Mk3 Staging Mechanism

Water Rockets NSW

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air.command
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Mk3 Staging Mechanism

Postby air.command » Fri Aug 06, 2010 9:39 pm

Hi Guys,
Over the last couple of months we have been developing and testing our new Mk3 staging mechanism. We wanted to come up with a simple system that was easy for anyone to build out of common materials and required no special tools.

Image

It was a fun challenge, as we looked for common items that people would readily have access to or could modify, when we had a fully equipped workshop with a lathe to make the bits we would have normally needed.

We had some early setbacks, but we now have a mechanism that seems to be working fairly well and can be built for a few dollars.

Here is a full explanation of how the stager works:
http://www.aircommandrockets.com/howitworks_4.htm

A tutorial on how to build it:
http://www.aircommandrockets.com/mark_3_stager.htm

And here is a flight report with video from 4 different test series spanning the last 2.5 months. The stager has worked well on the last 8 out of 8 flights.

http://www.aircommandrockets.com/day94.htm

We’ll bring it to Doonside to continue the tests on larger rockets, as the local park is just too small.

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

rocket_troy
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Re: Mk3 Staging Mechanism

Postby rocket_troy » Sat Aug 07, 2010 12:26 am

Very nice George! Great eloquent design & engineering and nice work on the documentation and video too. Hope to get up there and see one of them fly one day soon.

keep up the innovation,

TP
ERG #02

Kryten
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Re: Mk3 Staging Mechanism

Postby Kryten » Sat Aug 07, 2010 7:43 am

Great work as usual.
Are you launching this tomorrow?
"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
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Re: Mk3 Staging Mechanism

Postby air.command » Sat Aug 07, 2010 8:56 am

Thanks guys. :)

Kryten: Unfortunately I won't be able to make it this Sunday because my in-laws are leaving mid morning to go back to the states.... my mother in-law says: "George, would you mind taking us to the airport?" ... to which I responded... "I don't mind at all, there is nothing I like more than taking my mother in-law to the airport" :D ... I'm glad she has a good sense of humor.

Darn, and it looks like it's going to be a nice day too. I'll bring the stagers to the next launch.
Crop Circles: ... just a bunch of guys looking for their rockets ....

PK
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Re: Mk3 Staging Mechanism

Postby PK » Sat Aug 07, 2010 9:48 am

Love your work George!
How sensitive is the mechanism to different springs and compression?

Really looking forward to the "converting a washing machine pump for liquid oxygen use" turtorial.

Some may not know, but back in the day, George was the first to get a Hoover Delux to recieve SBS!

:-)
DigitalSportsWatchCo (nee PK)

air.command
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Re: Mk3 Staging Mechanism

Postby air.command » Sat Aug 07, 2010 10:40 pm

PK wrote:How sensitive is the mechanism to different springs and compression?


:D Thanks PK. That is a good question. When we first tried it, we used three of the springs, but it just was not reliable enough, and so we added a fourth and that fixed it for the smaller rockets. You can adjust the spring tension by trimming the length of plastic tube body. We found that around 0.8Kg or greater of force pushing the stages apart was enough to achieve staging in all the rockets we have tried so far. We built two of the stagers with springs from a range of older quick connectors, and they both worked fine, so it wasn't really sensitive to the variations in springs from the different manufacturers. The mechanism only needs to move 5mm from the fully locked to the fully open position, so the compression distance is quite small when compared to the length of the spring ~60mm.

Faster flying rockets with higher deceleration during separation may require a stronger spring, but if the booster has a higher base drag it may not need a stronger spring. This will be the next set of tests, with a much bigger nozzle on the booster, and acceleration in the 10-20G range.
Crop Circles: ... just a bunch of guys looking for their rockets ....

Andrew Burns
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Re: Mk3 Staging Mechanism

Postby Andrew Burns » Sun Aug 08, 2010 7:45 am

I'd predict that the base drag of the booster would always be higher than the base drag of the sustainer unless you're doing something reaaally odd looking so unless you're flying supersonic then drag would always aid rather than hinder you.


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