Stephan's Sonex #1627 Builder's Log

Aerovee

The Aerovee engine comes as a kit directly from AeroVee Conversions, a subsidiary of Sonex. It is the official engine supported by Sonex Aircraft. The Aerovee is a 2180 cc VW long block racing engine. 

I have read from various sources that the engine package is a collection of various racing parts from different manufacturers. Sonex does perform their own quality control checking on the critical components, but the builder still needs to cut the push rods to size and verify that the weights are within specifications.

I am not an engine expert, so I defer to people that have been in the business of engine development for decades, such as Great Plains Aircraft Supply Co. and RevMaster. I consider them to be the definitive authority on VW engines for aircraft use. Both these engine manufacturers have replaced the #4 bearing with a larger bearing capable of handling both the torsional, vibrational and gyroscopic loads typically seen when swinging a 8-10 pound prop. 

The theory behind it seems straightforward. The #4 bearing was originally meant to drive an accessory pully. The original designer (Porche) never intended the kinds of loads on both the bearing and the crankcase that the Aerovee engine is undoubtedly generating when switing a 10 pound prop. I would love to get my hands on an Finite Element Analysis (FEA) report on the internal stresses of an Aerovee engine. Sonex hasn't provided this so the issue of the prop hub and #4 bearing are not put to bed yet.

I came across the following FEA analysis heat map detailing internal stresses and is based on a standard VW engine block. This is only here for informational purposes, because I do not know to which extent the original VW engine has been modified in the AeroVee. 

The above image is courtesy of MotorAv. At least one company has analyzed the suitability of the VW engine as an aircraft engine (swining a prop load, instead of an accessory pulley) and determined that a redesign is necessary.