jayd3

I have some OK Cubs I want to get out and use but don't know to much about them anyone know them well ?

Jay

Pond Skipper

do you have a pic of your selections

combatpigg

My Feedback: (3)

I don't think a OK Cub based project has ever been featured here.
I'd run one on 15% nitro and 20-25% oil.
I'd also try to find the old nylon 6x2 or 6x3 props that might still be around at swap meets, or auction sites.
A plane like a scaled down Lazy Bee built as lightly as possible would be fun to try.

HighPlains

My Feedback: (1)

What size of engine do you have? .049 .074 .099 .19 .29 .35? I think they made a .14 too. Most fuels back then were caster oil based with various amounts of nitro up to about 25%. A 1/2 pt. of fuel cost 45 cents with a gallon going for a whopping $4.50 from an ad from 1959.

jayd3

I want a park flyer if I may still use that term ? seem AMA now defines a park flyer as electric only ? What's with that ?
I have a few OK cubs from .024 to .099 reed and front intake. I'm thinking a nostalgic old timer look ? HAl Debolts Live wire Kitten (which I built one of back in the day but had no money for radio or engine) was made for an Atwood .049 but it was a bit heavy I think and not so pretty.
Someone has taken up the OK engine line they have a very small web site with very little info, I ordered a catalog, will let you all know what I get

Jay

049flyer

My Feedback: (18)

Seen lots of OK Cubs. Owned a few OK Cubs. Never seen one run. Better have a backup engine.

aspeed

I ordered a few quite a while ago. I think I got 4 or so. Two worked, the others only barely ran off a prime. The ones that worked were about the same power as a Baby Bee. Really not bad for the year they were designed. When I bought them, the ad did warn that they were for display, no so much for running. It may be the same company as is selling them now. I have one on this plane. I am not sure if it is a running one, I did fly it with the Babe Bee IIRC.

gcb

I have not had trouble running Cubs. You need to use ~20% lube, 15%-25% nitro. They have a low compression ratio so 25% is good.

You may need to add taper to the needle. Some of them have a very blunt needle that goes from slobbering rich to lean in less than a turn. I just use a file to taper the needle some.

I have various .049 models, .074's, .09's, a .14 and a .19. The last two are LOUD!

Walt Musciano used them for years in the models he designed for Scientific.

George

DaveyMo

George

My OK Cub .049 performs reasonably well, albeit with a very touchy needle valve. Here's a pic of the needle. Questions: 1) Would you taper just a bit on the end of the needle or try to do a more gradual taper across the whole quarter-inch exposed here? 2) Do you turn it in a lathe or just rotate it a bit by hand when using the file?



Thanks!

Dave Mo

ffkiwi

Ideally you'd want to taper the full exposed length-and yes I would use a lathe to ensure concentricity (as best I could, given its already in a thimble!). A far better solution is to buy one of Hank Nystrom's fine thread needle assemblies (www.texastimers.com) fit it-and forget about OK Cub needle problems thereafter. Personally-unless you're an inveterate fiddler-I'd leave Cubs alone-they weren't a patch on Cox for consistency nor performance. There are some people-mainly the FF /SAM world who can get them to run well-but this takes a lot of fiddling, and mixing/matching of parts. There is a lot of engine to engine variation with Cubs-especially the 049 models-if you like the challenge-by all means go ahead-if you just want to fly with a minimum of hassle-there are better engine options.....
If you DO want to fiddle-then the NFFS site (and their forum) is probably a good place to start looking for detailed information. An extensive article on reworking Cubs was published in the NFFS Digest in the 1990s-and may well be in the archives in electronic form.

ChrisM
'ffkiwi'

DaveyMo

Chris:

Very good! You've given me a lot to go on regarding this little engine. Two good sources for improvements and an informed opinion will help greatly with my project. Yes it is kind of an ugly duckling, but I probably fall into that category of a fiddler. Plus high performance is a secondary consideration in my flying as my goal is to introduce young people to control line flying.

The Texas Timer site is nifty - lots of unusual niche stuff for our hobby.

Again Chris, thanks for taking the time to craft a highly-informative response!

Dave Mo...

ffkiwi

Dave-it IS possible to get quite reasonable performance out of OK Cubs-going by the articles mentioned. Equally it can take a lot of fiddling, replacing and substituting of parts and extensive testing to achieve this. For some people the amount of effort involved simply isn't worth it (like me-I have too many engines, too many model projects to devote the sort of time and effort required)-others may enjoy the challenge of 'making a silk purse out of a sows ear..' Even Cox Texaco 049s-which I would argue were a lot better made than most OKs-required a lot of fiddling and parts swapping to get a really good runner than would run a long time.....and it requires that you own-or have access to-multiple copies of the same engine in order to do so

I have been a customer of Hank (Mr Texas Timers) for about 20 years or more-and never had cause to regret it...

If you are going to invest in spares for the OK, then I wouldn't hang about waiting-Ted Brebeck-the grandson of the original founder, still run the company-but I've read somewhere on line that he's finally retiring from that job and shutting up shop-at the end of this year. Ebay of course, still represents a pool of available OK engines, as well-though most would be well used-and you don't often find OK spares-as opposed to complete engines-listed there.

If you want to know more about OK themselves, there was a book-written by the same Ted Brebeck-published ca 1995, titled 'They should have kept the Bear' [a reference to 'Herky' the OK bear mascot used in their advertising for a period] which gives a comprehensive history of the company.

ChrisM
'ffkiwi'

gcb

Well, I don't have a lathe so I used the "redneck" approach by pinching the needle using sandpaper with one hand and twirling it with the other. Not a high-performance fix, but it worked. BTW, I have only found this problem on a few later OK .049's. Perhaps some needles missed a production step where taper should have been added.

George

Edit: Update! I checked my Cubs and it seems that all with the standard supplied needle had the blunt taper except the ones I altered. This includes my .14 (the .19 has a replacement needle/spraybar). So you have the option of adding taper, replacing the needle assembly, or moving the needle very carefully.

mtntopgeo

My Feedback: (12)

Got a few .074 cubs, & have tried to do some minor mods. Best info source I've found for OK Cub mods is "Mattes Engine Rework". Some of the stuff is quite involved though, and at some point (for general sport flying) you'll have to realize that it's easier to just bolt on a more modern engine. However, it's kinda neat to be able to take an "oldie" & make it run better. couple of items to emphasize.....Yes, the needle is a bit blunt. I've used a lathe, & I've also just used a 3/8 drill motor (clamped in a vice) to chuck up the needle. Both methods worked fine.. !!! ..................Do not use one of the early (cox/cub/etc) multi use tools, with the little hook, to loosen the sleeve from the case. Damage will result. ...... Needle assembly. can only be pushed in one direction. ...............Also the wrist pin can only be pushed in one direction. If you go wrong here, you'll unknowingly destroy the little end of the rod, and it will let lose of the piston within a very few flights afterwards. ......... Minor changes in prop sizes doesn't appear to cause a lot of performance change. If the engine is happy & the airframe is "average", you're probably gonna be in the 6x4,6x3, 5x4, 5.7x3 area. I've pretty much settled on a 5.7x3 as my "do everything" prop. ..................... If you're gonna use an electric starter, put a drop of some heavy lube between the case & the prop driver before each start. (Some guys clearance that area, & install a floating brass or fiber washer) ......... For 1/2a, things always have to be lite. This is even more important with the little OK Cubs, considering their low power output. Dry weight of my EPP "Dago Red" is about 8&3/4 OZs. The .074 handles that quite well. ...... Low compression is the norm, so a healthy slug of nitro is advised. I've heard of guys going up to 45%, but I have never tried over 25%. Also 25% castor will keep the thing living longer. Hope some of this stuff helps you reach your goal. ............ George K.

DaveyMo

Chris, George and George:

What a great discussion on OK engines - lots of background here for my use and for posterity. In the way of complementing you each in the vernacular, all I can say is: "you da man"! Thanks!

Dave Mo...

donnyman

jayd3

I still have several O.K. Cubs. in my teen years they were "THE" engine to have. Lots of castor oil and nitro and you could have a ball going around in circles. they would haul a free flight bird outa sight.

man the memories!!!!!!!!

dckrsn

Here's a .049B retrofitted with a fine thread(128tpi)
needle valve assembly from Texas Timers.
It's the...er..Cub's knees.
Bob

BobHH

My Feedback: (18)

Been flying a .049 Cub for years in my Minnie Mambo with Ace pulser. Runs well on Sig 1/2A fuel with plenty of castor. Been very reliable.



Bob Harris

Dan Vincent

A friend of mine in Scotland tells me using a thin wall aluminum tube to extend the venturi up above the exhaust ports helps fuel draw. I've run plenty of Cub engines and they would someime quit when hand launching. I think the longer tube might have helped fuel draw.

mtntopgeo

My Feedback: (12)

Actually, this has been my biggest challenge; trying to launch the thing and keep the engine running. If I richen it up enough to get through a hefty launch, then the engine is sputtering through the whole flight (except for the last 10 sec., when it is just about to run out of fuel). I've been setting the needle rich enough so that the engine just barely runs clean during the flight. With this set-up, if I do a nice, slow, underhand launch, the engine will usually make it into flight mode. I'll have to give the long alum. tube thing a try. Thanks for the tip. .......... George K.

Dan Vincent

A little less pitch on the prop might help too.

jayd3

While I don't know nearly as much as I'd like about how to tune these small engines, I have long believed the needle valve on many were not able to meter the fuel in small enough increments.
This belief started very long ago when as a very young man trying to start and run Anderson spitfire and other similar non reed valve engines,and even many Cox reed valve engines while much better seemed unable to be properly adjusted for just the right amount of fuel either running to rich or to lean and often alternating between lean and rich in flight.
Another clue is until or unless you "foul" the glow plug the engine will start and run out the prime but not draw fuel at the previous best NV setting.
I am very appreciative of any and all help.

Jay

jayd3

Thanks for all the good info and experience George!
And yes if we wanted more than nostalgia ... we would be flying electrics: 1/2 A engine technology peaked about 30+ years ago with reed valve and better rotary engines and Cub technology is 50+ years old.
There just has to be a way to understand what makes one a good starter and runner and another impossible to start both same model using same fuel and all?
Even with the engines that cox produced in the 1980 &90s when the only way to get a good Cox was by accident or buy a reworked from Kustom Kraftsman something was wrong ! but what ? and I don't believe it was the mylar reed valve, rather it has to be fuel delivery, timing, compression, or all the above.

Jay

LittleRock

Here is a CUB .049 project flown at the SMALL event in Little Rock last June.

LittleRock

Sorry for the photo size. Wasn't a 10 year old around to help.