Author Topic: Red Wing w/Magneto Ignition  (Read 1846 times)

Offline cwelkie

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Red Wing w/Magneto Ignition
« on: December 26, 2020, 09:20:31 PM »
Sometime back I'd purchased a Red Wing engine casting set as a treat for my retirement (thought I deserved a nice casting set with all the accessories and materials in one box - nice change from scrounging and dumpster/tip diving).  I retired earlier this year and finally good around to starting the Red Wing this past autumn.  All along I wanted to try a magneto ignition system on this engine just to be different and for the challenge.  It certainly helped that others had done this before and all I had to do was incorporate all the improvements they developed and add (I hope) a couple of my own.

In the end, this has been a highly satisfactory experiment.  I had hoped that I could get the engine to run on the magneto straight off but was prepared to revert to a battery ignition to "break-in" the engine.  As it turned out the magneto worked just fine from the start. The design is based on a design initiated by John Vietti and further improved by Don Grimm.  Model Engine Builder magazine issues 6, 10 and 26 have the related articles (I believe back issues are available through the magazine website).

My changes were to increase the rotational speed of the magneto slightly to improve low speed operation by using a smaller drive gear than used by Mr. Grimm.  I also used the original ignition "points" ground contact as an "enable switch" so that spark would only be generated when required.

There are still opportunities for fine-tuning but I'm happy run the engine as-is for awhile to let it break-in before I start further meddling. In the meantime I'll continue work on the cart/trolley I'm building for it.  (oh how I dislike woodwork - especially finishing?)

If you've ever thought about giving a magneto ignition a try perhaps my bit of success will help provide some incentive.
Regards, Charlie

[youtube1]https://youtu.be/Z2MLKbvPozk[/youtube1]

Offline Johnmcc69

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Re: Red Wing w/Magneto Ignition
« Reply #1 on: December 26, 2020, 11:43:35 PM »
A very pretty engine! Nice work!
 :ThumbsUp:
 John

Offline 10KPete

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Re: Red Wing w/Magneto Ignition
« Reply #2 on: December 27, 2020, 05:33:47 AM »
That's a beautiful runner, Charlie!! A few years ago I started looking into mags for a very similar engine but was stopped by unfortunate circumstances.

I'm curious about the mag; did you build it, buy it....?? It sure runs nicely. I don't have access to MEB magazines...

Thanks,
Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline cwelkie

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Re: Red Wing w/Magneto Ignition
« Reply #3 on: December 27, 2020, 03:28:09 PM »
Thanks John and Pete.

I did build the magneto using the information in the above mentioned articles to come up with a composite design.  Two key purchased components are the magnet (diameterically polarized cylinder) and the ignition coil.

Here are the supplier websites I used, respectively:
https://www.amazingmagnets.com/p-283-t550d-5.aspx
http://www.springmillsmfg.com/model-airplaine-ignition-coils.html

Construction used re-worked iron laminations from an old power transformer, stainless steel shaft and ball bearings in an aluminium housing.  Installation required the multi-faceted bracket to hold the magneto in the correct position while providing clearance for the cam lobe and a mount for what became the "enable contact". I cut a 12 tooth drive gear for the magneto shaft that runs on the 48T cam gear.

One of the above mentioned authors (i.e., Don Grimm) Has a website where he has posted research and background information related to magneto operation that may be interesting if so inclined.  It also includes photos of his own magneto and low tension igniter installations on a Red Wing engine:
http://dkgsite.com/


Offline 10KPete

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Re: Red Wing w/Magneto Ignition
« Reply #4 on: December 28, 2020, 05:59:00 AM »
Thanks for posting those links. And that is an amazing magnet! I had no idea one could be polarized that way. No wonder your magneto has such a small profile!

I really need to get back to work on my engine....

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Roger B

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Re: Red Wing w/Magneto Ignition
« Reply #5 on: December 28, 2020, 12:03:59 PM »
Very nicely done  :praise2:  :praise2:  :wine1:

If I understand correctly you are running the magneto shaft at 4 times cam speed (twice crankshaft speed) with the timing cam driven by the cam gear. Did you need to ensure correct phasing of the magnet and the timing cam?
Best regards

Roger

Offline cwelkie

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Re: Red Wing w/Magneto Ignition
« Reply #6 on: December 28, 2020, 04:54:43 PM »
Thanks Roger.  Yes, the mag runs at twice crankshaft speed (four times cam speed). I'm using a delrin gear running on the original cam gear.

There are a number of events that need to be phased or timed:
1. The magneto contact breaker needs to be phased with the "maximum induction" point within the magnetic field. The points need to open just as the rotor passes the point of "highest attraction" between magnetic poles.

2. The magneto contact points open timing then needs to coincide with the engine's need for spark.  On this engine I'm using about 10' BTDC on the compression stroke.  I can set this by turning the magneto shaft within its drive gear and tightening a setscrew.  The key to not change the relationship between the magnetic field and the magneto points once set.

3. The last timing setting (on my Red Wing) is to get the timing of the original contact point set to ground while it overlaps the closing of the magneto contact breaker.  This ground must be made for as long as the magneto points are closed and provides a "mask" for all unwanted sparks due to the increased rotational speed of the magneto.  As an aside, I've had a play at just grounding this contact while the engine was running (i.e., allowed all the extra sparks to occur) with no obvious change.  I know that "wasted spark" systems are used to simplify many ignition systems but was concerned about extraneous sparks other that those at the top of the intake stroke causing problems.  More investigating is required ...

I hope that long-winded description helps.  At the very least it will shed some light on why it is exciting to get the thing to run at all!

Pete -  Yes these magnets make "the impossible" feasible. I should also mention that one of Don Grimm's improvements was to use a "magentic mask" around the magnet to concentrate the field all in an attempt to increase the rate of change and spark.  It is an interesting fabrication of alternating brass and steel segments silver soldered together and then machined into a ring that is "glued" to the outside of the magnet. When located corrected (i.e., NOT "shorting out" the field) it does add to overall efficiency. I've added a couple photos to show the early stages - sadly I didn't take any of the final product or the completed armature.


 

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