ZNLine Factory Enigma Build by Mark Novack

I will go into a little detail here. This procedure is not hard and certainly no witchcraft is involved, although the "big chief" JP does express a certain mood when preparing for this step. We use the YS DZ and the ZN motor mount and adapter. The ZN mount weighs about 80 grams, one of the lightest available mounts. Here is the mount and motor with the mount adapter on the engine.

Here is how it fits. Three 3mm screws into the tapped bosses on the mount. Note the elongated slots on the adapter. This allows small changes in thrust by simply loosening the screw, sliding the motor, and retightening the screws. CHAD, the white ring is a piece of Teflon, it serves as the ride bearing for the two halves to rotate against.

Here is the firewall, screw support ring, and mount. I want to explain a little bit about these pieces. The motor mount is, of course, machined aluminum with a Teflon ride bearing and a rubber buffer/tensioner. The screw support ring is CF laminated ply and spreads the load of the screws on the firewall. The firewall is carbon laminated Nomex hexagonal honeycomb. It is very stiff and light but can be crushed relatively easily with point loads. We fix that problem with the following procedure. The making of the piece is as follows. First the laminate is prepared and allowed to cure overnight in a vacuum bagging system. Once the sheet of carbon/honeycomb laminate is prepared, it goes onto the routing table where the outline of the firewall is cut and three circles of 2cm diameter at the bolt locations are cut only through one laminate and most of the honeycomb, leaving one side with no circles. These circle areas are removed and the three areas are filled with a special epoxy/micro balloon/dye mixture. This is allowed to cure overnight and then the routing operation is finished by cutting the motor mount slots through the epoxy reinforcement, all the way through the firewall. This will be evident in the next couple of photos. It takes basically four steps in three days to make a firewall that weighs next to nothing and when glued into the fuselage is practically indestructible.

The epoxy circles are evident in this picture. They take the point loads and spread the load out nicely. These are some serious nice firewalls.

Here is the nose ring (included with the motor mount) and the nose ring mount, also CF/ply laminate. This nose ring is about 5mm thick and spreads the load on the crankcase snout better than the o-ring style mounts. Aluminum inserts in the nose ring holes the screws that attach this to the nose ring mount.

Added is the spinner. Now we have all the material necessary to install the motor. Let's do it!!!

We have bolted up the motor mount and now we test fit the firewall. Here is a front shot.

Note the screw support ring to spread the load.

Next, the motor, with the nose ring on it's mount and slid onto the crankcase snout, slides into the opening.

Insert and start the three screws for the motor mount.

Next, install the drive washer and spinner backplate onto the motor.

Manipulate the motor by the crank, aligning the spinner back plate with the nose of the fuselage (the fuselage has been designed so that evenly spacing the spinner from the nose of the fuse automatically sets the correct thrust angle) so that there is about a .5mm clearance. Now, before tightening everything down and gluing, feel around the fuselage and look too at the area on the outside where the firewall is. Any lumps or bumps caused by pressure on the fuselage by the firewall pressing against it? If so, note their location, remove the whole assembly and sand off a little amount of the firewall and refit. This does not need to be a press tight fit. In fact, it should be a nice, even, but gentle fit. No pressing the fuselage. That will distort the fuse walls, at best causing an ugly lump when painted, at worst...well, we won't theorize the point, we will simply make it fit perfectly. The nose ring should allow enough play to get the spinner exactly (not close, not good enough, but exact) centered. Here is a photo as JP tugs on the motor, getting the position perfect. 

Once satisfied, mark the inside of the fuselage along the edge of the firewall and nose ring. Then place a bead of epoxy a little bit behind the mark so that when the firewall and nose ring are installed they will grab onto the epoxy and form a little fillet. We want enough glue so that it is completely solid, but not at all sloppy. Tomorrow, the motor will come out and a final, beautiful bead will be smoothed into position with a finger at the front and back of the firewall and nose ring. Here JP uses an extended spatula to get the glue where he wants it.

Epoxy in place, fit everything back into place. The epoxy has micro balloon, fibrous cotton (we do not want a runny mixture here), and dye in it. The dye is a product from the epoxy manufacturer and does not affect the strength as it is less than 1% of the mixture (more like .1%). We use the dye because with the carbon fiber all around, it looks absolutely great when finished. Here, the motor is in and braced into place. The weight on the fuse belly keeps that flat part pressed evenly and flat against the firewall. Now, we will be VERY VERY careful when anywhere near the assembly. If this gets bumped off, somebody's getting knocked out!!! grin! Pretty easy, eh?

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