Electronic glo-plug ignition?

[petertha]

Found this excerpt in an OS 5 cyl radial manual. They suggest what I assume is pack made from typical Ni cells in parallel to get the 1.2v and (6A-hr) capacity. Equates to 7.2 watt-hrs equivalent, pretty close to our guess..

 

[SmithDoor]

Your right the hobby shop started selling electric start for model engines.
The first electric start in 1960's was AC motor off Cadillac and in some case the end off a cane and a little machining to all fit.
FYI I was about the third one to a electric starter. My father had South bend 9A so just machine out. Used well stem 416 stainless steel. My first time with 416 stainless steel it work harden like glass.

The old timers like using the there finger. Till prop hit finger on cold day and did dance and sound like sailor.
The next time came field they nice new off shelf electric start with motorcycles battery. A new starter from hobby shop in the 1970 was around $100.00.

Today after build my engine I am using a cordless drill and end of cane with matched adapter for drill.

Dave

There's nothing especially original about this proposal-this is what aeromodellers and boat modellers have been using to start their glowplug engines for about the past 50 years...certainly since the 1970s-when electric starters became more common...in the form of the near ubiquitous 'power panel'....which runs off a 12V motorcycle or gel cell rechargeable (or latterly-a 3S Lipo, for those who have them)-providing 12V to the electric starter, 12V or 6V to the electric fuel pump (either integral to the panel, or plugged in as a separate accessory) and a purely nominal '1.5V' to the plug....in fact the plug supply is usually a PWM controlled pulsed 12V supply, since it is current that heats the plug element. Virtually all current panels use this system....and in some you can hear the pulse rate as an audible 'singing' of the panel when in operation. Most employ a manual pot to adjust the pulse rate-coupled with an ammeter, to adjust the average current to that needed by any particular plug to give a good glow...which could be anywhere from 1-1/2 (some of the cheaper beginner 049 engines) up to about 4 (heavy duty or racing plug) amps...there are a few that employ a sensing circuit that automatically adjusts the current to the load-but these tend to be a bit pricier.

As jack620 has posted above-the technology to do this reliably and effectively has been around since the mid 70s-using arduino is a case of 'gilding the lily'...and the early models didn't even use mosfets-just the available power transistors of the day...frequently the old reliable 2N3055.

With the increasing dominance of Lipo batteries in the modelling scene, there are a few newer options that involve voltage regulators rather than a switchmode approach-but these are intended to be used with a single suitable 1S Lipo, dropping the nominal 3.7V (4.2V at full charge!) to a safer 1.5-2V for glowplug lighting....these don't seem to have made big inroads into the glowplug starting market yet....but give them time...

ChrisM

 

[SmithDoor]

You can buy off shelf voltage Regulator up to 5 amps
https://www.jameco.com/z/LM338T-Nat...stable-Positive-Voltage-Regulator_192284.html

Dave

 

[tornitore45]

Peter, if you remember I went through the research of what exactly the plugs voltage and current specification are when I was designing the supply for my Edward 5.
At that time I realized that much info on plug war recirculated but not many had actually measured V and I on plugs.
Since I was going to use an unconventional approach I needed to know what the correct voltage for a plug was.
I was going to use a transformer and power the plugs with AC.
So I powered up a couple of plugs an look at the filament, judging the right color to be a bright red but not quite orange.
The conclusion was that plugs want 1.2 V and take 3 A at that voltage. They are still red at 1.1V and looks like they are about to melt a t 1.5V.
What I found was predictable since from the advent of NiCd, over 50 years ago, the plug manufacturer have optimized the plug to work with NiCd Cells.
NiCd are specified as Nominal 1.35V. Lowest discharge to 1.1 V and maximum charge to 1.5V
When a freshly charged NiCd cell is attached to a plug the voltage is lower that 1.5V since that was the final charge voltage when attached to the charger. The voltage under load drops quickly to about 1.35V so there is no danger to blow the plug with a long exposure to 1.5V

In summary NiCd cell are perfectly matched to glow plug.
The right "heat" plug can keep an engine idling but if someone is inclined to keep the plugs on, a modest current like 1 A may be sufficient to give the extra heat that is lost at idle.

As for linear regulator, they are fine for low power application or when efficiency is not an issue but I think they are the wrong solution for On-Board supply of the plugs. What is the advantage of a higher voltage battery reduced by a linear regulator?

 

[petertha]

Thanks for the refresher Mauro. Just to clarify, there is no advantage at all to higher battery voltage being reduced to glow plug voltage. It makes things more complex. I was just saying if you want to use one of the lithium chemistry cells like polymer or ion, then you are stuck with their nominal output voltage, call it 3.5 - 4.2 range at their lowest cell count 1S. Way too much for an individual glow plug as you say. Therefore if a person wants to go this way then a step down regulator is required between battery & plug. The excerpt from OS 5-cyl radial manual reinforces the easy choice is NiCd pack exactly as you say.

 

[Peter Twissell]

A flow plug is a resistive heater and as such, is to some degree self regulating.
As the coil hearts up, it's resistance increases, limiting the current flow.
I have two glow plug drivers, one of which has a NiCd cell the other has a sealed lead acid cell. Either works with all the plugs I have.

 

[petertha]

Example of a ground start, single plug, glow driver with high capacity lithium battery. It has different modes & features. Yes, its spendy. I'm not advocating, just mentioning.
https://www.rcatsystems.com/store/lithium-glow-driver.html
Another multi-cylinder driver project. All above my head, but maybe some of you electronics savvy types might be interested.
https://www.eevblog.com/forum/proje...-engine/?PHPSESSID=er6m4nh77jij5v7gc4sv7cj980

 

[cdn flyr]

I am surprised no one has mentioned "idle bar" glo plugs that we used in the early days of throttled/exhaust restriced glo engines, when fuel/air mixtures were not well regulated, and engines riched out at idle. The concept was a platinum? bar across the bottom of the plug to retain combustion heat at low speed conditions. The plug was powered only for starting. Too simple?

 

[bluejets]

I am surprised no one has mentioned "idle bar" glo plugs that we used in the early days of throttled/exhaust restriced glo engines, when fuel/air mixtures were not well regulated, and engines riched out at idle. The concept was a platinum? bar across the bottom of the plug to retain combustion heat at low speed conditions. The plug was powered only for starting. Too simple?

Don't think they are made anymore.
That plus worked with loop scavange 2 stroke not 4 stroke.

 

[Chris Murphy]

Your recall is a bit faulty-idle bar plugs were definitely used in the earlier days of two stroke R/C engines-but the bar was simple steel-in some cases welded, in others machined as part of the plug body. The ELEMENT of the glowplug was a platinum coil-or in most cases an alloy of platinum and some of the other pt subgroup elements such as Rhodium and Iridium....the 'idle bar' merely served to protect the element from poorly atomised fuel droplets in the richer mixtures found at idle-which would otherwise have cooled the element excessively. In practice-they worked well-but advances in both engine design and carburettor design in 2-stroke R/C engines have rendered their ongoing use unnecessary. As commented above by bluejets-hard to find these days-except perhaps as n.o.s on ebay or estate sales.....and of doubtful value in a 4-stroke*

* there are some special nature 4-stroke glowplugs still manufactured SPECIFICALLY for 4-stroke R/C engines-such as the OS 'F' plug....which tend to have slightly different shapes at the combustion chamber end compared to a typical 2-stroke plug-and one or two other specialist plugs intended for operation on non methanol fuels. The 4 stroke plugs work well in the appropriate engines-though not all model aero/car/boat 4-stroke R/C engines require them-some run fine on the standard 2-stroke glowplugs.

ChrisM
'ffkiwi'

 

[Bentwings]

Don't think they are made anymore.
That plus worked with loop scavange 2 stroke not 4 stroke.

While I don’t use glow engines any more those kinda went out of favor when the newer fully ported engines became popular I’d buy a whole card of non bar plugs at the hobby shop forvthe hot rod ducted fan engines I used. Idle bar plugs worked on the exhaust throttled engines but the barrel valve engines worked better with the standard plugs I think the idle bar plugs slowed them to run hotter