RE: Scratch Built Ignition???
 

The CH Ignition only has the automatic advance you speak of if you buy it for extra. The small weekwhacker conversions they sell don't have automatic advance as it is not needed. These engines are small and low compression and by setting them at a full advance of about 28 degrees they still start without kickback and idle slowly enough. The automatic advance is recommended for larger and/or higher compression engines.

Take care,
AV8TOR

RE: Scratch Built Ignition???
 

Can somebody post a few photos of the Tm6 ignition circut ? Thanks Capt,n

RE: Scratch Built Ignition???
 

Hi CaptinJohn,

The JH Website shows pictures of the circuit board, components, and coils at:

URL> jerry-howell.com/ignition.htm

Bruce

RE: Scratch Built Ignition???
 

Unfortunately, www.jerry-howell.com is not currently available (I hope it's only temporary). [sm=crying.gif]

The good news is I have another site bookmarked with circuit diagrams of the Tim4, Tim6, and Tim7 ignition circuits, based upon 12V. By changing the component values, it should work with lower battery voltages. This person is using them for a homemade radial engine.

By the way, he also documents how he built his own spot welder... Scary stuff [sm=stupid.gif]

RE: Scratch Built Ignition???
 

Care to share the link?

RE: Scratch Built Ignition???
 

Hi strato911,

I had the link up around 6:30 PM but can't raise it now. It must be a temporary Problem.

Bruce

RE: Scratch Built Ignition???
 

[link]http://www.5bears.com[/link] will get you the schematics and a whole bunch of other neat stuff.

dave

RE: Scratch Built Ignition???
 

Sorry, I thought I had. I should have re-read my post before clicking "OK"

Zagnut has already posted it for me. http://www.5bears.com/tim4.htm has the ignition circuits.

_____________________________
I try to learn from other people's mistakes...
I won't live long enough to make them all myself.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯
Dennis aka Strato911
MAAC 43408

RE: Scratch Built Ignition???
 

Just got back from a 3 day trip!!!! Thank you ALL for the return data. I am very interested in scratch buit ignition systems. Keep up the good work. Smooth landings.... Captinjohn

RE: Scratch Built Ignition???
 

I have a copy of of the RCM article and also have an ignition system built from a kit by an outfit called Fuji Max. It was given to me by a friend who is an electronics guru. I have not tried it as yet, but was assured it worked fine. Seems like the only thing that is hard to do is to wind the Toroid coil.

RE: Scratch Built Ignition???
 

My first partner wound the toroid coils, took 2 to 3 hours....Then we bought some, $12.50 each...Then I found some for $6.50..Easier to buy a circuit from C&H...:)
That wimpy little coil in the picture won't last as long as a real one...Weak insulation....They were/are made for about 3 volts, the CD circuits put about 300 into the primary, put out 20,000+, enough to spark over 1/2 inch in dry air, depends on the current draw, somewhere from 150 to over 300 MA.....At some point the spark jumps from the output wire about 1 inch along the coil, looking for a ground....I have seen a bakelite carb insulator with a 1/8 inch deep track burned into it when the owner of the engine grounded the coil to the carb bolt..It's insulated, so the spark just followed the path of least resistance, the bakelite block...Usually the sensor goes out first, but this one didn't..Wish I could find some sensors like that..:)

RE: Scratch Built Ignition???
 

Hi
RCIGN1 would you mind shareing your source for $6.50 coils would be apreciated

RE: Scratch Built Ignition???
 

The $6.50 coils are the toroids, NOT the spark coils...I have about 300 toroids, how many do you want ?
I buy my SPARK coils from C&H......

RE: Scratch Built Ignition???
 

can you explain the diffrence between the two It was my understanding that the torids were being used in the ch type of ingition you now have me very curious I must have gotten in the middle of the conversation

RE: Scratch Built Ignition???
 

The toroid coil is used on the circuit board, along with some other components, to step up the 4.8 volts to somewhere around 300 to zap the spark coil...The circuits used on the other ignition are not CD ignition, and only control the voltage to the Modelectric spark coil..These coils were used about 50 years ago for the spark ignition engines with points...The coils work fine when used as designed, but the insulation won't hold up for long to the 300 volts from a modern CD ignition system....

RE: Scratch Built Ignition???
 

Ok let me see if I have this right the coils like the modeltec work with igntions of the I think its called a keting type like howells but the toroid are used in the cdi much as a capacitor in a points type ingnition would be used I hope I have this in my mind correctly and am explaining myself I'm still trying to get my head around this ign. stuff thanks for your patients RCIGN1

RE: Scratch Built Ignition???
 

The capacitor in a points type ignition, connected across the points, is used to supress the sparks that are made by the points opening and closing..Modelectric coils are made for points ignition where the voltage to the coil is less than 12 volts...I think the insulation is some kind of wax material that doesn't stand up too well..The CD coils are made to take the 300 or so volts from the CD ignition...There is a relatively large capacitor in the final stage of a CD ignition, it takes the 20,000 or so volts from the CD circuit and sends it to the spark coil when the circuit is triggered by the Hall sensor...
I don't quite understand it either, but it works.. :)

RE: Scratch Built Ignition???
 

The Howell type is a Kettering or saturated coil type of ignition. The current flows through the coil (dwell time) and when it is stoped the magnetic field collapses making a spake. High rpm or short dwell time reduced spark out put.
The CDI uses the toroid as part of the dc to dc converter need to charge the HV cap.
The converter takes 4.8v dc and converted it to 300v dc and charges the HV cap with it. When the ignition is triggered the energy in the HV cap is dumped into the coil. The coil sparks as the magnetic field builds up. The coil is acting like a transformer rasing the 300v pulse to a 25,000v pulse making a spark.

RE: Scratch Built Ignition???
 

Yes I'm starting to get a better pic. on this I read the Bob Short book and quite frankly since my stroke this stuff gets in my thick head slowly. In his book Short does in fact use wax in his coils but I wonder if one could sub. very thin epoxy or is this not a good insulator? thanks guys

RE: Scratch Built Ignition???
 

I made my first prototype of a CDI ignition today, from parts cannibalised from an old UPS. It is based on the RCM schematics, but i made some changes to make it fit the components i used.

I put some info/pictures on my web;
[link]http://home.online.no/~jon-mj/cdi_ignition.htm[/link]

Sorry for the crude construction - i will make a PC board when i have the electronic advance system finished.

There is no schematics yet, all i have at this time is a hand-made schematic.
I will put the schematics on the web next week.

RE: Scratch Built Ignition???
 

RCIGN1,
Are your coils already wound or is it just the core? Do you have the specs on the windings if they are already wound? Thanks Ron

RE: Scratch Built Ignition???
 

I have no idea..There are 3 pairs of wires coming out..TKG knows what they are, maybe he'll see this ....

RE: Scratch Built Ignition???
 

if you guys go back to the beggining of this thread you'll find that ANeat posted a link to the rcm construction article of this ignition.

alot of ignitions today use a dc-dc converter wound on a bobbin and double E-core. much easier to do than the toroid and can probably be found ready made. i'll dig for some links to post later.

dave

RE: Scratch Built Ignition???
 

jmj
Hi, I have a Homelite 38 cc converted and running with CDI , I take the HV coil from a Honda XT 600 , the Honda Transalp have the same coil, very ruged construction, tolerate all abuse I can make , short circuits, open circuits, open ground (sparks everywhere, not recomended), very cheap, you can take from a motorcycle repair shop, even the discarded.
You test, it is only three leads to change, new are also cheap.
Good luck
Jose

RE: Scratch Built Ignition???
 

RC no idea what the wind ratios are. Most were custom wound for the special needs.
But one should be close enough to work ina homemade CDI.
Leads are input(primary), output(secondary), feedback.

RE: Scratch Built Ignition???
 

Hey guys:
I have the TIM-6 ignition now mounted on my ryobi. It seems to be working great.
It will hand start very easy. I am going to try to get the engine mounted back in my plane and see how it does in the air. I turned down my flywheel and installed a magnet from CH, it's a little larger magnet ( gives me a larger dwell angle). Set it at 30deg. BTDC. Has anyone tried a 6 volt battery with this system? The 4.8v battery seems to work fine, but was wondering if I would get a stronger spark at 6v.


Sukhoi_One

RE: Scratch Built Ignition???
 

ANY spark that will jump the gap and run the engine is enough..More spark will not make the engine run any better, and migh cause RF interference in the radio....

RE: Scratch Built Ignition???
 

Hey fellas I just found this thread and am wondering if any of these units would work well with a Q35 w/points so i would'nt have to use a pickup coil and magnet.I'm mostly wanting to shed weight off the engine.I'm not afraid to do a little kit building ,soldering,whatever.Any and all help appreciated.[&:]

RE: Scratch Built Ignition???
 

at [link]http://www.5bears.com[/link] you'll find a couple of simple circuits for use with points. theses are for kettering ignition, if you want CDI then the RCM ignition in th beggining of this thread is a good choice


dave

RE: Scratch Built Ignition???
 

Ok Dave thanks alot.BTW whats kettering ign. I know what CDI is and can i use the coil that came with the q35 or do i need a different one.This would also be of interest to me as I also use Ryobi's but I know i would have to trigger them somehow.Thanks again and this is a very interesting and informative thread.[&:]

RE: Scratch Built Ignition???
 

kettering ign is the type used on cars and such, the old Q35 is also this type...the energy for the spark is stored in the big heavy coil instead of a light little capacitor

you most likely can use the old coil, i have done this with old mcculloch coils but even after sawing away the un-needed part of the core they are HEAVY

don't know about the ryobi coil, even if it isn't CDI it will still have all kinds of transistor crap potted into the casing and i doubt you'll be able to hook it up right, i may be wrong though


dave

RE: Scratch Built Ignition???
 

HI: Very good stuff here!! If anyone can post any photos of the systems they are using please do so. This is a good time to do so. One picture is worth a thousand words. Thanks Capt,n

RE: Scratch Built Ignition???
 

Anyone wants another "blue light special" I will sell you a built and tested circuit and a hall sensor and magnet for $35 plus shipping..It takes 200 ma at any speed and will run on 4.8 or 6 volts..I have used these for 16 years and they are very reliable...They are larger than the C&H circuit....You will need a spark coil ..This is the bare circuit only, no box..
Coils are available from C&H, boxes from Radio Shack....I don't recommend Modelelctric coils because of the high voltage input from the CD circuit.....

RE: Scratch Built Ignition???
 

Hey guy's I'm pretty well convinced I'm going to use Jerry Howells TIM 6 kit and Modelectric PE coil on my Q35 with points to trigger it.This should work out fine for me cheap and reliable.I'm merely interested in shedding some weight.Does anyone know how to make a hub to take the place of the flywheel just to strengthen the area where the crank threads end in case of crash.I'm thinking of using a Ryobi flywheel as iI have several spares and the taper appears to be the same.Question is how to cut the center out? Thanks all help much appreciated.[&:]

RE: Scratch Built Ignition???
 

Make a hub that exactly fits the crank diameter and put the threads deeper into the hub....

RE: Scratch Built Ignition???
 

I had one machined from a solid aluminum cylinder.

RE: Scratch Built Ignition???
 

I have taken the center out by drilling multiple holes all around the center, then knocking the center out and dressing it round on a grinder. Sometimes you can also use a hole saw to drill the center out.

Look up my post on "cheap prop hubs".

Take care,

AV8TOR

RE: Scratch Built Ignition???
 

Very cool your gonna think I'm lying but I even wondered if that could be done.I have 3 or so disposable Fwheels so I think I'll try on at least one.Thank you VERY much for that input , now I don't think I'm crazy.[&:]

RE: Scratch Built Ignition???
 

You're welcome.

I converted my first motor (to electronic ignition as well), when I was living in Mexico, and had nothing more than a battery powered Dremel, a file, a hacksaw, and a drill with me! With patience, you can do anything!!

Good luck and have fun,
AV8TOR

RE: Scratch Built Ignition???
 

You got it Dude check out my before and after pics of a plane a buddy of mine crashed on it's 3rd. flite and refused to repair it so he gave it to me.This is the one I'm working on ign. project for BTW I'm going to try JEH system as that Q35 has a very health set of points and I know they last forever with trans. ign. Thanks again[&:]