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'nother crazy idea, R/C mobile launch pad

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LarryH

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I know this might not be the best idea and it's probably been hashed over many times before, R/C launch controllers are considered dangerous by some because of the chance of radio interference and rockets firing when they aint supposed to, BUT having said that, it's just TOO TEMPTING to build one, a launch pad that will go where ever you want it to go at the mere wiggle of a control stick, and then adjusting your launch angle at the touch of a button, and finally sending a rocket into the wild blue yonder simply by smashing down a button(or sequence of buttons) on an R/C controller.

Several months ago I purchaed an R/C airsoft tank made by Hen-Long(in Hong Kong), pretty much a standard fare R/C tank with one amazing exception..... the gun REALLY fires! Yep, they fire little 6mm plastic BBs using a gush of air, these tanks go for a little over $50, they're really a good value, but they have one fatal flaw, one part in the firing mechanisims gear box is extremely weak and prone to breakage under normal use, this part has broken on me a number of times, and it renders the gun useless, it seems every time I glue it back together(super glue, or plastic cement) it will hold up for a couple rounds, and then break again, I gave up on trying to fix the gun, just had too much working against me.

I've decided rather than to have a useless toy sitting on a shelf that I'd try to utilize it for something else, then the idea struck me that maybe if I ripped the motor and gears out of the gun gear box and attached a couple lengths of wire to the wires that fed the motor and then routed them through the gear box and out the end of the gun barrel, that I might have a means of using the tank as an R/C rocket launchpad with built in launch controller, and why not... being a tank it is easily able to handle bumpy or grassy terrain, is very manuverable thanks to the skid steer system a tank utilizes, and would just look cool as a rocket launching platform. I decided to test my theory, I ripped everything out of the gear box, connected the two wires to the wires the motor used to be connected to, and routed them out the end of the barrel, then I connected an Estes ignitor to the two wires and fed in the firing signal from the transmitter..... sure enough the ignitor lit up just as I expected it to! Previously I wasnt sure if there'd be enough juice to light up the ignitor, but now I know there's juice to spare.

I've come too far now, I just have to see it through all the way, what I further intend to do is mount a blast deflector and 1/8" launch rod directly to the top of the barrel.... this way with the gun up/gun down control from the transmitter you would have some control over launch angle, as a safety device the tank comes with a switch on top of the turret that enables/disables the guns firing mechanism, I intend to attach a 2 foot metal rod to this switch to act as sort of a launch key, this will afford me some extra safety, but I still would want to be a little farther away than two feet if the rocket prematurely fired.... not a perfect system, but as long as I stick to small engine rockets(no larger than B) there shouldn't be any real reason for serious concern.... It'd probably be a good idea to wear safety glasses while prepping a rocket for launch.

A little disclaimer may be in order here.... dont try this unless you are FULLY aware of all risks involved and can make an intelligent decision as to if you think the added risk is worth it or not. Launching a rocket by means of an explosive propellant is already an inherently potentially dangerous activity, the project mentioned above only adds another level of risk, and should not be attempted unless you are prepared to protect yourself and those around you from that risk.


Having said all that(man I'm a windbag!), what ya'll think about it??????
 

shockwaveriderz

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my only comment on this is that you potentially might be in violation of the Model Rocketry Safety code, to wit:

Ignition System. I will launch my rockets with an electrical launch system and electrical motor igniters. My launch system will have a safety interlock in series with the launch switch, and will use a launch switch that returns to the "off" position when released.

If you can design in the above then go for it....send pics
 

Justy

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How large is this tank? Is it still going to be stable enough when you've got a 3' metal rod sticking out the top?
 

LarryH

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Thanks for the input shockwaveriderz, I've actually already thought of this, and truth be told the tank already has these features built in, in order to fire the rocket, two buttons must be held down simultainiously on the transmitter(a safety interlock of sorts perhaps?), when you release these two buttons all signal to the firing mechanism stops, that's not taking into account the switch on top of the turret that enables/disables the gun mechanism from recieving a signal(which in my opinion qualifies as another safety device), I think the two buttons on the transmitter required to fire the rocket could even be taken a step further and make one of the buttons removeable to act as a safety key of sorts.... the fact is no matter what way you look at it, this method of launching a rocket is going to present a bit more risk than the standard method of launch, but that doesn't mean that we shouldnt do it, it just means we need to be even more aware, and alot more carefull, even the standard launch method has holes in it that allow for human error or electrical/mechanical failure to cause an accident, we prevent these accidents from happening by being aware of the risks, taking precautions and preventive measures to guard against them, and keeping our equipment in good working order. I'm a little off topic by bringing firearms into this conversation, but a basic principal of firearms safety applies to just about any activity that could be potentially hazardous, and that rule is... "NEVER depend solely on a mechanical safety, they CAN fail, always rely on good judgement, and safe handling procedures to prevent a potential tradgedy.". I think this rule most certainly applies to rocketeering as well.
 

LarryH

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Justy, the tank is 1/24 scale, it is 17" long, 6.5" wide, and 5" tall, estimated weight is 2 pounds, should be stable enough for A and B engine launches.
 

mojack82

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Larry H:

I've done some thought exercises about this concept as well (I know, I know, ideas are cheap, execution is the hard part...) In fact, with the proper gear, one could even add extra elements in the NAR-mandated safety interlock series that Shockie mentioned - going beyond the current Estes, Quest, etc type controllers.

The gist of the operation would ideally be: manually load rocket, manually connect igniter(s) leads to clips, manually insert clip connector(s) to circuit on launcher, remotely move launcher to position, remotely adjust launch angle, remotely arm circuit, verbally countdown, remotely launch, automatically disarm circuit.

I'm not familiar with the particular controller/tank unit you've been describing and how many "switches" you have available. Unfortunately, what I've been mulling over takes a rather sophisticated/complex RC transmitter/receiver that can cost a fair amount of money - probably $200 or more. A six-channel, programmable Futaba 6XAS-type would suffice. This concept also requires finagling switches, contacts, etc. Check this url for specifics:

http://www.futaba-rc.com/radios/futk30.html

Basically, for open-circuit redundancy, one should put a minimum of two open contacts in series (or more if you're concerned about stray RC signals inadvertently activating any combination of servos - very low risk with newer PCM-capable radios) on the launcher itself. These servos can be activated with on/off toggles on the RC controller (ie, landing gear, bomb bay doors, etc) or detented switches (engine rpm slider, trim slider). The closing of these circuits would also need to activate a light/buzzer on the launcher to provide positive arming feedback to the operator. At this point, the circuit is "armed" but still open, just like the traditional, manual, launch controller.

Next, the ideal launch mechanism would close the circuit yet automatically open it when released by the operator. A what-if design solution here is to use one of the "dead man" levers on the RC controller (aileron, elevator) to close the launch circuit at full throw. These levers return to neutral when released, opening the circuit. An advantage here is the circuit opens without having to consciously and manually remove a launch key - good when you need to chase your rocket & your attention suddenly becomes diverted away from the status of the launcher circuit.

This is probably more data than you wanted, but what the hey - it gives me a chance to flesh out the concept in my mind and open it to others to find any unseen pitfalls. Bottom Line: yours is a very doable idea and it's possible to do it while maintaining and quite possibly enhancing launch safety.

Jack
 
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