Air starting 6 motors but in 2 stages

Planning a rocket for a show stopper

54mm central
3x 38mm
3x 29mm

I might change to a total of 6x 38mm's

So I have nothing right now. I'm wanting to use different motor effects so a good means to get a timed delay/stage/air start is a must

What should I use?

There are several options out there.....

The MARSA 54L is a good unit and so is the Raven 3.
The MARSA 54L has a wireless interface available to remotely fire the outboards via the pyro board.
You can fire the out-boards via the pyro board and still have the 4 channels for other things.


JD

Hey Petey- how's the weather in Bristol these days? What you want to do sounds impressive and on the surface SOUNDS simple, but is in fact a rather daunting complication. See the other current airstart threads here and you'll get another view of the complexities involved. From experience the Marsa54 or LCX/HCx G-Wiz alts MAY give you what you want, but strictly timer based ignition has dark clouds over it as these may not trigger the motors with the rocket in the proper attitude. Note I said attitude and NOT altitude. I wish I had an easy answer to say "Use XYZ" but there really is a lot of math involved to configure an airstart for optimal use. Obviously there can be arguments over G-switch triggering vs. baro sensors vs. acel sensors and you have to note mercury switches have been outlawed. A project like this gets ass-heavy real fast and the attending mass makes for a rocket that slows very quickly without boost. Don't forget AP takes time to 'pressurize' so you also have to include that backwards from the ignition while the rocket has sufficient airspeed to remain (hopefully) vertical. Long walks outside the nominal recovery area are most likely in the event of off angle starts and I have horror stories of power prangs under boost-one which destroyed a perfectly innocent 35m camera. Okay-the ribbons of film coming from the crater was hilarious, but I digress. I'm not trying to be a buzz-kill-hell, I'm working on something like this for LDRS 35! (LCX or Xavien F.I.S.T. based) But just know it's a lot of work and more than just hooking up an extra set of wires to a timer. Straight smoke and good chutes, brother!

Hey dude. It's hot currently. Dam hot, was at a local RC show today and burned. How you keeping dude?

Yeah she's going to get heavy like you say. This was partly why I went for the 54mm so it had that kick.

I'm happy to use a time to set them off after say said motor burn time. So if the 54mm is a 2 second burn I'll set 2 seconds.

The one plus is they will be CTI so shall work.

It's only for a show in this full config. I'll likely switch between a cluster and single 54mm back down to 38mm

Been thinking this over some more.

54mm Central is a 100% yes
38mm x3 is also 100% yes

Question is 38mm or 29mm x3 for the 3rd section.

GO with the 6 x 38 mm mounts.
That way you can do; sets of 2 or 3.
While still being able to fly 29 mm with adapters.


JD

JDcluster said:

GO with the 6 x 38 mm mounts.
That way you can do; sets of 2 or 3.
While still being able to fly 29 mm with adapters.


JD

Click to expand...

Hey that's not a bad call that! Top man

So what electronics

MARSA with a wireless network. I really want to set something up with this stuff. Less wires = less work = good.

DizWolf said:

MARSA with a wireless network. I really want to set something up with this stuff. Less wires = less work = good.

Click to expand...

Few issues. It ain't cheap. It's too much tech and cost wise for what I want. It's a lot more involved that I need it to be.

The timer idea is looking better

Pete,,
Never forget,,
You can always adapt down,,
You can never adapt up...

Marsa 54L....
Extremely simple,, super easy to navigate through the menu options..
No need to connect to a computer to set up for flight,, only if you want to download flight data...
You can do everything you want to do with out the network as long as you can run a piece of wire....



All glass,, all scratch,, 54 mm central,, 2-- 38 mm outboards....
Wayyy too cool.........

This coming Saturday,,, I'm hoping for the most photogenic flight ever....
The Aerotech 38 / 720 J 340 MetalStorm's thrust curve has a spike at ignition...
Europa Express is very heavy for a 3" build...
7 to 1 thrust to weight for the first 1/8th of a second then 5 to 1 for the rest of the 1.8 second burn...
The J 340 MetalStorm is white smoke / white sparks....
I am concerned about the rocket laying over a bit off vertical,, so though I think it would be a cooler flight to watch if I waited longer to light the 2 -- I 225 FJ ( black smoke ) outboards I don't want the rocket slowing down,, so I'm going to light them early...
I'm going to set the Marsa 54L to light the outboards at --
say-- 1.8 seconds figuring it'll be 2.2 or 2.3 by the time they come up to pressure.....

Teddy

( I hope I'm not puttin the whammy on the flight by posting this ,, lol... )

Oh yeah,,
Complete redundancy..
Primary-- Marsa 54L run by an Eggtimer rocketry electronic switch and fed by a 2s 300 mah 70c lipo... ( to do the airstarts )...
Secondary-- Eggtimer run by an Eggtimer rocketry electronic switch and fed by a 2s 260 mah 35c lipo.....
Tracking is in the nose cone---
Primary--- Eggfinder TX fed by a 2s 800 mah lipo,, antenna remote under the nosecones bulkhead....
Secondary-- Big Red Bee 70cm beacon,, fed by a 1s 1000 mah lipo that'll run it fer days around the clock....... ( these just never seem to fail ) .....

Wish me luck............

Jeff,,
You goin to Great Meadows this Saturday ????

Teddy

Pyropetepete said:

Few issues. It ain't cheap. It's too much tech and cost wise for what I want. It's a lot more involved that I need it to be.

The timer idea is looking better

Click to expand...

Pete,

Not saying this is the best or only way, but my 8" 45lb Holy Cow has been successfully double air started with a pair of PerfectFlite Mini Timer 4's. it has a central 76mm and six 29mm outboards. You do need to do the math correctly. I've also air started up to four 38mm's with a single Mini Timer 4 with a regular rechargeable 9v. These were all CTI motors though, their burn times are very accurate, they come up to pressure quickly, and light with a regular E-Match. Also make sure you have way to adjust your nose weight based on your motor configuration to keep your CG in the right spot.