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I finally converted a Dollar Tree find I had intended to do years ago. Found another one this month, a plastic Bell for Christmas. Size is 4.3" diameter, and 4.5" tall. Flies like a Flying Saucer, ejects the engine and uses "drag recovery".
Didn’t take any build photos, but it was pretty simple (I built this the morning of the launch, in under an hour). Glued a very short nose cone into the engine mount tube (the rounded nose helps to align the front end in the recessed part of the top tip inside the bell), and the tube length was enough to leave the last 1” of the engine hanging out, to allow for a fluorescent streamer to be wrapped around it (not so much for safety, as to find the engine on the ground later since the flying site is a soccer field). In the image below, you can just make out the wrapped streamer.
The centering ring was a BT-20 to BT-70 ring. I drilled a launch lug hole into the ring, so that the lug would be about 1/32” from the BT-20 (18mm) tube.
I slid it onto the mount tube, and pushed the assembly into place and CA glued the ring to the mount tube, but did not glue anything else at that time. After drying, I used a sharpie to trace around the outer part of the centering ring, to mark inside the bell where the ring would be. Then removed the mount/ring assembly, and used a Dremel with a grinding bit to roughen up the whole area marked off by the sharpie (1/4" above and 1/4"below) so that 5 minute epoxy would be able to grab onto it (otherwise epoxy would not stick for long).
I drilled a lug hole into front of the plastic bell for the top end of the lug to poke thru. Put the mount assembly into it a few times, with loose lug to work out the distance. Was a bit tricky to get the distance right, hole ended a bit oversize.
I put the mount assembly back into the bell, and CA’ed the lug into place, making sure the alignment was good and that the lug was parallel to the mount tube, with the desired 1/32" gap. The lug was extra-long because it also serves to hold the streamer wrapped around the engine, from unwrapping (so, the bottom of the lug is about even with the bottom of the engine casing).
Finally, mixed up plenty of 5 minute epoxy and applied it all around the roughed-up area inside the bell. Then put the mount assembly into it for the last time, making sure the top of the lug poked out the hole in the bell, and let it cure as I packed up things for the launch.
Flew it along with another Dollar Tree find, an old Snowflake bowl, converted into a saucer (have not seen those at Dollar Tree in years).
Here it is after flight. You can see a bit of the long launch lug sticking out.
Video:
Didn’t take any build photos, but it was pretty simple (I built this the morning of the launch, in under an hour). Glued a very short nose cone into the engine mount tube (the rounded nose helps to align the front end in the recessed part of the top tip inside the bell), and the tube length was enough to leave the last 1” of the engine hanging out, to allow for a fluorescent streamer to be wrapped around it (not so much for safety, as to find the engine on the ground later since the flying site is a soccer field). In the image below, you can just make out the wrapped streamer.
The centering ring was a BT-20 to BT-70 ring. I drilled a launch lug hole into the ring, so that the lug would be about 1/32” from the BT-20 (18mm) tube.
I slid it onto the mount tube, and pushed the assembly into place and CA glued the ring to the mount tube, but did not glue anything else at that time. After drying, I used a sharpie to trace around the outer part of the centering ring, to mark inside the bell where the ring would be. Then removed the mount/ring assembly, and used a Dremel with a grinding bit to roughen up the whole area marked off by the sharpie (1/4" above and 1/4"below) so that 5 minute epoxy would be able to grab onto it (otherwise epoxy would not stick for long).
I drilled a lug hole into front of the plastic bell for the top end of the lug to poke thru. Put the mount assembly into it a few times, with loose lug to work out the distance. Was a bit tricky to get the distance right, hole ended a bit oversize.
I put the mount assembly back into the bell, and CA’ed the lug into place, making sure the alignment was good and that the lug was parallel to the mount tube, with the desired 1/32" gap. The lug was extra-long because it also serves to hold the streamer wrapped around the engine, from unwrapping (so, the bottom of the lug is about even with the bottom of the engine casing).
Finally, mixed up plenty of 5 minute epoxy and applied it all around the roughed-up area inside the bell. Then put the mount assembly into it for the last time, making sure the top of the lug poked out the hole in the bell, and let it cure as I packed up things for the launch.
Flew it along with another Dollar Tree find, an old Snowflake bowl, converted into a saucer (have not seen those at Dollar Tree in years).
Here it is after flight. You can see a bit of the long launch lug sticking out.
Video:
