Conversion - T2 Schneck
Inspired by the articles in SPORT AVIATION on the subject of “Conversion of Volkswagen Engines for light Aircraft”, and needing a project to keep my workshop buzzing, I embarked recently on one of the most fascinating experiences of my life. While I was still debating the question, “Should I or shouldn’t I mak a conversion.” I happened by a junk yard and saw a badly burned VW. The car was of quite recent vintage and the engine compartment looked relatively untouched. Suddenly. I decided to see if I could make a deal for the engine.
Upon investigating, I found that somebody had beaten me to the engine but had traded in another engine that swallowed a valve and had been pretty badly beaten up. The trade-in was in a basket, fully disassembled. I looked it over, and found the case was OK, the heads and rocker action were in good shape and the shaft, although needing grinding, was repairable. The connecting rods. camshaft and timing gears were also in good condition. Adding it all up, it appeared that all of the essential parts were serviceable, so I bought the basket of parts.
After thoroughly cleaning the parts. I purchased a new set of cylinder barrels, pistons, rings, wrist pins. valve springs, push-rod housings, rod and main bearings, and oil pump gears, and had the crankshaft reground. The cost was surprisingly low. The next step was to design the conversion parts that needed to be added to make the engine suitable for air craft use. The magneto drive was worked out simply by the use of a Continental O magneto gear mounted on the rear end of the crankshaft driving a similar gear on a Scintilla Mag. A cast aluminum-alloy case for mounting the magneto and tachometer shalt connection was designed and a pattern was hacked out. A very simple machining job finished this portion of the project.
To attach the magneto drive gear to the crankshaft presented a small problem, but it worked out nicely when I found a machine shop capable of machining metric threads. A new bolt replacing the original flywheel bolt was a simple solution, and it served also as a portion of the tachometer drive adapter. This adapter was mounted on the rear case in direct line with the crankshaft centerline. A thrust bearing washer was Installed under this new bolt and pinned to the crankshaft, using the same dowel holes formerly used for the flywheel.
The engine-driven fuel pump was replaced by a crankcase breather attachment. This consisted (If a cast aluminum-alloy pad into which a pipe plug is screwed. A tube extends through the pipe plug to the surface of the crankshaft. The distributor and distributor drive shaft were omitted, and a cast aluminum-alloy cover with a gasket was installed to cover the distributor shaft outlet hole. The generator mount arm was sawed off near the case, and a east aluminum-alloy hinged cover was mounted on the opening. A spring locking wire was installed arm cavity is used as an oil filler neck.
The most delicate problem, that of attaching the propeller, was solved by cutting a taper on the front end of the crankshaft and machining a propeller flange with an internal taper to match. The existing key is used to lock the flange to the shaft. The flange is held firmly in place by a special metric screw which fits the existing crankshaft threads, A stainless steel locking Plate, which lies against the front face of the propeller flange, locks the propeller retaining screw. Great care in fitting the tapered flange to the shaft taper is absolutely essential. The surfaces, whether ground or turned. must be lapped together and checked with Prussian blue to assure really good contact.
The VW oil cooler is not needed on the aircraft conversion. To replace it an aluminum-alloy casting was designed and drilled internally to complete the oil line circuit. As an added convenience, an additional tapped outlet was added In this casting for connecting a pressure line. This line is a better location for oil pressure than the oil pressure outlet on the crankcase front face. An intake manifold made of 1¼ in. diameter electric conduit was fabricated. The manifold runs down below the aft end of the crankcase similar to the old OX-5 manifold. Several types of carburetors are available lo replace the original VW downdraft carburetor.
The completed engine runs beautifully and “as smooth as glass.” Fuel consumption is very low and the basic engine is so beautifully designed that maintenance is bound to be quite simple. Above all, the total cost of the engine. including the pattern material and some small special tools, exclusive of magnetos and carburetor was only $325.00.
The project was one of the most enjoyable and satisfying that I have ever tackled, and the end result is power plant that has what most of us “oldsters” would have loved back in the days when Ed Heath was iloing wonders with a rebuilt Henderson engine. The installation drawing and photos of the engine bare and installed on a little sport biplane indicate how nicely the engine fits into light aircraft.