Just won a Cox .15 Sportsman

Nice looking Sportsman , I was looking for the video of mine running some years ago but its been removed Anyway it is a nice easy starter and ran good just a test run no plane for it though. I am sure you will enjoy the engine would love to see you get it mounted on a plane and give it a whirl !

It's seems hard to find a Sportsman in decent shape. I have one that is junk, bought years ago. I like the way the Sportsman and Spacehopper look. The .15 must be awfully loud.

Hello friend GallopingGhostler , congratulations on your new acquisition!
I have two Sportsman .15, I bought them separately, each one from their own owners, they are very little used.
I made some modifications, without damaging the original parts, so if you remove the parts you put on, you can return it to its original state.
What I did was adapt the carb from a .30 4 stroke engine, just use the barrel air valve to get control of the rpm and that's how I converted them to RC.
I also made a muffler for one of them, as it is very noisy, it really makes a lot of noise and with the muffler it is a pleasure.
Here I leave some videos.
I have dedicated part of this work to Mr. Dale Kirn, who was the creator of the Stortsman .15 engine.
A shout out to my friend Brad who gave me the idea to put in an air valve for engine control.
P.S. I love your cover photo!! LLLLUUUUPPPPIIIINNNNN

Congrats, George! I'm sure you will have it looking a treat when you get your hands on it. I've always thought the Sportsman had a sleek and fast look to it.

I have one, never run, that likely will stay that way. I expect it will end up in some estate sale for $10.

Thank you all, for the encouragement! Helps me to know I made the right decision to purchase it! More to follow when I receive it.

MauricioB wrote:I have two Sportsman .15, [...] I made some modifications, without damaging the original parts, [...] What I did was adapt the carb from a .30 4 stroke engine, just use the barrel air valve to get control of the rpm and that's how I converted them to RC. I also made a muffler for one of them, [...] Here I leave some videos. I have dedicated part of this work to Mr. Dale Kirn, who was the creator of the Sportsman .15 engine. [...]

Eses videos son muy interesante, también tu obra propria como un mecanico ¡es muy excelente! These videos are very interesting, also your own work as a mechanic is very excellent!

MauricioB wrote:P.S. I love your cover photo!! LLLLUUUUPPPPIIIINNNNN

Lo me gusta mucha la revista de Lúpin porque la ayudame comprender el idioma de español. I really like Lúpin magazine because it helps me to learn the Spanish language. Yo lo leo a menudo. I read it often. También lo dame una razón que reírse. Plus, it gives me a reason to laugh. Tengo muchas gracias cuando en otro foro encontraba esa enlace de red. I am very thankful when in another forum I found that network link.

MauricioB wrote:

Yo veo un ganador potencial para el próximo concurso mensual del motor de Cox. I see a potential winner for the next monthly Cox Engine Contest.

Looks like some fun for sure George!
Thank you Mauricio~

I have snagged two Olympics and 2 Sportsman's - 3 with vintage aftermarket throttle exhausts.
Inner half circle shells with outer throttle sleeve.

Cox .15 aftermarket throttles:




Cox slide throttles.

1/2A Nut wrote:I have snagged two Olympics and 2 Sportsman's - 3 with vintage aftermarket throttle exhausts. Inner half circle shells with outer throttle sleeve. Cox .15 aftermarket throttles:

Brad, love those aftermarket throttle rings, they permit SPI to work effectively yet allow the engine to properly idle. Also, yours have the snap starter, was this aftermarket, too? Too bad Cox discontinued the Sportsman (and Olympic).

I gather that it was a cost cutting measure, the Tee Dee derivative, the Medallion .15 was cheaper to produce since it used the base parts (crankcase, crankshaft, and upper parts with one less bypass) from the Tee Dee with less expensive and simpler machining, simplified venturi system, with at least the same power as the Sportsman.

thank you for your comment.
The Sportsman also has another extra advantage, it can rotate the propeller clockwise or counterclockwise, when experimenting with models and propellers, the engine is a great contribution.
You know, my Sportsman has never been planted, it always runs perfectly, it doesn't need to pressurize the tank, since the suction generated by the crankcase is more than enough in sharp climbs.
I like the Sportsman! ... making the silencer is another great advantage, you can fly it in any club, since the desibeles are allowed and it's nice, I DO NOT DISTURB the marching sound of it.
A few years ago I presented it in the Engine of the Month, but it did not get many votes, I suppose that many people have not used it with all the possibilities that this engine has, I think that if you have a Sportsman .15 soon, you will have an engine with many possibilities of use.
Maybe I'll present it again in the engine of the month, who knows!

here is a model airplane enjoying a Comanche with a Storsman .15...surely it will take many of them back in time.
Although I was born in 1971, I feel that the time from 1958 onwards regarding all these Cox creations, must have been a great encouragement to many enthusiasts, I think it must have been a wonderful time for the hobby and for Cox!

Today It arrived, now have it in my hands. It sort of resembles a rear rotor Tee Dee, if Cox were ever to make one.

It has new like compression indicating that it was probably run, but not much. The plier marks on the prop thrust washer isn't as bad as it appears in the photos. The burrs will clean up nicely with some very gentle filing and rubbing down with Mother's Mag and Aluminum Polish. It resembles a rear intake Tee Dee, does not use SPI, which is interesting. Entonces el silenciador hecho por Marcio estaba práctico porque el motor no tenga SPI. Then the silencer by Maricio was practical as the engine has no SPI.

The top fin on the steel cylinder does show some pliers tooling marks, but not bad also. Some gentle filing of the burrs on the fin and touch up with bluing with clean that up.

Someone did clean and oil it because it shows no Castor drag. The glow head looks new without any clip marks on it.

Regarding loudness, I imagine it will probably be as loud as a Testors .19 Red Head or OK Cub .14/.19. Anyone who flies unmuffled control line aircraft will probably feel comfortable with its sound.

More to come ...

Went to the garage digging in my desk drawer.


I found a Hayes AL-15 long motor mount that fits this Cox .15 Sportsman (el Deportista ). Don't mind the background engine clutter (no necesita preocupar porque lo no importa ).

Just also wanted to mention, @Mike1484 sent me a kit of parts for my Sportsman .15 a few weeks ago.

Parts: Reed Retainer, Reed Valve, Needle Valve & Spring x2, Prop Screw, original muffler and snap spring starter.

The muffler is only missing the circular spring cover, but it would be easy to make something to substitute and restore full muffling capability. Thank you, Mike!

He also sent a photocopy of the Feb. 2023 Model Aviation Magazine cover with a note that it was he and his R/C club that helped the high school kids in the cover photo.

He only asked that I in return, pass the favor along.

Tonight, placed an order for two .15 wrenches from @ExModelEngines.

I'm enjoying this thread George, congratulations on getting a Sportsman and appreciating Mike for helping you out.

When back in the mid seventies I moved from flying to mainly collecting, the Cox Sportsman was one of those "had to haves." I had been dealing with an internet friend Bill Dahlgren Jr. on several engines and he mentioned that he had a Sportsman. Thought you might enjoy reading about it.





The Sportsman. I haven't seen it for years. Either I sold it/gave it away or it has slipped back into the inner sanctum of my collections dark places. The Russians are in the box collecting dust.

Those are really nice letters by your friend, Bill Dahlgren Jr., thanks for sharing them, Bob.

When you mean Internet, aren't you referring to the later years when you were still communicating with Bill? I was communicating with engine and model design guru, Joe Wagner in the late 1990's to early 2000's by E-mail. He had an Internet PDF small engines and airplanes newsletter that he'd compile from various people E-mailing to him their experiences. Maintained a downloadable FTP archive of these newsletters. (How many remember, File Transfer Protocol?)

In the late 1980's to early 1990's, I was still working bulletin boards on a 1200 Baud (120 characters a second) modem. A bit earlier, was using a Radio Shack Color Computer II in 1986 and working bulletin boards on a 300 Baud (30 characters a second) modem. Then upgraded to a used CP/M-80 Xerox business computer, after to an IBM/XT then AT clone. Had IBM mainframe E-mail by remote terminal at work. The go-to software office suite then was Wordstar 3.0, all text base.

Typewritten 1976, that was a while back, 47 years to be exact. I was still in my rudder only years. Similarly, I have a typewritten letter by William W. (Bill) Winter in the 1980's, may be late 1970's. I've misplaced it, may be in a box in the garage. Then, I had two Jetex 50 engines in their original bubble pack cardboard containers, reminiscient of how they sold things back in the 1960's. With no source for fuel pellets then, I decided to mail both to him as a gift.

He wrote me back a really nice letter, even explaining how he has a blast flying his Buzzard Bombshell. Got it up high enough, caught a thermal and for the next upteen minutes, was soaring with all fuel exhausted, contributing how I can further enjoy the sport. Been promising to post that letter, whenever I come across it again.

Yesterday was kind of quiet in this forum, perhaps because it was the last day the US federal and many state income tax filings were due?

Yes, snail mail and typewriters evolved into internet and keyboards over the years. I first met Bill through a magazine article probably one of the modelers. We traded engines and experiences. Like everything else time overcomes and I haven't heard from him lately.

That's Great George , nothing like goodies to fix one up right ... Way to go Mike ! Bob that's a crazy right there LOL I was reading it as it popped up first w/o reading the header and it thought WTH then went back and seen 1970 DUH ( i havent read it all but first 2 pages )

My first computer crashed taking everything with it, but I saved some of his letters.  Now I save my pictures to memory sticks.

His dealings with the Russians.



And my P-38 just after I finished it and before it got all beat up.  (I sent everybody pictures of my P-38 )

Interesting read, Bob, thanks for sharing. People are people, too bad those your friend were dealing with weren't faithful. Only Russian engines I have now are the Norvels.

At one time, I was thinking about buying a Ural sidecar motorcycle. Now with the embargo with their country, probably support for that motorcycle is nill, unless it is okay to buy parts supplied through others.

"Ural sidecar motorcycle"
you accidentally misspelled it, you forgot the "IN" in the middle.
This is joke a dear friend of mine, practical physicist, ex Russian Army, graduate of Moscow Polytechnic told me. Its true.

I've owned and ridden them. great bikes, if you know what they are and how to use them. 45mph. don't even THINK about going on the freeway.

You don't need to buy parts, everything on it can be repaired with a hammer and some duct tape.
but if you need parts, anything from any year will fit any Ur(in)al - up till fuel injection.
IMZ has been importing them for years, and has a HUGE inventory as well - https://www.imz-ural.com/

Having owned one, if I really really REALLY wanted a sidecar, I'd buy a used, turnkey, ready-to-go BMW outfit. Like the one I built to replace my Ur(in)al
Make sure you get one with Earles front end. It will be faster, stronger, easier to maintain, and you won't constantly be swearing.

Ural is like a boat, the happiest days are the day you buy it, and the day you sell it (at a HUGELY discounted price, cause ya never wanna see it again)

cstatman wrote:"Ural sidecar motorcycle". you accidentally misspelled it, you forgot the "IN" in the middle. This is joke a dear friend of mine, practical physicist, ex Russian Army, graduate of Moscow Polytechnic told me.  Its true...  my Ur(in)al.

OK, missed that last statement. 

cstatman wrote:I've owned and ridden them.  great bikes, if you know what they are and how to use them.  45mph.   don't even THINK about going on the freeway.

Latest versions, they upped CC's to 850?, heard that sweet spot was 55 to 65 MPH (if need be), no more. Lots of 2 lane roads through NM, TX, AZ, CO, UT, KS, OK, etc. (BTDT ) So, one doesn't need to stick to the main highways.  

cstatman wrote:You don't need to buy parts, everything on it can be repaired with a hammer and some duct tape.
but if you need parts, anything from any year will fit any Ur(in)al - up till fuel injection.
IMZ has been importing them for years, and has a HUGE inventory as well - https://www.imz-ural.com/

Oh,   like the H-D's. About 10 years ago, the H-D Museum had extra copies of the 1940's H-D military Army Tech Manual (repair) they were selling for $15 each plus shipping. I bought 2 copies, became birthday presents for those in my then CMA motorcycle chapter that were moving out of the area.

I told them, "This manual should help you repair your H-D motorcycles. The bikes haven't changed much since then and now."
(Interesting trivial fact, soldiers found out that if they didn't lubricate the chains, let them run dry, they lasted longer in the desert dust than lubricating them. Seems the silica sand wreaked havoc with the bearing surfaces of the chain. Grease caused it to retain the sand and grind away at the metal. Also all kidding aside, only reason why I haven't owned an H-D has been the high cost of obtaining, plus they are theft magnets. Helps to own a bike that few want, like my Kawasaki Voyager XII, although still an excellent riding bike. Someone about 10 years ago stole one of the few original H-D's dated at the start of WW1, belonged to someone here in town. )

cstatman wrote:Having owned one, if I really really REALLY wanted a sidecar,  I'd buy a used, turnkey, ready-to-go BMW outfit.  Like the one I built to replace... Make sure you get one with Earles front end.  It will be faster, stronger, easier to maintain, and you won't constantly be swearing.

Oh, almost like buying a modern electric Tesla. (Heard about the cost of replacement battery and a fire trap if battery catches fire with you in it on the highway or gotten into an accident. One European contractor took his and blew it up with dynamite. )

cstatman wrote:Ural is like a boat,  the happiest days are the day you buy it, and the day you sell it (at a HUGELY discounted price, cause ya never wanna see it again)

One of those! Glad to see that my Cox .15 Sportsman isn't one of those boat type engines.