FTC rocket parachute deployment mechanism

Water Rockets NSW

Moderator: Moderators

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

FTC rocket parachute deployment mechanism

Postby air.command » Wed Nov 12, 2008 8:11 am

We've almost finished building our first FTC rocket. We see a lot of people building these so we thought we'd give it a go as well. It's been a fun challenge trying to get everything to fit into the FTC tube. I've put the details of our parachute deployment mechanism here:

http://www.AirCommandRockets.com/day69.htm

We went with a splitting nosecone because it meant we didn't have to push the parachute out of the tube. With this technique we can pack quite large parachutes as the nosecone can be simply made longer. There are no specially machined parts in the deployment mechanism, just a few lengths of FTC, 3 bottle caps, plastic egg, and a couple of paper clips. We wanted to avoid rubber bands due to the problems of their deterioration. We activate the latch with an RC servo motor controlled by our timer, but it should be adaptable to other timers or perhaps a MAD.

We hope to fly it at the next NSWRA launch day so we'll see if it stands up to the expected G forces.

There is a short video included as well that shows how it works.

Image


The image below shows the deployment mechanism mounted on top of the FTC rocket: (rocket is about 1.8m tall.)

Image
Crop Circles: ... just a bunch of guys looking for their rockets ....

krusty
Engineer
Engineer
Posts: 1306
Joined: Tue Nov 27, 2007 12:21 pm
Location: Noble Park, Vic, Australia
Contact:

Postby krusty » Wed Nov 12, 2008 8:58 am

That looks great!

I saw the parachute eject video on youtube last night - I love the way it pops open, very neat!

Where did you get the FTC and was it expensive??

Have you glassed the outside of the tube??

Krusty

(I was going to say that it almost looks like a real rocket - but figured you'd smack me one ;))

whipfest
Engineer
Engineer
Posts: 518
Joined: Sat Apr 26, 2008 5:32 am
Location: Hills district, Sydney

Postby whipfest » Wed Nov 12, 2008 9:13 am

krusty wrote:(I was going to say that it almost looks like a real rocket - but figured you'd smack me one ;))


I reckon a G80 would make it go alright....:twisted:

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Wed Nov 12, 2008 11:58 am

krusty wrote:Where did you get the FTC and was it expensive??


I had it ordered in at a hardware store. They had it listed in their catalog but didn't stock it. And yes it was too expensive. I think I paid about $70 for 4 six foot lengths. :( I was disappointed too because it was only 0.4mm wall thickness. There are apparently ones around that are around 0.8mm. (means they can handle more pressure)

krusty wrote:Have you glassed the outside of the tube??


We wrapped it with a single layer of glass fiber strapping tape. This raises the operational pressure from around 160psi to 200+psi. Burst pressure without reinforcing is around 190psi.

krusty wrote:(I was going to say that it almost looks like a real rocket - but figured you'd smack me one ;))


:D :D :D .... I hope to build real rockets one day .... I am just practicing :D

whipfest wrote:I reckon a G80 would make it go alright.... :twisted:


I thought about just sticking a real motor in it, but it would melt everything.

At 200psi it will have about 19Ns total impulse so I guess the motor equivalent would be a D310 (not a typo) the large nozzle insures the thrust phase is over in around 65ms.

I'm guessing it will sound more like a gunshot. It'll be interesting what breaks during the high G's.
Crop Circles: ... just a bunch of guys looking for their rockets ....

Kryten
Astronaut
Astronaut
Posts: 1976
Joined: Wed Oct 24, 2007 11:06 am
Location: Sydney

Postby Kryten » Wed Nov 12, 2008 2:53 pm

Should be ... interesting!
"Pub, ah yes. A meeting place where people attempt to achieve advanced states of mental incompetence by the repeated consumption of fermented vegetable drinks" (“Timeslides”)

october sky
Human GPS
Human GPS
Posts: 4078
Joined: Tue May 01, 2007 2:47 pm
Location: BRISBANE

Postby october sky » Wed Nov 12, 2008 5:17 pm

WOW A.C. You know your rockets and I mean it without referring to "real" rockets. :)

Very nice looking bird ! 8)
QRS Inc. NO: 003

Life Member

TRA #11616 L3

~RR~
Engineer
Engineer
Posts: 1127
Joined: Tue May 01, 2007 5:30 pm
Location: QLD

Postby ~RR~ » Wed Nov 12, 2008 5:54 pm

excellent work AC 8)
air.command wrote:At 200psi it will have about 19Ns total impulse so I guess the motor equivalent would be a D310 (not a typo) the large nozzle insures the thrust phase is over in around 65ms.

unreal... :shock: can't wait to see video of this..
Shane...
TRA # 11474

krusty
Engineer
Engineer
Posts: 1306
Joined: Tue Nov 27, 2007 12:21 pm
Location: Noble Park, Vic, Australia
Contact:

Postby krusty » Wed Nov 12, 2008 8:13 pm

air.command wrote:At 200psi it will have about 19Ns total impulse so I guess the motor equivalent would be a D310 (not a typo) the large nozzle insures the thrust phase is over in around 65ms.

I'm guessing it will sound more like a gunshot. It'll be interesting what breaks during the high G's.


It wouldn't be so much the water being forced out the bottom, but the rocket being forced off the top!!

That's insane :)

Krusty

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Wed Nov 12, 2008 8:27 pm

We'll point this one well away from the crowd. :D Before launch I am going to weigh the different components of the nosecone and multiply that by 100 and place an equivalent weight on the nosecone at the appropriate places to see if things buckle. I am expecting the parachute to exert several kilos of force on top of the rocket.
Crop Circles: ... just a bunch of guys looking for their rockets ....

astroboy
Astronaut
Astronaut
Posts: 1545
Joined: Wed Apr 25, 2007 5:06 pm
Location: Pandemonium, 9th Circle of the Abyss

Postby astroboy » Wed Nov 12, 2008 9:20 pm

Wow! Can't wait to see the clustered version!!
Satans stooge.

whipfest
Engineer
Engineer
Posts: 518
Joined: Sat Apr 26, 2008 5:32 am
Location: Hills district, Sydney

Postby whipfest » Thu Nov 13, 2008 3:33 pm

air.command wrote:We'll point this one well away from the crowd. :D


Yea, that worked well last time :wink:

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Fri Dec 26, 2008 2:49 pm

We test flew the FTC rocket at our local park last Sunday. It was perfect weather for launching so we couldn't resist.

The launch report is here:

http://www.AirCommandRockets.com/day71.htm

and includes a highlights video. (best viewed in hi-quality mode)

http://www.youtube.com/watch?v=M62--mVD0wc

At the higher pressures we were finding the rocket was bending quite a bit on launch. We will need to use stiffer reinforcing.
Crop Circles: ... just a bunch of guys looking for their rockets ....

Bones
Engineer
Engineer
Posts: 821
Joined: Sun Jun 24, 2007 10:04 am
Location: Wauchope!
Contact:

Postby Bones » Fri Dec 26, 2008 3:25 pm

That went great George.

Quicker to prep between launches?
"You could give Aristotle a tutorial. And you could thrill him to the core of his being ... Such is the privilege of living after Newton, Darwin, Einstein, Planck, Watson, Crick and their colleagues." - Richard Dawkins

www.suburbanrocketry.com

Kryten
Astronaut
Astronaut
Posts: 1976
Joined: Wed Oct 24, 2007 11:06 am
Location: Sydney

Postby Kryten » Fri Dec 26, 2008 4:02 pm

Certainly looks good.
You could stiffen it, but it will add to the weight.
I recently remembered something from my archery days - the "Archer's Paradox" - you can't sight directly along the arrow to the target, because when you release the string, the arrow bends due to inertia and the force being applied to the end. The arrow contines to flex from side to side on its way to the target
And we're talking about aluminium tubing, which would be more rigid than FTC tube.
So trying to remove all the flexing may not be justified
"Pub, ah yes. A meeting place where people attempt to achieve advanced states of mental incompetence by the repeated consumption of fermented vegetable drinks" (“Timeslides”)

air.command
Astronaut
Astronaut
Posts: 1907
Joined: Mon May 14, 2007 11:18 am
Location: Sydney, Australia
Contact:

Postby air.command » Fri Dec 26, 2008 4:50 pm

Bones: Yup, it was taking less than 10 minutes between launches. It was basically packing up the parachute and filling with water.

Kryten: You are right, adding stiffening would add considerably to the weight. We will need to compensate with more pressure. The problem with this rocket is that is just too long and too thin, just like the arrow and will always flex. I want to make a rocket out of T-12 tubing eventually which has a larger diameter so hopefully that will improve on the flex. The greater volume will also be a benefit.

I really want to give this fiber glassing of the body tubes a go this year to help reinforce the rockets. Santa magically knew this was the case and found a space under the tree for a lot of the fiberglassing equipment. :D
Crop Circles: ... just a bunch of guys looking for their rockets ....


Return to “Air Command Water Rockets”

Who is online

Users browsing this forum: No registered users and 1 guest