# Cluster Voltage??

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#### RedOctober

##### New Member
I have recently gotten into MPR and HPR. I have had no problems at all thus far with increasing size, weight, power etc. up into the H and I motor range. All of my rockets are doing well. I recently built a rail launch pad system and also built a new launch control. Our only problem thus far is we can not seem to build a cluster ignition system that works properly. Since we are doing this in the middle of a field, miles from the nearest 110v electrical outlet, we are stuck with using batteries. Here is the launch system I WAS using:

For A-F engines I used a 9v battery and a toggle/buton ignition which traveled from the 9v battery through speaker wire into my launch control box where the toggle is. Then the speaker wire proceeds about 50 feet to the standard launch pad where single motor ignition all day long is no problem at all, BUT cluster ignition has proven to be nearly impossible. With a 3 or 4 motor cluster, 1 or maybe 2 would light, and the rocket would shoot off course and wreck.

Here is what I recently built and have NOT tested yet:
We got a 12v, 230amp ATV/Boat battery and I rewired the launch control box with pure copper 14ga wire. So now the system is comprised of a large 12v battery, which proceeds through copper wire into the launch control box with the toggle and trigger, then out to the launch pad about 70-100ft away. Since I am now using copper wire, there should be no loss of voltage over the 70ft or so. But I am still hesitant to try a cluster motor ignition because my only cluster rocket is an E motor cluster. That would be a kind of expensive 'oops' if 1 or 2 of the 3 motors does not ignite correctly. Is 12volts enough to launch clusters?? Does the increase of amps make a difference? Over the length of copper wire I am sure the amps will reduce...

Basically, what I would really like is to hear how other people manage to launch clusters. We have tried so many times with cheaper motors. We are also building a G cluster saturn V replica, so we want to have this perfected before we go blast off $60 in motors and crash. Any suggestions would be greatly appreciated! I have read about some other people's launch control systems and some look very impressive but i see a lot of people mentioning 110volts. Anyways, thanks for any replies!! -RedOctober Chico, CA #### shreadvector ##### Well-Known Member See sticky thread near top of Beginner forum. Clustering is covered in the Classic Collection on the Estes Educator website (link is provided in thread). http://www.rocketryforum.com/showthread.php?t=539 You are on the correct path: Better thicker wire = less resistance to current flow. Better battery = ability to deliver lots of current without a huge voltage drop. Simple test is all you need: Hook up some igniters to your system. Hit the button and they should ALL ignite INSTANTLY. If there is a time lag, then you have something going on that is preventing current flow or you are using the wrong igniters. Quest Q2G2 igniters are perhaps the best igniters ever made and should answer all of your clustering prayers. #### Luv2launch ##### Well-Known Member You best bet is to build a launcher that has a relay and a batter right out at the pad.12 volts is enough to light just about any amount of motors but its best if you current travels the shortest distance possible to the igniters.Here is a link to a pdf file that at the end has the scematic for the relay launcher that I built (thanks Micromeister it works like a charm).Also for clustering composites don't use the copperheads get some first fire's at the least or dip your own. http://www.narhams.org/library/tech/006-Clustering.pdf So far the largest cluster I have put up with this launcher was a 5 motor with 1 d and 4 B's but they all ignited I have yet to try clustering with AP motors. #### RandyM ##### Well-Known Member One of the keys to clustering is Amperage more so than voltage. That is the reason for a relay type system. Amperage will be lost over that 70' even with 14ga wire. There is also a good plan on the infocentral section of Rocketryonline.com under ground support (build a launcher). I built on into a portable car battery jumper. It works great! #### luke strawwalker ##### Well-Known Member Ok, first thing is, throw that cheap 'speaker wire' that comes with Estes style controllers away... The absolute minimum you want to use on a launcher is twin lead 'lamp cord' like commonly used on 110 volt house lamps, toasters, appliances, etc. That thin wire simply cannot carry enough current to do the job, for anything more than a single ignitor. 12 volts is plenty for 99% of clusters, however, resistance is your enemy. "Pure Copper" wire has only negligibly less resistance than any 'standard' wire of the same size. The problem is, as your wires get longer, resistance lowers your voltage and hence amperage delivered to the ignitors, causing misfires. You can either 1) use higher voltage, like connecting two 12 volt batteries in series to create 24 volts, or more commonly 2) use heavier/thicker wire that has less resistance. Now running long lengths of wire gets prohibitively expensive and has diminishing returns, especially at the lower voltages we use. That's where a good relay system comes in. A relay system uses a launch controller to activate a relay at the launch pad, which then sends power from the battery beside the launch pad directly through short runs of lamp cord directly to the ignitors. That way the voltage drop and resistance is minimized, and the amperage available across the ignitors is maximized. Just be sure that the relay is not 'stuck on' before hooking up the leads to the ignitors. It's best to hook up the battery to the relay system after the ignitors are hooked up to make sure. A lot has to do with the ignitors you choose as well. Solar ignitors (Estes type) are notoriously questionable in their quality and consistency, even in the same package. You should check them for continuity at the very least before installing in the motor. Some folks go to the trouble of checking their resistance and matching the ignitors so they all have almost identical resistance, the reason: if the ignitors all have the same resistance, 1) you know they all have a 'good circuit' connections under the pyrogen, and 2) they should all heat up at the same rate, therefore the same time, for simultaneous ignition (in theory anyway). If you have a cluster with ignitors installed that have one with low resistance, and another with high resistance, the low resistance one will 'steal' current from the high resistance one, until it heats and ignites and burns through, then freeing up that current to go into the high resistance ignitor and heat it to ignition point. However, by that time the rocket may have lifted off and jerked the leads off the other ignitor, causing the motor not to light. Hope this gets you started off right. If you have any other questions, post them and I (we) will help you get up to speed on electronic ignition Good luck! OL JR #### Commonwealth.Net ##### Well-Known Member To get clusters to work every time you need to know a few things; 1) Always hook the igniters in parallel not series! In a series configuration once one igniter fire and causes An open circuit the rest get NO power! 2) Igniters require POWER (P=I*E ) Power equals voltage times amperage. 3) If we assume you are using non-Estes igniters they require a LOT of power. 4 A typical Aerotech copper head requires 12 volts at 3 -5 amps or we could say they require 36-60 watts of power . So a cluster of 3 would require up to 180 Watts of power. 5) Having a 230 amp battery does no good as you only need 15 amps! 6) You need to get the POWER to the igniters. Any long runs of wire and any dirty contacts will just kill your chances of getting a cluster to work. Never use more than 20 feet of wire, larger wire is better but not always required. Remember E=I*R where E=voltage I= current and r= resistance. As you can see with a 12 volt system and only 1 or 2 ohms or resistance due to dirty contacts and wire you total power flow will be reduced to 6 amps or 72 watts so if you need 180 watts to fire 3 igniters you have FAILED!!!!!!! 7) Use a relay so that your power run is limited to only a few feet! Use more than 12 volts!!! Voltage overcomes resistance and allows power flow! We need POWER! 8) I would glad to chat with you any Saturday at the store 734-282-1055 ask for Steve. 9) In short (lol) use high voltage, more than 12. Have clean contacts, eliminate any resistance buy using large diameter wire, use a relay switched system to keep the power travel short. A capacitive discharge system works every time! One member of HUVARS created a system with 300-400 volts out with a total power delivery MUCH Higher than ANY 12 volt system! Remember even with a 230 amp 12 volt battery, RESISTANCE limits how much current will flow! A high voltage system will work better as it can overcome resistance. A cheap way to do what you want is to buy a 12 volt car inverter! 12 volts in 120 out. Buy a 200 To 250 watt system and you will fire all igniters EVERY time. This is a cheap way to go, under$20.00 you do lose a continuity check, but who cares. Use a controller to put 12 volts to the inverter, a relay system is still a good idea. When activated the inverted will supply 200 watts of power at 120 volts and ALL igniters will fire - every time!

Why do I know this?
A+ Certified Computer Technician
3 Years of electronics education
Passed RITS 2 year program while taking the entrance test!
Own my own electronics business for 10+ years.
I can follow the formulas I spoke of above.
Last but not least I HAVE DONE IT !

#### Verna

##### Well-Known Member
Hi Red,

There are several small details that are important to cluster launching but it sounds like you have built a system that is more than enough for a few Estes igniters, provided you have strong grip clean clips, no cold solder joints, nuts, screws, no loose connections, etc. You mentioned you have been using a 9 volt battery and I'll assume you're talking a standard transistor radio battery, which won't do the job.

Most people who cluster have a personal preference for a power source but nothing beats a 12 volt lead acid car battery, say 500 cold cranking amps or better. When launching clusters you want plenty of reserve. If I recall correctly Estes igniters use less than 1 amp each, so if your battery is pushing 500+ amps, you won't be needing a relay system unless you just want to go that way.

Just about all we fly are clusters with 3-5 engines. We use a simple home made system and control box that uses a couple of l.e.d.'s and a door bell button. We bought a 100' heavy duty outdoor extention cord and installed a set of clips with teeth on them on one end, the toothless kind you get with an Estes launcher don't always grip the igniters well enough for me.

Normally we set our pad up about 30' from the control box and the rest of the cord stays rolled up at the launch table. We then run another heavy duty extension cord with jumper clips on it, to our pickup's battery and that's it. When we push the button they go instantly.

Get as fancy as you like but all things being as they should, all you really need is a good car battery.

Verna

#### MarkII

##### Well-Known Member
I haven't tried these products myself, but Pratt Hobbies sells a nice looking pad relay system. You can get just the relay add-on:

http://www.pratthobbies.com/proddetail.asp?prod=PRM-12

or else pair it with their universal launch pad system:

http://www.pratthobbies.com/proddetail.asp?prod=ULS-M1

The vendor has an excellent reputation.

In your original post, you talked about not having access to a 110v electrical outlet, and being limited to using batteries. From what I understand, direct current battery power is always required, even if you set up a launch pad right next to your back door. AC house current should NEVER be used to power a launch pad!

Mark \\.

#### cornyl

##### Well-Known Member
Everything listed above is great advise!!!
But there are even more details that are cluster killers.

Surface area is key when connecting to battery terminals. Do not use micro clips with teeth as the current just flows thru just the teeth (serated) portion of the clip. And usually the current only flows well through half of the clip since the current flow relies on the hinge mechanism of the clip. If you really want to reduce resistance and increase reliability solder a wire across the micro clip just to make sure. (Unfortunately the more heat you add to the clip the weaker the hinge gets.)

I have soldered wire directly to my lead acid battery terminals with no problem.

Try to use flat -smooth clips at the ignitors for more surface area, therefore lower resistance.

Make sure all of your solder joints are good and clean! No crimp or wire tied or punch down connections in your entire circuit.

If you are extending your ignitors make the leads are no longer than needed.

Use some type of strain relief at the pad . You do not want the ignitors pulling out as soon as the ignitor starts to light.

Make sure your clips are shiny-shiny clean. Not silver looking not gray and absolutely no black. Clean with 320 sand paper as needed.

If you are using some type of car jumping system do not use the 12v jack because it is fused. Even if it works you are heating up the fuse which creates more resistance. I suggest hooking onto the wire side (not the hinged side) of the jumper cables with your clips.

Good luck!

#### Meat

##### Well-Known Member
I launched my c 6 cluster rocket using the battery in my car and that cheap speaker wire estes puts on their launch controller : /

#### RedOctober

##### New Member
Thanks everyone for all of the responses! We really appreciate it! and we definitely will give you a call tomorrow at your store Steve. I'm going to be proceeding with the modifications to our system this weekend, I will post here and let everyone know what direction we went and how it works.

#### DM1975

TRF Supporter
A cheap way to do what you want is to buy a 12 volt car inverter! 12 volts in 120 out. Buy a 200 To 250 watt system and you will fire all igniters EVERY time. This is a cheap way to go, under $20.00 you do lose a continuity check, but who cares. Use a controller to put 12 volts to the inverter, a relay system is still a good idea. When activated the inverted will supply 200 watts of power at 120 volts and ALL igniters will fire - every time! I have a question on this. Do I need to use a full sized car battery or can I continue to use my 12V gel cell and Mercury igniter lighter with an inverter? #### JRThro ##### Well-Known Member TRF Lifetime Supporter TRF Supporter A cheap way to do what you want is to buy a 12 volt car inverter! 12 volts in 120 out. Buy a 200 To 250 watt system and you will fire all igniters EVERY time. This is a cheap way to go, under$20.00 you do lose a continuity check, but who cares. Use a controller to put 12 volts to the inverter, a relay system is still a good idea. When activated the inverted will supply 200 watts of power at 120 volts and ALL igniters will fire - every time!
200 Watts of power at 120 volts AC is only 1.67 Amps.

200 Watts of power at 12 volts DC is 16.7 Amps.

Why would an inverter be a better choice than just using the car battery in the first place?

#### Reinhard

##### Well-Known Member
And a 1 Ohm load on a 120V/200W inverter behaves nearly like a short circuit. I don't think these devices can put out the calculated 14.4kW even for short times. On a cluster it gets even worse...

Reinhard

#### Handeman

##### Well-Known Member
TRF Supporter
Besides the lower amps available, when you up the voltage to 120VAC, you have the same shock hazard with the inverter output as you do with your house wiring. Not good in wet grass with metal launch pads.

Personally, I wouldn't go near a 120VAC launch controller system.

#### DM1975

##### Upscalien
TRF Supporter
OK, so should a 12V 12Ah sealed battery be sufficient enough to light clusters up to a G? Is their anything I should be doing or using other than just hooking my battery up to my igniter lighter and then hooking up the igniter lighter to the clusters?

This is the battery that I am using http://www.amazon.com/Battery-volt-Drop-Ship-Pack/dp/B00002EQAF

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#### Ford Prefect

##### Wondering Hitchhiker
I have found in lighting my clusters that Power doesn't necessarily equal light. If you want to make sure it lights make sure your wires can carry a bunch of AMPS. The More Amps you can carry down to the igniter leads (bigger leads helps 2) The Better.

#### JRThro

##### Well-Known Member
TRF Supporter
Thanks everyone for all of the responses! We really appreciate it! and we definitely will give you a call tomorrow at your store Steve. I'm going to be proceeding with the modifications to our system this weekend, I will post here and let everyone know what direction we went and how it works.
RedOctober, is it safe to assume that you are NAR or TRA certified for HPR up to at least the motors you are using? H, I, and clustered G's?

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
It's not the Voltage guys, its the current (amps) needed for successful clustering of BP motors.

I've used the same 26amp/hr Gel cell for launching 2 to 12 motor BP clusters for years with any of my various relay systems.

The old rule of thumb concerning available battery power and cluster ignition is 2 amps per igniter. this system has worked very well for me over the decades with litterally thousands of clusted motor launches with only 13 total unlit motors in all that time.

#### bobkrech

##### Well-Known Member
Anyone have experience with the Ray-O-Vac 12V lantern battery?

http://www.acehardwareoutlet.com/(xiq0j5eguxnhmd55zxlsigra)/ProductDetails.aspx?SKU=32562

What's the clustering potential of this battery?
Absolutely zero.

Lantern batteries are expensive and not rechargeable. They will not provide a lot of amps which is what you need to launch clusters.

Lead acid gell cells of 7 AH or 12 AH capacity are the cheapest and most reliable power source for launchers. They are typically $15 to$25 dollars at an electronic supply hour because they are used in emergency lighting systems. Emergency car starter work fine, are in a nice package, and come with AC/DC chargers. See http://www.rocketryforum.com/showthread.php?t=2465

At our CMASS club launches we successfully fire a 31 motor cluster rocket using our standard 12 AH gell cell powered relay launcher. Contrary to the some of the comments listed here, it is perfectly legitimate to use igniters in series provided you feed them 2 to 3 times the all-fire current so they ignite the pyrogen in a millisecond or so. The 31 cluster rocket use a combination of series parallel wired igniters. They were individually tested prior to installation, after installation, after being hook in series and only then were they connected in parallel. Every igniter lit promptly.

As was said earlier in this thread by Micromeister, igniters need current, not voltage to fire. The voltage developed across the igniter is simply V = RI. For Estes igniters, the resistance is 0.8 ohms and the all-fire current is 2 amps. This says that you supply V = 2 * 0.8 = 1.6 volts across the igniter, it will light. It's not rocket science, it's Ohm's law. Any more current just make the igniter initiate the pyrogen faster. If you double the current, it goes at least 4 times faster and 3 time the current at least 9 times faster because that's how much more power you put into the igniter and it's power that determine the activation time. Pyrogen ignites at about 600 F, and the wire doesn't melt until about 2000 F. A series string of ignite will all activate before any wire melts so you don't have to worry about the wires breaking due to igniter activation, however you do have to worry about breaking the wires during installation so that's why you have to check the continuity during installation and hook-up. You can series wire 2 or 3 Estes igniters on a 12 volt system without a problem. Simply go to any gell cell manufacturer's website and down load the data sheet for a 7 or 12 AH gell cell. The typical 7 AH gell cell will source 30 amps for 5 minutes and the typical 12 AH gell cell will source 40 amps for 10 minutes. The internal impedence is very low so they can source 10 times this current for a short time if the wiring resistance is low enough. A really good relay launcher might have a resistance of 0.1 to 0.2 ohms if the clips are clean and the wire gauge is large enough. This wiring resistance will source 120 to 60 amps respectively if the clips are shorted. It takes over 140 amps to weld the contacts in a 12 volt automotive relay, so you should be good to go.

Boris Katan has described his methods in great detail in his Toginator posts. I suggest anyone interested in large clusters read them. Powering a launcher with 120 volts from an inverter is just plain dangerous and totally unnecessary; a potentially lethal solution wating for an accident.

Bob

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#### DM1975

##### Upscalien
TRF Supporter
Micromeister and Bobkrech, thank you for the great information. That is exactly what I was looking for.

#### Handeman

##### Well-Known Member
TRF Supporter
OK, so should a 12V 12Ah sealed battery be sufficient enough to light clusters up to a G? Is their anything I should be doing or using other than just hooking my battery up to my igniter lighter and then hooking up the igniter lighter to the clusters?

This is the battery that I am using http://www.amazon.com/Battery-volt-Drop-Ship-Pack/dp/B00002EQAF
I'm sure that battery will work, but for $20 less you can get a car battery charger and a lawn tractor/motorcycle battery that will work just as well if not better. I went the motorcycle battery route because I already had a battery charger and the motorcycle battery was on sale at the local autoparts store for$19.95. It's rated for 80 Cold Crank Amps It's more then enough to light clusters all day.

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#### peter_stanley

##### Well-Known Member
I've been using a 12V gel cell with an old Aerotech launch controller for clustering with no problems. I've tested up to 7 (probably kind of high resistance) homemade igniters and all lit simultaneously.

#### JRThro

##### Well-Known Member
TRF Supporter
Absolutely zero.

Lantern batteries are expensive and not rechargeable. They will not provide a lot of amps which is what you need to launch clusters.

Lead acid gell cells of 7 AH or 12 AH capacity are the cheapest and most reliable power source for launchers. They are typically $15 to$25 dollars at an electronic supply hour because they are used in emergency lighting systems. Emergency car starter work fine, are in a nice package, and come with AC/DC chargers. See http://www.rocketryforum.com/showthread.php?t=2465
I use a 7 AH 12 volt lead acid battery with my controller and have flown up to 3 motors with it with no failures. I say "up to" only because I haven't *yet* flown my 4-motor cluster rocket.

At our CMASS club launches we successfully fire a 31 motor cluster rocket using our standard 12 AH gell cell powered relay launcher. Contrary to the some of the comments listed here, it is perfectly legitimate to use igniters in series provided you feed them 2 to 3 times the all-fire current so they ignite the pyrogen in a millisecond or so. The 31 cluster rocket use a combination of series parallel wired igniters. They were individually tested prior to installation, after installation, after being hook in series and only then were they connected in parallel. Every igniter lit promptly.

As was said earlier in this post, igniters need current, not voltage to fire. The voltage developed across the igniter is simply V = RI. For Estes igniters, the resistance is 0.8 ohms and the all-fire current is 2 amps. This says that you supply V = 2 * 0.8 = 1.6 volts across the igniter and it will light. It's not rocket science, it's Ohm's law. Any more current just make the igniter initiate the pyrogen faster. If you double the current, it goes at least 4 times faster and 3 time the current at least 9 times faster because that's how much more power you put into the igniter and it's power that determine the activation time. Pyrogen ignites at about 600 F, and the wire doesn't melt until about 2000 F. A series string of ignite will all activate before any wire melts so you don't have to worry about the wires breaking due to igniter activation, however you do have to worry about breaking the wires during installation so that's why you have to check the continuity during installation and hook-up. You can series wire 2 or 3 Estes igniters on a 12 volt system without a problem.
That's great information, Bob. I always assumed the igniter wire broke when the igniter lit, and I'll continue to do so since wiring a relatively few igniters in parallel hasn't been a problem thus far. But it's cool to hear and to know that it is possible to wire igniters in series and have them ignite successfully as long as you don't put too much power into them, or more accurately into the first one that ignites and breaks the wire.

#### DM1975

##### Upscalien
TRF Supporter
I'm sure that battery will work, but for $20 less you can get a car battery charger and a lawn tractor/motorcycle battery that will work just as well if not better. I went the motorcycle battery route because I already had a battery charger and the motorcycle battery was on sale at the local autoparts store for$19.95. It's rated for 80 Cold Crank Amps It's more then enough to light clusters all day.
I just use this because I have two of them for my kids 4 wheeler. I will probably get a motorcycle battery later on. I still have a charger from when I had my Harley so the battery would be all I need to get.

#### Handeman

##### Well-Known Member
TRF Supporter
I just use this because I have two of them for my kids 4 wheeler. I will probably get a motorcycle battery later on. I still have a charger from when I had my Harley so the battery would be all I need to get.
If you bring the kids along to the launch, they won't be riding the 4 wheeler. Take the battery along, problem solved.

#### Handeman

##### Well-Known Member
TRF Supporter
....snip.... I always assumed the igniter wire broke when the igniter lit, and I'll continue to do so since wiring a relatively few igniters in parallel hasn't been a problem thus far. But it's cool to hear and to know that it is possible to wire igniters in series and have them ignite successfully as long as you don't put too much power into them, or more accurately into the first one that ignites and breaks the wire.
I've made some of my own igniters and while testing, got very good spark and flame, but if I let go of the button within a second or two, I could push it again and get more spark and flame as the last of the "dip" burned off. I think the most I was able to get was four bursts of flame from a single igniter. When it was all done, the wire was still not burned through and would get a medium red to orange when the button was held down.

There really is no reason to burn through the heater wire on an igniter and probably more reasons not to. The wire is only there to get hot enough to get the pyrogen to burn, that's what ignites the motor. In the case of my homemade igniters, keeping the wire hot kept the "dip" burning, bubbling, and sparking and producing the heat needed to ignite the motor.

With clusters, you want enough current to cause all the igniters to burn the pyrogen, but not burn through the wires right away, especially if you have any in series.