Large Scale Central

Rocket launcher car idea

Modeling
#1

So Eric Mueller’s thread on model rockets has the juices flowing. I want to build a small flat car with an operating launch pad for a small single stage rocket. This is something I have thought would be fun to build ever since I started scratch building in large scale.

I am thinking it could be as simple as some sort of servo controlled actuator that lifts the rocket from horizontal to vertical with a push of a button. Then another push of a button ignites the igniter. I can’t believe this would be overly complicated. But I am not at all intelligent when it comes to little electrical gizmos. I am thinking a simple LED remote controller would work giving me a simple 2 channel remote. One to operate the lifting mech and another to light the igniter.

But I have no idea where to even start for an actuator that will lift something 90 degrees and stop and then a second push of the same button returns it. Is this even a thing? I think I have the skill to make the actual mechanism but how would I make it so it goes 90 degrees with one push of a button and then 90 degrees back with a push of the same button?

#2

May have answered my own question. Amazon has some smallish 12v rotary actuators. While they don’t automatically stop rotating they lock in place when there is no voltage. I have an old RCS RX and TX that is center off. I am thinking I can use the motor controls to run the actuator up and down and then one of the trigger buttons for the igniter.

Does that sound plausible? BTW I am not looking to make this anything that is prototypical. It is purely whimsy so how it looks is not ultimately important.

#3

Maybe a simple servo controller? I just received 2 of these today for a crossing gate project.

https://www.vasileelettronica.com/controllo-per-servocomando?lang=en

#4

Oooo…That looks even smaller and easier (terminals) than the Sparkfun board. Doesn’t have two position settings. Not sure if I don’t need that.

#5

Fun idea. In addition to raising the platform, you’ll need a metal flame deflector; perhaps a flame chute to keep heat away from the cars.

#6

It has a slightly larger footprint than the Sparkfun. 3x taller due to the screw terminals.
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#7

I was going to say just that!

Your other option is to buy a small kit that would not need a “transport-erect-launch” (TEL) vehicle. Estes’ “Mosquito” is quite tiny, and you could probably ripple fire three off a flat car of some 6" launch rods.

One other thing you might consider is lateral supports that would lower to brace the TEL against rolling over. These rockets do put out quite a bit of thrust!

Eric

#8

Dan,

I like the looks of that a lot. Might have to play with one of those. I can already see that the actuation is run with a momentary switch. So inputs from some sort of a remote RX should work. But does it lock in a certain position or does it automatically return to “zero” when de-energized. That would be problematic. Once raised into firing position it would need to stay there until “asked” to return.

Jon,

I was thinking either a flat metal plate like they use on the launchers that are normally used which would be the simplest. But I kinda like the idea of the chute. That could be fun as well.

Eric. I had not even considered having rockets stationary in the vertical position. I do know of the little mosquito rockets. A MLRS system could be very fun. I already was thinking the rocket I would use wouldn’t be a whole lot bigger than a mosquito anyway. I want to use a small engine like a 1/4 or 1/2 A so that I am not trying to chase rockets all over the neighborhood. So was considering a small rocket (maybe longer than a mosquito) that ejected the engine instead of a parachute. Trying to keep the thing reasonable and simple.

At any rate there is some serious food for thought.

#9

The rocket launch car sounds like a really cool idea. Didn’t Lionel have something like that? Germany during WW2 probably did.

You could cheat a bit on the lift up and drop down mechanism. When the train gets in place the rocket is lifted and launched and when all eyes are watching the flight you sneak back and drop the launch pad back down by hand and the train is on its way home. :grinning_face_with_smiling_eyes:

It would be neat to also build the support cars for this such as the fuel transport and the mission control car with a satellite dish and antennas on the roof.

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#10

What Estes calls Tumble Recovery. Always was my preferred system. I rarely got back any rockets that had chutes.

You can make any model that is light enough into a tumble recovery model. Drill a hole about 5/16" just below the nose cone and glue the cone solidly in place. You need the hole so the ejection charge doesn’t over pressurize the body and explode! You also need to eliminate the motor clip. There should be a friction fit for the motor, but not too snug!

#11

John,

It has been years since my rocketry days. I don’t remember ever drilling a hole on the tumble recovery rockets I made. I thought you wanted the pressure to shove the engine out. I do remember omitting a clip, though. I thought the same forces that pushed the cone and chute out where instead used to push the engine out.

Todd,

i love the idea of an entire train dedicated to rocket launching. But that is more ambitious than I was considering. I had thought about a manually lifting launch rod, but part of the fun would be to have it all automated. We will see where it goes.

#12

A quick google search and the place I bought components from is still around, Apogee Rockets. They sell all the individual components to design and build your own rockets instead of kit rockets. Just in case anyone cares.

A little more brain storming and I am wondering if I need a fancy actuator at all. Thinking about how the RCS RX and “center off” TX work on our train motors to start stop change directions and speed control all with a turn of a knob, couldn’t a simple DC motor be used? The motor would be able to reverse directions to both raise and lower the launcher. It would hold its position when de-energized in the center position. I happen to have a spare RX and TX

#13

Devon, There are 2 modes: Return to zero on release and “toggle” (press to move - press to return.) They are both demonstrated in the video including soldering of the jumper necessary to enable.

#14

That would work perfect then. Watching it yet again that is really exactly what I need. Given that it adjusts for both speed and travel and then having the option to have it move into position with one push of a button and then return with a second push of a button is perfect. I am thinking a very simple remote control LED light controller like Dave Bodner played with would be all a person needs to operate it. The board is capable or running two servos. Which I am thinking could run the servo and instead of a second servo use the second output as a firing mechanism to light the igniter.

#15

Estes tumble rockets came with a hole pre-punched. No drilling required. You do want pressure, but only enough to eject the engine, not burst the tube.

#16

Devon, what’s wrong with a simple servo plugged in to your RX (which is actually a small DC motor and lots of gears!) ? We use them all the time on steam engines for moving throttles and reversing levers. They have a shaft that takes a lever to move 90 degrees. The rest is just mechanical linkages.

#17

Well, ignoring the railway mounted big guns (Check out Gustav Dora,) there is this little gem - a V2 rocket on a mobile launcher. Just the prototype you were looking for!

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#18

I was thinking exactly this myself. My only concern is having it stop once its in position automatically instead of me having to “keep an eye on it” which would in itself be fine. Its where I was going with using just a simple DC motor.

#19

Years ago, when I was much younger, instead of worrying about recovering a rocket we did this. Take the rocket engine, glue 3 cardboard or balsa wood fins to the bottom. Small cardboard cone to the top and glue on the launch guide straw. Painted a bright color they would fly up and out of sight!

You could easily have 3 or 4 on a flat car with a metal deck. Use launch poles as long as your railroad overhead will fit.

Note, the fins would extend below the bottom of the rocket engine about an inch.

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#20

Thats an interesting idea.