Magneto launch controller

All commentary aside, a plunger type launch control seems quite appropriate for a fair number of launches (a number of my own included) I have observed.

sooner.boomer said:

Something like this?

View attachment 282748

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.

Click to expand...

Yea, pretty close, though I had pictured mine to look just like the the original TNT detonators. Weathered barn board box, with a big rusty T-handled plunger, brass screw terminals, cloth wrapped wires...you know? Old school

For some odd reason, can't find -those- on Ebay?! Hmm...?

sooner.boomer said:

Something like this?

View attachment 282748

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.

Click to expand...

that looks so cool, basically exactly what I was imagening. I can't help with the issue though sorry. I've heard that magnets can become non magnetic but I don't know how or if it's fixable. Did it use to work properly?

bobkrech said:

No. Why would you want to.

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Why go beyond 3FNC? That's all you need to make a rocket. Anything else just adds weight and complexity, not to mention expense.

To me, it looks like a fun and interesting challenge, with no practical application whatsoever. It's just fun and different. That alone is reason.

mbecks said:

that looks so cool, basically exactly what I was imagening. I can't help with the issue though sorry. I've heard that magnets can become non magnetic but I don't know how or if it's fixable. Did it use to work properly?

Click to expand...

As far as I know it worked. No one I asked knew anything about how it worked, or what project the rockets were used on.

McKailas Dad said:

Yea, pretty close, though I had pictured mine to look just like the the original TNT detonators. Weathered barn board box, with a big rusty T-handled plunger, brass screw terminals, cloth wrapped wires...you know? Old school

For some odd reason, can't find -those- on Ebay?! Hmm...?

Click to expand...

You're not looking at the right ebay vendor. Try the Acme listings.

I think you probably could build one. The hardest part will be the magneto. Unless you want to wind your own (not that hard to do*), perhaps you could find an old one in good shape from a car or motorcycle. The next hardest parts would be the long "rack" gear and the gear on the mag. The rack/gear need to disengage at the end of the stroke so the mag can freewheel. You'll also need a switch at the very end of the stroke. A capacitor across the mag would give more energy output when the switch was closed. I think I'd want to use something with a high current capability, like a photoflash cap, for example.

Old tube-type TVs and monitors are great sources of wire for this sort of project (deflection yokes). I made a lot of electric motors back in my (much) younger days from this wire...

Hmm.. Seems to me that since this is a "What if ?" thread. Except for Sooner Boomer's work. Build a "Pulse spark" out of the old dead mower. Take the flywheel and magneto and mount it in some way? It wouldn't be a continuous v output, just a heck of a pulse! Don't know how much amperage it would produce.

Having played around with old pull start, no-battery lawn-mowers for a few decades, I can tell you that they do indeed pack quite enough amps to light your typical igniter. But I'm talking, lawn mowers that were from.... uh... 30 or 40 years ago or more. When checking to make sure the spark was working, I know of a fellow who got several really good shocks out of old pull start lawn mowers. Uh... not me of course... it was.... some other guy.

And even though I build and sell Wilson F/X digital launch control equipment, even I find this a fascinating idea. It just has the "cool" factor for a single pad controller.

But somebody's going to need to measure some actual current/amperage output before one can talk about the suitability of this system for anything other than single motor model rocket launches or possibly some mid-power motors. The longer the distance between the power source and the igniter clips, the more juice one needs to get the igniter lit.

Brad, the "Rocket Rev.," Wilson

I used a war surplus GN-38 generator from a field telephone and made a good launch controller that never needs batteries. You have to crank it for 45 seconds or so to build up the charge. Attached is an article I wrote but never got published.

View attachment Crank_Up_Rocket_Launcher.pdf

45 seconds! That's longer then a lot of flights., but I like it. Viable backup option when your batteries are dead.

Steve G

Cherokee said:

I used a war surplus GN-38 generator from a field telephone and made a good launch controller that never needs batteries. You have to crank it for 45 seconds or so to build up the charge. Attached is an article I wrote but never got published.

Click to expand...

What you've done is made a capacitive discharge ignition system. If you don't want to crank it up, you can take the photoflash circuit from a disposable camera instead of the hand crank generator, but beware, the voltage/current pulse can be dangerous and potentially fatal.

Try something like this. Telephone magnetos produce some serious juice. Don't accidently touch the terminals when you are cranking. It's an experience you'll likely not forget for quite some time.

https://www.ebay.com/itm/Magneto-Te...969973?hash=item464fe2bbb5:g:s84AAOSwmtJXUDhP

JR

https://www.ebay.com/itm/MEGA-POWER...938155?hash=item360342b82b:g:M2EAAOSwbdpWXiHK

I used one of these in a work application last year. We were using it with a fixed hand crank, and it would easily light up 6" long 32 gauge nichrome through a 50' 14 gauge extension cord.

Edward