049 Glowplug voltage

I've always read that for the Cox 1.5 Volt glowhead, not to use any more voltage than that. Some have better precise power supply for starting equipment and can push that somewhat, but for me, to be on the conservative side, I've never pushed my luck above 1.5 V.

If you have a power panel with a rheostat, you can measure across the plug until you attain 1.5 V, then that is your setting for that particular plug.

The drop from 3.0 V to 2.28 V with load applied could be due to the condition of your dry cells. If they are worn, the load voltage will also correspondingly drop.

When I was working as student help in the Geophysics lab, I'd be unsoldering 1.5 V Duracell D battery sets from the Ocean Bottom Seismometer electronics package. (They used direct soldering wires to the batteries instead of a battery holder, to eliminate unreliability of the connections in a marine environment.)

I was unsoldering the old pack, then resoldering in a new pack. It had roughly may be a dozen and a half batteries wired together in series, tapped in certain locations for lesser voltages.

These would sit on the bottom of the ocean floor in maybe 100 or so feet of water, to eliminate noise from vehicular traffic, etc. A down timer would trigger the NASA acquired explosive bolts also used to separate staged rockets, release a 100 lb. lead weight so package would float to the surface. A pressure switch would detect when package had surfaced, had a homing transmitter giving the retrieval ship a 4 hour window to find the equipment. (Any longer, ocean currents may carry it away from practical retrieval.) It had a precision shop built digital timer that would trigger the sequence, which could be up to 3 weeks.

Got permission from my supervisor to salvage and take home the good used cells. I'd measure the cells, those over 1.4+ Volts I salvaged, brought may be a dozen in my school backpack. Then made me a custom glow igniter with say, 7 of these cells in parallel. Set would last me the entire year.

That battery pack would ignite my .020 T/F Roaring 20 and Ace Littlest Stick Pee Wees, my .049 Golden Bee powered Q-Tee, and my OS Max .10R/C powered Schoolmaster through my college years. Good way to blow off steam after study sessions at the U.

Back to 2 cells, after that experience, the 2 seems to Peter out a lot quicker.

Jellis,
Can you post a picture of your glow plug? You may be reading such a voltage drop after loading down your batteries across a dirty glowhead, dirty glow clips, and mediocre wiring. These potential "failures" may have saved your plug. Are you checking the operating voltage by checking with the multimeter in parallel, or series? The multimeter needs to be in series to check your operating voltage.

Please check the glowhead's resistance and let us know what it is. I can measure one of mine tonight. From there, check how clean your clip contacts are. If you are using a typical Cox plug, the surface that normally sits in the head (or between find) needs to be shiny/clean. The part that snaps on the stud also needs to be clean. The wires are normally crimped, and the old crimps are normally corroded now. While the multimeter may show low resistance across each lead, the multimeter doesn't show resistance under load. I recommend not trying to light the plug with anything over 1.5.volts. Don't press your luck...no batteries in series.

I've gone to using a different kind of clip since returning to the hobby several years ago. I use standard multi-strand two conductor 18 gauge lamp cord not to exceed 2.5.feet. Four D-cells in parallel will light a Cox plug with no problem. My four were racked in a simple wooden box. My next flight day will be RCATS-powered.

Shoot me a PM...I may have a good solution for you. Christmas is just around the corner.

It is quite normal with old batteries. Use fresh 2 D alkaline cells in parallel.

I use a LiPo battery with DC-DC buck converter. It is cheap in this way:

https://www.coxengineforum.com/t11525-lipo-battery-for-starter#146864

Greetings. Thanks to all for your responses. It was requested that I add additional pictures and I wanted to complete my homework. Confession; when it comes to electrical tech my skill set is quickly exhausted. I attempted to take a resistance reading of the plug. I did this holding the blk pin on the tip and the red pin into the spring. What is the correct method for measuring the plug's resistance? What should the value be? In the 01 picture I'm getting a voltage drop from 1.47 to 0.65 with the clip on the engine and the two D cells in parallel. I hobbled a parallel connection so that might contribute to the drop? I wish I'd seen the battery tray and clip in the CEF Store before today.

Hi Jim,
I got your last PM...sorry for my late response. You should check from the tip to the "body." Try to avoid touching the glow element (spring) directly. If you look at the element, you can sometimes see the spot where it is spot-welded to the head, especially the spiral-wound element. The w-shaped one is spot-welded inside the cavity if I remember correctly...so you may not see the spot-weld.

Then connect your glow clip to the head without batteries, and recheck across the clip through the head. If all is clean and secure, you should see minimal increase in resistance.

This check doesn't check how much current the glowhead will require, just that it is a glowhead that is capable of passing current. If the multimeter shows "open" or "infinity," then the filament is broken and unrepairable. In other words, burned out. This can sometimes be seen just as a dead unfrosted lightbulb's damaged element can be.

Decent multimeters measure flow rate, or amps. Set the multimeter to measure amps and place it in series with your batteries. Once the clip is connected to the glowhead, the meter should show current draw. Not all glowheads or glow.plugs draw the same current, so you really can't go by that rate to call a glowhead good.

The real test is to properly connect a good battery-set to an um-mounted glowhead and look at the filament. It should be glowing brightly. If you have the glowhead on the engine, you may also look for the reflected glow on the top of the Piston when looking into the exhaust port.

I'll try to add more pictures tomorrow. Others may beat me, or describe other checks.

Oh, and another cheap check for your batteries is actually the standard two D-cell flashlight. If you don't get a good bright light from the bulb, those batteries won't do a thing for the glowhead. If the light illuminates brightly and dies in a
few moments, the batteries are soft ...again they won't do squat for your glowhead. This test requires no multimeters and is quite effective.

The resistance (R) of a COX glowplug is around 0.5 Ohm..hence the 1.5 V battery voltage (U) needed to send 3Amps (I) through the glowplug...U=I*R

You already know that, the resistance of coil is higher when it is hot. Only a reminder

Thanks for all the info! This is an awesome forum!

Yep, I frequent Harbor Freight, Harbor Freight is my friend. Being retired and not needing name-brand tools to earn a living, I'm also cheap when it makes sense, there are a few HF pieces in my collections. I'm a better DIY carpenter than DIY Elec Engr. The tools make most jobs better if in the right hands. Gotta go. Time to bake some bread.

Blessed Regards, Jim

Greetings forum. Here's the 21Nov update.

The excellent guidance from the forum recommended 4 D cells, which I intend to pursue. Last week I Amazon'd a holder for 2 D cell batteries so my experimentation proceeds with 2 batteries. I improved my cobbling skills on the wiring connections. Meter is displaying 1.512 volts across the clip. After connecting to the glow plug I'm getting .861 volts and GLOW. I didn't include a picture of resistance measure but it was bouncing .4 to .5 ohms. I'm supposing that 3 or 4 batteries in parallel will increase the amperage going to the glow plug. Suspecting that would make for quicker starting ?

Yep, my other HF meter.   Wanna guess where the batteries came from?  Tinkering will likely take a bit of a break during our Thanksgiving.

I think that you use zinc batteries. Alkaline type is better:

Thanks Levent for the comparison. I checked the HF batteries. They are Alkaline.

Hi Jim,

I wanted to give you a model for just how cheaply one can make a temporary test jig. Up for your consideration is a box that happens to be a smidge larger than 4 D-cells. These batteries just came out of a bundle I bought about two years ago. Please forgive me for the shortcut of not chucking them into a flashlight.

The bar at the positive end of the batteries is simply a file folder stiffener cut long enough to stab out of the box. It was super glued to the box at the right place for the positive "nipples" to contact. The negative side is cheap plywood with paper brads stabbed though, and buss-wire from 16 gauge wire. In short, nothing particularly significant nor semi-permanent. As they say on tv..."this is only a test."

Time for pictures:

Now let's connect a decent glowplug clip. This one is spring-loaded and can be somewhat disagreeable during disconnect. It only takes a bit of practice. The end connecting to the "battery box" is just alligator clips. The wire is long enough to cut the clips off of one should desire...or leave them to take advantage of the next battery box.

So let's do a simple, four batteries-in-parallel test. First up is a new Cox .049 glowhead. Then an old crusty one. One is the W filament (I took these before dinner-I can't remember now). The last one is a standard 1/4" glow plug. Note the strong, bright glow. Also note no multimeters were harmed in the making of these pictures...just four D-cells in parallel. It's worth doing the simple stuff first.

More pics as indicated above:

Very naughty 944-jim.....you do know those W element Cox heads are illegal?....and got Leroy Cox into a lot of trouble-as someone else held the patent (K&B? Allyn?-I think the Fury 049/06/074 heads used the same element style) and Cox hadn't sought permission to manufacture them. They took Cox to court over it-and he lost the case.

I have no idea how many w-element heads Cox made....but they're rare beasts today. AFAIK they were only made in the 049 size....

ChrisM
'ffkiwi'

rsv1cox wrote:

ffkiwi wrote:Very naughty 944-jim.....you do know those W element Cox heads are illegal?....and got Leroy Cox into a lot of trouble-as someone else held the patent (K&B? Allyn?-I think the Fury 049/06/074 heads used the same element style) and Cox hadn't sought permission to manufacture them. They took Cox to court over it-and he lost the case.

I have no idea how many w-element heads Cox made....but they're rare beasts today. AFAIK they were only made in the 049 size....

ChrisM
'ffkiwi'

I did not know that.  I may have to treat mine more lightly.  When I was buying a lot (100+) of Cox .049 engines - If I found one I would remove it and place it in a compartment of my parts box sorta just rolling around.  Might have to put a tissue in there.  

Sounds like there is an opportunity for our entrepreneurs to come up with a 'Cox head caddy' in the same way as you can buy standard glowplug caddys-the type that take 4 or 6 or 8 spare plugs. we've a couple of people here who do 3D printing...and this would be a fairly easy project to turn out..you wouldn't even need to thread the holes-just a snug push fit would suffice... Jason? new222? ...any thoughts?

ChrisM

Chris,
I missed that detail regarding the W plugs. Now I'll have to check all of mine to remove them from circulation! Shoot, it's bad enough I can't fly wherever I choose...now I have to watch out for the Copyright/Patent Officials.

944_Jim wrote:Chris,
I missed that detail regarding the W plugs. Now I'll have to check all of mine to remove them from circulation! Shoot, it's bad enough I can't fly wherever I choose...now I have to watch out for the Copyright/Patent Officials.

Jim-dinna fash yersel....as the Scots would say. Given that the case dates to the 1950s-I'd say the patent has well and truly expired by now.... ....and I don't think anyone else is making W shaped element plugs or glowheads these days to have gone to the effort of renewing the patent.

ChrisM