Easy scratch launcher with controller.

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Keith Medlkock

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Hi all. I haven't messed with rocket stuff in many years, but now that my daughter is 4 I'm introducing her to the hobby. I built a launcher that has the controller integrated. Its nothing special since the design was based on what I had laying around in the garage, but I though I would post it just in case it gives someone else an idea for their project. Have fun and be safe!

Here's the launcher from above. There are two levels for perfect orientation. The pad tilts and locks via the 1.25 inch SCH 40 PVC unions. The pad is just a .75 inch thick piece of hardware topped with zinc plated steel and fastened to the PVC structure with .25/20 bolts. The center of gravity is very low.
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Close up of pad
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Base with pad removed. It will have an 80/20 10 series 4 foot rail attached to the pad, and the tilt unions will double as breakdown points for transport.
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This power supply is attached directly to the underside of the pad and uses a relay to activate. Lamp wire to the clips and phone cord to the controller.
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Inside of controller. It's just a simple lighted arm switch with a momentary launch button. There are no batteries since it gets power from the pad.
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Controller safe.
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Controller armed.
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Pad inverted to show mounting of power supply.
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Close up of clips. I shrink wrapped alternate jaws to make them single lead ignitor friendly.
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Nicely done. How large is your pad...3' x 3'? For added safety make a couple hold down stakes from metal coths hangers or plastic bgs filled with dirt. Place them over pvc pipes. This will keep the pad from tipping or moving on launch. Happy flying with your daughter.
 
Thanks, the base is 30.25"x30.25" and cg is about 2" off the ground so should be pretty stable. If it moves at the first launch, I'll pour thinest mortar into the base pipes.
 
That's actually a wonderful idea for angle adjustment....

Nice Pad!
 
that one clip is going to give you trouble over time, you're feeding power through the pivot pin...a little corrosion and no power.
Rex
 
Good point and you have an incredible eye for detail! Playing devils advocate, I would argue that in practical application, the act of exercising the clip will continually clean any corrosion from the joint, and that the total surface area of the pin is more than adequate for the power requirements.

However, from a design standpoint, had I insulated both non pin jaws and simply inverted one clip on a single lead application, that certainly would have been the superior design and regardless of whether the igniter fires or not, any joint resistance will result in decreased battery life.

Since it's already done, I'll use as is. I'll take a resistance reading now as a baseline. If and when it fails, I will update this thread with the resistance reading at failure to increase the knowledge base.
that one clip is going to give you trouble over time, you're feeding power through the pivot pin...a little corrosion and no power.
Rex
 
No need to "argue" about what will happen in practical application. Those of us maintaining club equipment will tell you that the non-soldered side of the microclip will not get a reliable current flow as crud and corrosion builds up in the pivot joint of the clip. We have seen it for decades on hundreds of clips and it became particularly evident when people tried to use copperheads with the tape on the wrong side.


It will work for a while, then you will need to fix it.

Is therre a removeable safety interlock on the controller (or do you pop it off the cables)?

I'm a big fan of simple PVC pads which can be made in lots of cool configurations.
Good point and you have an incredible eye for detail! Playing devils advocate, I would argue that in practical application, the act of exercising the clip will continually clean any corrosion from the joint, and that the total surface area of the pin is more than adequate for the power requirements.

However, from a design standpoint, had I insulated both non pin jaws and simply inverted one clip on a single lead application, that certainly would have been the superior design and regardless of whether the igniter fires or not, any joint resistance will result in decreased battery life.

Since it's already done, I'll use as is. I'll take a resistance reading now as a baseline. If and when it fails, I will update this thread with the resistance reading at failure to increase the knowledge base.
 
Lol, the irony of arguing that there's no need to argue. :p Still playing devils advocate, I would also mention that in addition to the copper pin, there's also a copper spring conducting between the two jaws. Her's the first reading so we can determine exactly how fast the clip fails, which as you already know will happen eventually.

Number of ignitions: 0
Resistance: 0
Capacitance: 0

The controller works as follows...

1) Verify no power at the clips
2) Connect clips to igniter
3) Open red mechanical cover that prevents accidental arming
4) Toggle switch sends power to the momentary switch and illuminates a bright red led to warn that the launch button is armed.
5) Press the red momentary button to activate the relay coil and send power to the igniter.

No need to "argue" about what will happen in practical application. Those of us maintaining club equipment will tell you that the non-soldered side of the microclip will not get a reliable current flow as crud and corrosion builds up in the pivot joint of the clip. We have seen it for decades on hundreds of clips and it became particularly evident when people tried to use copperheads with the tape on the wrong side.


It will work for a while, then you will need to fix it.

Is therre a removeable safety interlock on the controller (or do you pop it off the cables)?

I'm a big fan of simple PVC pads which can be made in lots of cool configurations.
 
N.F.P.A. Code requires a removable safety interlock to render the system safe.
 
Oh no! My rocket launcher won't be up to NFPA code! :eyeroll:

But all joking aside, if I manage to screw up the 4 individual mechanical safeties on my current setup, a 5th isn't going to save me from my Darwin Award. :wink: I may end up with a 5th safety anyway, but to serve a different purpose. I can see the potential trouble having to untangle the 30ft of cord leading to the controller so I may add a simple DC jack on the controller. When I was a kid, we shoved a rod in the ground, positioned a 9v right by the igniter and pushed it with a stick, lol! Always fun to think back and wonder how any of us turn into adults.
 
I like the simplicity of the launcher, the low c.g., the easy-to-find materials, etc.

The circuit looks basically good, the stuff like removable safety link can be added.

Only "minus" for me would be that I am an old fart now, and I don't like crawling on my belly to see where to place igniter clips. I also don't like the combination of launch rod tips about three-four-five feet off the ground and kids being around to prep for launch and not paying attention to getting poked in the eye. I like launchers up on stands about four or five feet tall---but then that kinda goes the opposite way from your design idea.
 
Overall it looks good but personally I prefer pads with 3 or 4 legs on the ground -- in my experience pads built upon square or circular flat bases tend to wiggle and wobble due to bumps in the ground surface.

You could convert this into a nice 4-legged launcher with 4 additional PVC parts -- 2 corner joints and 2 leg pieces. (You could also splurge for end caps for the legs but IMO they are not really necessary.)

The wiring looks good -- a safety interlock would be simple to add.
 
IMG_6731.jpgIMG_6802.jpgIMG_6801.jpgIMG_6799.jpg
After a few years, the launcher is still working perfect, but we've made a few upgrades.

1) Filled the base with acrylic fortified anchor cement.
2) Installed a 9ft rail for better stability with the new G-Force.
3) Installed a voltage monitor in the controller to indicate when batteries need replacement. After years, we still haven't had to replace any batteries!
4) Silicone conformal coated the circuitry to protect from oxidation.
 

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Hello Keith,

I agree that it looks very cool. And your list of upgrades is impressive as far as they go.....

But good grief, since you did not mention it in your list of up-grades, somebody has to ask.... In the three and a half years since the first post in this thread, did you ever add a "removable safety interlock?"

If the answer is yes, then I'll say, Great System well done! Bring it out to my club's launch, I'd love to see it in action. (If the answer is yes, then Skip down to my name at then end of this post)

But if the answer is no, then I really don't care how cool your integrated launch-pad/launch system looks, your system is not safe. And, no, its not just because the N. F. P. A. Code says its not safe. Both the National Association of Rocketry and the Tripoli Rocketry Association safety codes require a "removable safety interlock" because no system without one is safe. The rule requiring the "Removable Safety Interlock" has been around for a very long time because experience has taught that it is necessary.

Not safe is not cool.

Sorry for the harsh tone, but somebody has to stick up for safety. And I'm a guy who knows a thing or two about how to build safe launch systems.

Brad, the "Rocket Rev.," "Stickler for Safety" Wilson
Tripoli #01630 L-3 TAP
NAR #70929 L-3 L3CC
Wilson F/X Digital Launch Control Systems
 
Hello Keith,

I agree that it looks very cool. And your list of upgrades is impressive as far as they go.....

But good grief, since you did not mention it in your list of up-grades, somebody has to ask.... In the three and a half years since the first post in this thread, did you ever add a "removable safety interlock?"

If the answer is yes, then I'll say, Great System well done! Bring it out to my club's launch, I'd love to see it in action. (If the answer is yes, then Skip down to my name at then end of this post)

But if the answer is no, then I really don't care how cool your integrated launch-pad/launch system looks, your system is not safe. And, no, its not just because the N. F. P. A. Code says its not safe. Both the National Association of Rocketry and the Tripoli Rocketry Association safety codes require a "removable safety interlock" because no system without one is safe. The rule requiring the "Removable Safety Interlock" has been around for a very long time because experience has taught that it is necessary.

Not safe is not cool.

Sorry for the harsh tone, but somebody has to stick up for safety. And I'm a guy who knows a thing or two about how to build safe launch systems.

Brad, the "Rocket Rev.," "Stickler for Safety" Wilson
Tripoli #01630 L-3 TAP
NAR #70929 L-3 L3CC
Wilson F/X Digital Launch Control Systems

No worries. I'm accustomed to you rocket guys' "There's only one correct way to do things" mentality. I'm not saying that as an insult. I do understand that NFPA rules are in place to protect mfg companies from liability, others from negligence at club/public events when there are parents not properly supervising children and Darwin Award candidates. Fortunately, though, at home we have more freedom.

Ironically, we actually have more safeties in place than the commercial controllers I've seen at the hobby store. Here's how it goes if you're curious. Our daughter shoots recreationally and we treat it the same way. When someone is 'down range' hooking up the motor, etc, nobody is touching the unarmed controller. Then, to launch...

1) Flip up the safety cover
2) Once the cover is up, arm the controller by toggling the arm switch, which then indicates arm state by a bright red LED and now, also an illuminated voltage readout.
3) Push the button!

I still do have a plan to add a 4 pin jack to the controller simply to make it easier to untangle the cord. That will have the added benefit of acting as something that qualifies as your safety interlock, as I understand it. I'll update this thread if/when I get that done.
 
IMG_6806.jpgLooks like your idea won out. It never rocked, but I could only level it in one direction. I added four adjustable legs made of .5 inch allthread and embedded couplings. It added two lbs to the total weight, so I guess added stability as a bonus!

Overall it looks good but personally I prefer pads with 3 or 4 legs on the ground -- in my experience pads built upon square or circular flat bases tend to wiggle and wobble due to bumps in the ground surface.

You could convert this into a nice 4-legged launcher with 4 additional PVC parts -- 2 corner joints and 2 leg pieces. (You could also splurge for end caps for the legs but IMO they are not really necessary.)

The wiring looks good -- a safety interlock would be simple to add.
 
Don't take it personally Keith. Most posts like yours get the same response sooner or later, when the controller doesn't include a piece of the launch circuit that can be removed and put in your pocket. Still hoping to meet you and your daughter at a DARS launch sometime.
 
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