I am using the MZ-34 from Leon Massa at Compact Radial Engines in Surrey BC Canada. This is a single cylinder 28 hp engine. This engine was originally designed in Italy by Zanzottera as a back pack powered Parachute engine. Leon has up dated the engine with Nikasil coatings and absolutely exquisite machining and internal compression releases.The engine comes with a pull starter and an electric starter as an option. I have eliminated both of these features on my prototype to save weight. I will need to redesign the wings to an all wood design to save enough weight to allow for an electric starter, more on that later!!
The main reason I bought the MZ-34 is because of the mounting system. It uses 4 radial shear type mounts placed around the center line of the crank. This is similar to the mounting system of a Radial engine, but not quite as refined. It is however greatly improved over a flat bed mount like the Rotax 277.
Years ago I worked for Ford Motor Company in the NVH lab (Noise, Vibration and Harshness) our job among other things was to isolate vibration and eliminate noise. One of the basic principals of vibration isolation is to convert the vibration into heat. This is accomplished in a rubber mount system by absorbing the vibration by shearing the rubber. In order for a rubber mount to work, the fuselage side of that mount must be held fixed in all 6 degrees of freedom. Any movement in any axis will result in vibration transmission. So far this is all theory on the Robin, because I have not yet started the engine. You can all drop by in a few months to see if I have to eat some Humble Crow Pie!!! But you have to start with a theory!!
So here is a side view of the engine installation
Notice the 4 struts that connect from the longerons to the fire wall. The fire wall is a structural foam and glass sandwich of 1/4" 4.5 lbs PVC foam and 120 style fiber glass. This will eventually be covered by a layer of Quartz Fiberfrax for a heat shield. The fire wall itself has a great deal of in plane stiffness in the inboard/outboard and up/down directions, this effectively accounts for 4 of the six degrees of freedom. The struts account for the stiffness in the fore/aft direction. There will be an out of plane vibration mode due to the angle of the struts, but that is again reacted by the in plane stiffness of the fire wall.
The engine was mounted in space per the layout of the plans and the location of the 4 attach points were located. A hole saw was used to cut through the fwd face of the fire wall only. Glass inserts using 1/4" commercial NEMA grade fiberglass plate were fabricated and bonded into place. A doubler of two ply's of 120 glass were laid up over the top of the inserts.
|core removed prior to insets installation|
|MZ 34 Engine installed|