burtcs
Posts: 456
Joined: 12/20/2004
From: Corvallis,
OR, USA
Status: offline
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It is not my intention to be a wise guy, know it all or a guru. Questions have been raised and remarks made about Texaco - say what? It's time everybody got good at this. In my case it's 1/2 RC Texaco but it could be Free Flight and of course it need not be 1/2A at all. I love this event and the more guys that get with the program the better. Whether you fly competition or just sport fly for duration the same stuff applies.
S.A.M rules dictate what you may or may not use if you're going to compete in SAM events. Since I compete it these S.A.M. events, that good enough for me. Per S.A.M.:
"1/2 A Texaco engines must be Cox reed valve .049's with an integral fuel tank of not over 5.1 cc capacity. These must be basically "stock" engines as typified by the Texaco Jr., or Babe Bee designs. Other Cox reed valve engines such as the Black Widow, or Golden Bee designs are acceptable as long as the larger 8cc tanks are replaced by the 5.1 cc tank, such as found in Cox #1596 conversion kit, containing the smaller tank assembly. The only modifications allowed are: Moving the fuel pickup from the middle to the bottom of the tank, addition of a muffler, and/or addition of a needle valve extension."
This pretty much means no bladders, turbo chargers or CDI ignitions, just Cox stuff. You can put these engines together from bags or cans of parts but the Cox Texaco engine was a good starting point until the fuel capacity was changed (it used to be 8cc).
When I started playing with this event I purchased three new Cox Texaco engines. Two for runners and one for parts. In those days they cost $25.00 US each, this didn't break the bank at the time. They were really shiny and pretty - no junk. These were run/broken in with eight inch (8-4) props.
How were these engines different, I mean just because Cox anodized them a different color and called them Texaco's didn't mean anything, that was just petty marketing. As near as I can tell there is no difference in the crankcase. It was a straight taper type. Early Cox engines had a taper to the crank bearing, later engines had the reinforced straight section for our flush friends with electric starters. This means nothing if you use a starter spring. If you insist on grinding away at your crankcase with an electric starter the straight case would buy a little time before you trash the engine. You can use either type.
It was pretty clear that putting an eight-inch wood prop on would lower the RPM but not all that much. (Please note that 8-inch props come in different flavors, 8-3, 8-4, narrow and wide blade etc, you have to try some) It would load the engine down to about 9000-RPM but that's way to fast. Normal 1/2A fuel was too hot and sport RC fuel was too cold. I discovered the engines would run (kind of) on 10% nitro. I did alot of bench running just observing the engines during and after break in. It was apparent that I needed to retard the ignition if I wanted to swing these large heavy props. This is easy to do - drop the compression (which determines advance or retard). On a Cox reed valve this is done by adding or removing head gaskets. You get one with every glow head, save them you'll need them later.
Like all Cox reed valves these engines would come apart as they ran. Heads would come loose, tanks would come loose, cylinders would come loose, needle valves would unscrew etc. etc. In each case the engine would stop running long before the fuel ran out. I found I could glue these things together with silicon sealer/adhesive. This stuff would gum up the treads and stuff didn't come loose anymore. But, anytime I wanted I could still take stuff apart - pretty cool. Glue the head, cylinder and fuel tank to crankcase screws and pack the sealer into the screw head counter seats also.
Before I started using Silicon sealer, I noticed that every year I had to install a rebuild kit. I needed to do this because there is a small seal between the tank back and the tank that was leaking. This caused erratic engine runs. Replace the seal, the erratic runs stop and the engine runs consistently. Since the tank back no longer comes loose or rattles causing wear on this seal I've stopped tearing my hair out. This did bite me in the backside this year (4th year on the Model) - you decide. I changed it out.
Like all Cox reed valves, the engines were just as likely to start backwards as forwards unless I really spun the prop over to start it This is tough to do when it's mounted on a model. It didn't help that I removed the taper in the cylinder. I started using the ratchet spring starter; this allowed the engine to run in one direction only when it started. This was good but it was clear that the constant contact starter spring was robbing horsepower. I wanted that back. I now use a clip on (snap???) starter spring, not the constant contact ratchet type.
The cylinder had TWO intake ports like the Black Window - no SIP as near as I can tell. It was not a single port design like the Baby Bee. It used a rectangular type Mylar reed valve with the plastic gasket/retainer, this works well. The Tank was off the wall. It has a very small passage from the needle valve to the reed valve. This was smaller than the 5.1cc Baby Bee tank. This was where Cox did their throttling. I wouldn't worry about it, the Baby Bee tank with mylar reed valve works fine.
Cox used a five fin glow head on this engine, it looked cool but the three fin sport heads (the ones we're taking off of the Sure Starts) work just fine - save them. Why they put a five fin glow head on this engine I don't have a clue, somebody must have thought the engines would overheat. They don't. The real problem these engines have is they run cold and die. Retarding the ignition with head gaskets keeps them from overheating - so, you have to warm them back up. To do this I elected to go with the Cox muffler. This allows the engine to stay warm and it also throttles it down a bit. The really cool thing about the muffler is the engine purrs like a kitten. It turns the engine into a flying cartoon - excellent.
Since S.A.M. rules specify Cox reed valve engine, that's what we gotta use. The rules do not say whether it has to be new or worn out. I wear the piston and cylinder out with lapping compound - 800 mesh or finer. I want the piston to protrude from the cylinder about 1/16" with no noticeable drag. The downside is this lets the engine rev up, the upside is that when you lower the RPM with head gaskets you've recovered the lost fuel for the run. Every time the piston goes up and down you've just used up .049 chi of fuel mix, you might not have needed to do this if the model will fly with less RPM. The engine need not prop over in a snappy fashion; I'm using a starter spring to do that.
Reed valve needle valves are a traditional pain in the neck. They are too loose in the threaded needle valve seat and the springs don't hold them in place. At one time the firm (now gone) Kustom Kraftmanship offered a Texaco backplate with a needle valve extension. It also happened to have a collet-locking nut on it and fine threads. I got three Texaco units and one Black Widow backplate. These needles no longer turn in or out from engine vibration. It is unlikely that you can find one of these available now; you'll have to devise your own way of doing this. Silicon tubing and a washer is the first place I'd start. The fine thread is no big deal. Mine tank backs aren't for sale.
The fuel line Cox uses in the tanks is also an issue. It works ok for the first year, then you had to replace it. When they're new they work fine. After about a year they get stiff and they begin to straighten out drawing fuel from the center of the tank - not good. With the current price of rebuild kits, this gets expensive (did I mention I'm also a cheapskate). Use a piece of K&S aluminum tubing to make a new permanately curved fuel line that picks it's fuel from the back of the tank. KK used to sell these, toughen up and make your own. Your engine will now suck down all the fuel in the tank.
With my Texaco engines I have to fly the wing. Fortunately small old timers are pretty nice little wing flyers and gliders. If you're a 3D or SWR kind of guy you may not like this event - you can't fly to prop. This is a Radio Control venture; it's not a steerable freeflight. I once watched a guy latch a new model with his transmitter sitting on his table - the receiver was turned off. I've watched guys holding their transmitters launch their models - the receivers where turned off. A certain Moderator did this, we allowed the flight and he did take first with it. My personal starting drill is to turn the radio gear on, check the control surface functions and then proceed with starting the engine. If they are going to run they start right up, if they don't I stop and find out why.
I think the same issues exist with Cox Pee Wee's and the cure the same. A couple extra head gaskets and a seven inch prop - dreamy. I have an old Super Tiger 23 that I bought in Hong Kong back around '71. I finally began using it but noticed one very unpleasant aspect. It burned up a glow head with every engine run (usually 10%). I tried cold plugs but still no joy. I finally got mad (yea that always helps) an carved out a new 0.015" head gasket with some K&S stock and my trusty jewelers saw. The engine was over compressed with a single 0.015 gasket just right with two with 10% nitro. I had bugs in my teeth after that. I suspect that coming from Hong Kong, Super Tiger may have been thinking FAI fuel. The point of this tale is that there is nothing sacred about the compression ratio - feel free to change it. Cox engines made this easy to do and rember your milage may very.
Regards - Steve B.
Bruce feel free to edit this as you may see fit...
< Message edited by burtcs -- 1/9/2006 6:57:36 PM >
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