Glow-plug coil inductance-could it matter?

In a DC system inductance is moot. If it is present it will only slightly delay startup, in this case heating.

Phil

Very interesting! Thanks for your thoughts. I was going to bring some "known to be new" glow plugs to work to see if there was any variance in their inductance.. or their resistance. I don't really know how I would apply any differences noted.. but it would still be interesting if there were a wide-range of variance.

In this case resistance would be a better indicator on glowplug operability. And like Jason mentioned the inductance would be super low.

It’s a no go or go thing. If it tests good than you can run it and see if it stays lit. A glowhead is a simple device and pretty easy to troubleshoot if not working correctly.

Wasn't it platinum or other rare earth metal (iridium, etc.) coating on the nichrome wire heating element responsible for catalytic glow ignition with methanol? I had plugs that checked out electrically OK, but somehow otherwise degraded. An E-Bay buy, a card full of old Swanson red hot standard long plugs worked beautifully out of their bubble pack. Then a week later, were duds, engine sputtered but wouldn't run. Pulled out a new one from the package, had good flights. Then next week, same deal.

Yet, I had an old Enya #30 standard long plug that came with a 1965 Enya .09-III TV, which worked week after week. Been a long time since those plugs were available.

Wouldn't you say there is more to the chemistry / electrical physics to the heating element, than inductance in the nano-Farad range or simple resistivity of the wire?

Maybe someone could give us some history on the invention of the glow plug used for model airplane engines. I would be very interested.

I believe a couple of things may be going on with glow plugs:

Some key people who knew how to manufacture good ones have departed this earth and there's some "skimming" going on in the precious metals departments of the remaining manufacturers.

coxaddict wrote:Maybe someone could give us some history on the invention of the glow plug used for model airplane engines. I would be very interested.

Here is the nickel tour:

Glow plugs in model engines differ from those in full-size diesel engines. Full-size engines only use the glow plug for starting. Model engines use a glow plug as an integral part of the ignition system because of the catalytic effect of the platinum wire, on the methanol-base fuel they are designed to run on.
Glowplug - Wikipedia
Wikipedia › wiki › Glowplug

And the quarter tour:

https://www.craftsmanshipmuseum.com/Arden.htm

Moving right along:

http://www.modelenginenews.org/people/arden.html

ticomareado wrote:I believe a couple of things may be going on with glow plugs:

Some key people who knew how to manufacture good ones have departed this earth and there's some "skimming" going on in the precious metals departments of the remaining manufacturers.

I am willing to bet this is what’s happening, but I bet it’s always been happening. This is the world we live in.

Wow! Thanks for all the info!

Another $0.02

Patinum was used inside the combustion chamber of the engine the Wright Brothers built.  The points were platinum tipped and inside the combustion chamber.

http://www.wright-brothers.org/Information_Desk/Just_the_Facts/Engines_&_Props/1903_Engine.htm

A pretty unique engine in so many ways.

Amd they built it with a drill press and a lathe. No computers or difficult math. Over a workbench. Just a little bit of know how and a little bit of luck.

Huffman Prairie is located on Wright-Patterson AFB. 7yrs I drove by the by their site on the way to work. Only stopped and looked a couple times. Birthplace of aviation.

In a thread here we discussed earlier that even if the glow head tests electrically good it may be subject to ageing and in addition, some deposits from stale fuel components may also diminish the glow.

I have a couple of overused COX heads that still test electrically good but hardly glow even if I turn the Hobbyco starter panel knob to max. The filaments in these heads typically show a grey-ish deposit sitting on them. I am not sure if it was the castor that some folks here said was to be blamed, or other, highly hygroscopic components of the fuel that tend to absorb humidity form air if left in an open bottle too long?

balogh wrote:I have a couple of overused COX heads that still test electrically good but hardly glow even if I turn the Hobbyco starter panel knob to max. The filaments in these heads typically show a grey-ish deposit sitting on them. I am not sure if it was the castor that some folks here said was to be blamed, or other, highly hygroscopic components of the fuel that tend to absorb humidity form air if left in an open bottle too long?

I've observed the same thing with my Cox glow heads after many engine runs. I never put a magnifying glass to it. If I did, might be closer to the truth. I gathered that the nichrome wire material after many heat cycles, was finally breaking down. It did not have the wholesome appearance of a new one, it looks very frail, fragile, easy to break. Sometimes the coil would shrink back towards the top post in the head.

I only used the long gone "bell battery", a very large round single cell 1.5V zinc carbon battery about 10 inches high and 3 inches in diameter.



Yet once they got to that state, they'd blow, the element would break, no longer have conductivity. Back then over 30 years ago, glow heads weren't that expensive, I'd just buy another to replace.

Perhaps it was a breakdown of the heating element from extreme thermal activity?

George those cells were reintroduced a few years back. Now with updated technology the old EN6 cell is known as the EBR40 or HO6 cell. They're about $20.

Ken Cook wrote:George those cells were reintroduced a few years back. Now with updated technology the old EN6 cell is known as the EBR40 or HO6 cell. They're about $20.

Ken, at that cost is a good reason why I wouldn't buy it. Back 30 - 50 years ago, they were readily available everywhere, would last me a good season or two. They had the same Rayovac styled battery at Hobby Shack in Fountain Valley back in the early 1980's. Nowadays even the rechargeable glow igniters with a charger are cheaper.

When I worked at Bekesey Lab at the University of Hawaii as a paid student worker in the mid 1970's, we'd pull the soldered in "D" sized Duracells from their ocean bottom seismometers and throw them away then solder in new. (Batteries would power these instruments, about a dozen and a half were soldered into a battery pack.

Since we were throwing them away, I asked the boss if I could salvage some, which he allowed me. I took the best of the throw aways and take them home. There, I made my own battery pack with about 8 cells soldered in parallel. That battery pack was my ignition source for my glow engines on my RC planes I flew while at the U.

A couple years ago I made my own glow ignition battery with a 4 D-cell battery case from Radio Shack that I modified for mounting cells in parallel. Used that set up a couple seasons, but the cheap plastic broke easily. Now I have a power panel.