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How should I ignite multiple engines at the same time?

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rahlberg

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I have a scratch build rocket which will have 5 D12-0's for thrust. What would be the best way to reliably (this is key!) ignite all 5 engines at the same time? Would standard igniters be enough? Should I double up on the ignites per engine? Any other suggestions?

Thanks

Russ
 

Mad Rocketeer

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Hi Russ:

Welcome to the forum. You're going to like it here. Tons of good advice.

The main things are probably:
--- A good launcher system based on a relay, heavy wiring, and a powerful battery.
--- Wiring the igniters in parallel.
--- Balancing the igniters (similar amount of pyrogen on the tips, similar electrical resistance, etc.)
--- Making sure the igniters are properly installed in the motors.
--- Keeping your thumb on the launch button until the rocket is in the sky. Flying single motor rockets tends to train us to release the button once we hear the whoosh. As clustered motors will probably light at slightly separated moments, despite our careful preparation, it would be possible to cause only part of a cluster to fire by releasing the current too soon.

Jim Flis, a master rocket designer and a cluster expert of long experience, gave a good checklist toward the bottom of the first page of this thread. Jim's company, FlisKits, has some really nice cluster models too.

Finally, keep in mind that with 5 Ds, your safe distance (i.e. the minimum length for the launch controller wire) has gone up from 15 feet to 30 feet. Don't skimp on that.

Might want to practice with a two-motor cluster before flying five, just to get in the swing before risking a larger rocket. That's advice Jim gave me, and I believe it's good.


Steve
 

BobH48

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Originally posted by rahlberg
I have a scratch build rocket which will have 5 D12-0's for thrust.
I hope you're referring to a booster and you have a sustainer stage with an ejection charge and recovery system.

Do a search on clustering and you will find a lot of information on this topic.
 

Micromeister

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Welcome to the forum: Like bob48 mentioned we have a ton of info on cluster ignition here.
5 D12's is my favorite maximum LMR 4.4oz of propellant motor combination.
To Fly this model you will need at very least a Notum to airmen from the FAA.
A heavy launcher base is best, minimum 30 feet between the launcher and controller...more is alway better, and A High capacity HOT battery. I would suggest a Relay ignition system over a standard system. 30 Plus years flying clusters with a heavy duty relay system has produced tons and tons of successful 3 to 10 motor clusters with a total of 9 unlit motors. It's not the only way to ignite clusters but it's the most consistantly successful way;)
If you interested in this method, may I send you to the library section of www.narhams.org Look under Tech-Tip-006 BP motor clustering. It's a start to finish How-to with motor wiring, relay launcher schematic & diagrams and launcher parts lists. Goes into depth on igniters and igniter preperation, Pre and post insertion igniter testing and battery selection.
Hope this helps.
 

phaar

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My Team America team used clip whips which we made ourself. They were so reliable that we are now selling them! www.underdogrockets.com -you can get them there for cheap. We used a 4 D12 cluster in our booster stage and never had a failure!:D
 

Stymye

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Hi Russ,welcome
I'm also wondering about the motors
are there any other motors besides the (5) D12-0's?
because you will most likely need some type of ejection to deploy the recovery system.
 

Micromeister

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Originally posted by phaar
My Team America team used clip whips which we made ourself. They were so reliable that we are now selling them! www.underdogrockets.com -you can get them there for cheap. We used a 4 D12 cluster in our booster stage and never had a failure!:D
Do you mean something like this? These Clip whips will handle up to 8 motors. Good quality connection whips are a help but are only a smal part of the reason for your clustering success. Trust me if you hook up your very best clip whip to a weak battery or have one or two bad igniters you whips won't make a bit of difference;)
 

Micromeister

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Here's a little better look at what those Clip whips connect to.
 

Micromeister

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What a great bunch of niffty stuff John!

Russ:
TRF isn't really just a commerical, but a Great source for just about anything you could want rocket related.

Phaar & Flying:
You'd be doing your customers/Cluster flyers a very big service if you switch from the stamped jaw alligator clips to a smooth (Flat) jaw clips. Flat jaw clips give a better igniter wire contact footprint, and easier cleaning to insure good electrical contact. Even better would be to switch to Stainless Steel Micro clips. There is only one source for Stainless micro clips but for the good of the hobby i'm more then willing to share the info:
Lakewood Products inc.,
Po Box 3431
705 Tower Drive,
Medina MN 55340
Phone 1-800-749-8894 or 612-478-8926,
Fax 612-478-8928.
Speak with Mike Fanberg.

The Clip your looking for is 1-1/8" x 3/8" micro alligator smooth jaw Test clips #200122-001

There is a minimum order of 100 pieces, at the time I purchased clips for myself and Narhams the price was 1.00 per clip. These clips outlast every other type hands down, they are entirely stainless steel the body is 303 alloy the spring is 304. I replaced the clips on my personal Solar/Relay launcher over a year ago, the clips still look like they are brand new. No filing of the clips is necessary, simply wipe them off with a paper towel and Fantastic cleaner. Very Very Nice clips.
You can e-mail Mike at mikefanbert@lakewoodproductsinc.com or look at the clips they produce on line at www.lakewoodproductsinc.com You'll be looking for "test clip" in the porducts section. Last year you could not order on line.
Hope this helps
 

AlexM

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We have made the switch to flat jaw clips. Got to change it on the website.
 

jflis

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Originally posted by rahlberg
I have a scratch build rocket which will have 5 D12-0's for thrust. What would be the best way to reliably (this is key!) ignite all 5 engines at the same time? Would standard igniters be enough? Should I double up on the ignites per engine? Any other suggestions?

Thanks

Russ
Russ,

welcome to the forum and to clustering :) If you're like most of us posting to this thread, you will love the results of clusters.

If interested, I can send you a "Hints and Tips" sheet on clustering. Let me know.

jim
 

rahlberg

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Wow...thanks for all the info and quick replies.

I've been flying single engine rockets for some time now and have experimented with a double engine launch (which have worked great). I just wired up two igniters in parallel and everything went fine. For reliabilty, I was using a 12V car battery to make sure there was enough juice for ignition.

I was looking to get into a larger cluster of engines for launch and thought I'd ask if you guys used other techniques for ignition.

Jim, I'd appreciate it if you sent me your Hints and Tips. Please email rahlberg@oakdaleaircraft.com

Thanks again everyone.
Russ
 

Micromeister

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Russ here's a motor wiring graphic I use all the time.
Hope it helps.
 

Micromeister

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If an lpr modeler has access to black powder (most don't) I suggest a PVC spider over a flashpan. doesn't char the bottom of the model.
But like I said most of us LPR/MPR cluster lovers don't use loose BP.
 

rahlberg

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John,

Can you give me more info on your PVC spider/flashpan method. I've heard about flashpanning multiple engines to get a good ignition.

Thanks for the wiring diagram.

Thanks

Russ
 

jflis

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Russ,

I've sent you the pdf file for the hints and tips on clustering. Let me know if I can be of any further help :)

jim
 

Micromeister

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No thanks, I'll stick with Nichrome/pyrogen igniters.
 

jflis

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Originally posted by Micromeister
No thanks, I'll stick with Nichrome/pyrogen igniters.
Yep, i'm with you :)
 

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