Bob Shores Model Engine Ignition Book

[GreenTwin]

Perhaps I am the last model IC engine builder on earth to discover this book, but I am new to model internal combustion (IC) engines and their ignition systems, and so am just now discovering this great resource, by Bob Shores.

This book clears up a lot of the mysteries surrounding model engine ignitions.
Very helpful for the beginner IC engine builder.

I purchased an original copy of this book.

.

 

[GreenTwin]

I don't know much about Bob Shores, but I ran across this mention of some of his work.


https://craftsmanshipmuseum.com/artisan/bob-shores/

 

[GreenTwin]

I am planning on using the standard (old school) ignition coil, points, condenser, spark plug on the Ball Hopper Monitor engine, and so I was keen to read about what Bob Shores had to say about that.

I was reading along, and then Bob said that the 12VDC (or whatever supply voltage you are using) to the primary side of the ignition coil was DC current, but the secondary side of the ignition coil, which is the wire between the coil and the spark plug, was alternating current.

This sort of made my head spin, and I thought "That can't be correct".

But Bob was indeed correct, and explained that the condenser (which is a capacitive device) and the secondary coil winding set up a resonant condition, and an oscillograph of the coil output is indeed sinusoidal.

Bob mentions it as a resonant circuit/resonant current, and I think think that is probably a more accurate description of the current instead of calling it "alternating current" (not to get hung up on semantics).
I think of "alternating current" as a steady state condition produced by some rotating machine (an alternator), but that is just my slant on AC.

The secondary currrent going to the spark plug is a transient condition, not a continuous "AC-alternating current" condition, if that matters to anyone.

And technically, if you put an oscilloscope on the DC side feeding the coil at 12VDC, you would see that it would probably not be a flat DC line either, but something that is varying with the output of the coil, if you adjusted the sensitivity of the scope.
The DC current would probably rise steeply, and then resonate a bit, before settling down to a flat line, when the circuit was turned on, and maybe as the coil operated.
I think Bob said the coil draws a steady-state current as long as the points are closed, which seems reasonable.
It would probably be fair to say that the 12VDC current is also alternating, using Bob's logic, which is why I don't call transient circuits "alternating".

And Bob talks about the dwell, and how that affect the circuit, and battery life (if you are using batteries).

It is a most interesting book, and explains a lot about model engine ignition circuits.

I am going to try my engine with an old-school coil, points and condenser, and not use a buzz coil.
A buzz coil should not be necessary under any condition, but others disagree, so I will have to build an engine and test that theory.

But according to Bob Shores, you are actually getting a buzzing/arcing action when the points open, and I am sure a slow motion video of a sparking spark plug would show that. It would be a varying arc for a much shorter period of time than a buzz coil.
A buzz coil is just too crude of a method for me to use unless it just becomes absolutely necessary (I don't think it will become necessary).

.

 

[BaronJ]

Hi GreenTwin,

My take on "Kettering" style ignition systems is Bob Shores is right ! If you consider the ringing from the ignition coil, then that is an alternating waveform, even though the initial voltage pulse into the coil is a DC voltage.

 

[GreenTwin]

And if you think about how a transformer works, then if there is momentary ringing in the current on the secondary side of the transformer, then that is going to induce a proportional ringing (alternating current as Bob calls it) in the primary side for a short period of time, which would be absorbed by the battery or power supply.

The duration of the spark at the plug is very short, so I guess the ringing is for milliseconds or less.

Everything in the circuit would be good if the components can withstand the ringing/pulsing.

The secondary winding is no doubt insulated to a high level.

Sometimes ringing like that will momentarily exceed the rating of a device, especially a solid state device, and ruin it.

.

 

[HMEL]

I am planning on using the standard (old school) ignition coil, points, condenser, spark plug on the Ball Hopper Monitor engine, and so I was keen to read about what Bob Shores had to say about that.

I was reading along, and then Bob said that the 12VDC (or whatever supply voltage you are using) to the primary side of the ignition coil was DC current, but the secondary side of the ignition coil, which is the wire between the coil and the spark plug, was alternating current.

This sort of made my head spin, and I thought "That can't be correct".

But Bob was indeed correct, and explained that the condenser (which is a capacitive device) and the secondary coil winding set up a resonant condition, and an oscillograph of the coil output is indeed sinusoidal.

Bob mentions it as a resonant circuit/resonant current, and I think think that is probably a more accurate description of the current instead of calling it "alternating current" (not to get hung up on semantics).
I think of "alternating current" as a steady state condition produced by some rotating machine (an alternator), but that is just my slant on AC.

The secondary currrent going to the spark plug is a transient condition, not a continuous "AC-alternating current" condition, if that matters to anyone.

And technically, if you put an oscilloscope on the DC side feeding the coil at 12VDC, you would see that it would probably not be a flat DC line either, but something that is varying with the output of the coil, if you adjusted the sensitivity of the scope.
The DC current would probably rise steeply, and then resonate a bit, before settling down to a flat line, when the circuit was turned on, and maybe as the coil operated.
I think Bob said the coil draws a steady-state current as long as the points are closed, which seems reasonable.
It would probably be fair to say that the 12VDC current is also alternating, using Bob's logic, which is why I don't call transient circuits "alternating".

And Bob talks about the dwell, and how that affect the circuit, and battery life (if you are using batteries).

It is a most interesting book, and explains a lot about model engine ignition circuits.

I am going to try my engine with an old-school coil, points and condenser, and not use a buzz coil.
A buzz coil should not be necessary under any condition, but others disagree, so I will have to build an engine and test that theory.

But according to Bob Shores, you are actually getting a buzzing/arcing action when the points open, and I am sure a slow motion video of a sparking spark plug would show that. It would be a varying arc for a much shorter period of time than a buzz coil.
A buzz coil is just too crude of a method for me to use unless it just becomes absolutely necessary (I don't think it will become necessary).

.

There was originally a radio transmitter called the spark gap transmitter. It is similar in operation to the ignition systems of engines. A DC current is impressed across a coil and broken by a contact breaking the field. The magnetic field of the coil collapses and induces voltage in the coil. The antenna has capacitance built in and resonance due to the length of the wires and the capacitance which yields radio frequency current. This is an alternating current. However there are multiple of frequencies developed and that was transmitted as a pulse. Spark gap transmitters are no longer allowed because interference in the radio band. An ignition system is similar in design except the coil is designed to yield very high voltages. This is due to the winding's ratios and how the magnetic field is controlled another subject if you will. However for ignition you only need one hot pulse for firing until the engine is ready to fire again. But the physics are still there so resonance will occur but probably at several frequencies for a very short time due to the system impedance. A buzz coil just keeps exciting and discharging the plug as long as the distributor points to it. So the theory is correct just not sure how much is practical to use.

Model engines have a unique problem in that it is difficult to scale the wiring and components as the size is reduced. However it is also difficult to generate the current necessary to support the voltage needed. And I find the solutions by modelers to this problem fascinating.

 

[peterl95124]

I have Bob Shore's book, I have wound some coils, its mostly a fool's errand, the wire is so fine that you will break it, multiple times, you will unwind and start over many times, on the other hand you can buy very small EMGO 24-71532 moped coils that work great. I have one inside the base of my Hansen Diesel (copy, that runs on gas), and a pair of them for my V12. HTH, YMMV, VWPBL.

 

[GreenTwin]

I found the how-to-wind-coils section very interesting too, but there is no way I will try to duplicate a modern coil found on small commercial IC engines.
It is good to know how it is done though.

There are some items that I prefer to purchase, such as gear sets for IC engines.
I have gear cutters, and an indexer, but I don't have much time, and so I purchase gears.
One has to weigh the time available with what one wants to accomplish, and make time-effective choices.

.

 

[GreenTwin]

When they teach you electrical circuit forumulas, generally one assumes that the formulas are "clean", ie" V=I*R*cos theta, end of story.

I had one factory owner call me and say he was having power problems, and that we needed to find out why, since we designed the electrical system.
The power company came out, and put recording meters in two places for a week.
After a week, the power company said "There are no power company problems".
We said "Can we see the captured data?".
They said yes, and showed us a recorded screen graph.

That was an eye opener.
I had never seen so much voltage fluctuation, spiking, etc. in my life, and I realized there is a LOT of noise and spiking going on in a power system.
The Owner said "Ah haaaaaaah, proof that the utility company is causing my electrical problems".
The power company guy said "Wrong, this is normal. We sell you power at X cents per kwh, and guarantee + - 10 voltage swing maximum; so we are well within this criteria".

This was nearly a 1 million sq.ft. facility, so I asked the manager to show me exactly which equipment he was having trouble with.
He showed me a PLC cabinet.
I asked him to show me a PLC cabinet that he was not having trouble with, and that cabinet had a Sola voltage regulator on the 120VAC feeding the PLC.
I asked him "Where is the voltage regulator on the cabinet you are having problems with?"
He said "We did not put one on that cabinet".
I said "Put a voltage regulator on all PLC cabinets, and stop calling me about power distribution problems; you don't have power distribution problems; you have normal voltage swings and voltage drops".

So the mathematical forumulas get you in the ballpark as far as understanding the fundamentals current flow and voltage, but as Bob Shores points out, there may be more than meets the eye going on behind the scenes.

Utility company power distribution systems distribute bulk power, but it is dirty.

A plant power distribution system needs multiple levels of voltage-clamping surge protection, and often need voltage regulators on sensitive electronics.
And VFD's need in input reactor to prevent harmonics being fed back into the power sytem, and an output dv/dt filter, to prevent spiking the motor windings and the motor feeder.

I recall the power company use to superimpose a high frequency signal on their power lines, and use that for communications.
It is surprising all the things you can do with electricity.

Here are the ignition items I purchases for the Ball Hopper Monitor.
I don't like electronic ignition systems because if the electonic module fails, there is no repairing it.
For a car, electronic ignition is the best way.
For a model engine, I will stick with the old-school material.

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[Mike Henry]

Perhaps I am the last model IC engine builder on earth to discover this book, but I am new to model internal combustion (IC) engines and their ignition systems, and so am just now discovering this great resource, by Bob Shores.

This book clears up a lot of the mysteries surrounding model engine ignitions.
Very helpful for the beginner IC engine builder.

.
https://ia601005.us.archive.org/8/i...ion_Coils_and_Magnetos_by_Bob_Shores_text.pdf

Is the book still under copyright, perhaps held by Bob's heirs?

 

[GreenTwin]

I would guess the book is still be under copyright.

It could be a case of nobody left in the family to claim the copyright, in which case I guess that leaves the book in a gray area.
I think the book can be purchased online in printed or pdf format, but I wonder if the seller purchased the copyright ?

I am not sure how one goes about finding out about a given book and its copyright, but going strickly by date, Bob's book is still in copyright.

It is also possible that the heirs allowed it to be open-sourced, since it is posted on a reputable book archive site.

I found one source selling the book online.

I don't mind paying for books, but I would not purchase from some undocumented 3rd party, since they likely would not have proof of copyright ownership.
I have seen many things sold on ebay (books, drawings, etc.) by people who did not own the copyright, and actually contacted ebay about copyright violations.
There response was "If you are not the copyright owner of the material in question, then we don't want to hear from you"; this was in regards to Coles drawings that were being resold by an unauthorized person; and are still being sold that way.

.

 

[BaronJ]

Hi Guys,

As far as I know, Bob made all of his works "Open Source". Not for any commercial use ! Though I do know that there are people selling his drawings.

 

[DKGrimm]

I started my foray into model engine ignition with Bob's book. I gained a great deal of respect for the man and for the work he did. His vast experience and insight let him to kind of an intuitive feel for things. He gives good advice.

But I have found over the years that trying to understand the "why" and "how" of ignition will lead into a very dense jungle of perplexity. The problem is that ignition is primarily a transitory event. It's not DC. It's not AC. It's a transient. It involves all frequencies, from DC to light. For one example, a coil will have a measurable inductance at any given frequency, but it will also have resistance and capacitance, and these all change when measure it at different frequencies. Capacitors, resistors, hookup wire, and even how the wires are routed all have their own stories to tell, and all are interrelated. An ignition system is thousands of times more complicated than it should be, and at best can only be described approximately.

I have spent most of my career as an electrical engineer working on things like switching regulators, radio interference suppression, lightning protection, and stuff like that. I also have spent a good amount of time in my home shop testing and analyzing magnetos, Kettering ignition systems, and Capacitor Discharge (CD) systems. I wish I could say that I have become an expert on the subject, but that would be a lie. I have written four working papers on magnetos and coils with some observations and some speculation on what this all means. They are loaded with EE jargon and may read like a foreign language unless you have a feel for sets of differential equations, but if you read around all that you may find some intuitive sense of what I think is really happening. The whole point of writing these was to invite people to critique my concepts. I really would love to hear from those of you who understand things better than I do. Look for those four papers (along with other irrelevant stuff) at D K Grimm Shop Files.

 

[Mike Henry]

It seems to me that in cases like this it is incumbent upon the community to make a diligent attempt to contact the heirs of copyright holders before publically posting or linking to downloadable versions of copyrighted material, both books and model designs. Conjecture from the Internet doesn't quite cut it. That's just me, though.

 

[GreenTwin]

I tried to locate the model group in Florida that Bob was a member of.
There is no sign of it still existing on the net.
There are no contacts for or about Bob I can find across the net.
If Google can't find Bob's heirs, then chances are they can't be found.

Basic needle in the haystack situation, but I did try to find someone/something, so effort made.

Should someone come forward with a legitimate copyright, I would gladly contribute to them.

I would caution anyone about purchasing Bob's book online, unless proof of copyright ownership is provided by the seller.

.

 

[GreenTwin]

I started my foray into model engine ignition with Bob's book. I gained a great deal of respect for the man and for the work he did. His vast experience and insight let him to kind of an intuitive feel for things. He gives good advice.

But I have found over the years that trying to understand the "why" and "how" of ignition will lead into a very dense jungle of perplexity. The problem is that ignition is primarily a transitory event. It's not DC. It's not AC. It's a transient. It involves all frequencies, from DC to light. For one example, a coil will have a measurable inductance at any given frequency, but it will also have resistance and capacitance, and these all change when measure it at different frequencies. Capacitors, resistors, hookup wire, and even how the wires are routed all have their own stories to tell, and all are interrelated. An ignition system is thousands of times more complicated than it should be, and at best can only be described approximately.

I have spent most of my career as an electrical engineer working on things like switching regulators, radio interference suppression, lightning protection, and stuff like that. I also have spent a good amount of time in my home shop testing and analyzing magnetos, Kettering ignition systems, and Capacitor Discharge (CD) systems. I wish I could say that I have become an expert on the subject, but that would be a lie. I have written four working papers on magnetos and coils with some observations and some speculation on what this all means. They are loaded with EE jargon and may read like a foreign language unless you have a feel for sets of differential equations, but if you read around all that you may find some intuitive sense of what I think is really happening. The whole point of writing these was to invite people to critique my concepts. I really would love to hear from those of you who understand things better than I do. Look for those four papers (along with other irrelevant stuff) at D K Grimm Shop Files.

Don-

Your white papers are an impressive group of work.
Yes, I can read and understand all the differential equations; they forced us to learn that stuff in school, but it was not fun.

I will have to take time to read each one in detail.

People often ask me "Do you sit around and do math (calculus) all day ?", and the answer is "No"; I just do basic addition, subtraction, multiplication, and division. But the thing about knowing calculus is that you can read and understand the forumulas that describe how electical and other equipment work. Math is basically a foreign language; a shorthand language of sorts, and it is not really as complex as it looks once you get a feel for it.

My approach to working with electrical equipment is to use a "black box" approach, when the equipment is complex.
I look at what happens to the inputs and outputs, and the responses under various conditions, and then remember the general functions of devices, and not all the math equations, and not the specifics of every device inside of the equipment such as the exact workings of every pin on a microprocessor.

If I really need to, I can drill down into the specifics of a particular unit/device, such as what I had to do with a large synchronous motor exciter the other day, that was built onto the shaft of a 5,000 hp motor. Lots of discrete components built into the little control package on the end of that exciter, and it all had to be mapped out. The potted electronic parts had to be discovered via the black box method.

It is easy to go down the rabbit hole with electrical stuff.
I tend to stay on the power/controls side of things, and avoid things like field theory and all the minutia of communications signals.

I have always wanted to make a magneto like the ones seen on the old hit-and-miss engines, and that is on my "to-do" list.
Given time, I think I can make one.

Thanks for the multitude of research.
Most fascinating for sure.
I may have more comments after I read your papers.

.

 

[GreenTwin]

This looks like Bob's obit.
Some names of kin listed here.

"Robert Shores" appears to be a pretty common name, with lots of white page listings.

I sent the "Miniature Engineerig Craftsmanship Museum" in Carlsbad CA a message, and asked if they had contact info for Bob's next of kin, or if they had any info about Bob's book copyright.

The museum was in contact with Bob right before his death, and so perhaps they can shed some light on his book, or who may have inherited the rights to it.

One ISBN number I found for Bob's book does not show up in any ISBN search database, so that is puzzling.
I don't see any page from an original copy of Bob's book to verify the number.
Anyone have an original book by Bob that can verify the number?

It would be nice to know the official status of this book, given how important the information in it is to the model engine community.

.​

https://www.legacy.com/us/obituaries/tampabaytimes/name/bobbie-shores-obituary?id=10459187

https://craftsmanshipmuseum.com/artisan/bob-shores/

 

[GreenTwin]

I have purchased an original used hardback copy of Bob Shores book, and so I will be legitimately quoting and referencing from it using the "Fair Use" doctrine.

.

 

[Vietti]

The book is available from modelengineignition

Jerry Howells son. $30

 

[GreenTwin]

But the question was raised "Who owns the copyrights to the book?".

Does modelenginignition own the rights to sell the book ? (or does he have proof that the book was transferred to the public domain by Bob or whoever?)

.