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  • July 17, 2019, 03:37:16 PM

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Author Topic: Lightest electronic ignition setup?  (Read 519 times)

Offline Mark Mc

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Lightest electronic ignition setup?
« on: January 09, 2019, 12:44:22 PM »
A post on another forum has me interested in trying a little experiment, but I'm not doing well finding a light ignition setup that meets my wants.  The only one I found is a little heavy and tops out at 10K RPM.  I'm looking for a light CDI that I can run from a small 2S or 3S battery and run a prop up to about 14K.  I'm not electronics savvy enough to try and design my own, so I'm looking for something pre-made or in a DIY kit.  Anyone know of such a critter?

Thanks,
Mark

Offline Bill Adair

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Re: Lightest electronic ignition setup?
« Reply #1 on: January 10, 2019, 01:49:27 PM »
Mark,

Good luck with finding a lightweight ignition system!

The limiting factor always seems to be the ignition coil, and the battery required to use one!

Bill
NW Fireballs
Not a flyer (age related), but still love the hobby!

Online Tim Wescott

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Re: Lightest electronic ignition setup?
« Reply #2 on: January 10, 2019, 02:13:31 PM »
I got curious and did a web search, came up with this site.  I know absolutely nothing about the vendor, except that I've seen the TIM kits mentioned before.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dane Martin

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Re: Lightest electronic ignition setup?
« Reply #3 on: January 11, 2019, 08:14:51 AM »
Voltage is a limiting factor, Mark. Most coils are meant for no more than 4v (going from memory). A huge reason for the cdi voltage and price increase over what we use is the fact that, the CDI controls ignition timing advance, vs our engines which is mechanical. The CDI on the bigger engines has a voltage regulator built in, so they can "handle" the higher voltage. Really, it was just for market popularity because everyone who flys big RC pushed to go to a 2s li-po rather than a 6v Ni-cad.

Would any of Larry's stuff work with a 1s for you?
http://www.modelflight.com/larrydavidson.html

Offline Mark Mc

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Re: Lightest electronic ignition setup?
« Reply #4 on: January 11, 2019, 03:20:15 PM »
Tim,  thanks for the link.  That one did not pop up on my internet searches.  My Google-Fu must be weak.  I have an e-mail in to them to see what the max RPM of their lightest system is.  The highest they show for one of their ignitions is 12K, and I'm looking for around 14K.  I'm looking at doing a .15 sized engine turning an 8 inch prop.  I suppose I could go to a 6" or 7" pitch, but I'd like to stay around 4" or 5" pitch.

Dane, I looked at that site, but it seems to be only for points ignition engines, and the engine I want to play with is not a points engine.  But thank you for taking the time to look for me.   (edit:  Oops! looks like they do have an option for the TIM4 with a Hall sensor.  I'll have to email them for more info.)

Mark

Online Tim Wescott

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Re: Lightest electronic ignition setup?
« Reply #5 on: January 11, 2019, 08:56:03 PM »
Tim,  thanks for the link.  That one did not pop up on my internet searches.  My Google-Fu must be weak.  I have an e-mail in to them to see what the max RPM of their lightest system is.  The highest they show for one of their ignitions is 12K, and I'm looking for around 14K.  I'm looking at doing a .15 sized engine turning an 8 inch prop.  I suppose I could go to a 6" or 7" pitch, but I'd like to stay around 4" or 5" pitch.

Dane, I looked at that site, but it seems to be only for points ignition engines, and the engine I want to play with is not a points engine.  But thank you for taking the time to look for me.   (edit:  Oops! looks like they do have an option for the TIM4 with a Hall sensor.  I'll have to email them for more info.)

Mark

If this is for an old-timey engine, then you probably don't want to spin it that fast.  If you're talking about running a modern 15 on ignition, then sure.

I suspect there's things you can do to squeeze some more power out of the combination.  For starters, ask them about their CDI system -- a properly built CDI system should be good for more RPM than a points & condenser system or the simple TIM-style transistorized systems (which, if I'm not horribly wrong, just replace the action of the points with a transistor).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Curare

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Re: Lightest electronic ignition setup?
« Reply #6 on: January 11, 2019, 09:11:04 PM »
I would say the lightest would be a "petrol"  gasoline glow plug.

https://www.towerhobbies.com/cgi-bin/wti0001p?I=LXEJRG
Greg Kowalski
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Offline Mark Mc

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Re: Lightest electronic ignition setup?
« Reply #7 on: January 11, 2019, 09:38:23 PM »
The engine on the other board that got my interest up was a Cox .049 running on ignition.  Obviously too small to fly a plane on ignition with all the extra components.  But I was thinking of trying a Medallion .15 with a MECOA glow plug adapter head on CDI.  Yeah, I know.  But what can I say.  I'm a Cox fanboy.  I was thinking about stuffing it all into a Stunt Trainer:

https://outerzone.co.uk/plan_details.asp?ID=3939





Offline Jim Kraft

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Re: Lightest electronic ignition setup?
« Reply #8 on: January 12, 2019, 10:46:13 AM »
Not many of the old spark ignition engines from the 40's are recommended to run that rpm. But there are a few. The Owick instructions say to put on an 8 or 9 inch prop and run it as fast as it will run to clean out the carbon. I have not tried that, but it would be well over 14,000. The Orwicks have stronger point springs than most, and for high rpm need to be set at around .006 to .008. With a hall effect transistor i am not sure there would be a limit to a point far beyond 14,000. I am pretty certain the old control line speed planes and early tether cars with Dooling's McCoy's and possibly Atwood Champions ran around 14.000 rpm.

So you could just use a standard three volt coil, and transistor for switching, and a magnet hall effect for the pickup. Then using a Lipo battery you could end up with a pretty light weight system. Larry Davidson would probably have all you need.
Jim Kraft

Offline FLOYD CARTER

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Re: Lightest electronic ignition setup?
« Reply #9 on: January 12, 2019, 01:31:27 PM »
Sadly, my friend Jerry Howell passed away a few years ago.  He produced a version of my TIM design.  The TIM-4 transistorized coil driver will work with a Hall Effect pickup.  Larry Davidson has these.

CDI units are somewhat limited in RPM.  The internal storage capacitor takes a finite time to re-charge between sparks.  Shortening this charge time means a more robust circuit and stronger batteries.   You could end up with something heavier and more complex than practical for small engines.
"Growing old is easy.
 Staying old is hard"
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Online Tim Wescott

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Re: Lightest electronic ignition setup?
« Reply #10 on: January 12, 2019, 03:27:22 PM »
Hey Floyd!  Since we have your attention -- would a 3V coil on a 6V battery work with a suitable ballast resistor to keep the current reasonable for the coil, and lower the L/R time constant?  Sure you'd waste a lot of energy as heat, but LiPo don't weigh that much, and it seems a simple way to get the coil current back up rapidly.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline FLOYD CARTER

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Re: Lightest electronic ignition setup?
« Reply #11 on: January 13, 2019, 01:27:49 PM »
Yes.  And my '55 Chevy Bel Air had a large ballast resistor in the coil circuit.  How do I know?  It failed open, and the engine didn't make a sound.
"Growing old is easy.
 Staying old is hard"
AMA #796  SAM #188  LSF #020


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