Home made CDI question
11-10-2010 | 10:55 PM
#1
Thread Starter
Senior Member
Joined: Jan 2009
Posts: 841
Likes: 0
Received 0 Likes
on
0 Posts
From: Salinas,
CA
Home made CDI question
I have been following the CDI thread with great interest. I commend the diligence and persuit of the goal. The journey is a reward in itself, I understand.
Thing is I would like to make an ignition and actually fly it. Another hobby of mine is making radios from scratch so, I know not to grab the hot end of the soldering iron and how to read a schematic. I don't want to buy or wind a miniature coil. The computerized advance seems to be the stumbling block on the Gompy unit. It seems to me that for my level of electronics building experience a mechanical advance would be perfect. I see one company still uses them on their engines. I have found schematics for transistorized ignitions that use miniature coils and hall sensors. I want to take it to the next evolutinary level but not get into a programable advance.
Does anyone know where to find a schematic for making one that uses no coil? It needs to be something that is light enough to use in an airplane. I have hundreds of pounds of electronic compontents of all kinds. I am pretty sure I have what is needed in my "junk box".
Thing is I would like to make an ignition and actually fly it. Another hobby of mine is making radios from scratch so, I know not to grab the hot end of the soldering iron and how to read a schematic. I don't want to buy or wind a miniature coil. The computerized advance seems to be the stumbling block on the Gompy unit. It seems to me that for my level of electronics building experience a mechanical advance would be perfect. I see one company still uses them on their engines. I have found schematics for transistorized ignitions that use miniature coils and hall sensors. I want to take it to the next evolutinary level but not get into a programable advance.
Does anyone know where to find a schematic for making one that uses no coil? It needs to be something that is light enough to use in an airplane. I have hundreds of pounds of electronic compontents of all kinds. I am pretty sure I have what is needed in my "junk box".
11-10-2010 | 11:12 PM
#3
Thread Starter
Senior Member
Joined: Jan 2009
Posts: 841
Likes: 0
Received 0 Likes
on
0 Posts
From: Salinas,
CA
RE: Home made CDI question
Easiar to make too. I have been looking at this site:
http://www.floridaame.org/
look under "Tips and links"
Then choose "ignition tips"
David Kerzel goes through ignition systems in a systematic way at stops at CDI igntions as the next installment. So far he has not gotten to it. I have been hoping he will write it up on the site. I see he did it for the magazine. I am not a subscriber though.
http://www.floridaame.org/
look under "Tips and links"
Then choose "ignition tips"
David Kerzel goes through ignition systems in a systematic way at stops at CDI igntions as the next installment. So far he has not gotten to it. I have been hoping he will write it up on the site. I see he did it for the magazine. I am not a subscriber though.
01-16-2011 | 12:13 AM
#4
Senior Member
RE: Home made CDI question
ORIGINAL: Scota4570
I have been following the CDI thread with great interest. I commend the diligence and persuit of the goal. The journey is a reward in itself, I understand.
Thing is I would like to make an ignition and actually fly it. Another hobby of mine is making radios from scratch so, I know not to grab the hot end of the soldering iron and how to read a schematic. I don't want to buy or wind a miniature coil. The computerized advance seems to be the stumbling block on the Gompy unit. It seems to me that for my level of electronics building experience a mechanical advance would be perfect. I see one company still uses them on their engines. I have found schematics for transistorized ignitions that use miniature coils and hall sensors. I want to take it to the next evolutinary level but not get into a programable advance.
Does anyone know where to find a schematic for making one that uses no coil? It needs to be something that is light enough to use in an airplane. I have hundreds of pounds of electronic compontents of all kinds. I am pretty sure I have what is needed in my ''junk box''.
I have been following the CDI thread with great interest. I commend the diligence and persuit of the goal. The journey is a reward in itself, I understand.
Thing is I would like to make an ignition and actually fly it. Another hobby of mine is making radios from scratch so, I know not to grab the hot end of the soldering iron and how to read a schematic. I don't want to buy or wind a miniature coil. The computerized advance seems to be the stumbling block on the Gompy unit. It seems to me that for my level of electronics building experience a mechanical advance would be perfect. I see one company still uses them on their engines. I have found schematics for transistorized ignitions that use miniature coils and hall sensors. I want to take it to the next evolutinary level but not get into a programable advance.
Does anyone know where to find a schematic for making one that uses no coil? It needs to be something that is light enough to use in an airplane. I have hundreds of pounds of electronic compontents of all kinds. I am pretty sure I have what is needed in my ''junk box''.
BCCHI
01-16-2011 | 07:50 AM
#5
My Feedback: (8)
Joined: Feb 2009
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
From: Washington, PA
RE: Home made CDI question
Bill is correct, you need a high voltage coil to make a spark. If flying is more important than building then go buy an RCexl ignition. You can't build and troub leshoot cheaper than that. If you derive a lot of satisfaction from building, then have at it.
Attached is a photo of a mechanical advance as well as photos of a schematic that has been published on another forum for an ignition that does work.
Attached is a photo of a mechanical advance as well as photos of a schematic that has been published on another forum for an ignition that does work.
01-16-2011 | 08:10 AM
#6
RE: Home made CDI question
Use a Piezoelectric Crystal to generate the high voltage. You do not even need any other electronics, just rig a device to strike the crystal at the time you need the spark. I think Briggs or someone used/tried the concept for small engines a long time ago. The advance would have to be mechanical. As Yogi said: "You could look it up". Good luck.
Sincerely, Richard
Sincerely, Richard
01-16-2011 | 08:21 AM
#7
Senior Member
Joined: Nov 2005
Posts: 805
Likes: 0
Received 0 Likes
on
0 Posts
From: Hamburg,
PA
RE: Home made CDI question
Here's the picture of my ignition that I have been building for 30 years..very reliable..can be used with a timer board or mechanical advance as you wish.
John
John
01-16-2011 | 08:33 AM
#8
RE: Home made CDI question
ORIGINAL: gr8flyer55
Here's the picture of my ignition that I have been building for 30 years..very reliable..can be used with a timer board or mechanical advance as you wish.
John
Here's the picture of my ignition that I have been building for 30 years..very reliable..can be used with a timer board or mechanical advance as you wish.
John
Thanks.
Sincerely, richard
02-10-2011 | 08:56 PM
#9
Member
Joined: Mar 2006
Posts: 47
Likes: 0
Received 0 Likes
on
0 Posts
From: Canon City,
CO
RE: Home made CDI question
You need a coil for a CDI ignition system (actually 2 coils). The easy way to make a toroid coil is to use a 2 part coil form with a plastic bobbin. These are commonly used by ham radio builders. The coil cores are very cheap, and very easy to wind. Amidon Associates is a common supplier. Check on line to see if they still sell them. If not, there are other companies that supply them.
02-11-2011 | 04:55 PM
#10
Thread Starter
Senior Member
Joined: Jan 2009
Posts: 841
Likes: 0
Received 0 Likes
on
0 Posts
From: Salinas,
CA
RE: Home made CDI question
What is the size and mix of the coil form specified. I have bunches of them but I would have to cross refrence. When winding the coil do you lay one layer on top of the previous or is some of it done biffilar? Is there fish paper in between if they are layered? What order to the layers?
02-11-2011 | 08:39 PM
#13
RE: Home made CDI question
John, that is a pretty neat set-up. I like the Lord mounts too. I was always going to try a set of lord mounts bu have not. Did they work good? Looks like you are handy, and having fun creating with your mind & hands. Good going! BestRegards Capt,n
02-11-2011 | 08:57 PM
#14
Senior Member
Joined: Nov 2005
Posts: 805
Likes: 0
Received 0 Likes
on
0 Posts
From: Hamburg,
PA
RE: Home made CDI question
The Lord mounts work excellent for me. I've had some real shakers in my day that would have torn an airframe apart..added the mounts and that solved the problem. You really have to use locktite on all nuts and bolts though for insurance! Same principle as Chip Hyde's engine mounts..rubber isolators. The DuBro units with rubber also work if you have a beam mount type engine. These weed eater and chainsaw conversions shake a bit if you remove the over-balanced flywheel and magneto in favor of a CDI system.
I have quite a few other small conversions that worked out well. My last one was a small Shindaiwa weed eater engine..still not sure of the size but it had double rings and high compression for it's size. Ran it with a 16-10 prop and got a little over 7,000 rpm at full advance of 28 degrees with my CDI. Good enough to fly my 60 sized Big Stik. 7-1/2 lbs. all up weight. Should give pretty good vertical.
John
I have quite a few other small conversions that worked out well. My last one was a small Shindaiwa weed eater engine..still not sure of the size but it had double rings and high compression for it's size. Ran it with a 16-10 prop and got a little over 7,000 rpm at full advance of 28 degrees with my CDI. Good enough to fly my 60 sized Big Stik. 7-1/2 lbs. all up weight. Should give pretty good vertical.
John
02-12-2011 | 04:38 PM
#15
RE: Home made CDI question
ORIGINAL: gr8flyer55
If you meant my cdi system, here's a photo of it connected to a Cox 1.4 cu.inch chainsaw conversion I did.
John
If you meant my cdi system, here's a photo of it connected to a Cox 1.4 cu.inch chainsaw conversion I did.
John
I have one of the Cox Rhino 1.4 engines like you have converted. Mine came to me with a spark plug to glow plug adapter. I was going to try gas-glow, but may now use the RCEXL ECDI sytem I have and run it spark ignition with gasoline. Have you had to rebuild the carb, and are parts available and from whom?
I need a hub/prop adapter. Where did you get the one you have?
What performance figures are you getting from the Cox/Rhino?
Thanks.
Sincerely, Richard
02-13-2011 | 07:11 PM
#16
Senior Member
Joined: Nov 2005
Posts: 805
Likes: 0
Received 0 Likes
on
0 Posts
From: Hamburg,
PA
RE: Home made CDI question
I made a 4 bolt carb adapter for it and put a small Walbro on it
I only have a 16-10 Zinger on it and running it very rich I am getting around 6500 rpm..more when I lean it out I am sure. It does need a bigger prop though. Had another just like it on a Nosen Citabria and it had an 18-6 and flew well, plenty of power for a 12 lb. airplane.
I also made the prop adapter for it for the 1/2" shaft with a 10-32 retaining screw and key in the slot and a setscrew. Worked well enough to run it so far. Magnet imbedded in the back face for the Hall Effect sensor.
John
I only have a 16-10 Zinger on it and running it very rich I am getting around 6500 rpm..more when I lean it out I am sure. It does need a bigger prop though. Had another just like it on a Nosen Citabria and it had an 18-6 and flew well, plenty of power for a 12 lb. airplane.
I also made the prop adapter for it for the 1/2" shaft with a 10-32 retaining screw and key in the slot and a setscrew. Worked well enough to run it so far. Magnet imbedded in the back face for the Hall Effect sensor.
John
02-13-2011 | 07:24 PM
#17
Senior Member
Joined: Nov 2005
Posts: 805
Likes: 0
Received 0 Likes
on
0 Posts
From: Hamburg,
PA
RE: Home made CDI question
The original plastic carb has small reeds inside it for the pump and inlet areas.. They are actually the exact same thing as on a Cox .o49 reed valve intake system. Kind of star shaped brass. If yours are corroded as many of them were, there ya go..replacements are available from hobby shops. Make your own gaskets.. Orignally mine had the plastic carb with aircleaner, but it was cracked and not serviceable, so I used a Walbro on it.
The engines rattle alot, due to the extra crank extention they have..lots of end play..didn't hurt a thing however since it runs fine for me. I did use Yamabond to secure the rear seal though since must have shrank due to heat and age..hasn't leaked yet. Make sure the 6 bolts for the cylinder head are kept tight or the gasket will blow.
John
The engines rattle alot, due to the extra crank extention they have..lots of end play..didn't hurt a thing however since it runs fine for me. I did use Yamabond to secure the rear seal though since must have shrank due to heat and age..hasn't leaked yet. Make sure the 6 bolts for the cylinder head are kept tight or the gasket will blow.
John
