By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Forum House Ad Zone

Ignition coils for small engines

All Topics | Latest Posts

Search for:  in Thread Title in  
<< First < Prev 1 2 3 Next > Last >>
John Wood108/12/2009 14:52:10
avatar
116 forum posts
Many thanks to all for the helpful replies. I am currently using the Hall effect system from Just Engines and a trembler coil (buzz box) from LA Services (Engineers Emporium). Both work very well although I am getting a fatter spark from the trembler. I will try both systems on the Pioneer petrol engine currently under construction.
 
All the best
John
steve williams 310/12/2009 19:51:04
28 forum posts
49 photos
hello ihave just completed a 23 cc 4 stroke single
i used a all small 12 volt motor bike coil a 1/4 42 tpi plur from hemingway and i run a micro switch on the cam runs lovely first engine ive made so very inexperienced but chuffed. struggling now to make a good carb now on third attempt good luck
Mike.H.13/01/2010 11:00:24
5 forum posts
Hi all
   Coils available from automotive sources though functional are often too large for model use . I recently owned a renault Megane which had one coil per cylinder built onto the end if the plugs . The primary on these was 12v and the whole assy was quite small . There may be some mileage in modifying these .
 
   Mike H.  
Mike.H.13/01/2010 11:00:33
5 forum posts
Hi all
   Coils available from automotive sources though functional are often too large for model use . I recently owned a renault Megane which had one coil per cylinder built onto the end if the plugs . The primary on these was 12v and the whole assy was quite small . There may be some mileage in modifying these .
 
   Mike H.  
popsie18/01/2010 17:43:20
2 forum posts
Hi all! Happy New Year!
I have run a  standard car ignition coil by charging the capacitor to 150 - 200 volts and discharging it through the coil. this removes the need for standing current of 3amps from the battery. I'm trying to see if i can run it from scrap disposable camera flash units, as these run on 1.5volt batteries. WATCH THE CAPACITOR IN THESE UNITS as they pack a WALLOP!!!
Stephen Wessel10/07/2010 15:23:37
3 forum posts
Hi. I'm new to this site. Re electronic ignition for small engines I have been using various modules on my 9 cyl rotary with a Hall effect switch. Recently I've been having start up trouble as follows: engine starts as normal,runs up to speed then cuts completely, all lasting about 3 seconds. You can repeat this ad nauseum but engine will never keep going. Frustrating as it has worked beautifully up to recently, flying a Sopwith Pup very realistically.
 
Lack of fuel was an obvious possibility but long since ruled out. Timing & plugs are  correct. I found today that the Hall sensor now doesn't work at all. So my questions are:
 
a) what happens to them to cause failure? 
b) might gradual failure cause the symptoms observed?
c) how do I choose a new one bearing in mind my knowledge of electronics is almost zero?
 
My current module is a Zenoah running off 4.8V
 
Any help much appreciated. Thanks
 
Steve
dixie10/07/2010 17:01:37
31 forum posts
Hi all Try Minimag .co.uk    Now under new management
Bogstandard10/07/2010 19:31:15
263 forum posts
With reference to the above post and Minimag.
 
Julian, the new owner, is resurrecting what Jim Shelley had to give up a few years ago due to ill health. That is the Minimag magneto. 
 
He has now running a prototype low speed magneto for running on hit and miss engines, which, when finished/ will solve most of the coil/battery problems.
 
He is beginning to give out info and taking Q&A in this post.
 
 
Bogs
John Wood122/07/2010 18:51:33
avatar
116 forum posts
Hi Steve, most interested in your use of Hall effect ignition.  The sensors are quite susceptible to flux caused by being too near to the EHT. I always keep the plug lead etc as far from the sensor as possible.
 
Thanks to everyone else for suggestions re coils, I now have a couple which work well sourced as spares from mopeds, not the smallest but my application is not that small so it doesn't matter this time.
 
John
Stephen Wessel22/07/2010 19:20:51
3 forum posts
Hi Dixie and John.
Thanks for the link to Minimag. Julian there was very helpful and sent me a new sensor which is now set up and ready to go. I shall remember your valuable tip John about keeping the HT well away. It could indeed have been a bit close and may have caused the trouble. Engine is now ready for start up so we shall see.
 
Steve
Stub Mandrel22/07/2010 21:23:29
avatar
4318 forum posts
291 photos
1 articles
I'd love to see articles describing how to make a trembler coil and a magneto in ME. Certainly not covered for 10-20 years?
 
I have a small electromagnet (like a single coil transformer 3/4" across with only 'E' laminations). Flashing a magnet across the end gives a 4v p-p output. It's easy to see how a step up coil could make that into a useful spark, but i don't know how.
 
Perhaps there is an old ETW design that could be republished or updated.
 
Neil
Ian S C23/07/2010 13:49:18
avatar
7468 forum posts
230 photos
I notice that Jan Ridders in his latest artical in ME on a simple 2-stroke I?C model engine suggests using a 6 or 12V automotive coil, and don't use the small coils as used on scooters, mopeds and lawn mowers.Ian S C
Richard Parsons23/07/2010 15:07:28
avatar
645 forum posts
33 photos
 

Steve - Hi there. This is an old old problem. Search as you might you will not find the cause EXCEPT for the plug! Get a brand new plug. A plug will work well for hundreds of hours and then fail if it is left for any time. I have had this happen many times with garden tools, scooters, and chain saws all of which had been laid up for some months.

Dick

JasonB23/07/2010 16:18:53
avatar
25215 forum posts
3105 photos
1 articles
Posted by Stub Mandrel on 22/07/2010 21:23:29:
I'd love to see articles describing how to make a trembler coil and a magneto in ME. Certainly not covered for 10-20 years?
 
Modl Engine Builder had an article on making a small Mag complete with drawings, you should be able to get back issues.
 
Jason 
Robert Miller 123/07/2010 23:34:27
19 forum posts
On a somewhat related note, does anyone know how much energy is required to ignite the fuel air charge in a small engine?  With that figure, it shouldn't be too difficult to make an electronic magneto to suit.  The circuit in common use in chainsaws, string trimmers, lawn mowers, and the like is found in the1979 US patent  #4,163,437. 
 
A word to the wise, these things have no protection for the darlington transistor so if there is no spark path, the stored energy goes into blowing up the transistor.  IOW don't pull the starter cord with the spark plug disconnected.
 
Bob
Bogstandard24/07/2010 03:54:45
263 forum posts
Jan Ridders has had great success by the use of piezo units out of gas lighters, no coil, points, electronics etc, just a direct connection to the plug, fired direct from the piezo unit operated by a cam.
 
I don't know how durable they are, but some of his engines run great using them.
 
 
 
Bogs

Stub Mandrel26/07/2010 20:51:54
avatar
4318 forum posts
291 photos
1 articles
Thanks for the link to Jan's site, I've only seen his stuff in ME before. Like Cherry Hill he's someone whose work you can recognise just by the way it looks!
 
I will have to learn Dutch!
 
Neil
Bogstandard26/07/2010 21:37:10
263 forum posts
Neil,
 
Somewhere on each page of Jan's site you will see an 'English' button.
 
Clicking that will allow you to read all.
 
 
Bogs
John Wood115/09/2010 09:47:43
avatar
116 forum posts
I am currently using a coil and condenser from a moped and found that I had to increase the capacitor value by wiring a 220n component across the original in order to get a decent reliable spark, the engine now runs well.
 
John
Andrew Johnston15/09/2010 12:05:38
avatar
7061 forum posts
719 photos
First, to answer a question posed a few posts ago. The best I can find on the internet as to the energy needed to ignite a air/fuel mixture is a few hundred micro-joules. However, most ignition systems generate many orders of magnitude more energy than this, often 100-200 milli-joules. I suspect some this is required for reliable ignition and some is marketing bo@~%ks, particularly in the retrofit automotive area.
 
I am in the slow process of designing my own microprocessor controlled ignition system for my hit 'n' miss engine. So far I've got 6kV out of a home made coil, with a 10:1 secondary: primary turns ratio. One of the goals of the design is to use coils that do not need the more normal 100:1 turns ratio.
 
Two other questions I have been unable to answer are; how is the breakdown voltage of air affected by the air/fuel mix, and how does the breakdown of air vary with increasing pressure. As air pressure decreases the breakdown voltage characteristics are well known; it's called Paschen's law. But I've found nothing about breakdown voltage versus increasing pressure. I do have some contacts in the professional IC engine reseach area, so I guess I'll have to fire up those contacts (pun intended) when I get back to working on my ignition system.
 
Regards,

Andrew
<< First < Prev 1 2 3 Next > Last >>

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Shopping Partners
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate