I’M READY FOR MY SCREEN TEST, MR. WEINSTEIN

I’M READY FOR MY SCREEN TEST, MR. WEINSTEIN

6 October 2020

When things go wrong with your CO2 engine’s operation, there is a host of malfunctions or complications that could be at fault. In some cases, the same symptoms may be caused by one of two separate but distinct malfunctions. Let’s face it, troubleshooting a CO2 engine can be a frustrating task.

Generally, these can be broken down to two basic conditions: CO2 [liquid or gas] is going somewhere where it shouldn’t, when it shouldn’t: or CO2 is not going somewhere when it should. It’s this second case I’ll be addressing here ~ the unseen neglected charger screen.

Let’s describe a scenario ~ when you put a fresh CO2 cartridge in your charger for your first flight of the summer.* You poke that charger on the filler for about 60 seconds for a good charge. Removing the charger, you get a good pop, flick the prop and nothing happens – or maybe a little popcorn fart of a run. Now, the most important thing to do is nothing. Light a smoke and think. I can think of a few system problems that may be manifested here. I’ll address some of the others later, but now we’ll focus on the screens.

In the MODELA, GMOT and Brown Jr. chargers there is a brass screen in the plumbing system. Its purpose is to protect the integrity of the engine’s plumbing and to stop metal, corrosion and paint from nicking, scoring and otherwise wearing of the plastic and chromium plated surfaces of the check balls. In one flying season, a scratch on a chrome-plated ball, during all the wide temperature swings from sub-zero to hot day, expanding and contracting that scratch will soon cause a void in the plating and flakes will soon evolve from the void, and be ingested further in the engine, abrading other parts, metal and plastic alike. The screen usually does a suitable job stopping these particles.

The Brown screen is found in the bell portion of the brass filler.
It’s hard to see, especially if it is older and covered with crud. If it’s bright and clean, reassemble the filler. Make sure the filler’s stopper stick or ball can move and not stuck. If you can, unscrew the tank fully from the system and with the charger, shoot a brief blast through the filler to ensure the gas flow is not impeded between the filler and the tank. Why? While not strictly scientific method, CO2 motor troubleshooting is most efficiently accomplished by moving from the known to the unknown.

The MODELA/GMOT style charger on the other hand, has its crap-trap in
the head of the charger. To access it, unscrew fully the head from the charger body. There is a slot across the head, use the GMOT charger wrench, if you have one, to unscrew the retainer nut. Pull out the rubber neck seal and piercing needle and voila! there it is. Unlike the Brown screen which is a single
circle of brass screen, the GMOT style is a screen sandwich with the “buns” being two 9mm circles of brass screen with a similar diameter section of some fibrous material.

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I have seen many Modela and GMOT spares kits, but never one including this piece. (If I was to try to replace this material, I would start with some sort of synthetic material used for air filtration. Cotton or wool I believe would be more prone to retain moisture.) Maybe, and this is just speculation, it might help diffuse any liquid CO2 before it heads down to the cylinder. Maybe only Dr. Modela knows for sure. Like the Brown, clean or verify it’s clean, reassemble and make some sort of gas flow check.

So here we are. We don’t know why our motor is misbehaving, but we at least know it’s on the engine side of the screen

*Usually you neglect to clean, dry and oil and wrap your engines in paper for the winter, as most of us, at the time, rarely think the last flying session as the last one of the summer. Time and moisture around copper and brass in an enclosed system is inviting corrosion. Take care of those screens, will ya?

 

JOHNNY GOES BACK TO BLIGHTY THE HARD WAY

ANTICIPATION

  Part of being and crusty old man is always comparing today with “the good old days.” If you’ve followed CO2 Model Flying for more than a short time, you’ll have noticed that this is my true medium. I can’t think of one hobby shop within a hundred miles, and I live between two major cities in that same radius. I remember reading in the 1970’s the old timers decry that something called “mail order” was killing the independent hobby shop businesses. I believe that sort of thinking was just farting in the wind, for if you look through some of the old model airplane magazines of the ‘30s through the ‘50s they were replete with mail-order advertisements. The reality is that those magazines were available not in spite of advertising, but because of the advertising. My first CO2 motor, a Shark, was bought in 1977 from the big Polk’s Hobby ad that used to be in FLYING MODELS. My second was a Telco from the Sig catalog soon after.

  A couple of months back I finally after decades gained that which what I coveted in youth. The Comet Ercoupe kit. I have fondled this kit in multiple hobby shops as a youth, rattling the box to hear the contents as they were sealed in cellophane and I couldn’t see what was in the box. Maybe many, many sessions with a Freudian psychologist would uncover a deep seated socio~sexual fixation with multiple vertical stabilizers. The Skyfarer, yeah, baby, yeah. B-24 Liberator, oh you tease. I blacked out when I saw my first Super-Connie.

  

 I always passed it over that kit, favoring a Guillows Sopwith or Tern Aero kit. Sterling had a line of scale kits that had a gimmick when flying ~ the Nieuport shot rockets and a Piper Cub “crop-dusted” with talcum powder. I just think of all the kit lines available on the shelves at Mini-City, the hobby shop of my youth in Escondido, California ~ kit makers like Sterling, Comet, Peck-Polymers, Jetco, Carl Goldberg, Tern Aero, Hi-Flier, Sig, and of course Guillows. And these are just the kits that appealed to me; Control-line and Radio Control and gliders held no fascination to me. I think Peck and Guillows are the only two left that currently supply kits.

  I finally came across an Ercoupe kit on the EBay that was complete, affordable and didn’t gouge on shipping. So here’s what I got: plans, printwood, sticks, plastic prop and wooden wheels. These were the good old days.

 My first thing was to roll up the plans and next time I went to Lodi, stop by Staples and have them scanned to a flash drive, and print out a full-size copy to build upon. Why scan? Well first and foremost, with these new machines called “personal computers” you can take that PDF file and increase the vertical stabilizer 115%, 120%, whatever you desire. Do you remember doing that manually on graph paper? And then just print out that part of the plan with the enlarged stab. How many scale models wallowed under the rubber torque with a tiny vertical or horizontal stab?  Think Eindecker. Think Spirit of St. Louis. As well, If I wanted to make that 2 foot span Ercoupe into a Peanut scale, enter 46% in the print box and *poof* an 12.96 inch span Ercoupe.

 
 But cutting printwood? I don’t have rheumatoid arthritis (yet) but I do have the kind of arthritis that clenches my fingers into a rigid claw: the same strain of arth-a-ritis Fred Sanford had whenever there was work to be done.

  A couple of years ago I bought a couple of what are known as short-run kits of old obsolete kits long out of manufacture. When it comes to free-flight scale kits they are relatively inexpensive; most are in the 15 -30 range depending on how “long” the kit is for example, stringer stock, molded canopy, decals and the like. But the real clincher is the LASER CUT WOOD.  And there are not one or two people that make and sell these kits, but a lot. Just a simple, cursory Google search turned up around ten; two or three had the very same Comet Ercoupe for around twenty clams. Many of these guys will do custom kits of a kit you can find nowhere else. These are the same as the “Mom & Pop” hobby stores we wax nostalgic for. Service and selection. These are the guys keeping the hobby alive.

  And it goes without saying EBay also keeps this hobby alive. Kits and CO2 motors that haven’t seen a store shelf in this century and now are coming back into the light. We grumble because they are no longer $2.98 but thirty bucks. But we know that’s what the market will bear. For such items it’s the only game in town.

  

  But consider this: a Telco motor from Sig in 1980 cost me $19.95, now you can get an original easily on EBay for a C-note, give or take. Considering 40 years of an average real inflation rate of 3.8% annualized, that 20 bucks in 1980 is pretty damn close to a hundred today. And, mind you, for something that is no longer manufactured.  And someone else stored it for you for forty years.

   

  Again with the computers, another bit of the future that is now is the 3-D printer. Small parts can be accurately made on a printer, and are. And a basic 3-D printer, software included, can usually be had for around a hundred and a half. All those plastic parts, ball seats, pistons, charger seats for our Modelas and Telcos ~ maybe, just maybe could be needed by someone with the requisite skills with a 3-D printer and imagine how many CO2 motors can be resurrected into the twenty-first century.

  

   So in closing, fear not. Yes, the hobby is changing. It will never compete with video games to lure in the youngin’s, it’s an old man’s game. Their generation has no Charles Lindbergh, Eddie Rickenbacker or Wiley Post. The last aerial heroes I had in my youth were that guy who pedaled that man-powered airplane across the English Channel or Matthias Rust. That’s OK. My kids deified a guy named Tony Hawk and now I hear there is a professional video-game player pulling more than a mil a year, and he’s around 20 years old. Start arguing with them about this and then be prepared to defend Junior Samples or Tiny Tim.

  

   So why anticipation? After acknowledging all these modern day boons to model airplaning, it reminded me of a line in that popular song in 1971 that a woman sung about ketchup . . .

“and stay right here, ‘cause these are the good old days”

  

 Ok, I’m tired. I’m taking a nap then heading downtown to shake my Hurri-cane™ at some whippersnappers. Join me, won’t you?