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Torque Master Engine
  Reduction Drive


torque-master-5.jpg (30072 bytes)TORQUE MASTER 
Reduction drive unit by 

AIRDROME AEROPLANES newest product is our TORQUE MASTER GOODYEAR EAGLE SYNCHRONOUS DRIVE reduction unit. Commonly referred to as a PSRU (propeller speed reduction unit). The purpose of installing a reduction unit on your aircraft is primarily for efficiency reasons.



  • As a propeller tip speed increases the efficiency decreases.

  • The larger the diameter of the propeller the more effective disk area it has. 

  • To increase disk area is to increase thrust

  • It is common practice to decrease the diameter of the propeller to increase its rpm to get more horsepower from the engine. 

  • As a general rule of thumb if you increase the engines rpm that will increase its horsepower

  • If you reduce that rpm by half thru a reduction unit you will double the torque output of the engine.

  • Horsepower is not the determining factor for sizing a propeller.

  • Torque is the determining factor for sizing a propeller.

  • It is more efficient to go with the larger diameter propeller at a lower rpm.

  • If you increase a propellers diameter from 60" to 84" it will increase its effective disk area by 96%.

  • Any increase in the props effective disk area. will increase its output .


  • Self Tracking sprockets thus flanges not reg. that normally wear belts by forcing them to track.Belts provide shock damping to crank shaft. Eagle belts do not require retensioning, as do V belts

  • Drive face width angled tooth results in 90 % more area than straight-faced belts of the same width

  • Noise comparison on average these drive reduce noise by 19 db

  • Bearing load reduction over 30% as a result of less tension required 

  • Product efficiency at 98.5 % efficient it is the highest in the market that translates to more useable power at the prop

  • Belt strength comparison eagle belts stretch less than 20% of their poly chain counter parts under a full load 


  • Driven off the pulley end of the engine this unit offsets the crank only 5.875 "

  • Ratio is 2.125 /1 

  • Engine at 3800 rpm / prop is at 1788 rpm for prop up to 96" in dia with a tip speed of 749 fps

  • Bolt on no welding or machining 

  • Prop loads carried by the case not the crank

  • Standard rotax bolt pattern on prop flange

  • Weight approximately 11 lbs 

  • Fits all type 1 vw engine cases from 1600cc up to 2275 cc

  • Torque master reduction unit $1295


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20010-2011 Airdrome Aeroplanes ~ 929 NW Road 1571, Holden, MO 64040 ~ 816-230-8585