‘Lava Lamp’ - 3” rocket w/ 38 mm motor mount

[James Owen]

Hello everyone. Here I intend to show off my progress as I build a rocket of my own design, Lava Lamp.

It’s a 3 inch rocket around 3’8” tall including the motor retainer with a 38mm mount. The rocket will recover on a 36” chute with a spill hole and will have a chute-release at 750 feet.

Disclaimer: I’m a beginner and so some of my work here isn’t the most beautiful.

I started out by coupling together a couple of 3” shipping tubes (3” is the inner diameter, so it is technically a bit bigger around) and filling all the spirals with wood filler.

The body tubes were secured with BSI 30min epoxy. They were also covered in epoxy stains because I put too much epoxy on the coupler.

I Resin (SLA) 3D printed some centering rings to put on my motor mount tube. The forward-most one acts as the shock cord mount, and the aft-most one has screws for my motor retainer. This was then installed in the body tube with BSI 30min epoxy.


I then cut some fins out of acrylic sheets on my little desktop CNC machine (if you can, get one of these. They’re super fun).


Then I 3d printed an alignment guide and cut some fin slots.

The slots came out a little rough but they’d do the trick.

After test fitting the fins, I used JB-weld to put them in, then added some fin fillets.



After some sanding, the booster was done except for rail buttons and paint.


My motor retainer is a resin printed part designed to the best of my ability to be virtually indestructible. Obviously it is breakable but it should easily survive the ejection charge from the motor.




That’s all I have so far — I’ll keep this thread updated and post pictures of the flight!

Up next:
Rail button installation (they will screw into the centering rings, and will be spaced about 13” apart)
Parachute installation
Nose cone (as of making this post it is currently being 3D printed)
Avionics bay

 

[Hobie1dog]

A rather Unique Motor retainer.

 

[James Owen]

A rather Unique Motor retainer.

Yes, it is a bit unusual. I printed a couple of them with the same settings and used one for durability testing. It’ll handle ejection fine on this rocket but definitely wouldn’t be the best method for larger rockets. It’s just using what materials I had available.

 

[Hobie1dog]

so where does the Lava lamp theme come into effect?...are you going to paint it to look like a lava lamp on the side?

 

[James Owen]

so where does the Lava lamp theme come into effect?...are you going to paint it to look like a lava lamp on the side?

Yeah, that’s the plan.

 

[cvanc]

Hey lay off the self criticism! Your work looks great - geez you shoulda seen my first rockets.

One comment on your design: 3D printed parts are not known for handling high temperatures well and I worry about your motor mount rings. Fortunately for you the only way to test it is to fly it! Enjoy the hobby.

 

[James Owen]

Hey lay off the self criticism! Your work looks great - geez you shoulda seen my first rockets.

One comment on your design: 3D printed parts are not known for handling high temperatures well and I worry about your motor mount rings. Fortunately for you the only way to test it is to fly it! Enjoy the hobby.

Thanks!
I should clarify: all of my 3D printed parts except the fin slot alignment guide are SLA/Resin 3D printed. 3D printing resin doesn’t have a melting point like plastics obviously do (resin ablates instead of melting) because it doesn’t print by extruding a layer at a time, but rather by UV curing each layer.

 

[neil_w]

One comment on your design: 3D printed parts are not known for handling high temperatures well and I worry about your motor mount rings.

That is mostly true of FDM-printed PLA; these are SLA-printed resin. And it occurs to me now that I have no idea about the heat-tolerance of resin parts.

<googling>

Looks like it varies among resin varieties, no idea what is used here. There are high-temperature resins available.

<ninja'd by OP>

 

[James Owen]

Looks like it varies among resin varieties, no idea what is used here. There are high-temperature resins available.

I’m using a high—temp resin that should be plenty capable of handling the heat, especially with the insulation of the motor mount tube.

 

[Velocity Aerospace]

I want to get a small cnc machine, but I don't want to get one that's cheap and doesn't work. What do you use/would recommend?

 

[James Owen]

I want to get a small cnc machine, but I don't want to get one that's cheap and doesn't work. What do you use/would recommend?

So there’s a ton of options out there, but there are some features you’ll definitely want to have.

[edit] the next reply has some great info from someone more experienced than me.

 

[alexzogh]

How small, what is your budget, and what do you want to cut?

In addition to my monster CNC, I have two small CNC's I really, really like.

First is a DMC2. I use it for metals.



it's fully enclosed with a coolant and lubricant system. Can cut anything metal I throw at it, but the bed size is small. You can build it yourself, or have it shipped built. I built mine, just so I would know how to fix it when it broke.

https://www.shariffdmc.com/product-page/dmc2-cnc-kit-build-it-yourself
Second one is a Carvera.



Also fully enclosed, but no coolant system. Instead, it has an automatic tool changer. This allows you to use multiple different bits on one project without manually changing anything. Also has accessories like a 4th axis rotary (round objects), PCB fabrication (make your own boards), a laser cutter/engraver, and decent software. Comes ready to go.

https://www.makera.com/collections/machines/products/carvera
Both are expensive. I saved a lot of money 'backing' them on Kickstarter but I would say both are worth the price they are currently selling at.

The Carvera is especially impressive if you are new to a CNC. Lots of automation is built in, and if you use their free software you can go from model to cad to cam to machine control in one product with things like touch-off sense, probe, and vacuum built in. I wouldn't try any metals harder than aluminum in it though.

 

[James Owen]

Looks like alexzogh nailed it. Great recommendations.

 

[Velocity Aerospace]

How small, what is your budget, and what do you want to cut?

In addition to my monster CNC, I have two small CNC's I really, really like.

First is a DMC2. I use it for metals.

View attachment 560371

it's fully enclosed with a coolant and lubricant system. Can cut anything metal I throw at it, but the bed size is small. You can build it yourself, or have it shipped built. I built mine, just so I would know how to fix it when it broke.

https://www.shariffdmc.com/product-page/dmc2-cnc-kit-build-it-yourself
Second one is a Carvera.

View attachment 560372

Also fully enclosed, but no coolant system. Instead, it has an automatic tool changer. This allows you to use multiple different bits on one project without manually changing anything. Also has accessories like a 4th axis rotary (round objects), PCB fabrication (make your own boards), a laser cutter/engraver, and decent software. Comes ready to go.

https://www.makera.com/collections/machines/products/carvera
Both are expensive. I saved a lot of money 'backing' them on Kickstarter but I would say both are worth the price they are currently selling at.

The Carvera is especially impressive if you are new to a CNC. Lots of automation is built in, and if you use their free software you can go from model to cad to cam to machine control in one product with things like touch-off sense, probe, and vacuum built in. I wouldn't try any metals harder than aluminum in it though.

Wow. That's a lot more than I can afford right now. I will keep them in mind for later though

 

[alexzogh]

Wow. That's a lot more than I can afford right now. I will keep them in mind for later though

I would focus on what you want to cut. If you are just thinking wood, fiberglass (fins) and the like, one of the light duty, inexpensive Chinese 3018 'clones' is a great place to start without breaking the bank.

A new one, with a semi-enclosure, can be had for $250 or less if you don't mind putting it together.

something like this: https://www.ebay.com/itm/394258147050?hash=item5bcb9de6ea:g:0CEAAOSwTphiZMoP

 

[KenECoyote]

Fantastic build!

If you don't mind me asking, have you used acrylic for rocket fins before?

I've used acrylic years back for some lp scratch builds and was disappointed with it's fragility. Maybe the ones I used was too thin.

I was thinking of using Lexan afterwards (which has more flex and give), but had already purchased a bunch of large acrylic sheets (the cool fluorescent types!).

 

[SolarYellow]

In high school, I had drilled some holes in polycarbonate (Lexan) without issue. A friend brought me some sheets of clear plastic that I thought would be the same, but I cracked the heck out of them trying to drill the acrylic. Would definitely go polycarbonate for rocket fins. It's what R/C car bodies are made out of and can take a heck of a beating.

 

[James Owen]

Fantastic build!

If you don't mind me asking, have you used acrylic for rocket fins before?

I've used acrylic years back for some lp scratch builds and was disappointed with it's fragility. Maybe the ones I used was too thin.

I was thinking of using Lexan afterwards (which has more flex and give), but had already purchased a bunch of large acrylic sheets (the cool fluorescent types!).

Thanks!
Yes, I have used acrylic for fins before and I make sure to use the higher-strength cast acrylic and it seems plenty sturdy.

 

[Hobie1dog]

. Would definitely go polycarbonate for rocket fins. It's what R/C car bodies are made out of and can take a heck of a beating.

+1

 

[James Owen]

Build update:

Haven’t worked on it as often this past week but it is still slowly coming together.

The nose cone has been 3D printed (in 2 sections to reduce print time) and the shock cord has been anchored to it.


The infill on the resin printer made this interesting pattern:


And here is the rocket with the nose cone on:


Next:
Attaching recovery system to the quick link on the shock cord
Rail button installation
Paint
Launch!

 

[jqavins]

Looking good. What motor do you plan to put it up on? It certainly looks made for a cert flight.

 

[James Owen]

Looking good. What motor do you plan to put it up on? It certainly looks made for a cert flight.

I plan to fly it on an Aerotech I140 white lightning, but unfortunately UROC doesn’t start up their monthly launches until March so it’ll be a little bit of a wait.
It sims to roughly 3600’ with a chute release at ~800 feet.

 

[James Owen]

Finished the rocket today! I ended up dropping the original paint scheme, meant to look like a lava lamp, for something simpler. The name doesn’t fit as well anymore but oh well .

Here it is freshly painted on the estes launchpad I use as a paint stand:

(this was painted in a much more open area and moved to the corner so there wouldn’t be as much wind)

I also finished another rocket today, which is an Estes Star orbiter (Renamed Checkmate) with structural modifications that I plan to use as a test-bed for new avionics and things for an upcoming… secret… project.



Lava Lamp will fly on March 18, I’ll make sure to post pictures and videos of that here.

 

[Hobie1dog]

Where did you end up painting it with all that snow laying around?

 

[James Owen]

I may or may not have painted some of the snow…

 

[jqavins]

Finished the rocket today! I ended up dropping the original paint scheme, meant to look like a lava lamp, for something simpler. The name doesn’t fit as well anymore but oh well .

Pro tip: names are easier to change than paint schemes.

 

[James Owen]

Pro tip: names are easier to change than paint schemes.

Not in my experience. I’m absolutely terrible at coming up with names, but I don’t struggle much with choosing colors or patterns at all.

 

[lakeroadster]

Oh man... this rocket needs an epoxy filled payload section.... so cool.

​

 

[James Owen]

Oh man... this rocket needs an epoxy filled payload section.... so cool.

View attachment 564803​

That looks awesome. I wouldn’t know how to make that but if I did I would definitely do it.

 

[mbeels]

If you still wanted the lava lamp look, you could consider a vinyl wrap. https://stickershock23.com/ does a great job for that type of stuff, you could contact Mark and tell him what you want and he'd help you out. But if you don't, I think it looks good as is, you'll l have a contrasty color scheme which should be easy to find.