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Anglicky v odbornch pedmtech"Support of teaching technical subjects in EnglishTutorial: Engineering technology

Tutorial:Belt drives

Prepared by: Ing. Jaroslav Hbl

Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

BELT DRIVESTorque is transmitted by friction forces between pulleys and belt mounted around driving and driven pulley.

BELT DRIVESADVANTAGES OF BELT DRIVESEasy and cheap productionPossibility of more shafts driven by one beltQuiet operationDamper of operating shocks Protection to overloading

BELT DRIVESDISADVANTAGES OF BELT DRIVESHigher bearing loadBelt slippage on pulleyBelt stretcher is necessaryIntolerant to high temperatures

BELT DRIVESGEAR RATIO

Rule for friction gears by slip is:

= slip coefficient

BELT DRIVESTYPES OF BELTING

open, b) crossed, c) open with idler pulleys, d) half-crossed

BELT DRIVESTYPES OF BELTINGHalf-crossed with idler pulleys, b) open with tension pulleys, c) open with more shafts drives

BELT DRIVESTYPES OF BELTS ACCORDING TO SHAPEFlat belts they are used exceptionally today.V-belts.- classical cross-section most common- narrow for higher speed- wide for disk friction drives- toothed for valve train drive of combustion engines- multiple they have bigger load wearing capacity than common belts.Circular cross-section belts for special use (similarly to rope gears).

BELT DRIVESTENSION MECHANISMTension mechanism increases pressure force which has to make higher friction force in belt. It eliminates belt lengthening in operation and makes the angle of pulley belting higher.

By drive slide on the skids, b) by tension pulley with balance weight,Self-tension reaction momentum drive is placed on the cradle

BELT DRIVESTENSION MECHANISMWays of belt tension:

Belt shortening used only for flat belts at constant axis distance. Ends of the belt have to be connected after belt shortening by glue sticking or connection fitting. By tension pulleys it is advantageous because it makes the belting angle bigger. By axis distance extension drive must be placed movably. By self-tension drive is placed movably and belt is tensioned by gravitation )force effect of drive).

LiteratureStroje a zazen I, J. Doleek, P. Gajdo, V. Novk Strojnictv I, J. Doleek, Z. HoloubekStrojnictv II, J. Doleek, Z. HoloubekModern strojrenstv, Josef Dilinger a kolektiv

Write down the rule for gear ratio.

Name types of belts.

Disadvantages of belt drives?