Falcon 9 "deployable" legs

[CPA - not an Engineer]

I'm mulling building a 4" Falcon 9 with a Crew Dragon. Total length would be in the 70" range and at that size, I thought it would be really cool to have the landing legs actually deploy. Based on my profile name I'm not an engineer
so I'm having a little trouble figuring out how to actual deploy said legs.

To be scale realistic I'd need the booster stage to be around 40 some inches, with dual deployment ebay above that. So that would give me a realistic looking Falcon 9 with the second stage and the Crew Dragon being a combined upper stage.

An option in my head is to bind the legs with a rubber band or zip tie and then cut the cord. But the ebay would obviously be a long way away from the landing legs, and to keep things away from the ejection gasses I'd likely have to have a cable cutter running down the outside of the booster stage. I don't necessarily like that idea.

So what design thoughts do you have?

 

[David Schwantz]

Use an Eggtimer Proton to activate servos to deploy your legs.

 

[CPA - not an Engineer]

Servos were also rattling in my head but I know next to nothing about them. How would that actually work? I can't wrap my head around running cables inside the body tube since the motor mount is right there where the legs are.

 

[David Schwantz]

Legs are spring loaded. Use a flexible pushrod, cable inside a sheath, as a pull pin. During flight the cable, pin, is engaged to hold the legs closed. During descent Proton sends signal to servos to pull cable which will deploy legs. Since the cable is captured, to prep rocket for another flight, just stow legs and engage servo again.

 

[MidOH]

Can the 3rd channel on a Missleworks RRC3 be setup like the main charge? Set it to 200'?

And have it ignite a cable cutter, that'll cut a zip tie holding the spring loaded landing gear in.

 

[David Schwantz]

Never used a RRC3. I am sure someone that has will chime in.

 

[dhbarr]

If you bind the legs with a rubber band, a Jolly Logic Chute Release could hold the said band until just before touchdown. I'm picturing tabs that go through the wall, band and release interior to the airframe.

 

[MidOH]

Can you run a hollow tubular shock cord, and run your wires through it? Not thick wires. Just tiny vinyl coated stuff. You'd have to coil the shock cord neatly instead of z folding. But that's no big deal. Try higher voltage to make up for the thin wire. Maybe a 3s1p lipo.

 

[boomtube-mk2]

Well, I hope to see this fly successfully in the near future.
Just take into consideration that you are adding a lot of weight to the backend of your rocket.
Especially if the landing legs are constructed out of metal strong enough to survive the impact of landing.