Boost was stable with a B6-4 motor, but at ejection the head popped off! The rear ejection worked fine, and the main body found.
But, the head was lost. No C6-5 second launch today.
Second up was the downscaled Centuri UFO INVADER.
It performed as advertised, turning over at apogee and landing on the spring wire legs.
Space X has nothing on this 1976s kit!
Boost was labored but straight up with a C6-3 in the tail.
An older Chinese Quest B6-4 had a noisy boost with an altitude guess at 325 feet.
The 12" parachute was large enough for recovery on the newly mowed field.
You can see how small the ASP Micro HAWK next to the BT-55 diameter model.
I like to add a Micro-Maxx launch for some variety. Boost is always fast. Altitude was an estimated 75 feet.
I asked for extra eyes to follow the descent but with the shiny streamer it was easy to track.
Only launched four rockets today. It was very hot and might be my last launch until Florida cools off next October.
Chris, could the Robot be made with a standard ejection of the nosecone? The model looks fine to me.
ReplyDeleteHi Bill,
DeleteIt could, but the BT-20 "neck" is a small diameter for the chute deploy. I was trying the rear eject for something different.
Thanks Chris, now I understand.
DeleteI should add,
Deletethe distance between the top of the motor to the shoulder of the "head" is very short. Not enough room to pack the chute and wadding. The engine is somewhat forward inside the body to move the C/G.
Not sure if this idea would work or not:
DeleteThe "nosecone" would consist of the head-and-neck section, as well as the centering ring that becomes the "shoulder" of the robot. The forward end of the motor mount would extend forward to just below the level of the shoulder,. The "nosecone" would then connect to the motor mount tube via NB-20 noseblock. To add a bit of rigidity to the "shoulder" part we could add a "rim" that will fit inside the main body tube. The "doughut" shaped opening between the motor mount tube and the main body tube would act as the parachute compartment.
With the rear ejection configuration, he'd be landing on his noggin all the time -- so we probably want to strengthen the join between the head and neck -- perhaps if we cut a hole in the head tube for the neck, we'd have an opportunity to have glue fillet at the join both on the inside and outside of the head tube.
DeleteHi Naoto,
DeleteThe Robot neck isn't surface (flat) glued. I did do a recess ("donut hole" in the shoulder ring) so the neck and head would be more secure. I'll have to beef that up a bit more.
Hi Naoto,
DeleteEven with the rear ejection, the 12" chute lowers the model slow enough. It was the ejection charge that broke the head loose, below at the neck. Cutting a neck hole in the sideways mounted head tube could be beyond the skills of most modelers.
If the join between the head and neck failed due to pressurization of the ejection charge, then perhaps a disc glued over the end of the neck tube would keep the neck tube from being pressurized?
DeleteHi Naoto,
DeleteThere is a disk blocking the ejection into the neck and head assembly. It was just a glue joint that failed.
Ah, I see. Is there ballast in the head? That might lead to additional stress on joint between the head and neck.
DeleteHi Naoto,
DeleteThere is clay weight in the head. I really think I had a strong ejection and not enough glue on the neck joint.
Basically what I was getting at was that when the shock cord reaches its full extent and goes taut that there would likely be stress (in tension) at the head and neck joint -- and will probably end up greater with ballast in the head. This would occur in both the rear eject as well as nose eject configuration -- so you'd definitely want a good strong bond at the head and neck joint -- perhaps a few glue tabs at the joint (to increase the bond area) could help.
DeleteLove the Robot idea.
ReplyDelete