Building the Astron Explorer with 3d printing! (a build log)

[R3verb]

So over a year ago now, Estes had a really good black Friday sale and I bought a bunch of rockets. The last one I need to finish is the Astron Explorer which is just a crazy rocket. It basically uses 3 external tubes to carry the ejection charge from the motor section to the recover section. Honestly a very cool design but there's LOTS of room for error. They have you using paper templates to make multiple slot cuts and they are all supposed to line up and be perfect.

This seemed like a great excuse to do some 3d design/printing! I took some careful measurements and created a couple of cool jigs that should help me get these perfect:



The idea behind these are that the tubes (BT-20s and BT-55s) slip right down into a hole that is just big enough for the tube. There is a center plug that comes up into the middle of the tube, giving you something to cut against. Then there are slots in the body of the print that you make your cuts through. Everything is measured out so that you can bottom out the tube in the jig and you get the exact right distance from the bottom of the tube to the slot. Once they are printed I'll take some pictures. We'll see if this works!

Other than these, I'm going to try and build this one by the books. I've never done an Estes kit with the standard paint scheme so I think that's my plan for this one. The only thing I might do is put a small payload section in the nose for an altimeter. I've got some bt-55 couplers lying around so might be fun.

Finally, I got the engine mount built by the books:

OK, I'll update when these are all printed out and I do some cutting!

 

[R3verb]

Ok so these thing worked so well. Here’s a picture of the completed templates after printing:



After printing I decided to cut out the regular paper template and see how closely they lined up.





So you can see my slots start about 1.5mm below the stock template and end about .5mm below the stock template. I’m going to update these in the files so that somebody else can use them later but I decided to just go with it since a test fit looked like everything and would still work (and I didn’t feel like doing another 4.5 hours of printing. The other thing that wasn’t perfect was in the smaller of the 2 hexagon templates the tube was a tiny bit loose. I fixed that for the taller one. With all of that done, I made my cuts and man did they come out clean:



I really can’t understate how happy I am with these. They make it dummy proof to cut these slots in the tube and I’ll for sure be using this on bigger rockets. I’m going to clean these models up and put them online if anybody is building this model and wants them in the future. I actually thing I figured out a way to combine the two hexagon templates into one so that you don’t have as much to print and I’m going to get the tube for perfect and then I’ll share links.

Lastly, I got the bottom nose cone glued up and the little plug made for the top tube tonight.



That’s it for tonight. Tomorrow I’m going to print some tube cutting rings so that I can do a payload section. More 3D printing on the way!

 

[R3verb]

Models have been updated and uploaded:

https://www.printables.com/model/407937-estes-astron-explorer-tube-cutting-templates/files
Hopefully these help somebody else in the future!

 

[Huxter]

Awesome - thank you! The Astron Explorer is a very beautiful rocket. I have yet to fly mine tho! Please let us know how yours flies!

 

[R3verb]

Got 2 things done today. First, I 3D printed a tube cutting guide and cut 3” off the top tube for a payload section:




And second I got the by-20s attached. I really love these jigs that come with this kit. Very smart and easy (I love jigs, can you tell?). Gunna let this all setup and start on the payload section tomorrow. Not sure what my plan is but I’ll figure something out .

 

[Huxter]

Great cut - looks sharp! I, too, love jigs and have 3d printed many!

 

[R3verb]

Alright everyone, sorry it's been a while but the bird is basically done!



I do have one quick question. So as you know, I cut a few inches off the top of the body tube for a payload bay. How do I keep the nosecone from coming off during ejection? I'm a little worried to just do a friction fit and lose my altimeter. Any suggestions? The only thing I could think of was to do a elastic cord that would but cut short enough so that I'd have to stretch it to get the nosecone off or possibly a cord from the nosecone that goes down though the payload bay and then gets tightened up with a knot or a pull string.

Any ideas? I'd love to get this guy in the air soon!

Casey Levinger

 

[4regt4]

Plastic rivets? That's what I use on my payload bay nose cones.

Hans.

 

[Huxter]

Good question - the nose cones do tend to fly off! I'd friction fit AND tape the outside of the NC to the payload bay!

 

[R3verb]

She flew today! I ended up just masking taping the nose cone on and going for it. Worked like a charm. I flew the Estes altimeter and hit 483’. The only issue I had was that I flew it on a D12-3 and I think it needed more time on the ejection. As soon as the ejection charge went, I saw 2 pieces coming down. Turns out the rocket was all there but the chute had ripped from the chute line. it tumbled down but between the big fins and the tall grass I got it back with 0 damage. Time to buy a new chute and some longer timed motors and go again.

I did notice something interesting. I put 5 pieces of ejection wadding in there and they weren’t even charred. I’m assuming since the ejection gasses have to go through the tubes it’s way less hot but now I’m wondering if I need wadding at all. I might switch to just a fireproof bag around the parachute.

PS sorry for the short video, thought I was taking a burst of photos, guess not!

 

[R3verb]

I flew the Star orbiter again last weekend on a super cold January day. I packed a new 18" Estes chute since the last one just blew away. I also put a little 6" on the nose cone as I still haven't come up with a great retention system for it (remember that the main is now connected to a small payload section. This was a good call as the nose did separate on the way down. The only issue was a broken fin even after a super gentle landing. I'm going to add some epoxy filets before the next flight. This rocket has HUGE fins and a tiny body tube so there's a lot of stress on those joints. If you're building this kit in the future, I'd highly suggest fin filets from the start.

Other than that, now it's just getting the nosecone to not come off mid-flight. I have some removable rivets, I might go that approach. I'd like to get this rocket to fly 1 time with no issues; it's so cool to watch it go! Next flight my plan is to fly the altimeter again.


View attachment Video.mov

 

[Huxter]

btw, no wadding is ever needed with ducted tubes or baffles. What did it fly on this time - did you ever get ie a D12-5 for the longer delay? Was that delay better?

Thanks for the video!

 

[neil_w]

I do have one quick question. So as you know, I cut a few inches off the top of the body tube for a payload bay. How do I keep the nosecone from coming off during ejection? I'm a little worried to just do a friction fit and lose my altimeter. Any suggestions? The only thing I could think of was to do a elastic cord that would but cut short enough so that I'd have to stretch it to get the nosecone off or possibly a cord from the nosecone that goes down though the payload bay and then gets tightened up with a knot or a pull string.

Any ideas? I'd love to get this guy in the air soon!

Time for me to repost this, I guess.


See also: https://www.rocketryforum.com/threads/diamond-cutter-build-thread.129671/post-1537200

I'm sure there are better ways to do this, but I am generally enthusiastic about the approach. I have used it on 4 rockets now.

Also: https://www.rocketryforum.com/threads/payload-bay-nosecone-positive-retention-methods.163008/

 

[R3verb]

Time for me to repost this, I guess.


See also: https://www.rocketryforum.com/threads/diamond-cutter-build-thread.129671/post-1537200

I'm sure there are better ways to do this, but I am generally enthusiastic about the approach. I have used it on 4 rockets now.

Also: https://www.rocketryforum.com/threads/payload-bay-nosecone-positive-retention-methods.163008/

Omg I love this idea. Do you have it on printables or thingaverse? I need an excuse to print more lol. My one concern is that it’s an Estes nose cone so there’s no good place to attach it. Cut the shock cord mount and just glue in a wood centering ring? Also, this is a BT-55 tube. Is it a parametric model or sized for one specific body tube? Thanks for the advice, this looks like an awesome solution.

 

[R3verb]

btw, no wadding is ever needed with ducted tubes or baffles. What did it fly on this time - did you ever get ie a D12-5 for the longer delay? Was that delay better?

Thanks for the video!

I had a few e12-4s so I went with one of those.

 

[neil_w]

Omg I love this idea. Do you have it on printables or thingaverse? I need an excuse to print more lol. My one concern is that it’s an Estes nose cone so there’s no good place to attach it. Cut the shock cord mount and just glue in a wood centering ring? Also, this is a BT-55 tube. Is it a parametric model or sized for one specific body tube? Thanks for the advice, this looks like an awesome solution.

It's not parametric, it's just a crude design I hacked together in TinkerCad using my very meager CAD skills.

I have built and used BT50 and BT60 versions. I have a design for BT55 which I created for someone else but as far as I know has never been printed and tested, so you might need to do some tweaking. I certainly need to do some sanding and adjusting of each part until I like the fit (just a bit snug, but smooth). STL files are attached; I think I can also export to Fusion360 if that's your CAD tool of choice, or I can share it on TinkerCad. Let me know.

I feel certain there must be a better way to do it, but the design has worked for me so far, although it requires care and precision to install properly.

As for mounting it on a plastic nose cone: What I would do is cut off the tapered part of the shoulder, glue on a wood bulkhead, and then attach the twist lock to that. You need to be sure that the bulkhead is on *very straight* to ensure proper twist lock operation (one of the weaknesses of the design).