Ignition

[Rayanth]

Was just poking my nose into that $30 ignition system thread elsewhere on the forum and realized, I am not thoroughly familiar with how the common miniature engine ignition systems work.... anyone have a link to a good explanation?

I've got a basic understanding of some of the components, but not how they connect to work together. I know a hall effect is used to trigger the 'coil' to send a spark, but not how one adjusts the location to set timing...(or even where it's mounted)...

Of current interest, due to my 4360 project, is if one coil/magneto/whatever things scale down to, has a limit of how many cylinders it can drive. The full scale has 4 magnetos, one for each bank of 7 cylinders, but I can make some of those dummies, or spread the components of one magneto across the 4 spots, if one can drive 28 cylinders....

I digress... I tend to think while I"m typing, bad habit I know =) Back tot he question - anyone have an article that gives a good explanation of the whole ignition system? I'm quite familiar with the *mechanical* workings of engines, but the electrical stuff not so much.

Thanks
- Ryan

 

[b.lindsey]

Take a look at Roy Sholl's site, he has some info regarding radials there as well.

http://www.cncengines.com/

Bill

 

[Rayanth]

Bill,
I thank you for the link (another for the bookmarks) but I'm afraid I'm still a bit confused

I'll try to find another way to google for it tomorrow... there's so many false hits on anything related to RC these days, it's almost not worth trying

- Ryan

 

[gbritnell]

The search function works real well for this forum and there have been numerous discussions on the subject. For example, go to the 'work in progress' category and type ignition in the search box and you will get a myriad of hits.
As far as answering one of your questions I don't think you'll get an answer from this forum as I have never seen anything posted on one of these engines before. Even in my trips to NAMES and Cabin Fever I have never seen one running so you're entering new territory. In miniaturizing an ignition one could probably operate 9 cylinders with one distributor so you would need several for your project.
gbritnell

 

[Dave G]

Hi Ryan, I built one of Ageless engines 9 cylinder radials a few years ago. I used the contact points and a condensor with a automotive coil driven by a 12 volt battery. I tried to buy a electronic ignition kit from Jerry Howell for it and he wouldn't sell it to me. He related to me that he had tried to use them on a radial before with no success. Seems when the bottom spark plugs oil foul there was a tendency for the system to fry itself. Thats why I used points. I have used Roy Sholl's systems on other engines with great success and am curious to see how well they hold up on a radial. I had to make my distributor cap taller because of the spark jumping to the point arm inside the distributor. I think with a radial you need a good spark to help overcome the oil fouling problem inherent to a radial and the distance between contacts in the cap can't be to close or the spark will jump from contact to contact. This is just one of many problems trying to design an engine to scale, especially a radial. My thinking is you will need 4 distributors of 7 cylinders each which shouldn't be to difficult to make with each having it's own coil. Basically 4 separate systems working together all driven from one battery. my $.02 and good luck with the project, Dave
Also, Don't forget to phase the distributors when designing them.

 

[Lakc]

There isn't really one answer to your question, because there are so many different types of ignitions out there. As this subject is becoming rather near and dear due to my own projects, I happen to have a half dozen or so tabs open at this very moment.

Here is a decent overview site, but beware, it does contain some errors.
http://www.jetav8r.com/Vision/Ignition/CDI.html

There are two long discussions regarding home built ignition systems here:
http://www.rcuniverse.com/forum/m_743937/mpage_1/key_ignition/tm.htm
http://www.rcuniverse.com/forum/m_3422690/anchors_3430679/mpage_1/key_/anchor/tm.htm#3430679

Which lead to a pair of very interesting sites with ignition systems on which I intend to do some experimenting with soon.:
http://www.electronics.gompy.net/
http://ot40.com/cdi_ignition.htm

Now miniature magneto's exist, but it partly depends on your definition of miniature. Voltage wont scale down, and this fact will affect magneto ignition systems the most.

 

[Rayanth]

Thanks for the links, Lakc, I will try and go over them later in more depth.

I've tried searches on the forum, but I just get lots of hits about what ignition system someone used, and not much info about how they work. My google-fu has been failing me lately.

My issues here, are that I'm not the electrician in the family, that was my dad... I understand mechanics very well, but if you start adding wires, I get confused

All I know is what components there are ( to an extent, it seems I'm confusing several different ignition system types into one generic, even there), and that somehow, something tells something else when to make a spark, and which spark plug to do it on... sadly, that's the extent of my knowledge in this area :wall:

- Ryan

 

[Lakc]

Its not an easy subject to google, as there are many ways and means, as well as local dialect influences on the various conversations.
Its been a long time since I did any pic programming, so I am overdue in a sense. One of the reasons I am building my current engine is to test ignition system designs, I was just hoping to have it running on glow ignition first. There have been numerous threads on various ign troubles lately, so a need is definitely there.

 

[John Rudd]

Lakc...
I'm greatly indebted to you...

I read the threads over at RCU only to find aload of dead links...
You have provided the missing link (no pun intended ) to the main author's site...

Thanks again...

 

[Rayanth]

John, I am curious about your avatar picture...it's a great looking plane, but the amount of detail in those scale people looks nothing short of amazing, were they handmade from plans? ;D

I do intend to dive into those links in more detail. I guess my biggest issue is figuring out what goes where. I understand that in the common system, a hall effect sensor is triggered by a magnet passing by it, but...what is the magnet attached to? A flywheel or takeoff gear that's linked to the crankshaft?

The plans i've done most of my work building in cad so far have been for glow engines, which use compression ignition (like a diesel), and thus don't have a need for an ignition system beyond warming up the glow plugs prior to start. It's the switch to sparkplugs and the complex electronics behind it that I just can't seem to fathom yet. I'll keep on it.

Ryan

 

[John Rudd]

Ryan,

At the risk of being of topic...

The avatar I have is real, I spent my 50th b/day at Kissimee flying an AT6..What you see in the picture is real!

Back to the topic...
Yes the trigger mag is attached to a flywheel...That triggers the pic mocro into firing the thyristor, discharging the invertors generated charge(stored in the capacitor) into the ignition coil.

All the pic is doing is mapping the trigger point relative to engine speed..

 

[Rayanth]

So.... for a 7 cylinder, the pic fires 7 times for each time the magnet comes around, spacing them out based on rpm? Or does it take 7 hall sensors?

 

[Lakc]

Lakc...
I'm greatly indebted to you...

I read the threads over at RCU only to find aload of dead links...
You have provided the missing link (no pun intended ) to the main author's site...

Thanks again...

Glad to be of help! A little detective work, and url guesswork, mostly because I really wanted to see the links myself. ;D

So.... for a 7 cylinder, the pic fires 7 times for each time the magnet comes around, spacing them out based on rpm? Or does it take 7 hall sensors?

While people can and do use the flying magnet routine, I prefer one hall and magnet with a simple steel disc with 7 slots in that case. Less parts, you can space the slots to match the minute differences in firing angle due to the master rod geometry, and flying magnets tend to induce voltage into everything they move by.

 

[Rayanth]

I had forgotten that was a route, briefly read something on it and forgot about it 8)

So 7 sensors, each mounted opposite a stationary magnet, with a rotating disc between, with cutouts to match when I want to fire.

Times 4, for my 4 rows. I wonder if I can modify the circuit boards to be stacked in a way, so that they can fit in a scale 'magneto' casing, and thus still maintain the scale look.

 

[Lakc]

So 7 sensors, each mounted opposite a stationary magnet, with a rotating disc between, with cutouts to match when I want to fire.

No, you only use 1 sensor and seven slots. A ferrous disk essentially turns your magnet off inbetween slots. You may be able to use 28 slots and 4 coils if you get really fancy. As for fitting things into a scale magneto, as I mentioned earlier, it all depends on your idea of scale. High voltage doesnt respect scale at all.

 

[Rayanth]

No, you only use 1 sensor and seven slots. A ferrous disk essentially turns your magnet off inbetween slots. You may be able to use 28 slots and 4 coils if you get really fancy. As for fitting things into a scale magneto, as I mentioned earlier, it all depends on your idea of scale. High voltage doesnt respect scale at all.

Did I really type 7? I blame my phone and its microscopic keyboard I meant one, really I did.

I do wonder if I could use four sensors, though, and just one disc. Seems if I offset the sensors jet right, that would have the same effect. Each driving its own 'pic'...

As for the scale magneto thing, I wasn't actually suggesting a magneto, just reshaping the circuit board to fit in a housing that looks like the four fullscale magnetos, to maintain the visual effect.

-Ryan

 

[Ctmouse]

I'm in need of some direction as I need a new ignition System for this mini Tractor Motor it has a set of points Condenser and a coil from a lawn mower (the coil is bad) this was used to provide spark to a NKG CM 6 Plug I was using a small 12 volt battery for the coil Which I believe I fried the coil! I'm in the begining stages trying to bring this back to Life.
This was built my an uncle way back in the day and has sat in the basement for decades now. I really Don't have much history on it other than it did run back then. after some research it appears to be a version of a HUMBLEY Oil Pull tractor. I am hoping to replace the ignition and get it to run again. I believe this would be just an air cooled motor that has forward and reverse capabilities. ant help on this project or suggestions would be greatly appreciated. Not sure how to get this posted in the correct forum! sorry I will keep trying

thx Rick

 

[kchmn]

I'm in need of some direction as I need a new ignition System for this mini Tractor Motor it has a set of points Condenser and a coil from a lawn mower (the coil is bad) this was used to provide spark to a NKG CM 6 Plug I was using a small 12 volt battery for the coil Which I believe I fried the coil! I'm in the begining stages trying to bring this back to Life.
This was built my an uncle way back in the day and has sat in the basement for decades now. I really Don't have much history on it other than it did run back then. after some research it appears to be a version of a HUMBLEY Oil Pull tractor. I am hoping to replace the ignition and get it to run again. I believe this would be just an air cooled motor that has forward and reverse capabilities. ant help on this project or suggestions would be greatly appreciated. Not sure how to get this posted in the correct forum! sorry I will keep trying

thx RickView attachment 109119View attachment 109120View attachment 109121

Rick, That would be a Rumley Oil Pull, They were a well known manufacturer back in the 1920's I believe they were bought out by Allis Chalmers. That should be a water cooled engine from the looks of it, at least I can't see any cooling fins on the cylinder, and the square box on the front served as a radiator. Nice model, I hope you can get it running. Kirk

 

[WOB]

So, Rick, what is your question? If you want to retain the traditional points to trigger a new ignition system, the S/S CDI unit will work well. Many people opt to use a Hall effect trigger on a new engine, but since you already have a set of points it makes sense to keep them. The S/S unit is easy to wire up and is compact. I have used it on a couple of engines with satisfaction.

WOB

 

[Ctmouse]

Rick, That would be a Rumley Oil Pull, They were a well known manufacturer back in the 1920's I believe they were bought out by Allis Chalmers. That should be a water cooled engine from the looks of it, at least I can't see any cooling fins on the cylinder, and the square box on the front served as a radiator. Nice model, I hope you can get it running. Kirk

Rick, That would be a Rumley Oil Pull, They were a well known manufacturer back in the 1920's I believe they were bought out by Allis Chalmers. That should be a water cooled engine from the looks of it, at least I can't see any cooling fins on the cylinder, and the square box on the front served as a radiator. Nice model, I hope you can get it running. Kirk

Yes it water cooled just took it all apart and cleaned the little vane pump. thx for the info! Rick