An Agglomeration of Andromedas (HPR)

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Wally Ferrer

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I'll then "thread" a kevlar loop down and around the bolt. The two ends will exit the top of the tube. If I have a long enough piece, it will connect directly to the Av Bay. If not, I'll attach another piece between its ends and the Av bay

If I ever want to inspect or replace this loop, it will be a simple matter to pull the existing cord and thread a new one in.

This will allow me to use the engine ejection as a backup.
And yes, I know I could buy something equivalent, but except for the bolt and a bit of time, this cost me nothing......
How deep inside the tube are you planning to locate it? I'm guessing you would only need enough room for a drogue, but even that needs some space, and getting deep in a 2" tube without getting epoxy all over the sides can sometimes be a real pain... But I like the idea for the ability to replace it...
 

Wally Ferrer

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Drilled and tapped the holes for the coupler. #6 for the metal screws to the top, #4 for the shear pins for the bottom.
Here is something I have not had the opportunity to do yet,Les. Do you use a tapping die right into the fiberglass, or is there any prep to the fiberglass? My assumption is not, the fiberglass is likely strong enough, but I feel a need to ask. I suppose one could use some sort of t-nut inside the coupler, but I don't ever see any mention of that. I also want to thank you for sharing your build- it has been very helpful. :goodjob:
 

les

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For the shear pins and the metal screws to secure the AV bay, I always just tap the FG directly. All the stress is in shear on the screws. You'll see some folks just drill a through hole for the shear pins and tap the nylon screws to keep them from falling out.

For the rail buttons, I felt the fin was thick enough to also just tap directly. It seems to hold well enough.
And if I do run into an issue, then yes - a longer screw and nut on the other side....

And I've been following your build as well - coming along nicely - and I'm tempted to contact Performance Hobby for the same cone as yours.....
 

les

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Used some bondo to clean up the joint between the carbon rod and wood dowel. It also helped seal the grain of the dowel.

IMG_6267.jpg


A little primer and no one will know....
 

les

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Worked my recovery retention.
Epoxied the metal rod to the CR. When installed, the rod will be on the bottom with the harness around the bolt. The ejection will pull the rod into the plywood.

IMG_6328.jpg


Then came up with a means to rough up the internal body tube. I used 2 different tools.
A dremel with and extension taped to a dowel, and a sanding pad using drill extensions.
I had some issues with the drill sanding pad so I added a layer of sandpaper

Shining a light through the tube, it looks pretty good to me (but I can't get a good pix)

IMG_6327.jpg
 

les

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Very little. In August we got a new puppy, then suddenly in Nov my wife needed a hip replacement.
So I've had to tend to her, handle the 5 month old puppy, work (from home), provide care to a disabled Grandson, clear 100' of driveway from the snow storms that dropped 4' in 2 days (my son and I took turns on the snow blower - was out 6x! (and now on Christmas Eve they are predicicting flooding with a sudden warmup to 50 degree and 2"+ of rain overnight) ..... basically life put this on hold. I even had to make the complete Thanksgiving dinner and desserts all by myself. Fortunately, no food poisoning!!!!!
I actually hope to get back to this after Christmas. My wife is healing well and getting around, the now 6 month old puppy is getting house trained (and my wife is now able to help), I have the week off through New Year's Eve (but I do need to see what this bloody warmth/rain is doing with the snow pack tonight).

Stay tuned - it shall be completed!!!!
 
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Tim51

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Very little. In August we got a new puppy, then suddenly in Nov my wife needed a hip replacement.
So I've had to tend to her, handle the 5 month old puppy, work (from home), provide care to a disabled Grandson, clear 100' of driveway from the snow storms that dropped 2' in 2 days (my son and I took turns on the snow blower - was out 6x! (and now on Christmas Eve they are predicicting flooding with a sudden warmup to 50 degree and 2"+ of rain overnight) ..... basically life put this on hold. I even had to make the complete Thanksgiving dinner and desserts all by myself. Fortunately, no food poisoning!!!!!
I actually hope to get back to this after Christmas. My wife is healing well and getting around, the now 6 month old puppy is getting house trained (and my wife is now able to help), I have the week off through New Year's Eve (but I do need to see what this bloody warmth/rain is doing with the snow pack tonight).

Stay tuned - it shall be completed!!!!
Oh man...sorry to hear you've had such a stressful time. Wishing you a peaceful (and safe) 2021, and your wife a swift and full recovery.
 

les

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actually found a typo - it was 4' of snow in 2 days........
Overall situation not that major - just left no time for rockets
Of course, to some not being able to work on rockets would be MAJOR..... ;) 🤣
 

les

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A little work done

Recovery retention - showing with just a wire instead of Kevlar...

IMG_6424.jpg
IMG_6425.jpg


Made a plunger to get it to the right position. Since it had been a while, I re-sanded the inside (not certain why - just seemed like the right thing to do....)
I was going to line the tube with newspaper so when I inserted the dowel with the epoxy it would not drip in the wrong location. This turned into a disaster as the newspaper tried to unroll and blocked dowel/epoxy.

IMG_6426.jpg
IMG_6427.jpg


I put a little dye into the epoxy to make it easier to see where it was. And a sneak peek down the pipe to check the fillet.

IMG_6429.jpg
IMG_6430.jpg
 

deandome

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enjoying the builds, but just curious; has anyone actually FLOWN this kit yet? That includes you, Tim!
 

les

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Got a little done again. Had planned to take some time off work. Out of 35 hour "work week", I actually only got 9 hours of vacation - worked the other 26........ sigh........

Before painting, I wanted to do a recovery test. Then I don't have to worry about scratching the paint.....

Z-folded and taped the shock cord. I used a spent DMS to take up space and seal the tube.


IMG_6535.jpg


Set up a 1.5g charge. No joy - didn't even break the single #2 shear pin.
However - I realized afterwards, I skipped a step in my setup that may have degraded the charge performance. :facepalm:

PS - sorry - I swear I took more pix, but not on my phone. I was a bit rushed in time.

Unfortunately, it may be a few weeks before I get to try again 😢

But a few questions / thoughts on shear pins
I am using a single shear pin for the lower tube to av bay connection. The main purpose of this pin is to prevent drag separation due to the higher drag forces on the tail (with the large sails and pods) versus the upper body. The forces should be low, based on the masses of the lower and upper sections, so the single pin should be more than sufficient.
Seem plausible?

There will be 2 pins for the nose cone. Even though the masses are lower, here we may more force due to the shock from the ejection charge and the shock if/when the apogee event occurs (if the shock cord hits its length limit). Again - does this seam correct?
Thanks
 

Nytrunner

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How heavy is your nosecone?

Folks multiply the weight of the nose by 20-50 Gs to get an estimation of the shock it can experience. Once you estimate that shock, you select the size and number of pins to use.

2-56 nylon screws have a breaking strength of ~25-30 lbs
4-40 nylon screws have a breaking strength of ~45-50 lbs.
 
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