Estes Aries SST, #1927, Build, Part 2, Engine Mount

The engine hook and Kevlar line relief notches are initially cut with a knife. 

Instead of picking out peeling out the wrap layer between the cut lines, I use diamond files to remove the recess. This makes a cleaner notch, especially on the Kevlar side. 

I don't apply a ring of glue then slide the centering ring onto it. Instead, I slide the rings on dry, apply spot glue at the joint and then smooth them. After the spot glue dries, it allows me to tighten the Kevlar wraps without the rings sliding around. Then apply full glue fillets

Note the upper ring is centered over and on top the upper bend of the engine hook. This makes a stronger mount - instead of the upper ring positioned above the upper bend of the hook.

Tighten the Kevlar wrap, then apply the glue fillet over the the Kevlar wrapped line.

An engine block wasn't included in the original kit, I added one, even with the tube top when slid against the top bend of the engine hook.

A 1/16" diameter heat shrink tube was slid down the Kevlar line and hit using the low setting from a heat gun.

Hold the heat shrink end down against the top of the upper centering ring. The after pics shows the tubing hugging tight over the Kevlar line.

Note the shrink wrap starts below the top of the engine mount tube. This protects the the low end of the Kevlar line.

New Way Lunar Jumper Build, Part 3, Engine Mount & Shock Cords

The engine mount assembly is standard. A slip over coupler holds down the middle of the engine hook.

Here, the Kevlar line is tied beneath the upper plywood centering ring.

There isn't much space between the outer BT-50 and BT-20 engine mount tube. A larger square knot could bulge out the BT-50 tube wall.

I used an overhand knot, but rolled the Kevlar over and under the wrap 4 times. This still allows the wrap to be pulled tight and keeps the line close to the engine tube.

The wrap is set into the wet glue centering ring fillet. The loose tail is cut off and also set into the glue fillet.

The picture to the right shows the heat shrink tube slip down to the top of the ring, protecting the Kevlar line. 

The short shrink wrap is slid over the tied knot joining the elastic and Kevlar line.

Near the elastic, be careful with your heat gun - 

TIP: Using the low setting on my heat gun, the elastic started to melt!

I had to cut off the old knot and re-tie the elastic and Kevlar. I might tie an additional piece of elastic to the shorter line joined to the Kevlar.

The second time, I kept more distance between the heat gun and the heat shrink tube.

Second try was good! (Maybe that's why two pieces of tubing were included.)

Estes Monarch Build, #7214, Part 3, Engine Mount

The finger tab was cut off and the engine hook flipped over.

A subtle curve was bent down the length of the hook for better motor retention.

The upper centering ring got a small punch for the added Kevlar line.

The upper ring was slid on just over the upper bend of the hook for strength. 

The rest of the mount was assembled as shown in the instructions.

A 1/16" diameter heat shrink tube was slid down the Kevlar line and against the top of the upper centering ring.

Thanks go to Rick Randoll of NewWay Space Models for this Kevlar heat protection idea. 

A heat gun on low setting shrinks the tube around the Kevlar line.

The inset picture shows the Kevlar line below the base of the lower ring, set into the glue fillet.

New Way Blade Runner, Part 3, Engine Mount

The rings are glued in place on their 1/2" marks made earlier.

Tie the Kevlar with a small square knot. Cut the loose tail off at about 1/2" long.

Press the Kevlar loop, knot and tail into the glue fillet.

Slide the heat shrink tube down the Kevlar line until the end rests on the upper centering ring. 

While holding the heat shrink tube against the upper ring - 

Apply heat using a hair dryer or heat gun on the low setting. It should shrink around and tighten over the Kevlar.

When tying the Kevlar knot, make it small and tight against the motor mount tube. There isn't much space between the BT-20 and BT-50 tubing.

Notice the Kevlar relief notch is to the outside edge of the upper ring. This keeps the Kevlar to the outside of the hot ejection charge.

BMS School Rocket, Build, Part 4, A New Kevlar Cord Protection?

I can't take credit for this idea - 

Props go to Rick Randall at New Way Model Rockets. He has incorporated this Kevlar protection cover in many of his LPR kits.

Kevlar lines start to break down and can fail at 10 to 15 launches.

Near the low end of the Kevlar, near the engine mount - Rick adds some heat shrink tubing over the Kevlar line. When you consider how hot a heat gun gets (to shrink the tube around a wire) it makes sense!

An black powder ejection charge is momentary, the heat gun take a few seconds to shrink around the Kevlar line.

Heat shrink tubing is not included in the School Rocket Kit. I found some on Ebay and am starting to use it in my builds.

For reference, here's a 1/16" diameter heat shrink tube slid over a 135 lb. LPR Kevlar line.

To fit it over the Kevlar knot under the engine hook,

I flared the open end a bit using a sharpened dowel. The flared end makes it easy to slide over the knot.

On the left,

The heat shrink is slipped down and over the knotted Kevlar line.

On the right,

A heat gun was used to shrink the cover tight over the Kevlar and knot. The hear gun was used on the LOW setting.

There is that square hole left on the other side. Some ejection gasses could escape out of the hole.

A small piece of scrap BT-20 was cut and glued over the hole.

New Way Letter - Go Build, Part 5, Engine Mount Gluing

Run the Kevlar line out the back of the engine mount.

I set the engine mount beside the main airframe tube to mark a dowel that will apply a glue line inside the tube. Note the pencil line where the glue will contact the upper centering ring.

Glue was applied to a dowel end and transferred inside the tube.

The mount was slid in with 1/8" of the engine hook exposed out the back end.

A length of heat shrink tubing is supplied to slide over the Kevlar line and down to the top of the engine mount. The tubing protects the Kevlar at the low end from the ejection charge.

To be honest - 

I didn't remember to slide the tube down the Kevlar line!

Here's some shrink wrap on Kevlar before and after being hit with a heat gun.

Considering how hot a heat gun is, the shrink wrap sleeve should give good protection to the Kevlar line 

Roll the Kevlar to keep it out of the way when sliding the mount into place.

The lower centering ring got a glue fillet smoothed out with a Q-tip.