The ignition system consists of two auto type spark plugs per cylinder that independently fire by both a single self-energized magneto and a Hall-effect 12-volt electronic ignition system. This system in effect eliminates total failure of the ignition system when used in tandem. The timing is fixed at 22 degrees BTDC. An electric 12-volt starter motor, which is mounted in the rear, has a built-in solenoid for reliable engagement and cranking. Also rear mounted is a 35-amp alternator with a built-in voltage regulator.
The fuel is supplied to the engine by an engine-driven mechanical fuel pump, an electric fuel pump (which you need to purchase) and then configure both in series. The carburetor is a single Bing 40mm constant compression that has very good automatic altitude compensating mixture control that gives a smooth delivery of power. A conventional valve train is utilized with two per cylinder with dual row cam rings and roller tappets for smooth valve movements by a pushrod and 1:1 rocker transmission. There is a dry sump lubrication via geared oil pressure primary and secondary scavenge pumps.
The propeller hub is driven by a precision ground and matched taper. The propeller flange specifications are standard and are the same as are used for a Rotax 912 Series. The gearing is by a planetary speed reduction unit at a ratio of 3:2 engine rpm: prop rpm. The propeller’s rpm fixed with a 76” diameter x 51” is rated at 2,400 rpm.
The minimum octane is 97 RON or 100LL aviation or high octane mogas is recommended. Compression ratio of 8.5:1 is standard. Fuel consumption with avgas 100LL or high octane mogas is 5.8 gal./hour at 80 percent power. Rotec recommends using a high quality, major brand, four-stroke motorcycle oil, like Pennzoil motorcycle motor oil SAE 20W-50 or Valvoline Dura Blend Synthetic SAE 10W-40. Rotec recommends time between overhaul (TBO) of 1,000 hours.
Beware of corrosion
Builders of experimental aircraft like to have all their parts ready for installation as needed and not have to wait for them to be delivered. This is also true with the engine and sometimes they are delivered and end up sitting in a corner waiting to be installed. This practice will eventually damage your new Rotec engine as corrosion will start. Remember rust never sleeps. In the manual, corrosion protection is outlined but Rotec also has additional recommendations that must be followed if the engines are not in use or are in storage. It is very important to take the necessary steps Rotec outlines to protect your investment.
On a personal note when I was employed at the Aviation Institute of Maintenance in Chesapeake, VA, I would send emails with technical questions about the R3600 we purchased for our WWI student project which was to build a Nieuport 24 aircraft using the Redfern plans. Rotec was very helpful with all our questions and provided the technical answers when we needed help. We even purchased other items like antique looking gauges and a propeller from Rotec.
With hundreds of these engines sold it won’t be long before you see one of these engines at your nearby air show and hopefully you will hear that distinctive sound of a radial engine in flight and maybe just maybe you’ll have a Fosters in your hand also. How great would that be?
Brad Groom has been an aviation enthusiast and an educator for more than 25 years. He has served in the U.S. Air Force, spent many years teaching foreign nationals how to maintain and troubleshoot aircraft for a defense contractor, part of the Navy Adversary Program Quality Assurance, and was employed in a FAA Part 147 school as an instructor and a manager. Currently he is the program coordinator for Centura College’s online aviation maintenance management degree program. He holds an Airframe and Powerplant certificate and a bachelor degree in technical education.