OS-F Glow Plugs

On Fri, 1 Jun 2007 22:03:39 +0100, "Steve W" wrote in :

I don't know the answer.

I use an orange box from Radio South (?) that has the answer built-in. It must look for resistance, because it raises and lowers the current to the plug as needed to burn out too much fuel or to keep from overheating the plug when the fuel flow is OK or lean.

I think some onboard glow lighters do the same kind of thing (McDaniel?).

So there IS an answer. If you insist on building your own circuit, I'd suggest that you do some tests with the OS plugs. Find out the top end by burning one to destruction. Make a note of the color you obtained at the peak. Set your current-control circuit to make it glow less than that.

If you're too cheap to destroy a plug to find the answer, you could probably get close by watching for orange-red. Red-red is probably too cold and white hot is about ready to burn out.

Seems to me that there are field panels that have a similar circuit in them, althouth I've never owned or used any.

Marty

Somehow when you posted this question the link to pictures of the engine got lost :-).

That answer deserves another question! Do you think a 14x7 is a good place to start for a prop on a 15cc four stroke -

It's not finished yet, but the head is almost done and I had to buy a plug to get the thread depth right, then I remembred I couldn't remember how much juice these things ran at.

I will post some pics, I still have to make the piston, rings, connecting rod, camshaft and carburettor. So a bit to do yet.

Steve

Boy, the prop size is going to depend a lot on how fast it's designed to go. I don't have any experience with model four strokes, so I don't know any more than that.

Are you aware of Ron's Model Engineering site?

On Sat, 2 Jun 2007 08:12:30 +0100, "Steve W" wrote in :

Yes.

I used a 14x10 on a YS .91 (15cc) four stroke yesterday. The YS is pumped, regulated, and "supercharged" (sort of), so it is toward the high end of the weight and power spectrum.

Glow plugs are usually lit by ~1.5 volts. I cobbled together a homebrew glow-lighter following an article in a magazine (more or less). I didn't use it long. I went with the Radio South Pro Driver II and haven't regretted the investment at all. It uses a 4.8,

Onboard intelligent glow driver:

Marty

Steve, I have been using glo plugs forwell over 30 years and I don't know for sure how much current they draw, so I'm wondering why you need that info? I use a small nicad battery to lite my plugs sometimes so you know that will provide adequate amps for starting. I also sometimes use a power panel. With a new plug I just turn it down to the minimum and crank it up slowly till the plug glows the right color or, if it is in the engine, until the needle on the power panel approaches green.

On Sat, 2 Jun 2007 16:35:51 -0400, "Ed Smega" wrote in :

I think he's planning to build his own glow-lighter circuit for his handmade 4-stroke engine.

Marty

I built my own glow plug power supply, it runs off a 12V battery and adjusts from 1V to 2V (sometimes you need to crank up the juice if the plug gets fouled, and 1.5V isn't enough to clean it). I use a small 12V lead-acid battery, but it can also connect to a car battery if necessary. The Cox .049 glow plugs draw about 2-3 amps (which is why those miserable battery packs go dead so fast and so often). The OS type glow plugs draw a less current, but it's still a good 1.5-2.5 amps. Different plugs will draw different amounts of current at 1.5V. You can light up a glow plug at about ~1.25V or so. The best way to judge it is to turn up the juice until the plug starts to visibly glow - just nice and red, not too bright. My engines always start with a minimal glow, I only turn up the power higher if the engine gets flooded or the plug fouls.

Yup that's it. I've only ever run two stroke plugs and that was years ago, just wanted to check where the OS-F types where run. Although this engine is an "aero" engine, I've no intent to fly it, notwithstanding the RC bug biting again...According to the designer it will weigh in at 1.4kg and on glow fuel will turn a 14 x 7 at 7500 revs. So not high performance! It can be configured for spark ignition too - but don't intend to go there.

Thanks

Steve

Great I can pick a couple of resistors from that info and use my 12v lead acid as a source. Cheers

What will you do with it?

Best of luck with it!

Stick it in a plane for heaven's sake - that's what it's designed for!

It sounds like a very interesting project. Good luck and have fun!

Good flying, desmobob

You haven't seen my project list! If it turns out well I suppose I could see if the local flying clubs have any interest in bolting into something.

Do you have any pictures of your engine posted anywhere?

I can post a couple of the early bits I've made, I can't get at all the pics just now though. The Engine is known as the "Nemett 15S" published in Model Engineer over the last months.