Author Topic: BB Level 3 project  (Read 16265 times)

Offline David Carter

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BB Level 3 project
« on: January 13, 2016, 01:49:28 PM »
Having received both Level 1 and Level 2 certification last year, it's time to begin my level 3.

I considered a lot of kits but eventually settled on a custom design and build. This is essentially a Roll Your Own from Rocketry Warehouse with some customization.

This project consists of a 4-inch diameter fiberglass airframe, capable of accommodating up to 75mm M-impulse motors. It is a 3-fin booster design, with lower and upper payload sections for drogue and main chute recovery gear. Topped with a 5:1 Von Karman nose cone, giving the rocket an overall length of 97 inches (length may change. I'll discuss why in a later post). Dry weight, including recovery gear and electronics, rounds out at ~277 ounces (17.3lbs.).

The primary flight computer for this rocket is the Altus Metrum TeleMetrum. The key advantage of using this computer is that it transmits flight information, including location as measured with GPS, via a ham radio telemetry link. Not only does it give you real time feedback about how the flight is going, it also greatly simplifies recovery. The backup is the Pico-AA2.

The rocket will carry onboard a Mobius HD video camera. The main parts of the camera will be carried internally in the electronics bay, while the CCD sensor will be mounted externally facing aft along the body. This will have a 3D printed sensor mount on the outside of the rocket, with the camera itself contained in the electronics bay. I never did like the thought of duct taping a camera to the outside!

In this thread, I'll document the build, as well as pose any questions that come up. In particular, I'll spend some time documenting the electronics bay and the design of the camera mount.
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline dbmccann

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Re: BB Level 3 project
« Reply #1 on: January 13, 2016, 07:48:31 PM »
Sounds very cool.   

Have you seen the shroud for the mobius?   A much neater way to hang the whole thing outside the rocket than duct tape :)  I use a few and enjoy them. 


Offline David Carter

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Re: BB Level 3 project
« Reply #2 on: January 13, 2016, 08:46:03 PM »
I have, but I'm not overly impressed. They're still pretty crude and aesthetically unpleasing. I've even printed one to confirm my opinion.

I've got bigger plans... possibly even two cameras, one with a wide angle lens and one with the normal lens. I still haven't decided, but I'm still working on the fit of the printed parts. I'm finding the precision is less than advertised.

I may still have the camera external like with the shroud, but it will be a better shroud.
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline David Carter

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Re: BB Level 3 project
« Reply #3 on: January 13, 2016, 09:01:19 PM »
This is more the kind of shroud I'm interested in. It's essentially half of a Von Karmen nose cone with a conformal shape for my body tube.
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline David Carter

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Re: BB Level 3 project
« Reply #4 on: January 13, 2016, 09:14:06 PM »
The mechanical portion of the build is underway. The motor mount is built, and the fins are attached. Working on all the fillets, but that is taking a lot of time as there are a lot of them. There's also not much room with a 75mm motor mount in a 4" tube. Rocketpoxy all the way.

Since there was no room on the centering rings for an eye bolt, I epoxied a section of nylon shock chord to the motor mount for shock chord attachment. With a standard 75mm motor, this will be a back up to the eye bolt in the motor itself, but it does allow me to fly a 54MM motor with adapter. And backups are never a bad thing.

I used an old pizza box for aligning my fins in the absence of a fin jig. You can never get enough pizza right?
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline David Carter

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Re: BB Level 3 project
« Reply #5 on: January 13, 2016, 09:15:48 PM »
Continued...
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline David Carter

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Re: BB Level 3 project
« Reply #6 on: January 13, 2016, 09:47:13 PM »
In the meantime, I created a custom ebay sled for the electronics. This is essentially a modification of existing designs, but since I had the capability, I tailored it for my electronics.

The main flight computer is the Altus Metrum TeleMetrum which also has GPS for tracking and a real time HAM telemetry link. There's lots of room in my 12 inch ebay for it and its antenna, but for best results the antenna should be vertical. My design includes a very basic antenna support.

The secondary flight computer is a PICO-AA2. Both computers use different batteries, so my battery compartment can accommodate both. The compartment has a screw on cover that will restrain the battery in all dimensions.

This may be overkill in some senses, but hey... because I can!
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline RKeller

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Re: BB Level 3 project
« Reply #7 on: January 13, 2016, 09:51:06 PM »
Really nice build! what 3d printer are you using?
Riley Keller
URRG
TRA#15415
L1 25 Oct 2014 Estes MDRM CTI H133
L2 25 June 2015 Rocketry Warehouse DYOK, CTI L1030RL 14.7k ft mach 1.57

I'm addicted to building stuff, rockets are just a way to get high

Offline David Carter

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Re: BB Level 3 project
« Reply #8 on: January 13, 2016, 09:55:50 PM »
Really nice build! what 3d printer are you using?

Robo 3D R1+. (http://www.robo3d.com)
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline mdutch

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Re: BB Level 3 project
« Reply #9 on: January 14, 2016, 09:34:09 AM »
David so far so good on you L3 build and this is a perfect way for me to review everything so I can sign off on the project when the time comes. I noted that you said you were using a nylon strap on the motor mount. This would be fine as all "M" motors don't have an ejection charge that could damage it, but some 54 motors do. So you would need to be careful using those.

Although from the pictures you post here that strap actually looks like a Kevlar strap, which is what I would have recommended and is better suited to withstanding powder burns.

One thing you might want to consider for your build is a tip to tip fiberglass application to beef up the fins to stand up to the G-forces a "M" motor will put the airframe through, especially where fin flutter is concerned.
There are many ways to accomplish this, here is one option: ( http://www.jcrocket.com/tttjig.shtml )

Keep up everything that your doing here and when your ready we'll get together and review and sign off on your packages before the actual flight.
Mike Dutch
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URRG & MRSI Founder
"I just Want to Fly ROCKETS"

Offline RickB

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Re: BB Level 3 project
« Reply #10 on: January 14, 2016, 11:48:54 AM »
Really nice build! what 3d printer are you using?

Robo 3D R1+. (http://www.robo3d.com)

Not to derail, but what are you're impressions of it?  I've been toying with the idea of getting one myself.  There are bunch of parts for various scale projects that I want to build that it would be really handy for, especially with the largish build volume compared to a lot of the other small printers.
Rick Barnes

Offline David Carter

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Re: BB Level 3 project
« Reply #11 on: January 14, 2016, 01:46:40 PM »
David so far so good on you L3 build and this is a perfect way for me to review everything so I can sign off on the project when the time comes. I noted that you said you were using a nylon strap on the motor mount. This would be fine as all "M" motors don't have an ejection charge that could damage it, but some 54 motors do. So you would need to be careful using those.

Although from the pictures you post here that strap actually looks like a Kevlar strap, which is what I would have recommended and is better suited to withstanding powder burns.

One thing you might want to consider for your build is a tip to tip fiberglass application to beef up the fins to stand up to the G-forces a "M" motor will put the airframe through, especially where fin flutter is concerned.
There are many ways to accomplish this, here is one option: ( http://www.jcrocket.com/tttjig.shtml )

Keep up everything that your doing here and when your ready we'll get together and review and sign off on your packages before the actual flight.

Mike, you're right about the Kevlar. I had to review what I ordered to verify :)

I've used plugged motors before. The delay times available were too low for my rocket so I had to rely on the electronics.

I must confess, I hadn't considered reinforcement beyond good solid fillets. I guess I figured 3/16" fiberglass would be enough. I've found a few calculators for fin flutter, but I can't access them from work so I have to wait until this evening. From what I can gather doing the reading though, if the fin is shaped correctly you shouldn't get much flutter. Reinforcing fiberglass with fiberglass is just using a thicker fin isn't it?

I guess that's why I got into this... to learn things  :)
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline David Carter

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Re: BB Level 3 project
« Reply #12 on: January 14, 2016, 01:52:55 PM »
Really nice build! what 3d printer are you using?

Robo 3D R1+. (http://www.robo3d.com)

Not to derail, but what are you're impressions of it?  I've been toying with the idea of getting one myself.  There are bunch of parts for various scale projects that I want to build that it would be really handy for, especially with the largish build volume compared to a lot of the other small printers.

I really like it. I took it out of the box and was printing in minutes. Some printers require a lot of DIY to get up and running, but this was pretty much plug and play.

I printed a few things, left the country for a couple of months, and when I came back and printed some more without issue. It was printing pretty much non-stop for about a week and a half doing prototypes and builds. I love it. There are contract services that will print for you using your model files, but if you require a series of prototypes then nothing beats having your own.

That being said, last night I seem to have gotten a clogged nozzle. I went to bed. I'll let you know how easy it was to clear that, but I can't imagine it being any worse than any other printer. Their online help is quite good, and by all reports so is their phone support. I have no first hand knowledge of that. Other companies though are notoriously bad about after sales support.
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!

Offline RickB

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Re: BB Level 3 project
« Reply #13 on: January 14, 2016, 04:01:01 PM »
Good to know, thanks for the info.  What are you using to generate the print files?  I can export to .stl from NX, which I use at work.  I also just discovered that Rocksim exports to .stl, but I'm not exactly sure what you'd get as a result...
Rick Barnes

Offline David Carter

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Re: BB Level 3 project
« Reply #14 on: January 14, 2016, 04:23:14 PM »
Good to know, thanks for the info.  What are you using to generate the print files?  I can export to .stl from NX, which I use at work.  I also just discovered that Rocksim exports to .stl, but I'm not exactly sure what you'd get as a result...

Using FreeCAD. It's open source and cross platform, which is important to me. But it's got some really annoying bugs you need to learn how to work around and takes some time to learn how to use it effectively.

There are a number of online and cloud based options out there, but a lot of the time I'm offline or on an unreliable connection so they aren't good options for me. Cross platform was also a concern as I travel with a Mac but have a PC desktop at home.

In particular, one of the cloud based options that looked pretty good, and would probably give you fewer headaches than FreeCAD, is http://www.autodesk.com/products/fusion-360/overview


Here's a good guide to modeling software: https://www.gliffy.com/go/publish/5271448

I've got an article coming up in the PSC newsletter that gives a pretty full write up on the options. I don't want to post it here because it's not published yet, but I can send it in an PM if you're impatient.
David Carter
NAR 98850, Level 3

90% of rocketry is sanding!