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This is a technique that I have standardized for any build where I want to install the motor hook, but leave the forward end of the motor mount open for longer motors.
I’ve just started building the Roachwerks 4x24mm Nike-Hercules that I purchased from a forum member. The kit included E size motor hooks (95mm length), but I still wanted the forward end of the motor tubes unobstructed.
First thing I always do is switch out the motor tubes to heavier wall versions. For 18mm motor tubes I switch to ST-7, and for 24mm motor tubes I switch to ST-9. These are available at Semroc/eRockets. The OD on these tubes are slightly larger, so you will have to slightly enlarged the ID of your center rings.
Below is the diagram for the motor tubes. I will be eliminating the hook slot and engine block.
Next step is to bend one end of the motor hook 180 degrees. Do this with a small pair of needle nose pliers. Be careful not to over-fatigue the metal. The kit included 8 BT-50 to BT-55 fiber center-rings, 2 for each motor tube. I added one more each of the green Estes type. I also added a ST-9 to LT115 CR as a hook wrap for more strength. I notched 2 of the rings and the wrap for the motor hook with a needle file. Below are the 3 CR’s and motor hook ready to mount on the motor tube.
I then dry fitted the rings and motor hook on the motor tube and marked all the locations according to the directions.
Notice that the forward end of the hook now faces upward.
An AT 24/60 casing and aft enclosure were used to position the hook for a 0.25in overhang.
I then applied wood glue on the motor tube and a dab of JB Weld on the hook where the rings will be located.
Note, I lightly sanded the motor tube with 400 grit, and cleaned and buffed the hook with 800 grit.
Another note, I filed down the motor hook a bit so it would not extend above the OD of the green center ring.
Slide the CR’s into position and wipe off any excess glue and JB Weld.
You can also just use an Estes 24mm motor and 0.25in of masking tape to position the hook. Tamiya 6mm tape is just about perfect!
That’s about it. I let the glue set before removing the motor casing.
Since the motor block is eliminated, you do need to make a aft tape thrust ring for BP motors. Composite reload casings and single use motors already have a thrust ring.
Update: You could also straighten one end of the motor hook, and snip it off. Then do a new bend at 90 degrees upward. I have done this when I thought that the metal was over-fatigued. You need to use 2 pliers to bend it , but it is still pretty easy to do. Also wear safety glasses! That piece of metal can fly when when snipped.
I’ve just started building the Roachwerks 4x24mm Nike-Hercules that I purchased from a forum member. The kit included E size motor hooks (95mm length), but I still wanted the forward end of the motor tubes unobstructed.
First thing I always do is switch out the motor tubes to heavier wall versions. For 18mm motor tubes I switch to ST-7, and for 24mm motor tubes I switch to ST-9. These are available at Semroc/eRockets. The OD on these tubes are slightly larger, so you will have to slightly enlarged the ID of your center rings.
Below is the diagram for the motor tubes. I will be eliminating the hook slot and engine block.
Next step is to bend one end of the motor hook 180 degrees. Do this with a small pair of needle nose pliers. Be careful not to over-fatigue the metal. The kit included 8 BT-50 to BT-55 fiber center-rings, 2 for each motor tube. I added one more each of the green Estes type. I also added a ST-9 to LT115 CR as a hook wrap for more strength. I notched 2 of the rings and the wrap for the motor hook with a needle file. Below are the 3 CR’s and motor hook ready to mount on the motor tube.
I then dry fitted the rings and motor hook on the motor tube and marked all the locations according to the directions.
Notice that the forward end of the hook now faces upward.
An AT 24/60 casing and aft enclosure were used to position the hook for a 0.25in overhang.
I then applied wood glue on the motor tube and a dab of JB Weld on the hook where the rings will be located.
Note, I lightly sanded the motor tube with 400 grit, and cleaned and buffed the hook with 800 grit.
Another note, I filed down the motor hook a bit so it would not extend above the OD of the green center ring.
Slide the CR’s into position and wipe off any excess glue and JB Weld.
You can also just use an Estes 24mm motor and 0.25in of masking tape to position the hook. Tamiya 6mm tape is just about perfect!
That’s about it. I let the glue set before removing the motor casing.
Since the motor block is eliminated, you do need to make a aft tape thrust ring for BP motors. Composite reload casings and single use motors already have a thrust ring.
Update: You could also straighten one end of the motor hook, and snip it off. Then do a new bend at 90 degrees upward. I have done this when I thought that the metal was over-fatigued. You need to use 2 pliers to bend it , but it is still pretty easy to do. Also wear safety glasses! That piece of metal can fly when when snipped.
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