A new Propeller Speed Reduction Unit (PSRU) is here:

specifically designed for your experimental Mazda powered aircraft. 

 Rated for up to 8000 engine revolutions per minute giving a prop speed of 2500 or 2800 rpm depending upon which gear set you choose.  It is an improved version of all previous similar PSRU's made for Mazda rotaries.  In short, all known failure modes have been eliminated.

Many improvements and modifications have been made, being designed with the latest CAD software and machined with CNC  accuracy.   Critical components are made in Australia and Colorado, USA, ensuring that no "dodgy" materials are substituted and all is of the highest quality. 

Using the proven and standard Ford gear set, the gearing is 3.17:1 or 2.85:1 which is ideal for the Mazda rotary aircraft powerplant.  It is designed to conservatively transmit 250 HP.  It has a thrust bearing which has not been featured on any affordable PSRU before now.

The new flex drive (aka: impulse coupling or cushion drive) is lighter at 2.5 LBS and includes a polyurethane 70 to 80 Durometer flex material depending on HP requirements.  Should this material fail the unit will still drive on a metal to metal basis which will get you to the ground safely.  This flex drive will also retro fit to any RWS PSRU and is 1.7 pounds lighter.

The flex drive is driven direct from the E shaft counterweight which eliminates any further stress from the flexplate, which was a source of failure on some previous units.

The prop shaft is machined from high strength alloy steel forged in one piece.  Bearing surface is a type of bronze alloy with oil fed thrust bearings on each end to take fore and aft thrust loads.

The standard Ford Planetary gear set of 3.17:1 or 2.85:1 is totally re-designed to take the modified splined prop shaft drive and is hardened for long life.  You can install a magnetic plug on the oil return line which will give a warning if there is any deterioration in the PSRU before it can develop into a disaster.

The ring gear in the planetary is no longer held by the "sprag" gear, but instead is machined into the housing under close tolerances only possible with CNC technology and locked in place chemically and also held with extended point screws.  This has eliminated the possibility of the sprag gear 1/4 inch holding screws shearing off under load which has happened in the past in high HP situations.

The specially machined input shaft is a one piece hardened and tempered unit with no drive pin to shear and ruin your day. The housing is totally sealed with O rings eliminating the need to plaster gasket sealer over yourself and the unit to stem oil leaks.

Designed and tested in Australia, all parts will be available from Australia or Colorado, USA to you. 


With cost in mind the unit will be sold as to whatever you the customer want.  You can make your own mounts, you can source your own bearings. You assemble the unit (sold as a kit only), anything that helps you with cost.

Total weight for the PSRU with standard mounting plate and mounting pads is a little over 42 LBS. with flex drive.

Cost is $5500 usd for the PSRU with flex drive plus shipping.

This PSRU has been successfully tested in OZ (Australia).   The first batch of 5 units are available now. As of 06/20/18 there are 4 units available.








Before shipping any product to you we will require a RELEASE of LIABILITY to be signed by you the purchaser and a witness and returned to us. 



   Rotor Power Reduction Drive (RPRD)


  • HORSE POWER                 250 hp max recommended

  • RPM                         8000 rpm max recommended

  • GEARING                     2.85:1 RPRD-2A
                                3.17:1 RPRD-3A

  • FORD PLANETARY GEAR SET     yes, 6 pinion

  • PROP SPEED                  2500 rpm

  • WEIGHT                      42 pounds

  • THRUST BEARING              yes

  • CHIP DETECTOR               optional

  • FLEX DRIVE                  yes (impulse coupling)

  • ROTATION                    clockwise (tractor)
                                counter-clockwise (pusher)

  • COST                        not available

  • DATE AVAILABLE              4 units available now, order below



Sold in kit form, you assemble with the instructions provided.


We would like to gauge demand for this PSRU; if you are building a Mazda rotary powered vehicle or have an interest would you kindly notify us?


If you have a Tracy Crook Real World Solutions Gear Reduction Drive and/or need the RD-1C Installation Guide, send us a message requesting a copy. 


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