External camera shroud on Mach + rcoket

[jkovac]

I've been using a Landru-made external camera shroud on a small rocket (Madcow Twitch) and have flown it on a J270 with no issues. I am now moving up to 54mm motor rocket with a 2.6" body tube, and will be flying K and L motors. Has anyone flown that type of a rocket with an external camera shroud? I like the shroud because it's easy to install, and the downward angle of the camera is great. I don't think it would shear off any easier than the fins would, but I wonder how it might affect the flight characteristics of the rocket. (I'm not concerned with a bit of altitude loss.) I asked landru about it and he said he's heard some reports of coning but nothing catastrophic. Any input appreciated.

 

[watermelonman]

I do not have the Landru version but I made two of my own from fiberglass. They definitely do affect the flight, though not dreadful. Check the K2045 and L935 flights in particular -
https://vimeo.com/user40316715

 

[mrwalsh85]

I attach mine using machine screws. Landru's shrouds work well. I have flown them past mach more than once. Works well. No damage. Haven't hit Mach 2.....yet.

 

[jkovac]

Thanks for the replies. Watermelonman, great videos. Looking at them, it appears the flights were stable and pretty vertical. Couldn't see any coning but maybe that's hard to tell from the video. In what way did the shrouds affect the flights?

 

[Spicer007]

I do not have the Landru version but I made two of my own from fiberglass. They definitely do affect the flight, though not dreadful. Check the K2045 and L935 flights in particular -
https://vimeo.com/user40316715

Watermelonman,

Great videos! What camera are you using and can you attach photos of how it's mounted?

Spicer

 

[watermelonman]

Thanks for the replies. Watermelonman, great videos. Looking at them, it appears the flights were stable and pretty vertical. Couldn't see any coning but maybe that's hard to tell from the video. In what way did the shrouds affect the flights?

I believe the Punisher L935 flight was helped off vertical by the unbalanced drag, and definitely lost a ton of altitude. I mentioned those two because they went the fastest of what I have flown.

There is another one, Punisher K570, with a ton of coning. I am not sure why I got so much more there but it must be due to the balance of the rocket and the speeds encountered.

 

[jkovac]

I believe the Punisher L935 flight was helped off vertical by the unbalanced drag, and definitely lost a ton of altitude. I mentioned those two because they went the fastest of what I have flown.

There is another one, Punisher K570, with a ton of coning. I am not sure why I got so much more there but it must be due to the balance of the rocket and the speeds encountered.

Thanks for the reply. I wonder if using two shrouds, one on each side of the BT, would be worth it in terms of more overall drag but better balance? I might try that, will let you know what happens if I do.

 

[watermelonman]

Thanks for the reply. I wonder if using two shrouds, one on each side of the BT, would be worth it in terms of more overall drag but better balance? I might try that, will let you know what happens if I do.

Happy to help! I bet my off balance drag was increased by the position on the body tube and shape of the mount. The second version stayed closer to straight. I will post a breakdown of which shroud was used in which position for each video, when I finally get around to taking a picture of the mounts for Spicer007.

 

[mrwalsh85]

[video=youtube;r1v-TqXjPG4]https://www.youtube.com/watch?v=r1v-TqXjPG4[/video]

Last Call on a L1000 DMS motor...

I have a video somewhere of same rocket on a Loki L1400...

And here's an as yet unnamed rocket on a AT L1390...

[video=youtube;n9bGfXZ5pzs]https://www.youtube.com/watch?v=n9bGfXZ5pzs[/video]

Hoping to do a M1297 in same rocket someday...

-Walsh

 

[jkovac]

[video=youtube;r1v-TqXjPG4]https://www.youtube.com/watch?v=r1v-TqXjPG4[/video]

Last Call on a L1000 DMS motor...

I have a video somewhere of same rocket on a Loki L1400...

And here's an as yet unnamed rocket on a AT L1390...

[video=youtube;n9bGfXZ5pzs]https://www.youtube.com/watch?v=n9bGfXZ5pzs[/video]

Hoping to do a M1297 in same rocket someday...

-Walsh

Cool. Did you notice any coning or other issues with the camera in place?

 

[ChrisAttebery]

I've been thinking about this quite a bit lately. I sold my Mobius a couple weeks back so that I can buy a better camera. I'm looking at the Sony X1000V and HDR-AS50. They both have better PQ than the Mobius. The AS50 can shoot up to 1080p60 and the X1000V can shoot up to 1080p120 or 4Kp30 (3840x2160).

I like the view pointing down the side of the rocket, but I'm afraid that it might cause issues on my Mach 1.4 L3 attempt. So I keep going back and forth on how to mount it.

1. Mount it completely inside the altimeter bay pointing straight out. This is the safest choice as far as flight dynamics are concerned but it will have the typical elevator ride viewpoint.

2. Mount it completely inside but use a small 90 degree optical prism to get the downward view I want. I like this idea but I'm not sure how to size the prism. I *think* it could have a smaller footprint than the next option though. Maybe a 1/2" square prism that could be shrouded to be more aerodynamic too. If any of you can help with this I'd like to work on it.

3. Mount it at an angle pointing down the side of the rocket and completely shrouded. The camera shroud would be roughly 1.2" wide and 4" long.

 

[jkovac]

I've been thinking about this quite a bit lately. I sold my Mobius a couple weeks back so that I can buy a better camera. I'm looking at the Sony X1000V and HDR-AS50. They both have better PQ than the Mobius. The AS50 can shoot up to 1080p60 and the X1000V can shoot up to 1080p120 or 4Kp30 (3840x2160).

I like the view pointing down the side of the rocket, but I'm afraid that it might cause issues on my Mach 1.4 L3 attempt. So I keep going back and forth on how to mount it.

1. Mount it completely inside the altimeter bay pointing straight out. This is the safest choice as far as flight dynamics are concerned but it will have the typical elevator ride viewpoint.

2. Mount it completely inside but use a small 90 degree optical prism to get the downward view I want. I like this idea but I'm not sure how to size the prism. I *think* it could have a smaller footprint than the next option though. Maybe a 1/2" square prism that could be shrouded to be more aerodynamic too. If any of you can help with this I'd like to work on it.

3. Mount it at an angle pointing down the side of the rocket and completely shrouded. The camera shroud would be roughly 1.2" wide and 4" long.

Hi Chris,

Those Sony cameras look great. But since I don't have the skills you do (been following your latest build thread - amazing) I'm only looking at the Mobius because Andrew D. makes a shroud for it, and also it has a removable lens and an available extension cable. So one thought I had was to mount the lens externally, pointing down, with some type of mini-shroud to protect it. Even that might be hard for me, so the other idea was to simply use two shrouds and two cameras so the load would at least be balanced. I'm not sure how much that would cost me in altitude and/or other flight issues.

 

[ksaves2]

I believe Derek Devilles Qu8k had the plastic shroud melt with Mach 2.5 to 3 ish flight. Keep that in mind if one is going to go at those speeds for any length of time. I've stuck a pretty large camera bulge on the side of
a 2.5 inch rocket and I really haven't noticed that it affects the trajectory. Kurt

 

[ChrisAttebery]

I've watched the Qu8k and CSXT videos today. The CSXT's downward video is really nice. I sent a message to Ky about their camera setup. Hopefully he'll get back to me.

I grabbed a screen shot of their camera mount. I'd say they mounted the camera and lens in the mount rather than using a mirror.


The camera shroud I pictured above would have a frontal area of ~1.33 sq/in. The Landru Mobius mount is ~.94sq/in. I think I might order a couple mirrors and see how small of one I can get away with if I mount it right in front of the lens. Even 25 x 38mm mirror at a 45 degree angle would only have ~1 sq/in of frontal area.

Another idea I had would be to mount the Sony camera pointing down with the lens as low as possible into the airframe. When I tried this with the Mobius I was able to get within 1/8" of the center of the lens before the view was obscured.

 

[Eyesinthesky]

I'm looking at the Sony X1000V and HDR-AS50. They both have better PQ than the Mobius. The AS50 can shoot up to 1080p60 and the X1000V can shoot up to 1080p120 or 4Kp30 (3840x2160).

I like the view pointing down the side of the rocket, but I'm afraid that it might cause issues on my Mach 1.4 L3 attempt. So I keep going back and forth on how to mount it.

1. Mount it completely inside the altimeter bay pointing straight out. This is the safest choice as far as flight dynamics are concerned but it will have the typical elevator ride viewpoint.

2. Mount it completely inside but use a small 90 degree optical prism to get the downward view I want. I like this idea but I'm not sure how to size the prism. I *think* it could have a smaller footprint than the next option though. Maybe a 1/2" square prism that could be shrouded to be more aerodynamic too. If any of you can help with this I'd like to work on it.

3. Mount it at an angle pointing down the side of the rocket and completely shrouded. The camera shroud would be roughly 1.2" wide and 4" long.

View attachment 284481

I've been building fairings for the Sony's for a while. Mine are based on Von Karmon equations and I have molds for different diameter body tubes. They are a little longer than 4" since I was trying to go with some aerodynamics. The camera has a 6 degree angle from the rockets center line axis.



Doug

 

[ChrisAttebery]

Hi Doug,

Nice fairing. The onboard videos on your vimeo acct look great too. I was concerned that the fairing might cause spin on a rocket this fast, but your videos were both relatively spin free. Do you have a picture of the GoPro 3 fairing?

Originally I was thinking about purchasing a 29mm nose cone, cutting it in half and use that as the fairing. Yours looks pretty close to what I had envisioned, but I wanted to mount the camera lower into the body tube. The rendering above used 29mm tubing as the fairing.

I guess I need to start working on this. May 21st is coming up quick.

 

[Eyesinthesky]

Hi Doug,

Nice fairing. The onboard videos on your vimeo acct look great too. I was concerned that the fairing might cause spin on a rocket this fast, but your videos were both relatively spin free. Do you have a picture of the GoPro 3 fairing?

Thanks, I'm almost too embarrassed to show the GoPro Fairing. It is a huge monstrosity campared to the Sony. I only built one prototype and one for the rocket for the GoPro.



The Camera is completely outside of the body tube so it is very large. This rocket did go to 23K on a N1000. Here is a link to the video from a different flight
[video=vimeo;110331442]https://vimeo.com/110331442[/video]
and the footage from a Sony in the nose cone
[video=vimeo;110331443]https://vimeo.com/110331443[/video]

Doug

 

[ChrisAttebery]

Those were the videos I had seen.

I'm more worried about instability than the extra drag caused by the camera. Your fairly seems to have passed that test.

 

[ksaves2]

Those were the videos I had seen.

I'm more worried about instability than the extra drag caused by the camera. Your fairly seems to have passed that test.

I had asked that question a few years ago and most said it really isn't much of an issue with instability as long as the rocket balances out for stable flight.
All of those fairings above look fine in spite of the self recriminations. I'll try and post a picture of my modified longnecked Banshee clone.
A video is here:

https://youtu.be/afxmZDhenaE

Look at the small fins. The 808, 720p camera in a home made plywood shroud just forward of the ebay. I have several videos that show perfectly fine trajectories.

The only problem I foresee is someone going Mach 2 and above for any length of time. Aerodynamic heating can melt a plastic shroud. For most of us sport fliers we won't even approach that "stupid fast" speed. Kurt