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Whats the Best way of igniting 5 C6-7 model rocket engines at once?

I'm hoping to launch a rocket with 5, C motors.
I do not have a gun powder licence so I cannot purchase D + motors.
Can anyone tell me what is the best way of igniting 5 model rocket engines. I Have an ignitor and I was thinking of wiring it all in parralel.
What do you think?

Oscar

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Prfesser7 years ago
The Solar igniters supplied with Estes engines should be fairly easy to fire.  Wiring them in parallel is a good idea but be very certain of your igniter installation.  Have you had ignition failures with other rockets?  If one engine fails to ignite, you are likely to end up with a pile-o-parts...  So practice with single engines until you're certain that you will get a launch every time.

Insert the igniters carefully and, however you connect the igniters to one another, be very certain that they are solidly connected and with no short circuits.

A simple launch system will do, but the power source ought to be an automobile battery or other battery capable of supplying more than a few amps of current.   No need to remove battery, just open the hood and clip to the terminals.  The wiring for the launch system should be 16 ga or heavier rather than the skinny wire supplied with the estes launch system.

Good luck!
If the ignition mechanisms are all uniform electronically should work parallel seems most sensible but check it out, I suppose it depends on the load the ignitor circuit can take.

What kind of thrust would five of these get? And what kind of price are they?

It IS about the load the circuit can take.

Each igniter I'm sure has a certain resistance, hopefully each once close to the other.

If in series each igniter resistor will receive equal current, (which is what I believe is what the manufactures site for "no ignite" and "all ignite" in amps). But the resistance will be way higher than if you put them in parallel. So you might not have enough voltage to achieve the current you need. Might not be a issue with only 5 igniters, but it depends on the resistance of each and how many you need.

V=IxR by ohms law or I=V/R.

Worst yet if connected if in series, because of tolerances between igniters, no matter how tight, one igniter will likely fire first and go open circuit, breaking the electrical continuity of the circuit of series igniters an instantly cutting off all current to the remaining igniters.

Putting the resistors in parallel lowers the total resistance .http://physics.bu.edu/py106/notes/Circuits.html

Therefor less voltage would be needed in parallel circuit given the same number of identical ignitors but the current won't be equal. Each igniter will have a somewhat different resistance within whatever the manufacturers tolerance is. They will likely NOT ignite exactly simultaneously because the igniter with the least resistance will receive the most current and ignite first. I doubt igniters can short circuit after firing which would cause most of the current to go that path and then bypass the other igniters.

At best it will go open circuit after it fires so no more of the current will flow that way and more current will flow to the remaining circuit and igniters.Then the next lowest igniter will blow, etc. This will likely be so fast that the rocket will NOT have taken off before all of the igniters have blown. This does require igniters that are built with good tolerances for both resistance value and trigger current.

In conclusion. I think connecting in PARALLEL seems best. It lowers the voltage requirements and prevents an open circuit igniter from breaking the circuit before all igniters have blown. But If you start talking about trying to ignite many many engines at once you are still going to have issues even with a parallel circuit just because of the fact that tolerance on resistance will divide the current unevenly and tolerance variation on trigger current.

oscarthompson (author)  killerjackalope7 years ago
each one produces 14 Newtons for about a second but avarages out at 9N per second. A pack of three would cost around £8 in the UK.

I was thinking of wiring in parrelel and im going to test to with just the ignitors first. I am using an estes ignitor.

Oscar
jj.inc6 years ago
Don't Link Them in Parallel!
You should use a fast burning material like rubbing alcohol or gasoline around the base. Electric igniters are IMPOSSIBLE to sync just ask Mythbusters. They use black powder but apparently you can't so find something else.
kai366 years ago
system f92's instructable https://www.instructables.com/id/Fireworks-Controller/
oscarthompson (author)  kai366 years ago
I am currently making the ible! Thanks, thats a great idea!
rwalker566 years ago
A couple of points:

1. Firing 5 C6-7s is doable, but this design needs to be tweaked first; the engines are arranged too far apart; they need to be much closer to each other to provide as near symetric thrust as possible should one or more of them fail to ignite. What you are doing is the art of "clustering:" engines. Not used much in sport rocketry for power since the advent of D and E engines and single use Aerotech Fs, but mostly for "shock and awe" at launch..lots of smoke and flames.

2. Multiple ignition is accomplished with the supplied Estes igniters and a 5 engine "clip wip". You can make your own or get one from Sunward Aerospace. Again, to wire the engines, you need them closer together.

3. Looking at your airframe, you have a heavy tube and C6-7 is not a good engine to try flying this model with. The engines will certainly lift the weight for a couple hundred feet, but the 7 second delay will have it coming back at speed into the ground before the chute opens. Heavy models need 3 to 5 second delays to give the recovery system time to deploy.

There are a number of books available to cover this subject, the best is Tim Van Milligan,s Model Rocket Design and Construction. It covers clustering and other rocketry design issues. Wishing you success.
 I want to take a shot at this one!...   The key is synchronization and synchroignition!   I dont know if this is a word but it makes sense!

Everyone has access to firecrackers.  These are the materials you need along with masking tape and 1 rocket igniter.

Lay down the tape and make a patch to cover the entire body of the bottom end where the engines are located.  

Next  Carefully remove the fuse from a number of firecrackers.  Do this over a piece of paper, next cut the firecracker lengthwise and carefully unroll and empty the contents on the paper.  Repeat numerous times!

   Now under the center engine cut a small hole in the tape cap.  insert igniter from back side to sticky side of tape and bend igniter tip so it sticks to tape.
  Now carefully sprinkle the firecracker powder to the tape, turn rocket so nose cone is at the ground, fill the nozzles with FC powder and tape the disk to the bottom of the rocket.
  When you connect the controller and fire the igniter lights the silver nitrate powder in a millisecond and ignites all engines simultaneously.
You may have a little bit if charing on the base but that can be fixed by covering with PC7 epoxy.  Its heat resistant to an extent and will protect the base of your rocket!


Let me know how this works for you.  I have done it in the past and have had excellent results!!! 
chemguy7 years ago
Umm.... I don't have a gunpowder license and I bought 10 D-12 motors at a toy store.
seandogue7 years ago
Sorta depends on what degree of simultaneity you really require.

I'd use 5 separate hotwire ignition circuits tripped from a single source. To minimize delay, I'd be inclined to use SSRs for the switches to each hotwire, with a single power source behind the five circuits. Each hotwire should be matched in resistance to its "brethren", so I'd also be inclined to make or buy three or four times as many as you need so that you can match the five closest values. You *will need a low resistance meter to match the hotwire ignitors. Finally, every feeder cable should be IDENTICAL in length to minimize resistance variance between the circuits.

Any and all variations in resistance will result in a finite timing variation.

You still have to deal with the fact that the actual ignition will still have a certain uncertainty, so don't expect perfection, just shoot for minimizing differences in the ignition circuits.