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| Re: rocket sparrow mk1 [message #46810 is a reply to message #46808 ] Wed, 11 April 2012 17:03 UTC |
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SO COOOL
Please upload video of flight
Duann Scott, Designer Evangelist, Shapeways
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| Re: rocket sparrow mk1 [message #46844 is a reply to message #46806 ] Thu, 12 April 2012 04:55 UTC |
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yes i will be launching tomorrow morning, weather permitting, and taking HD video at 60fps with a shutter speed as fast as i can get it (prob bout 2000th of a second)... and HOPEFULLY i will be able to retrieve the rocket and launch again.
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| Re: rocket sparrow mk1 [message #46962 is a reply to message #46806 ] Fri, 13 April 2012 19:11 UTC |
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Did you launch it yet?
What do you have in there for the core? I want to try one too. 
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| Re: rocket sparrow mk1 [message #46970 is a reply to message #46844 ] Fri, 13 April 2012 22:22 UTC |
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Hi Leo,
Your model concept looks great. I think it will fly just fine as designed. The motor retention mechanism is a stroke of genius. I love how the action clips the motor in one configuration and releases when sprung in the other.
Your fins seem a bit on the thin side at 1mm but I also see the reinforcements about mid-chord to keep them from flexing. You might want to move them towards the front, or leading edge, on your next iteration to put the thinner section in the slipstream.
I'm really curious how the model performs and how it handles the temperatures associated with the Estes motors. Please keep us updated!
Nice project!
Regards,
Mark
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| Re: rocket sparrow mk1 [message #46971 is a reply to message #46970 ] Fri, 13 April 2012 22:26 UTC |
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Leo,
By the way, as I was just looking at the pictures once again, you could design in a ring on the tips of the model to keep the fins from bending/flexing during transit from Shapeways to you. That ring will also help reduce flutter of each fin as it passes through the velocity gradient from zero to maximum velocity to ejection.
Just a thought!
Regards,
Mark
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| Re: rocket sparrow mk1 [message #46974 is a reply to message #46806 ] Sat, 14 April 2012 01:24 UTC |
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Hey guys.
No I have not launched yet, though I think i have found a nice spot (thanks to google earth that i wont loose the rocket after launch hopefully) and will definitely launch this weekend.
Yes for my next print i will either use the ring thing to hold the fins in the correct position for transport or have the fins separate and glue them to the body.
after the first flight i will make changes to the rocket as needed, though at $15 a print i wouldn't really be happy adding more material.
@Mary, u can buy the rocket engines at your local hobby store in many sizes:)
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| Re: rocket sparrow mk1 [message #47030 is a reply to message #47017 ] Sun, 15 April 2012 14:47 UTC |
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Leo,
Nice flight. That first boost looked pretty straight and true.
What are your plans for the next iteration?
Was the damage to the slotted body due to impact and what was the thickness of those parts?
Nice attempt and certainly an interesting project, since I am a model rocketry nut.
Congrats!
Mark
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| Re: rocket sparrow mk1 [message #47041 is a reply to message #46806 ] Sun, 15 April 2012 23:40 UTC |
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Part of the damage was due to the expansion of the engine when it heats up (the fit may have been a bit snug), i believe the fin break was on landing, and a small section near the cone was melted on ejection. All of these problems will be addressed in the next version:)
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| Re: rocket sparrow mk1 [message #47064 is a reply to message #46806 ] Mon, 16 April 2012 13:53 UTC |
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I was worried about your locking mechanism melting. Perhaps some flame resistant coating?
The Mad Moder
michael@shapeways.com
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| Re: rocket sparrow mk1 [message #47224 is a reply to message #47069 ] Thu, 19 April 2012 14:43 UTC |
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You should try this in polished alumide, more heat resistant, smoother so less friction..
Where are you based.
Duann Scott, Designer Evangelist, Shapeways
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| Re: rocket sparrow mk1 [message #47242 is a reply to message #46806 ] Fri, 20 April 2012 00:43 UTC |
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Thanks Duann:)
I might try the alumide next time.
I'm based in Perth, Western Australia.
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| Re: rocket sparrow mk1 [message #47245 is a reply to message #47242 ] Fri, 20 April 2012 02:15 UTC |
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Maybe you should change the design a bit, the sharp corners in the side "windows" are a bad idea, for example. Any transition should be smooth to avoid stress points. If heat is still a problem after reinforcement, do some kind of insulation at the problematic zones, using other material but keeping the fins and top in WSF.
As for roughness... sharks and other animals have rough skin, because it works reducing drag. Golf balls have small dots, instead of being smooth, to fly more. Who knows, maybe this is another case where non obvious is better. Rough cone and smooth body? Selective smoothing? ^_^
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| Re: rocket sparrow mk1 [message #47246 is a reply to message #46806 ] Fri, 20 April 2012 03:59 UTC |
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Hi Stannum.
Yes i had considered the roughness causing micro vortexes, as the windows with hard edges would do the same, reducing drag at the rear on the rocket.. much as a Ute (or pickup in american) creates a pocket of swirling air near the rear of the car and reduced drag (as proven on Mythbuster), not sure if its the same on the rocket, but seem right:S... though i will probably taper windows for next build.
Maybe i should use two materials, one for the body and one for the fins and nose cone... Alumide for the body as it has a greater heat tolerance.
The main aim was to have it as cheap as possible, and use bare minimum materials, so anything i add will mean subtracting material elsewhere....
my original idea was to just have a nose and fins that connect to the engine and nothing joining the two, but that seemed difficult to design.
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