Glowplug question

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Believe it or not, the length of the cord between the glowplug clip and the power supply makes a significant difference too.

Most glow plugs are made for 1.5 VDC. There used to be plugs that were also made for 2.0 VDC, but I haven't heard of them lately.

Average current draw is 1.5 amps. Yes, it varies, with the glow plug from brand to brand, model to model. That is why a varaible voltage is nice and why folks such as Sonic-Tronics still exist.

Ed, NM2K

Don't look for specific values for specific plugs. Test an unknown plug out of the engine first, start at low and turn it up until the whole filament glows a healthy orange but don't go so high it is bright. Then note the setting. If your power supply is current regulated then the leads don't matter. If instead it is a voltage source, then indeed the leads can affect the setting as Ed suggests, and they certainly have a noticable effect on battery driven systems. Wayyyy back I used to start PeeWees and Babe Bees with a 2V lead acid cell, but I had to use a long length of small gauge wire to limit the current. .049 plugs are designed for 1.5V sources. On my power panels, I have consistently observed the setting for Cox plugs is higher than for the 1/4-32 "regular" plugs I use, which would result in the overly bright glow you observed when using that setting for the plug in your OS.

In summary just set your panel so the plug looks right and note the setting, without worrying about the voltage or current ratings. Works for me.

OK, that is kinda what I thought. I use a voltage limited output, in fact it's based on an lm317. I don't have a return wire to sense the voltage at the glow plug, so it doesn't take into account any losses in the wires. However, I'm using 14 guage wire (I think), it's thick enough that an amp or two is not going to make any difference. Guess I need to redesign the circuitry to allow for a lower output. It worked fine with my Fox 15/19 engines, but then I never really noticed how bright the plug glowed.

I hooked it up last night, and it immediately ignited the fuel in the upper cylinder and popped quite nicely out the exhaust port, burning the hair off the back of my hand LOL. Lesson learned - don't hold hand in front of exhaust port when connecting to glow plug.

It'sd quite common now for people to use a single nicad / nimh cell of around

2000 mAh capacity. I don't know what the current draw is but most high capacity nicads supplied for modelling use will be suitable.

Hth,

Those cells have no problem powering a plug because they are only supplying current at about a 0.5 - 1.5C rate which is child's play compared to several C in electric power packs etc.