Sunward - King Tut's Pyramid

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Mine Flys great, powder the chute the heat gets to it and you get a half opening.
 
You'd need the Rosetta Stone to understand what's going on in here.
 
WOW!!!!!! Even on the big screen, I couldn't see that much detail! That had to have taken quite a bit of time to make those hieroglyphs. I just hope they didn't used Wallace Budge's translations. @ Wally Ferrer, THANKS!!!!!!!!
 
Khufu's Pyramid, smaller version of King Tut's Pyramid.
24 mm mount, rear eject with a pop pod with streamer recovery and pyramid with chute.
On the maiden the ejection charge cracked the sides. Too small a volume between the front of the pod and the bulkhead. Sanded down the pop pod rings to loosen the fit.
0809210611[1].jpg
0809210613[1].jpg
😁

And now I'm all SET.
 
You can make a decal with the eye of Horus to cover the launch lug hole!

So that's how you do a rear ejection, eh? just that simple, doesn't cock or jam? 'Cause @BABAR mentioned it's be a great way to bring back Launch Lab's "Bullet Bobby" and I agree but wasn't sure if there was anything more to it than that.
 
Top of the day, Tom!
Main problem with rear eject is limited volume for the laundry.
And the centering rings were too snug on the maiden so the ejection charge cracked the sides.
But it flew great and recovered nicely!
In fact I yelled and screamed so much that my throat was HORUS.
😁
 
kuririn said:
Top of the day, Tom!
Main problem with rear eject is limited volume for the laundry.
And the centering rings were too snug on the maiden so the ejection charge cracked the sides.
But it flew great and recovered nicely!
In fact I yelled and screamed so much that my throat was HORUS.
😁
Click to expand...
concur with @kuririn that limited space presents a challenge for rear ejection.

On a pyramid, one solution is that the lower plate should be AS LOW as the pyramid allows. This is basically the lower centering SQUARE (or triangle, if you do a three sided pyramid, not sure why I haven't seen anybody do this.) Since it's only function is to center the mount AND to keep the laundry in the rocket on boost, it does NOT have to be all that heavy duty, I suspect foam board would work nicely. The lower the bottom "deck", the more room you have for your recov)ery device.

On standard rockets, you have to think outside the box a bit. The standard approach is that the available space is limited to that between the outer diameter of the motor mount tube and the inner diameter of the main body tube. For something like a BT-inside a BT-20, or a BT-20 in a BT-50, that's not a lot of space. Not much can be done for the BT-5 to 20. But a nice trick for the BT-20 to BT-50 (or larger motor mounts and outer tubes) is as follows.

Say your mount is BT-20 and your outer tube is BT-50.

Cut your BT-20 motor mount long enough that you can put TWO BT-5 to BT-20 centering rings at the forward end (alternative I usually use a masking tape wrap the length of two centering rings around the hind end of the BT-5.) Build your BT-20 mount with engine hook if desires, attach your BT-20 to BT-50 rings to the BT-20 mount, but don't glue it into the body. This is a pod, it is going to be completely ejected at (or hopefully near!) apogee. Do NOT put in an engine block!

Slide two BT-5 to BT-20 centering rings on the hiney end of your BT-50 (you can get away with just one, or like I said, you can do a tape wrap)
The length of the BT-5 should run from the anticipated forward end of the motor mount (plus the two centering ring lengths) all the way either to the base of the nose cone (balsa cone) or if plastic cone, you can actually cut off the flat hind end of the nose cone (bulkhead?) and extend the BT-5 into the nose cone itself. If you do this, smear some glue or JB weld into the tip of the nose cone as it will get the ejection blast.

Why on God's Green Earth would you WANT to extend the BT-5 into the cone? because if you do, and if you need nose weight, you can attach it to the BT-5 segment in the CONE, and it comes out with the motor pod and is less weight on the main tube segment when it hits the ground nose first.

Get a cola can and cut a piece 4 inches long, just wide enough so when you roll it up, it fits into the BT-5. Glue this into the hiney end of the BT-5. Why? because when you duct the ejection gases of a larger motor into a smaller tube (in this case, an 18mm casing ejecting into a BT-5 tube), the concentrated head WILL burn through the tube just forward of the motor mount. Yes, Aluminum is flammable, but not easily so, and the short duration of the heat of an ejection won't hurt it, but it WILL hurt the cardboard tube if you don't use it. And NO, I don't think the use of a thin roll of aluminum can on the inside of body tube as an insulator violates the safety code.

Now put a forward centering ring from the BT-5 to the BT-50 (not BT-20) Where does this go? You need enough space forward of this ring for your kevlar that will connect the pod to the nose cone or the side of the forward edge of the body tube (remember, you are gluing or FIRMLY taping the nose cone in place.)

Okay, now slide the hiney end of the BT-5 with the two BT-5 centering rings into the forward end of the motor mount. The Centering rings will do TWO things. First, they will function as the motor block for the BT-20 motor mount. Second, they will center the BT-5 inside the BT-20 that will be centered in the BT50.

End result?

For most of the length of the rocket, you now have the space between the BT-5 and the BT-50, rather than BT-20 and BT-50. May not seem like much on paper, but trust me it is a LOT easier to pack.

You have an ejectable motor pod that attaches at the forward end to either the nose cone or the side of the body tube. Your shock cord WILL get hit with some hot motor blast, not much you can do about that except maybe stick a square of wadding in the pod before launch.

Attach your chute or streamer to the base of the BT-5 just forward of the motor mount. Run a second length of shock cord along the length of the BT-5 through the forward centering ring, this will be the attachment point for your shock cord attachment to the nose or body tube. Otherwise the opening shock and the weight of the rocket is hanging on the BT-5 tube for support, good way to bend or break the BT-5. Poor form.
 
BABAR said:
concur with @kuririn that limited space presents a challenge for rear ejection.

On a pyramid, one solution is that the lower plate should be AS LOW as the pyramid allows. This is basically the lower centering SQUARE (or triangle, if you do a three sided pyramid, not sure why I haven't seen anybody do this.) Since it's only function is to center the mount AND to keep the laundry in the rocket on boost, it does NOT have to be all that heavy duty, I suspect foam board would work nicely. The lower the bottom "deck", the more room you have for your recov)ery device.

On standard rockets, you have to think outside the box a bit. The standard approach is that the available space is limited to that between the outer diameter of the motor mount tube and the inner diameter of the main body tube. For something like a BT-inside a BT-20, or a BT-20 in a BT-50, that's not a lot of space. Not much can be done for the BT-5 to 20. But a nice trick for the BT-20 to BT-50 (or larger motor mounts and outer tubes) is as follows.

Say your mount is BT-20 and your outer tube is BT-50.

Cut your BT-20 motor mount long enough that you can put TWO BT-5 to BT-20 centering rings at the forward end (alternative I usually use a masking tape wrap the length of two centering rings around the hind end of the BT-5.) Build your BT-20 mount with engine hook if desires, attach your BT-20 to BT-50 rings to the BT-20 mount, but don't glue it into the body. This is a pod, it is going to be completely ejected at (or hopefully near!) apogee. Do NOT put in an engine block!

Slide two BT-5 to BT-20 centering rings on the hiney end of your BT-50 (you can get away with just one, or like I said, you can do a tape wrap)
The length of the BT-5 should run from the anticipated forward end of the motor mount (plus the two centering ring lengths) all the way either to the base of the nose cone (balsa cone) or if plastic cone, you can actually cut off the flat hind end of the nose cone (bulkhead?) and extend the BT-5 into the nose cone itself. If you do this, smear some glue or JB weld into the tip of the nose cone as it will get the ejection blast.

Why on God's Green Earth would you WANT to extend the BT-5 into the cone? because if you do, and if you need nose weight, you can attach it to the BT-5 segment in the CONE, and it comes out with the motor pod and is less weight on the main tube segment when it hits the ground nose first.

Get a cola can and cut a piece 4 inches long, just wide enough so when you roll it up, it fits into the BT-5. Glue this into the hiney end of the BT-5. Why? because when you duct the ejection gases of a larger motor into a smaller tube (in this case, an 18mm casing ejecting into a BT-5 tube), the concentrated head WILL burn through the tube just forward of the motor mount. Yes, Aluminum is flammable, but not easily so, and the short duration of the heat of an ejection won't hurt it, but it WILL hurt the cardboard tube if you don't use it. And NO, I don't think the use of a thin roll of aluminum can on the inside of body tube as an insulator violates the safety code.

Now put a forward centering ring from the BT-5 to the BT-50 (not BT-20) Where does this go? You need enough space forward of this ring for your kevlar that will connect the pod to the nose cone or the side of the forward edge of the body tube (remember, you are gluing or FIRMLY taping the nose cone in place.)

Okay, now slide the hiney end of the BT-5 with the two BT-5 centering rings into the forward end of the motor mount. The Centering rings will do TWO things. First, they will function as the motor block for the BT-20 motor mount. Second, they will center the BT-5 inside the BT-20 that will be centered in the BT50.

End result?

For most of the length of the rocket, you now have the space between the BT-5 and the BT-50, rather than BT-20 and BT-50. May not seem like much on paper, but trust me it is a LOT easier to pack.

You have an ejectable motor pod that attaches at the forward end to either the nose cone or the side of the body tube. Your shock cord WILL get hit with some hot motor blast, not much you can do about that except maybe stick a square of wadding in the pod before launch.

Attach your chute or streamer to the base of the BT-5 just forward of the motor mount. Run a second length of shock cord along the length of the BT-5 through the forward centering ring, this will be the attachment point for your shock cord attachment to the nose or body tube. Otherwise the opening shock and the weight of the rocket is hanging on the BT-5 tube for support, good way to bend or break the BT-5. Poor form.
Click to expand...
Well, I was specifically referring to your remark in the context of "Bullet Bobby". It seems like, for all the more 'chute you'd need there, and that fat little tube, a chute would fit reasonably well. But a 'chute is not a streamer and I wasn't sure how well a rear eject would work if just based on two centering rings. I figure if they just cock a bit, they could jam, but it looks like @kuririn is doing just that and if that's typical, Bullet Bobby could probably be rear eject. Whatcha think?

And @kuririn - Eye see what you did there... :)
 
I think that the Bullet Bobby would be the perfect candidate for conversion to rear eject.
I would go with single chute and no streamer. Pop pod remains tethered to the main body.
Tie one end of the Kevlar around the motor tube and just behind the forward centering ring.
The other end is tied to the loop on the nose cone.
Glue the nose cone in.
Attach the chute to the motor tube between the centering rings.
Pack the chute without wrapping it around the motor tube, i.e. fold to the side with shroud lines loosely inside the canopy. Plenty of room between the bt20 and bt80 tubes.
Sand centering rings for a smooth, not too tight fit.
Voila. You're in business.
Rocket will come down nose first saving the fins from landing impact.
 
Blast it Tom! said:
Sounds like a plan! Plus, I think it would look cool coming down with the body/nose cone intact, nose first!
Click to expand...
If you are landing on anything but grass, for flight purposes it wouldn’t hurt to put a square piece of tape (maybe some black electric tape, it is moldable and the right color for Bullet Bobby) on the nose apex. Put it on just before flight and gently pull it just after flight so you don‘t pull paint off. The DOWN side (pun intended) of rear ejection is the brunt of impact is on the cone, so may get dinged.

not sure but if I recall the build Bobby has some nose weight. If you extend the mount forward into the cone you can put this weight on the mount instead of the cone. Thats a little less force on impact than otherwise.

Straight Trails!
 

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