Pages 46-1 through 46-22. Engine prep and hanging

When the time came to actually hang the engine it was pretty exciting.  For the first time I would not need a stand under the tail tie down ring to keep the airplane from tipping over backward.  It could stand on its own three feet, proud and unsupported.  No crutch!  A quick perusal of the build manual, however, damped my excitement a bit.  A surprising amount of work was required to prepare the engine before hanging.

Since everything I was about to do required the use of a torque wrench, sometimes in awkward places where I couldn't see the dial on the Snap-On, I decided to calibrate the click-type Craftsman so I could use it if required.  In an earlier post I discussed calibrating the Snap-On with a known mass (not a bar bell weight!) and found it dead-nuts accurate.  A fresh calibration showed the same.  In the torque ranges required for engine installation the Craftsman was off by as much as 18%.  Glad I checked.

The first task requiring some thought was to check and set the five crank triggers shown in the picture below (five because one of them is a rev counter).  The gap between the tooth on the flywheel and the sensor is specified to be between 0.012 and 0.016 inches.  But wait a minute, I'm thinking, these Rotax

engines are broken in at the factory by being run on a dyno for about an hour.  Wouldn't that mean that the crank triggers are already set?  One  respected guy on the VAF forums just left them as is.  They're all tighter than the Van's spec, so I went ahead and set them.  This requires rotating the crank, which is accomplished by putting bolts in some threaded holes in the flywheel, removing a spark plug from each cylinder, and using a big screw driver as a lever.  When the prop is installed, turning the engine is much easier and has to be done a lot when fitting the spinner.  I still left the plugs out, however, with rags stuffed in the spark plug holes to keep trash and insects out.

The next challenging step required disconnecting four coolant hoses from the water pump in order to install the engine mount.  I've disconnected many a coolant hose on many a car over the years without any problem.  These were different.  Nothing I tried would budge them.  I finally fabricated the piece of wood shown and drove them off, still needing a little assist from the padded vise grips to supply a little rotation.  There was some coolant still in the engine which had to be caught in a shallow pan.

The engine mount is attached to the engine with four 10mm cap screws which must be accurately torqued to a hefty value which now escapes my mind but is obtained from Rotax Heavy Maintanence manual.  I was glad I checked the manual because it's a substantially higher value than is given in the standard bolt torque table.  The problem arises because it's hard to put a torque wrench on the upper

port-side bolt.  I've read where other builders removed the intake manifold to do this, something I really wanted to avoid.  These bolts must be rechecked at every annual condition inspection giving added incentive to find another way.  I ended up using a double box end wrench as a "torque adapter" as they're known commercially.  Keeping a 90-degree angle between the handle of the torque wrench and the box-end wrench means the torque reading in unaffected by the wrench (the position vector crossed with the force vector gives the torque).  There's a little segment of an Allen wrench in the end of the wrench not attached to the torque wrench which goes into the cap screw.

With the engine attached to the engine mount I was ready to move it to the airplane.  An engine hoist on rollers made this a simple, one-person operation.  Before attaching the mount to the firewall a couple of 3/8th inch holes had to be drilled through firewall, easy for me because I could do it from the front since I'd already installed the upgraded nose gear leg.  The poor souls who had to install the new leg to an already-flying airplane had to drill the holes from the inside, a much more involved task.