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skip_dye

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Good news.....I've finally talked my son's Cub Scout pack into doing a model rocket launch.

Bad news....It will involve about 200 kids and we don't have a multi-pad launch system.

Good news....I get to build one! (I have eight weeks).

I have to keep the cost low, since I'm flipping the bill. I have a bunch of Cat 5 cable at the house left over from installing a home network. Is the 24G wire in the Cat 5 cable too thin to run from the launch controller to the pads? I plan on using the 12V car battery I use for high power launches as the power source (or should I use a lower voltage source with the Cat 5?).


Thanks,

Alan
 

Handeman

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Good news.....I've finally talked my son's Cub Scout pack into doing a model rocket launch.

Bad news....It will involve about 200 kids and we don't have a multi-pad launch system.

Good news....I get to build one! (I have eight weeks).

I have to keep the cost low, since I'm flipping the bill. I have a bunch of Cat 5 cable at the house left over from installing a home network. Is the 24G wire in the Cat 5 cable too thin to run from the launch controller to the pads? I plan on using the 12V car battery I use for high power launches as the power source (or should I use a lower voltage source with the Cat 5?).


Thanks,

Alan
If you use a relay at the pads to send power to the ignitors and only use the Cat 5 for control wiring, you should be fine with a car battery hooked to the relay box at the pads. If you intend to hook the car battery up to the control panel and send the power from the control panel to the pads, then the Cat 5 is too small.
 

RandyM

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I have a couple of ideas that you could use, but how about answering a few questions so I know what would work best for you.

1. how much experience do you have with electronics?
2. Is this going to be use only for this launch?
3. what's your budget?
4. how many pads are you going to build this for?
5. Is this only for model rockets? (No mid power)
 

davel

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While perhaps a bit marginal, as long as all you are using is Estes igniters and using a 12 volt car battery, then you should be fine for 25' or so.
 

troj

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If you want a simple and easy way to run leads, and use something you (and other leaders) already have..... Extension cords. Borrow 25' extension cords from people, and use those -- using the ground prong, each cord can provide leads for two pads, with a common neutral.

-Kevin
 

ttabbal

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The CAT5 you wired your house with is probably solid core. It will probably not handle being rolled up and spooled out more than a few times without developing an open. For one launch it will be fine, but you will want some stranded wire for long term use. Use relays at the pads with a car battery and you will be fine including mid/high power so you can grow.
 

skip_dye

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Handeman-->At 24 gauge, that's what I figured.

RandyM-->

1) Enough to be dangerous. I have a EE degree. I've built mutli-pad launch systems before.
2) I plan to donate the system to the Pack. I'd like this to be an annual event.
3) Very little. It has to come out of my pocket. Therefore a relay type controller is would not be an option.
4) 15 pads was my plan. Two Cat 5 cables would allow 15 lines with a common ground.
5) This launch would be model rockets only, as I stated in the OP.


troj--> I've used those before. I'd like to keep the system compact, so a control box with 8 electrical outlets on it would be quite large. Plus with that many cords running to the pads, the that increases the trip hazards around the pad.

ttabbal-->I forgot about the solid core, but Cat 5 is cheap. Not looking to use relay system. The Cub Scout Pack is not looking to go into MP or HP. I have my own system for that. Also the field we are using is not suitable for MP or HP.



Thank you for the input. Plan B is to use 18/7 thermostat wire.


Alan
 

Handeman

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If you have enough Cat 5, the other option is to double up a couple of wires for each pad. Use two/three wires for each pad and two/three as a common return. You'll get more current with less resistance/heat and provide a little backup if you do get an open in one of the wires.
 

m85476585

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I would use 4 conductors per lead if you have enough, so each cat5 could do 2 pads and one could be the common return (use all 8 leads in that one if there is a chance you will be doing drag races).

Be careful that the car battery doesn't put out too much current, melting the wires. Maybe consider using a smaller battery, though anything too small might not be able to do 200 launches.

I just looked up a wire gauge table, and four 24 gauge conductors (.205mm^2 each) is almost exactly the same as one 18 gauge conductor (.823mm^2)
http://en.wikipedia.org/wiki/American_wire_gauge
 

Micromeister

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If at all possible try to keep your panel to pad cable at least 16ga. over the years we've had to replace everything thinner we've tried.
Besides the Wire harnest is going to be the LEAST expensive part of you project... just wait until you start looking at connectors LOL!
 

RandyM

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Since you are on a limited budget, I would just build a controller for 3 pads. Having done a few scout launches, 15 sounds like a management nightmare. Start small and you can always make it bigger if needed. 3 extension cords running to the pads would be a cheap and easy solution and would hold up much better in the long run. Thats my .02
 

powderburner

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I agree with RandyM, 15 launch positions does sound a bit like overkill.

I have used launchers with 3, 4, or 5 pads in the past and they have worked just fine with groups of around two dozen kids. I supposed you would still be OK with 6 or 7, but you get the point.

Also, a smaller launcher will be lighter, smaller, and easier to transport and set up. A smaller launcher (with fewer pads) will be a little cheaper and could let you get started sooner, and you can always build a duplicate launcher later to expand capacity (if you find you really need it).

If you really must have 10 or more launchers, it would still be a good idea to split that into two (or three). This would allow you to safely run your range with setup/loading on one launcher while a separate launcher is hot for launching (you would have to keep them at least 15 feet apart; I recommend more like 20 or 30). And having multiple separate launchers would give you a little redundancy in case one was acting up. Having complete redundancy in the launch controllers (two separate control boxes) would be even better, and would also allow you to "tailor" your setup for small groups or big ones.

Edit:
(Completely forgot) Cat5 wiring is about the last thing I would suggest for this application. Too small, too fragile, guaranteed to end up being too much trouble to maintain. Spend the bux and get a spool of speaker wire.

And while you're at it, start saving carpet scraps and squares to cover the wires laying on the ground. Even though you warn the little darlings to be careful of the wires, someone will always trip on them. Much better to have enough wire length to allow you drop the wire straight to the ground, run 15 feet away (under carpet cover), then straight back up a couple feet to the launcher, probably more like 20 feet of total wire length when you add it all up.
 
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skip_dye

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Handeman-> That option defeats the purpose of a multi-conductor cable.

M85476586 -> It's not 200 launches. We are hoping goal for 200 scouts, flying two flights each. Throw in dads, brothers, sisters, and me flying and we could hit 500 flights.

Micromeister -> Yes cannon plugs are expensive, but I've made a 16 pin plug before out of a couple of blocks of wood, metal pins, and metal sleeves. It was not pretty, but it worked great. Also, this system will not be used as a regular monthly launch system. I plan to donate it to the pack so they can use it once a year.

RandyM -> I've done multiple group launches over the years with a 15 pad system. Below is a picture of it. The largest group I've done with that system is about 100 kids. We knocked out just under 200 flights in 4 hours with that pad. However, that set up is MIA. Long story. Just about everything used to make that system was picked up as scrap somewhere or made by hand (cannon plug, switches, etc.)

powderburner -> With 400 to 500 launches expected, I think a dozen + pads is the only option. I plan to split the pads up into two banks. Each bank located about 20 feet from the controller, with a 90 degrees angle between them. This way I could launch on one bank, and reload the other. This way the pads would be about 28 feet apart. The rockets the scouts will be flying will be using 13mm motors. For added safety, I'll probably put up some type of curtain between the pads. The other option would be to stagger the times at which packs arrive to fly. Also, I like the carpet idea. Working for a company that manufactures carpet tiles has it's benefits.


Thanks,

Alan

pad.jpg
 

davel

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I'll reiterate. For occasional use, out to that 20 foot distance, using a 12 volt battery, Cat 5 wiring wiring will do you fine.

Yes, it is solid, and may tend to break after winding and unwinding it a dozen times, but if you are going to use it once a year that is not an issue. And besides, it is easy to replace.

Yes, it is a bit small in size. An Estes solar controller uses 26 gauge wire and only 6 volts out to 15 feet, so 20 feet of #24 with a 12 volt high current supply will work a treat. You may want to slow-blow fuse that 12 volt source to prevent the possibility of melting the wiring.

Just stick with the estes igniters or the new Quest igniters (If using the Quest, watch the continuity check current, they as low current igniters), and no clusters bigger than 3.
 

Micromeister

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Handeman-> That option defeats the purpose of a multi-conductor cable.

M85476586 -> It's not 200 launches. We are hoping goal for 200 scouts, flying two flights each. Throw in dads, brothers, sisters, and me flying and we could hit 500 flights.

Micromeister -> Yes cannon plugs are expensive, but I've made a 16 pin plug before out of a couple of blocks of wood, metal pins, and metal sleeves. It was not pretty, but it worked great. Also, this system will not be used as a regular monthly launch system. I plan to donate it to the pack so they can use it once a year.

RandyM -> I've done multiple group launches over the years with a 15 pad system. Below is a picture of it. The largest group I've done with that system is about 100 kids. We knocked out just under 200 flights in 4 hours with that pad. However, that set up is MIA. Long story. Just about everything used to make that system was picked up as scrap somewhere or made by hand (cannon plug, switches, etc.)

powderburner -> With 400 to 500 launches expected, I think a dozen + pads is the only option. I plan to split the pads up into two banks. Each bank located about 20 feet from the controller, with a 90 degrees angle between them. This way I could launch on one bank, and reload the other. This way the pads would be about 28 feet apart. The rockets the scouts will be flying will be using 13mm motors. For added safety, I'll probably put up some type of curtain between the pads. The other option would be to stagger the times at which packs arrive to fly. Also, I like the carpet idea. Working for a company that manufactures carpet tiles has it's benefits.


Thanks,

Alan
Alan:
Having done BSA Troop launches for many year, I agree you'll need more than a couple pads...Troop or Pack launches can get a little Crazy LOL!!! :D

My Personal system is a 17pad system with a 6 pad slitter make available 24pads. I got around the multi conductor trunk cable problem by using 30 and 35 foot lengths of 2/16ga stranded copper white jacket lampcord to each pad. Each pad has it's own at the pad continuity/off control. Instead of amphenol connectors I used R/S 4 pin mic connectors & plugs, while not nearly as expensive as the amphenol's they are still on the pricey side nowadays:(

The Down side to a satellite system is you have to arrange the pads in a semi-circle or series of semi-circles with individual launcher support "Poles" for each launcher. It is however a very nice system for large group launches like your talking about:)
Something like this might be another idea for your Packs system.

PS: All this stuff was produced in my tiny townhouse basement shop with a hacksaw and handtools, no heavy equipment needed.

Satellite Sys 30ft cable & Box-sm_02-03.jpg


Satellite Sys Pad Head-a-sm_06-90.jpg
 
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