2.1" 3D printed av bay

Hi everyone, its taken me quite a while bring together all the parts for this build however its finally complete so i thought i would share.

The av bay is designed to fit within a PML 2.1" coupler of 4" in length, and take a stratologger CF, battery, switch and all wiring. As i am sure many of you could imagine, space was tight.

The sled was the main goal, however i also printed some bulk heads and deployment charge holders, they feel very strong however i havent tested the bulkheads in anyway and chose to use laser cut plywood bulkheads and aluminium charge holders on my own av bay, so use at your own risk.

All of the files as well as some build photos are uploaded on the thingiverse, so feel free to use.

https://www.thingiverse.com/thing:2363308

Very nice!

Very nice indeed!

Nicely done. Thanks for sharing on Thingverse.

Sweet they look great. I have a fully 3d printed rocket that takes a 13mm motor. It is made of petg and I have found that if I pick it up quickly of reaching the ground it is soft from the ejection charge but normally by the time I get to it it is cooled down. What did you print this in?

The parts were all printed in ABS, i think my main concern with the bulkheads is their mechanical strength, rather than heat resistance. I would be very interested to hear of anybody who has used a printed bulkhead for a high power rocket, or high shock loads in general (im thinking sub optimal ejection forces). I am not quite ready to sacrifice a rocket to test if they are strong enough without some ground testing first.

Any update on whether the ABS bulkplates for this do have sufficient mechanical strength for deployment?

Any update on whether the ABS bulkplates for this do have sufficient mechanical strength for deployment?

Click to expand...

I have a 3D printed 4" NC that I use with two aluminium charge canisters (2g and 3g) for ejection. Much bigger area than a 2.1" and I have not seen any mechanical problems with it up to now, although I do spread the point load of the canisters with a bit of G10 just to take a bit of stress off it. I'll see if I can get a pic.

OverTheTop said:

I have a 3D printed 4" NC that I use with two aluminium charge canisters (2g and 3g) for ejection. Much bigger area than a 2.1" and I have not seen any mechanical problems with it up to now, although I do spread the point load of the canisters with a bit of G10 just to take a bit of stress off it. I'll see if I can get a pic.

Click to expand...

Thanks - that's good to know.

Here you go...


Also notice the charge canisters are towards the outside edge so their force is more on the cylindrical boss than in the middle of the flat face.

Further details here FYI:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019

I am currently printing up a 75mm version that takes the same sled. That's part of the reason for some of the internal details in the print. Can be used down to 54mm.

OverTheTop said:

Here you go...
View attachment 327062

Also notice the charge canisters are towards the outside edge so their force is more on the cylindrical boss than in the middle of the flat face.

Further details here FYI:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019

I am currently printing up a 75mm version that takes the same sled. That's part of the reason for some of the internal details in the print. Can be used down to 54mm.

Click to expand...

Thanks again - your builds are always excellent and I still go back to your classic 1/2 scale Nike Smoke build regularly (!) interested to see more but when I clicked on that link it says the topic no longer exists (...?)

OverTheTop said:

Here you go...
View attachment 327062

Also notice the charge canisters are towards the outside edge so their force is more on the cylindrical boss than in the middle of the flat face.

Further details here FYI:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019

I am currently printing up a 75mm version that takes the same sled. That's part of the reason for some of the internal details in the print. Can be used down to 54mm.

Click to expand...

That's beautiful but how do you close the tops of your two charge canisters?


Steve Shannon

Thanks Steve. Tops are taped with Kapton tape, and then another ring of tape around the side of the canister. Suboptimal really. Tape adhesion is an issue sometimes, especially when prepping in the field.

My current evolution of this is remarkably similar but with grooves for o-rings around the top lip. The tape is put in place, then an o-ring dropped over it to hold it all. The o-rings remove all of the uncertainty.

OverTheTop said:

Thanks Steve. Tops are taped with Kapton tape, and then another ring of tape around the side of the canister. Suboptimal really. Tape adhesion is an issue sometimes, especially when prepping in the field.

My current evolution of this is remarkably similar but with grooves for o-rings around the top lip. The tape is put in place, then an o-ring dropped over it to hold it all. The o-rings remove all of the uncertainty.

Click to expand...

I had mine close together like that on a rocket once and ended up moving them apart so I could tape all around them.
Now I simply use cap plugs to cover them, similar to the caps CTI furnishes to hold their igniters to their nozzles on their smaller motors.


Steve Shannon

OverTheTop said:

Here you go...
View attachment 327062

Also notice the charge canisters are towards the outside edge so their force is more on the cylindrical boss than in the middle of the flat face.

Further details here FYI:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019

I am currently printing up a 75mm version that takes the same sled. That's part of the reason for some of the internal details in the print. Can be used down to 54mm.

Click to expand...

Thats a truly amazing build OverTheTop, beautiful work.

I had come to the same conclusion with the 3D printed bulkheads. They are impressively strong, in my opinion they are up for the job.

Another alternative for holding the charge in, possibly for larger birds, is to thread the canisters to take screw caps of something like soda pop bottles.


I have also been known to cut an internal groove in the charge canisters to accept the top cap of a centrifuge vial (clip in). This works quite well in confined spaces and smaller rockets.

Hope I haven't hijacked the thread. And now back to your regular programming...

Finally got round to printing and assembling this, and really appreciating the elegant design. Decided to print the bulkheads in different colours differentiate main from drogue.. just one (possibly very stupid) question so far - what's the small grommet (circled) for?

Man that looks sweet! I'm curious about your switch-battery layout. Can you post a pic of the other side?

Have you looked at Ninjatek for the filament? So far I've been very impressed with how it holds up.

captbk said:

Man that looks sweet! I'm curious about your switch-battery layout. Can you post a pic of the other side?

Click to expand...

Sure - this is where Wrad's design really shines in my view. It's a standard microswitch inserted 'upside down' (if there were such a thing). Microswitch lever removed and replaced with a brass tube 'n' pin arrangement. The integral battery box has a gap to allow zip tie(s) for battery retention.

swatkat said:

Have you looked at Ninjatek for the filament? So far I've been very impressed with how it holds up.

Click to expand...

No I haven't yet - thanks for the tip.

Tim51 said:

Finally got round to printing and assembling this, and really appreciating the elegant design. Decided to print the bulkheads in different colours differentiate main from drogue.. just one (possibly very stupid) question so far - what's the small grommet (circled) for?

View attachment 328911

Click to expand...

Great to see the av bay in use! the grommet was used for extra retention of the pull pin as i didnt even use a bit of brass pipe to guide the pin.

Neat and tidy

OverTheTop said:

Neat and tidy

Click to expand...

+1...

Great to see the av bay in use! the grommet was used for extra retention of the pull pin as i didnt even use a bit of brass pipe to guide the pin.

Click to expand...

Yes of course it's bleedin' obvious now.. I knew it was a stupid question.. Anyway, ahem, moving on.. I should say I haven't actually 'put it to use' in the flight sense yet. Hope to make it to EARS Nov/Dec for a trial run installed in my 57mm scratch built:

The guys at the local print hub I use over in Hackney Road were very interested when I described to them what it was..perhaps some potential new club members there.

Finally got round to testing this e-bay over the weekend and happy to report it worked fine. The forward positioning of the microswitch hole was cause for a slightly unorthodox solution - a slot cut as shown. Shot of apogee event at 2315' in a rare patch of blue sky. Motor was a CTI H120 Red Lightning

I printed some bulkheads with built in charge holders. They ground tested with some over-powered charges great. Stronger than I expected. These were printed in PETG. I have not flight tested them yet, but I thought it might be a helpful data point. The shock cords did get a good snap on them with those charges and shear pins holding things together.

ttabbal said:

I printed some bulkheads with built in charge holders. They ground tested with some over-powered charges great. Stronger than I expected. These were printed in PETG. I have not flight tested them yet, but I thought it might be a helpful data point. The shock cords did get a good snap on them with those charges and shear pins holding things together.

Click to expand...

Interesting - please post details when you do. Wrad's file also includes printed charge wells, it was my choice to fit my own home made ones.