Magneto launch controller

Does anyone know of any magneto launch controls for rocketry? What comes to mind is those old fashioned plunger detonators used to ignight TNT. I was curious about creating one out of a magneto from a vehicle. That way you would not need to worry about batteries ever again.

Excellent question! I had started into looking into building one myself, using a small DC motor of sorts. I would think dependent on the size of gears and/or ratios of plunger to motor, 12-14 volts would not be that difficult to obtain. I had also wondered if the faster the plunger is depressed, the more voltage would be made available.

I was thinking of using a motor from an RC car, that is designed to operate on 14.4 volts...

I'll be watching this thread

This was the motor I had in mind, that I just so happened to have one laying around.



Hmm... I just chucked it in the drill press and spun it at 3100rpms, but barely got 1 volt out of it

mbecks said:

Does anyone know of any magneto launch controls for rocketry? What comes to mind is those old fashioned plunger detonators used to ignight TNT. I was curious about creating one out of a magneto from a vehicle. That way you would not need to worry about batteries ever again.

Click to expand...

https://cavecreekmuseum.org/wp-content/uploads/2013/11/AOM-Nov-2013.pdf

Pushing down on the plunger quickly spins up an armature and when the plunger hits bottom the stored kinetic energy in the rotating energy is converted into a high voltage electric pulse, similar to a capacitive discharge ignition system. The output in several thousand volts so it will drive a very long wire.

Bob

McKailas Dad said:

...Hmm... I just chucked it in the drill press and spun it at 3100rpms, but barely got 1 volt out of it

Click to expand...

tually
Thus a motor doesn't make a very good generator and a very bad magneto.

A magneto is much different than a motor. A magneto has two sets of windings, a primary winding that produces the initial voltage and a secondary winding that steps up voltage for an ignition spark. Check out this Youtube video.

[video=youtube;julmHkDTQWA]https://www.youtube.com/watch?v=julmHkDTQWA[/video]

Very good discriptive posts, but has any lone built one for the use of launching rockets that anyone knows of?

No. Why would you want to. A real magneto unit is going to weigh several pounds at minimum, and you can make a LiPo powered launcher weighing far less than 1 pound.

Or you can also get a wireless unit for $20 or less on Amazon that used regular batteries. Get some rechargeable NiMH batteries and be done with it.

https://www.amazon.com/gp/product/B00VUNAWSQ/?tag=skimlinks_replacement-20

https://www.amazon.com/dp/B00RIXYIDM/?tag=skimlinks_replacement-20

https://www.amazon.com/gp/product/B00RFCG3E8/?tag=skimlinks_replacement-20

Bob

Why?

I think it's a clever idea, and...different..outside the box.

I have 'old school' rechargeable batteries from a previous RC hobby. I'm not sure if they are Nicad or NiMh, but for me to buy a large enough Lipo and the charger to boot...-just- for a launch controller, was not a viable option the last time I checked. Granted, that was over 2 years ago and I'm sure prices are much less now.

Besides, how cool would it be to launch your bright red scratch built "TNT" rocket with one of these?

Fire in the hole!

I hate the answer "why". It's such a lack of creative thinking. The way I build my rockets is outside of the norm and would be way easier if I just used pre-made parts but I enjoy the creative process and challenge.

My curiosity again got the best of me.

You can get a small, hand crank magneto generator that produces 12-15 volts, for around $40.00, depending on the model.....

https://www.arborsci.com/deluxe-hand-crank-generator

I remember something like those from way back around 8th grade science class, those things pack a punch!

There ya go! Now build it!!


EDIT - I found hand crank 'telephone magnetos' all over EBay for -cheap-, but you certainly don't need THAT much power.

Here is one, starting bid... $9.00

https://m.ebay.com/itm/262279208769

Jeff - if memory serves, you would need to spin that motor at 20 - 30k rpm to get anywhere near 12v. you would need something like a 55 - 85t motor to bring that speed down to something reasonable.
Rex

Rex R said:

Jeff - if memory serves, you would need to spin that motor at 20 - 30k rpm to get anywhere near 12v. you would need something like a 55 - 85t motor to bring that speed down to something reasonable.
Rex

Click to expand...

Hmm, perhaps I could chuck it up to the Dremel?!

EDIT- Bet you didn't think I was really gonna try that, huh? Well, I DID!

Full blast, 35,000RPMs... 8 volts


Hey, Rex, you're a Lipo guy, could a decent ~12v Lipo and matching charger be purchased for less than say.... $50?

I was just searching HobbyKing, but I'm not sure what I'm looking at

Looks like these will do the voltage, but will they produce enough amperage to set off your typical AP igniter?

I haven't been 'shopping' for batteries etc. for some time so my knowledge is a bit dated(by about 5 yr.s). apparently one can buy a decent charger for $23(w/o power supply), haven't a clew what a 4000mah 3s pack(11.1v nominal) would run you now-a-days. most hobby shops should be able to at least give you an idea of price.
5 years ago had you asked, you could have heard me laugh from 50 miles away, my charger was about $200 and packs $70(each). of course those packs could probably be able to start a car(when new). those race boats could drain a 10k mah pack in about 4 minutes(figure that we were running about 1.5 horsepower motors in a boat 30" long)). I would suggest asking here about battery prices as a starting point.
Rex

terryg said:

Looks like these will do the voltage, but will they produce enough amperage to set off your typical AP igniter?

Click to expand...

Of what I read of the 'Genecon' model, it is capable of producing 200mA. What is the typical amperage required?

I remember the one in the classroom would send juice through the whole class while holding hands. The wimpy kids let go first lol. My science teacher was a twisted kinda guy...

McKailas Dad said:

My curiosity again got the best of me.

You can get a small, hand crank magneto generator that produces 12-15 volts, for around $40.00, depending on the model.....

https://www.arborsci.com/deluxe-hand-crank-generator

I remember something like those from way back around 8th grade science class, those things pack a punch!

There ya go! Now build it!!


EDIT - I found hand crank 'telephone magnetos' all over EBay for -cheap-, but you certainly don't need THAT much power.

Here is one, starting bid... $9.00

https://m.ebay.com/itm/262279208769

Click to expand...

That little crank is super cool. I wonder if you would need to add a switch so you can close the circuit when the crank is being turned at full speed and avoid the igniter just fizzling out.

I prefer the Professor X launch controller.

(Come on, somebody had to....)

Bat-mite said:

I prefer the Professor X launch controller.

(Come on, somebody had to....)

Click to expand...

Aw c'mon, I was Googling stuff until 7am....

Professor X ?!

McKailas Dad said:

Aw c'mon, I was Googling stuff until 7am....

Professor X ?!

Click to expand...

Dude, you never heard of the X-Men?!

I've been in a rockery vacuum for over two years. 29mm BP? $20 dual deploy?! And now Mind Control launchers?!!

Next thing you know, the Copperhead will be obsolete!!

Future shock!

Bat-mite said:

I prefer the Professor X launch controller.

(Come on, somebody had to....)

Click to expand...

oh man iv'e read this comment like 20 times since it was first posted and just got the reference. I feel dim.

mbecks said:

oh man iv'e read this comment like 20 times since it was first posted and just got the reference. I feel dim.

Click to expand...

Dim? Uh, don't feel bad, I didn't get it even long -after- I Googled it...

Sucks being old sometimes :/

Another thought on this would be to find one from a bicycle?!

https://www.bikeberry.com/bullet-head-light-generator-kit.html?gclid=CNqh7_2V9MoCFZGIaQodUFcHDg


Edit- apparently that's only .5 amps

Somebody HAS to have made a magneto launcher....???

Micromeister, are you holding out on us?

You need at least 3 amps, even more for clusters.

McKailas Dad said:

Dim? Uh, don't feel bad, I didn't get it even long -after- I Googled it...

Sucks being old sometimes :/

Another thought on this would be to find one from a bicycle?!

https://www.bikeberry.com/bullet-head-light-generator-kit.html?gclid=CNqh7_2V9MoCFZGIaQodUFcHDg


Edit- apparently that's only .5 amps

Somebody HAS to have made a magneto launcher....???

Micromeister, are you holding out on us?

Click to expand...

Mircromeister doesn't like the way I do rocketry so I think he avoids commenting on anything I start.

Folks

You have a misconception on how the plunger magneto systems works. It is a mechanical equivalent to a capacitive discharge ignition system.

In a CDI system, you use a high voltage DC power supply to charge up a capacitor. Once the capacitor is charge, you flip a switch to dump the capacitor charge through a load. In the plunger magneto system, pushing down the plunger starts a large mass spinning at high speed, converting a linear motion into rotary motion and putting inertial energy into a spinning wheel. Think of a kids plunger spinning top. When the plunger hit bottom, it closes an electrical switch which converts the inertial energy into a short duration, high voltage, high current electric pulse that discharges through the low resistance igniter. The inertial wheel actually stops shortly after the switch closes due to the conversion of rotational inertial energy into electrical energy. Just like a capacitive discharge system you have to deliver fractional Joule pulses in a few 10s of milliseconds, so you need a very electrical resistance in the circuit.

The same principle is used in dynamic braking in trains and regenerative braking in hybrid cars. The reason why your run of the mill telephone crank does not work it the internal resistance is high, so it will not produce high current, but rather low current for as long as you crank it.

Bob

I will surely confess, my electronics knowledge is quite limited, so bear with me.

If the small hand cranked magneto had enough power to zap 20-25 kids, (mentioned earlier) that would need a considerable amount of amperage, correct?

My teacher dared students (?!) to hold on to the wires as long as they could by themselves. I was pretty close to the longest, and my fingers swelled up like hot dogs. I think I still have static from that!

Of what I understand, it's the amperage that will kill you, not necessarily the voltage. Is that a reasonably true statement?

I'm thinking of back in the day when they were using the plungers for dynamite, and as long as the wires -had- to be, that would also take high amperage. (Correct?)

Obviously, they didn't have the electronic circuitry we have today, so how did they build them then?

I guess I could Google it, but it's an interesting thread, and others may wonder.

Bobkrech, you've got mail...

McKailas Dad said:

I will surely confess, my electronics knowledge is quite limited, so bear with me.

If the small hand cranked magneto had enough power to zap 20-25 kids, (mentioned earlier) that would need a considerable amount of amperage, correct?

My teacher dared students (?!) to hold on to the wires as long as they could by themselves. I was pretty close to the longest, and my fingers swelled up like hot dogs. I think I still have static from that!

Of what I understand, it's the amperage that will kill you, not necessarily the voltage. Is that a reasonably true statement?

I'm thinking of back in the day when they were using the plungers for dynamite, and as long as the wires -had- to be, that would also take high amperage. (Correct?)

Obviously, they didn't have the electronic circuitry we have today, so how did they build them then?

I guess I could Google it, but it's an interesting thread, and others may wonder.

Click to expand...

https://van.physics.illinois.edu/qa/listing.php?id=6793 Read this and figure it out yourself.

bobkrech said:

https://van.physics.illinois.edu/qa/listing.php?id=6793 Read this and figure it out yourself.

Click to expand...

Thanks for the link...

Something like this?



On the test bench because it didn't put out any voltage. The problem turned out to be that the magnet had lost its "mojo". How does that happen? How can I re-magnetize it? This was for launching sounding rockets.