mm: 2500
 
Ground clearance mm: 280
 
Engine — petrol, two-stroke, forced air cooling “Vyatka-150 M”
 
Engine power, HP: 7,0
 
Number of gears: 12 (3D ago)
 
Maximum transport speed, km/h: 15
 
Minimum operating speed, km/h: 0,5
 
Constructive weight, kg: 550
 
Trailer load capacity, kg: 1000

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