1949 O.K. CUB .074-----YAHOO !!!!!!!!!!!!!!

Kim Thu Oct 13, 2011 6:03 am

I GOT THE COOLEST FRIENDS!

So, there I was, MINDING my own business when, looking in my mailbox at work, I discover this! A 1949 .074 OK Cub ! One of our local flight instructors knew about my love of "Old Junk", and thought I might like to have this little jewel !

While it's prop screw is broken off in the shaft, hopefully, with a little careful machine work, I'll shortly have this little sucker coming back to life on my test stand ! A little 3-in-1 oil loosened it up and it appears to have good compression.

Life is GOOOOOOOOOOOOOOOOD !!!!!!!!!!!!

1949 O.K. CUB .074-----YAHOO !!!!!!!!!!!!!! 1_19

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andrew Thu Oct 13, 2011 7:48 am

Well, looks like those boys across the river have some good sense after all. What a great surprise to find. Waiting for the pics after clean-up.

andrew

SuperDave Thu Oct 13, 2011 9:16 am

Hate to admit this but, in their times, I actually prefered the OK Cubs over the Coxes because of their front rotary valves.

Kim Thu Oct 13, 2011 9:37 am

andrew wrote:Well, looks like those boys across the river have some good sense after all. What a great surprise to find. Waiting for the pics after clean-up.

andrew

Yep! We ain't ALL products of Sibling Unions!...(though I've got my doubts about some of my co-workers).... This is a big deal for me for sure! Now, just gotta get that pesky, broken stud outta my way !

SuperDave Thu Oct 13, 2011 10:01 am

Kim:

As to the broken prop screw DO NOT use the fabled "EZ-out" tool! Most often they break off and only compoud the problem by putting a piece of case-harden steel in the broken part.

The broken screw broke for a definite reason and is most likely due to being frozen in place then twisted off. I recomment the use of a solvent and MILD heat to loosen the broken part. Give the solvent plenty of time to penitrate into the threads.

Be patient and consider the possible consequences of any step you might take.

nitroairplane Thu Oct 13, 2011 10:45 am

SuperDave wrote:Hate to admit this but, in their times, I actually prefered the OK Cubs over the Coxes because of their front rotary valves.

But what about the tee dee and medallion engines?

GermanBeez Thu Oct 13, 2011 12:50 pm

oh, thats a nice one. Are the Crank Cases Cast Aluminum?

nitroairplane Thu Oct 13, 2011 12:53 pm

GermanBeez wrote:oh, thats a nice one. Are the Crank Cases Cast Aluminum?

I believe they are. Huh...

GermanBeez Thu Oct 13, 2011 12:55 pm

It Looks like it.
and i don't think they had automatic lathes in the early 50's... Smile

nitroairplane Thu Oct 13, 2011 12:56 pm

GermanBeez wrote:It Looks like it.
and i don't think they had automatic lathes in the early 50's...

I think they did but they were not common place as they became later.

Mark Boesen Thu Oct 13, 2011 2:45 pm

Hi Kim,

Nice find! I picked up a O.K. Cub 'Large case' .049 at a CL contest years ago, I had never seen one...and suddenly, it seemed I started collecting all sorts of 1/2a's!

A thought for removing broken screw, using a thin Dremel cutting wheel, carefully cut a slot in screw it doesn't need to be deep, just enough for the screwdriver to bite. Be sure to soak and use heat prior.

If there is no serial number on case, it was made after 1950-'51.

OK CUB PHOTOS: http://groups.yahoo.com/group/049Collectors/photos/album/408072958/pic/list

Mark

SuperDave Thu Oct 13, 2011 3:51 pm

nitroairplane wrote:
SuperDave wrote:Hate to admit this but, in their times, I actually prefered the OK Cubs over the Coxes because of their front rotary valves.

But what about the tee dee and medallion engines?

It always concerned me that Coxes had a proprietory glo head whereas others didn't using standard glo plug

nitroairplane Thu Oct 13, 2011 4:48 pm

SuperDave wrote:
nitroairplane wrote:
SuperDave wrote:Hate to admit this but, in their times, I actually prefered the OK Cubs over the Coxes because of their front rotary valves.

But what about the tee dee and medallion engines?

It always concerned me that Coxes had a proprietory glo head whereas others didn't using standard glo plug

That is true am engine that I recently got and might be your kind of engine is the DC wasp it has some serious charm IMO.
It is front rotary, no plastic parts on it, uses and standard glowplug and is made by one of the most reputable engine companies.
It is 0.76cc

microflitedude Thu Oct 13, 2011 5:01 pm

nitroairplane wrote:
SuperDave wrote:
nitroairplane wrote:
SuperDave wrote:Hate to admit this but, in their times, I actually prefered the OK Cubs over the Coxes because of their front rotary valves.

But what about the tee dee and medallion engines?

It always concerned me that Coxes had a proprietory glo head whereas others didn't using standard glo plug
That is true am engine that I recently got and might be your kind of engine is the DC wasp it has some serious charm IMO.
It is front rotary, no plastic parts on it, uses and standard glowplug and is made by one of the most reputable engine companies.
It is 0.76cc

a .76? That's a big motor...

SuperDave Thu Oct 13, 2011 5:06 pm

Or yet another idea to save the Cub:

Using drill press vice and a good drill press drill a hole in the broken part with a sharp bit EXACTY paralell to the engine's crankshaft. Pour solvent into the hole drilled and once again apply mild heat.

The differing coefficients of heat expansion between steel and alumuinum will allow the sovent to penerate thus allowing the threads to free the broken part. This way the solvent can come up from the bottom as well as down from the top.

Mark's Dremel tool/slot idea only has merit it the exposed broken part is long enough to accept a slot but will the slot be strong enough to accept the pressure from a a srewderiver removing the broken part?

fit90 Thu Oct 13, 2011 6:51 pm

Another idea that might be tricky on such a small scale: drill a hole down the middle of the offending screw, lightly tap a flat blade screw driver into the screw to form an indentation to later use with a flat blade screw driver, squirt a refrigerant down the drilled screw then immediately try to unscrew with a flat blade screw driver. When hitting the screw driver into the screw be exceptionally careful not to damage the crank with the screw driver or by forcing the broken screw further into the crank shaft.

Mark Boesen Thu Oct 13, 2011 9:05 pm

Hi Dave,

I've used this method on several occasions with great success where a bolt or screw was too small to attempt to drill into. The slot doesn't need to very deep, especially with an application like this where (hopefully its not bottomed out) and it only needs to be extracted with the help of some penetrating oil and heat.

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SuperDave Thu Oct 13, 2011 9:22 pm

Mark:

Sure but in this case believe the piece is seized in the threards and has been twisted off by force rather than broken off by vibration.

Regarding the removal attempt, it has to be thought out carefully in advance as there will very likely be only "one shot" at successful removal..

Mark Boesen Thu Oct 13, 2011 9:36 pm

I guess for some reason I was thinking the screw was snapped off from a figure '9'?

Your probably right, it was likely snapped off from being torqued down into the crank. It very well could be a one shot deal and then its time to look for a new crank.

**Admin** Thu Oct 13, 2011 11:01 pm

If you can't get the screw out, contact california-dan (I believe its Dan Sitter) from ebay. He did have some OK cub .074 crankshafts on ebay awhile ago. http://cgi.ebay.com/OK-Cub-074-075-Model-Airplane-Engine-Crankshaft-/350345731099

nitroairplane Fri Oct 14, 2011 1:50 am

microflitedude wrote:
nitroairplane wrote:
SuperDave wrote:
nitroairplane wrote:
SuperDave wrote:Hate to admit this but, in their times, I actually prefered the OK Cubs over the Coxes because of their front rotary valves.

But what about the tee dee and medallion engines?

It always concerned me that Coxes had a proprietory glo head whereas others didn't using standard glo plug
That is true am engine that I recently got and might be your kind of engine is the DC wasp it has some serious charm IMO.

It is front rotary, no plastic parts on it, uses and standard glowplug and is made by one of the most reputable engine companies.
It is 0.76cc

a .76? That's a big motor...

No it's .76 cc not ci so it is slightly smaller than the cox .049 a .049 is .8cc

Kim Fri Oct 14, 2011 6:39 am

Mark Boesen wrote:Hi Kim,

Nice find! I picked up a O.K. Cub 'Large case' .049 at a CL contest years ago, I had never seen one...and suddenly, it seemed I started collecting all sorts of 1/2a's!

A thought for removing broken screw, using a thin Dremel cutting wheel, carefully cut a slot in screw it doesn't need to be deep, just enough for the screwdriver to bite. Be sure to soak and use heat prior.

If there is no serial number on case, it was made after 1950-'51.

OK CUB PHOTOS: http://groups.yahoo.com/group/049Collectors/photos/album/408072958/pic/list

Mark

Thanks Mark!

It's fun to find stuff, and even more fun when stuff finds you! Appreciate the info on the manf. dates. My only book doesn't give a production date range, just a note that "early models had serial numbers", which mine doesn't.

The broken stud is almost flush with the end of the crankshaft, so I don't think any of my tools will be able to slot it without getting into the surrounding metal. When I finally get some free time AND a clear mind, guess I'll try the soak and heat route, and attempt drilling a VERY precise hole down the center of the stud.

If I can sense when the bit has gone the length of the stud, I may try more heat and soaking to get it working from both ends, unless of course, it IS bottomed out. If I can get the debris out of the shaft without too much damage to it's threads, figure I could just put a permanent stud in there, with a nut from the prop end. We'll see.

As SuperDave suggested, I'll stay away from the EZ-outs (had lots of previous heartbreak there!). If California Dan still has shafts for the engine (THANKS Admin!!), I'll probably get one on the way, though I'd really like to just give the engine a good flushing and airblast, and not disassemble it if at all possible.

I've been waiting for an excuse to buy myself a good quality drill press (been surviving with an old Dremel drill stand)...so this may not be a "free" engine after all!

Thanks to all for your input, info, and suggestions...it IS appreciated.

Kim

SuperDave Fri Oct 14, 2011 9:03 am

Kim:

As to a good drill press, go forth and spring for one; they have very many uses in a lot of different applications beside modeling. A hand-held drill motor just can't compare for accuracy.

For modeling I have table-top Craftsman with a 1/2" chuck as well as a nice set of bits. Be sure to get bit gauge as well to measure them correctly. Small bits break very easily so spares come in handy when they break. Get small center punches too.

Discard small bits when they become dull. A dull bit can cause it to "wander" when drilling. Sharpening a small bit is a waste of time in my experience.

PV Pilot Fri Oct 14, 2011 10:15 am

You might get lucky and just by drilling out the broken piece it will work free from the heat of drilling.

Another option is to drill oversize and retap for a slightly larger screw.

SuperDave Fri Oct 14, 2011 10:34 am

PV Pilot wrote:You might get lucky and just by drilling out the broken piece it will work free from the heat of drilling.

Another option is to drill oversize and retap for a slightly larger screw.

Any oversize drilling would have to "spot on" accurate otherwise the engine would experience "bad vibes" from off balance when running..

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1949 O.K. CUB .074-----YAHOO !!!!!!!!!!!!!!

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