Wednesday, November 12, 2014

24mm Engine Mount Improvements, Part 2

I think Doug Sams posted the tip about cutting off the finger tab and flipping over the engine hook.
The finger tab was cut off and the rough edges filed smooth.
The hook will be installed flipped, with the round bent finger tab side up against the engine block.
The cleaner bent square end will be at the bottom of the mount.

The picture on the right shows the mount assembled (dry fit, no glue yet) as shown in the instructions.
TIP: Don't glue the rings in place yet, dry fit everything first so you can make adjustments and an improved mount.

On the left is how the instructions have you assemble the engine mount.
The inset picture shows the mount with changes to make it stronger.

Instructions: The engine hook extends 1/2" beyond the back of the tube. I can't see any reason for this. Unless - the designers wanted the rocket to hit engine first. The fins on the Laser Lance look like they could break on a hard landing. Changes: The hook will be raised up so only 1/4" hangs below.
Changes: The black hook retainer ring will be raised slightly so the engine hook can be lifted easier  for the engine to slide in. With the black ring lower (left side) it's harder to lift the engine hook.

Instructions: The upper centering ring is glued even with the top of the engine mount tube.
Changes: Lower the ring position so it sits on top of the upper bend of the engine hook. A strong ejection could throw the engine back and tear the thin BT-50 engine mount tube.

TIP: When gluing on the split rear ring, slide it in the BT-55 tube to hold the split ends down. When it dries the ends will be tight against the engine mount tube.
A notch was cut in the upper ring to allow the Kevlar line to pass through.
After the upper ring was glued over the top bend of the engine hook, a length of Kevlar was tied under the upper centering ring.
There isn't much room between the BT-50 engine mount tube and BT-55 main air frame tube.
I didn't use a knot, that bulge might show through the BT-55.
Instead the Kevlar was wrapped underneath the loop four times. All was set into the ring glue fillet.

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