Airplanes and Rockets' history & copyright Google search American Modeler Air Trails American Aircraft Modeler Young Men Hobbies Aviation Flying Aces Saturday Evening Post Boys' Life Hobby Distributors Amateur Astronomy Celestron CPC 800 Deluxe Engines & Motors Balsa Densities Silkspan Covering Comics Hints & kinks Snoopy Telephone Peanuts Collection Charles Schulz Saturday Evening Post Electronics My Models Model Aircraft Articles Plans Model Boat Articles Plans Model Car Articles Plans Model Train Articles Plans Grandmother Clock 1941 Crosley 03CB Radio Model helicopter articles & plans Crosswords Model Rocket Articles Plans Restoration Projects Photos Peanuts Collection Model Aircraft Articles Plans Sitemap Homepage Hints Amateur Radio Personal Everything from the homepage Miscellaneous Activities Airplanes and Rockets Hero Graphic

Cox Model 789-3, 1½-Volt Starting Battery

Cox Model 789-3, 1½-Volt Starting Battery - Airplanes and RocketsInternal Parts of Cox 1½-Volt Starting Battery - Airplanes and RocketsLong before rechargeable nickel-cadmium (NiCad) and nickel-metal-hydride (NiMH) batteries were used for starting model airplane engines, we used standard primary type (non-rechargeable) 1.5-volt dry cells. In fact, the nominal 1.2-volt-per-cell potential of NiCad and NiMH batteries were barely high enough to sufficiently light the ignition coils in the glow heads and/or glow plugs, which were designed for 1.5 volts. Today's glow plugs work just fine on 1.2 V or 1.5 V.

I have written before about how as a kid on a very small modeling budget, I would often spend a long time flipping the propeller of my Cox .049 engines while using a single, worn-out D-cell battery (usually 'borrowed' from my father's only flashlight). One Christmas my parents got me a field kit that included a can of 25% nitro Cox fuel, a glow head clip, and a starting battery similar to the one shown here. This battery came from eBay along with a plastic model I bought from someone. It is now on display with the rest of the items in my collection of 'stuff' I used to have as a kid. Of course all of my original stuff was destroyed or lost over the years due to poor flying skills or neglect.

You can see in the photo that the Cox model 789-3 starting battery was comprised of three 'D' cells wired in parallel to produce three times the current capacity. If you are not familiar with how a glow plug works and why the glow element doesn't burn out when more current is available, here's why. The element wire it nichrome or some alloy thereof that is very sturdy and able to handle high temperatures. It has what is termed a positive thermal coefficient of resistance, meaning that as the temperature increases, so does the resistance. As long as the voltage supply is not elevated past the designed operating voltage, current draw is limited by the temperature of the element. If fuel on the element decreases its temperature, the resistance decreases and the current, if available, will increase until the element temperature is back to normal. That is why having a power supply with plenty of current capacity is important for getting an engine started even when it is partially flooded. In that way, the glow plug element acts sort of like a self-regulator to keep the voltage constant.

The cardboard box size is 4-0" high by 2-1/2" wide by 1-3/8" deep. External battery connection terminals are not included.

It is ultimately the current through the glow head element that will cause it to burn out (fuse), so increasing the voltage too much can cause enough current to flow to fry it. The more sophisticated field box power panels with built-in glow plug supplies use a pulsed current output to keep the element at a constant temperature.

Those three leaky D cells have been discarded, BTW, but the wires and glow plug clip attachment Fahnestock clips are taped in place for display purposes.

Website visitor George A. wrote to ask for the dimensions of the Cox starting battery box so that he can create one using his printer. He also needed high resolution images of all sides. The photos below show both sides of the flattened box, along with a ruler for scale. The scans have not been edited except to move the terminal clips closer to the box to keep file size down, so edit color and sharpness as you deem fit.

Cox 789-3, 1½-Volt Starting Battery Box, Flattened (side 1) - Airplanes and RocketsCox Model 789-3, 1½-Volt Starting Battery Box, Flattened (side 2) - Airplanes and Rockets

 

 

Posted January 7, 2017

About Airplanes & Rockets

Kirt Blattenberger, Webmaster - Airplanes and Rockets
Kirt Blattenberger
Carpe Diem!
(Seize the Day!)

Even during the busiest times of my life I have endeavored to maintain some form of model building activity. This site has been created to help me chronicle my journey through a lifelong involvement in model aviation, which all began in Mayo, MD. There is a lot of good information and there are lot of pictures throughout the website that you will probably find useful, and might even bring back some old memories from your own days of yore. The website began life around 1996 as an EarthLink screen name of ModelAirplanes, and quickly grew to where more server space ...

Try Using SEARCH to Find
What You Need.
>1,400 Pages Indexed
on Airplanes & Rockets!

Copyright 1996 - 2022
Webmaster:
Kirt Blattenberger
BSEE - KB3UON
Family Websites:
RF Cafe | Equine Kingdom

All trademarks, copyrights, patents, and other rights of ownership to images and
text used on the Airplanes and Rockets website are hereby acknowledged.

height line

Modeling Resources

Academy of Model Aeronautics (AMA) - Airplanes and Rockets
Academy of Model Aeronautics

Tower Hobbies logo - Airplanes and Rockets
Tower Hobbies

Horizon Hobby logo - Airplanes and Rockets
Horizon Hobby

Sig Manufacturing - Airplanes and Rockets
Sig Mfg

Brodak Manufacturing - Airplanes and Rockets
Brodak Mfg