Astron Cobra Upscale

Gary Byrum said:

I'm not sure if this actually fits in the LPR category but since it's based on a LPW model...... I'm 1/2 way done with an upscale of the old Astron Cobra using BT 80 reduced to a BT 60 sporting a motor mount for 3 - D motors. Has anyone built one on this scale? Pics?

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Yes, I built an upscale like this about 10 years ago. It is still one of my favorite rockets to launch. Mine has had many flights on 3XD12 motors. Here are some links to older photos that I have.

https://home.pcisys.net/~gelder/aug2007/maxi_astron_cobra1.jpg

https://home.pcisys.net/~gelder/aug2007/maxi_cobra_launch.jpg

https://home.pcisys.net/~gelder/jul08/cobras.jpg

https://home.pcisys.net/~gelder/jul08/maxi_cobra_launch.jpg

Gary Byrum said:

I'm not sure if this actually fits in the LPR category but since it's based on a LPW model...... I'm 1/2 way done with an upscale of the old Astron Cobra using BT 80 reduced to a BT 60 sporting a motor mount for 3 - D motors.

Click to expand...

Three Estes D motors is not HPR. With a propellant mass limit of 125g (combined), you can fly up to 5 D12 motors at 21.1 grams of propellant per motor.

If you leave out motor blocks and instead use aft thrust rings on the motors (ie, tape rings), you can fly longer motors in this bird. Three of the new E12's contain less than 125g (35.9 grams apiece).

One thing to consider is recovery. With fins like this, you can find yourself repairing them. When they stick out aft like this, you don't need a very hard landing to snap one. It just has to hit at an odd angle.

You might consider rigging the recovery harness so the payload section hits first. This will let the back end come down more slowly under chute after the nose end hits the ground.

Doug

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grog said:

Yes, I built an upscale like this about 10 years ago. It is still one of my favorite rockets to launch. Mine has had many flights on 3XD12 motors. Here are some links to older photos that I have.

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Thanks for sharing the photos. Nice lift off shots. Do you remember what kind of altitude you got with 3 D motors?

Gary Byrum said:

OK! It's near ready for Freedom Launch. Just a few touch ups and it's a go. The Duplicolor paint color made it a little difficult to to decide how to trim this one out but I'm reasonably happy with it. Yall just wish me luck getting 3 D motors to to fire all at once when I take this bish to Orangeburg.

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B E A utiful...I really like the trim out. And WOW..THREE D's Make sure to get some video, and some key chain cam video.

closet astronaut said:

B E A utiful...I really like the trim out. And WOW..THREE D's Make sure to get some video, and some key chain cam video.

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Thank you. I hadn't even thought about an on board video camera. Might just have to do that.

I've made one of these before, and I'm making one again.

I used a BMS 60-80 adapter, and a generic BT-60 nosecone.

It all started when I was given 60 D12-0's, by a guy using them at a scale shuttle test site at Lockheed. The project was long over, and he grew tired of losing his Omega or Lightnin' due to small launch sites.

I didn't lose (many) 2-stage D birds, but I realized I would lose plenty, if I kept this up. What do do with all those D's?

Decided to plug them, and fly them in an upscale Astron Cobra. I often used two plugged D12-0's, and one D12-5 with a little extra BP. Here's a link - it's near the bottom: here

There's a link to a super-slow mo of the Cobra flying on D12's, here

As I used 3/16 ply for fins, and had tip-to-tip'ed it with 2 oz fiberglass, I was pretty sure it would not break a fin. I sacrificed performance, but I was able to fly it on 3 x F24's, and E9's were easy.

Sadly, this machine and his little brother were stolen in 2010.

So I made them again.

I've got the Pre-Damon decals from Excelsior - still putting the finishing touches on the paint.

I had forgotten that I meant to post a vid of this flight. This was taken as the last ROSCO launch of 2013 in Orangeburg SC, and it's a redemption flight of the aforesaid failed attempt back in the days when my clip whips weren't what they are today. Anyhoo, here's a look-see at the flight and the aftermath.

https://s343.photobucket.com/user/glbyrum/media/CobraFlight2013_zps2298cc31.mp4.html

The photo is what I got back after the flight. All 3 engines were missing even though it was a successful flight. I am redesigning the engine mount so it doesn't suck oxygen/flame as much. This is probably the reason for the burn factor.

I agree, the recessed cavity probably lead to turbulence that sucked hot exhaust in and caused some burning, but it's odd that the engines... all of them... were missing. The hooks look like they would well secure the engines.

For this style of triple 18 mm mount, I've gone to a central retaining screw used with a washer for positive retention. No lost engines with that!

MArc

Marc_G said:

The hooks look like they would well secure the engines.
For this style of triple 18 mm mount, I've gone to a central retaining screw used with a washer for positive retention. No lost engines with that!
MArc

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That's not a half bad idea! Thanks. It's not too late either. The new motor mount is already built but not installed. I also left the engine hooks out as it appears with said heat factor they could have overheated and were weakened enough to release the spent engines at ejection. I opted to use engine blocks and go with friction fitting, but now I have another option.

MAN! That is one BEAUTIFUL build!!! I LOVE the paint job....very CLASSIC looking! The one thing i have yet to do is build a cluster anything, but i just found out that there is a company called BMS that makes the Estes clone of the Cobra......maybe that will be my first cluster job!! For your first flight, what will use use for power...D12-5s??? I wonder how high it'll go? I hope it launches(and recovers!) GREAT! Ill bet if there were plans/specs for your model, A BUNCH of people(probably including me!) would build that sucker!! GOOD LUCK!! Launch pics if possible.....PLEASE???

Bill Gibson said:

MAN! That is one BEAUTIFUL build!!! I LOVE the paint job....very CLASSIC looking! The one thing i have yet to do is build a cluster anything, but i just found out that there is a company called BMS that makes the Estes clone of the Cobra......maybe that will be my first cluster job!! For your first flight, what will use use for power...D12-5s??? I wonder how high it'll go? I hope it launches(and recovers!) GREAT! Ill bet if there were plans/specs for your model, A BUNCH of people(probably including me!) would build that sucker!! GOOD LUCK!! Launch pics if possible.....PLEASE???

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Thanks for the comps Bill. It's a pseudo up scale in that using BT 80 to BT 60 was close enough to go with. Uses a 3-3/16" long card stock shroud and a 60 NA nose cone. Just in case you overlooked it, there's a link to a vid of the launch in post #37 and I should have used 5 sec delay instead of 3 seconds. It flew very well.

Hey Gary,nice upscale and flight.I've just started to clone the Astron Cobra.I may have to do an upscale later also.

Devontmp said:

Hey Gary,nice upscale and flight.I've just started to clone the Astron Cobra.I may have to do an upscale later also.

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Thank you. Let me know if you want the dims. It's a pretty easy upscale and I have the schems for all of it.

Thanks,that would be great.I did a BT80 to BT60 for a 5x B engine cluster contest last year.I have a Scrambler I built back in the '70s.Clusters are cool to fly.