Author Topic: Multi cylinder ignition systems  (Read 4599 times)

Offline Roger B

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Multi cylinder ignition systems
« on: November 16, 2024, 08:00:50 AM »
Quote
Edit Jo: The following has been extracted from Vixen's Mercedes-Benz W165 Grand Prix engine in 1:3 scale thread so you can discuss multi cylinder ignition systems. Roger's was the first item from Mikes thread:

Small ignition systems are an interesting problem, as well as the voltage withstand you also need an energy store. This is the iron core in an ignition coil or magneto and the capacitor in a CDI system. There will be a limit on how small you can make a coil or magneto as there is a minimum energy is required to ignite the mixture.
« Last Edit: November 16, 2024, 08:13:07 PM by Jo »
Best regards

Roger

Offline BillTodd

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Re: Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #1 on: November 16, 2024, 09:22:42 AM »
I wondered if one could use one of those modern car type plug-cap type ignition coils with appropriate driver?

Offline Vixen

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Re: Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #2 on: November 16, 2024, 10:34:11 AM »
Thank you Roger and Bill,

You are quite correct. There is far more to small ignition systems than just the voltage. If you and our other members wish to start a discussion regarding small ignition systems, I will open a separate topic, which will be easier for everyone to find, rather than hidden with this dedicated engine build log.

Bill, the modern COP (Coil over Plug) ignition system and multiple CDI units were developed to eliminate the need for the spark distributor completely. I am sure modern COP and CDI systems will provide fertile ground for those interested in their development. A separate small ignition system topic would be a better place to discus their design and development

Cheers

Mike
« Last Edit: November 16, 2024, 11:53:54 AM by Vixen »
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Offline petertha

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Re: Re: Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #3 on: November 16, 2024, 06:23:56 PM »
There is far more to small ignition systems than just the voltage. If you and our other members wish to start a discussion regarding small ignition systems, I will open a separate topic, which will be easier for everyone to find, rather than hidden with this dedicated engine build log.

Bill, the modern COP (Coil over Plug) ignition system and multiple CDI units were developed to eliminate the need for the spark distributor completely. I am sure modern COP and CDI systems will provide fertile ground for those interested in their development. A separate small ignition system topic would be a better place to discus their design and development

I would welcome a dedicated post on this subject, specifically (my own selfish interest) distributers in conjunction with CDI. Project examples, do's & don'ts, hall effect triggers, wiring, plugs, ancillaries, advance/retard considerations, supply sources.... Of course coils are another way to go, so a great place to discuss differences. There seems to be more electrical hardware options and/or supplier changes in recent years. I have harvested a few designs & tips from various posts by others with more spark knowledge & practical experience as they come up on specific builds or ignition debugging, but it would be great to consolidate more details & collective wisdom. Special mention to Mike (Vixen) who was kind enough to share some pictures & overview of his CDI/distributer via PM of just such a retrofit. Replicating that for my purposes is on my near term to do list. (Hope you don't mind me showing your nice work as example.)

Offline Vixen

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Re: Multi cylinder ignition systems
« Reply #4 on: November 16, 2024, 10:57:05 PM »
As Jo said in the opening post, we have opened this new topic, titled 'Multi cylinder ignition systems'. : https://www.modelenginemaker.com/index.php/topic,12062.0.html

Here is the place and opportunity for our MEM members to discus anything and everything relation to multi cylinder ignition systems. This can include, but not limited to: magnetic Hall sensors types and configurations, points, ignition coils, CDI ignition, magneto ignition, batteries, spark plugs wires and connectors. Also distributor design and alternatives to the distributor.

Over to you    :thinking: :thinking:
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Sometimes, it can be a long and winding road

Offline BillTodd

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Re: Multi cylinder ignition systems
« Reply #5 on: November 17, 2024, 06:26:24 PM »
Ok, coil on cap  devices.

My thought was that these are reliable , small  and cheap (less than a tenner on eBay) , so could be used as a single coil  for a model engine.

I don't know the exact driving requirements, but it's probably a capacitor discharge circuit , which could be made quite small and efficient.




Offline Jasonb

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Re: Multi cylinder ignition systems
« Reply #6 on: November 17, 2024, 07:06:47 PM »
I've recently bought one of these which are cheap and will work on a couple of AA size batteries. at 60mm long excluding the lugs they are small enough to hide.

https://www.ebay.com/itm/203060489106

Graham playing with his

<a href="https://www.youtube.com/watch?v=3_U38qnyTC0" target="_blank">http://www.youtube.com/watch?v=3_U38qnyTC0</a>

And working on an engine, simple mechanical contact so no need for hall sensors

<a href="https://www.youtube.com/watch?v=lxbC2WvwXA4" target="_blank">http://www.youtube.com/watch?v=lxbC2WvwXA4</a>


Online Jo

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Re: Multi cylinder ignition systems
« Reply #7 on: November 17, 2024, 07:25:44 PM »
If you buy them directly from china they are even cheaper: https://www.aliexpress.com/item/1005007271445496.html

Jo
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Offline Jasonb

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Re: Multi cylinder ignition systems
« Reply #8 on: November 17, 2024, 07:31:09 PM »
Not by much once you have added the delivery and tax, comes out to £6.47
« Last Edit: November 17, 2024, 07:34:53 PM by Jasonb »

Online Jo

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Re: Multi cylinder ignition systems
« Reply #9 on: November 17, 2024, 08:01:13 PM »
I paid £7.16 inc VAT for 2 just now (with 100 crimps I needed for £1.36 to take it over the £8 for the free 8 day delivery). If they don't turn up in 8 days I get £1 off my next order.

Jo
« Last Edit: November 17, 2024, 08:18:12 PM by Jo »
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Offline Admiral_dk

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Re: Multi cylinder ignition systems
« Reply #10 on: November 17, 2024, 08:05:08 PM »
Quote
coil on cap  devices

Bill  - the Devil is in the Details  :LittleDevil:

Most modern Coil on cap devices - actually contains the complete 'Power Section' ....
So you apply +12Vdc., Ground and the 'Firing Signal' from the ECU and  :zap:

The more advanced ones even has a build in surveillance system, that can tell the ECU when all is NOT good, lower the Current through the Primary, if the RPMs are too low - etc. ...!

Oh and I have never heard of them as a CDI system internally ....

Per             :cheers:

Offline Roger B

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Re: Multi cylinder ignition systems
« Reply #11 on: November 18, 2024, 07:28:29 AM »
A lot of modern engine management systems monitor the coil current or voltage to determine if a misfire has taken place.

If my four stoke twin gets too lean it flashes over in the distributor between the rotor arm and the cam.
Best regards

Roger

Offline Vixen

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Re: Multi cylinder ignition systems
« Reply #12 on: November 18, 2024, 04:37:35 PM »
Using a resin printer to make a distributor cap. Some questions and answers




Photos and answers by Bill Todd

a)  What is the proposed plastic material? - Used aboive was elegoo ABS-like resin (there are many types)  . It has a texture very similar to fine car body filler and will harden more with time.

b)  What is the insulation resistance of the proposed material? You did tell me but I cannot now find that piece of information. -Non conductive, breakdown supposed to be about 35kV

c)  Can the printed material be polished, either chemically of mechanically? This may be important to prevent surface tracking.  - I could coat it in liquid resin then cure to give it a shine. It acts like a lacquer when painted on. Or, you can paint.

d)  The inside surface finish is probably more important to prevent surface tracking. I have designed in anti tracking fences on the inside to increase the distance between the cable contacts and the metal case but the internal and external surfaces will still need to be wiped clean regularly.
Mineral oils don't seem to bother it, It does soften with temperature , but doesn't melt. Might be worth looking for a high temperature resin.

e)  Is the print 100% solid or does it contain air voids? 100% solid

f)  Is the printed material easy to drill? Yes and can be threaded - works best with IPA lubricant
« Last Edit: November 19, 2024, 10:33:19 AM by Vixen »
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Offline gbritnell

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Mulit=cylinder ignition systems
« Reply #13 on: November 29, 2024, 01:08:17 AM »
 I know someone started a thread on the subject but I couldn't find it so I'm starting this one. This will be a comprehensive, in depth thread about all the facets of building an ignition for a multi-cylinder ignition system. That being said it will be for an engine of two but in most cases more than two.

 A little back story as to how I got where I am with ignitions. I first started building I.C. engines with casting kits for single cylinder hit and miss engines. This would have been in the mid 70's. All of the engines had a points type of breaker, sometimes a commercial set of points and other times a fabricated breaker. My first adventure into multi cylinder engines was when I designed my inline, OHV, four cylinder engine.
This would have been in the late 70's so there was no internet, or CAD programs, at least not for me. My engine was created 'on the board' with mechanical drawing tools. I had a subscription to Strictly I.C and Live Steam so reading on how others did things was the greatest reference.
 
 The multi-cylinder engines that I saw and read about at that time all had a distributor of some sort and the ignition used breaker points. The Elmer Wall engines and engines from English designers generally had points mounted outside of the distributor body due to their size. Although they worked there was only one engine that I knew of that had points inside the distributor. This was the Challenger V-8 which was marketed by Coles Power Models out of California. With the points being internal that made the distributor oversized in comparison to the scale of the engine but at least it looked more prototypical.

 The criteria for my four cylinder engine was to make a more 'scale' distributor with internal points. I came up with something dimensionally that I thought would work. It became fiddley with the small parts and spring but it worked and is still on the engine today.
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Offline gbritnell

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Re: Mulit=cylinder ignition systems
« Reply #14 on: November 29, 2024, 01:24:25 AM »
 The point arm was made from a piece of electrical panel board material. I don't know what is is called but it was a fiber reinforced phenolic material. The points came from a set of motorcycle ignition points. When I looked at the points I could see what looked like a braze line between the tungsten and point arm so I figures I would just heat it until the fusing material melted and the point would fall off. Wrong! I got it red hot and the tungsten never budged so I cut the end of the point arm off and silver soldered it to a threaded post. One affixed I then ground all the old arm away and ground the point down to the size I needed. You have to remember I had no internet that you could just look up 'tungsten'. Everything had to be made by hand by the best means possible.

 The cap was made from a material that Coles sold for the Holt engine. It was called Garolite. I had bought a piece of it and used it for both the cap and rotor. The wires were sourced from some high voltage lead wire that Radio Shack sold.

 As I move forward with this thread I will present pictures and explanations of all the ignition components I use today.
https://www.mcmaster.com/products/phenolic/shape~rod-and-disc/multipurpose-flame-retardant-garolite-g-10-fr4-rods/
Talent unshared is talent wasted.

 

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