WenMac MkIII 049, Cox BabeBee, FOX 15X and 19 Prop Screw/Crank Threads

[mike in SC]

I had trouble finding these thread sizes, especially the WenMac 049, so I wanted to record what I've found:

WenMac Mk III prop/crank thread = SAE 8-32
Cox Babe Bee 049 is SAE 5-40
My FOX 15x and 19 both have SAE 10-32 threads

(The FOX/MECOA manual for the 19 and 25 show a 1/4-28 thread, so must be multiple versions of that motor too...)

Wanted to share that info...

mike in SC

[rsv1cox]

Thanks Mike, I record those specs too, but then I lose them.

Years ago when I started getting into this stuff I was surprised that Cox could get away with a 5 shaft compared to Wen and others that had thicker crankshafts. I have bent Cox shafts in mishaps but never a Wen. It only took a couple of Cox Babe Bee's at $3.95 each to stop flying over concrete. I could glue back together the Scientific Hollow Logs but not the cranks. No Bernie or Matt back then, or the internet..........but I could have ordered one from the factory. Never did. Just bought another.

[roddie]

Thanks Mike, I record those specs too, but then I lose them.

Years ago when I started getting into this stuff I was surprised that Cox could get away with a 5 shaft compared to Wen and others that had thicker crankshafts.  I have bent Cox shafts in mishaps but never a Wen.  It only took a couple of Cox Babe Bee's at $3.95 each to stop flying over concrete.  I could glue back together the Scientific Hollow Logs but not the cranks.  No Bernie or Matt back then, or the internet..........but I could have ordered one from the factory.  Never did.  Just bought another.

Thanks Mike 1st off.. and Robert; you have a way of describing events "in text".............. that put me right there with you.. sharing your experience. I've never flown over concrete Robert. Only recently (within 5 years) was my 1st flight over asphalt.. and it was my first flight in 15+ years and I haven't flown since then...

Mike, I appreciate this post. I'm a #'s guy.. and enjoy knowing the specs. on my model-engines especially. The Cox .09 engines (TeeDee and Medallion) utilize a 6-32 prop-screw.

I try to maintain a stock of nuts and bolts (machine-screws) in the 2-56, 3-48, 4-40, 5-40, 6-32, 8-32 sizes for my American-made/small-displacement (1/2A) glow engines. I usually opt for the longest-length machine screws.. and cut/dress them shorter.. if needed.

[mike in SC]

I didn't know what Medallion and TeeDee were, thanks for that!

Wonder if Amazon has an assortment that would include those sizes of nuts?

Sometimes I get concerned I could strip threads if I tighten the prop nut too tight...

Have you ever used "stand-off" nuts?  Not sure which sizes may be available, but they are longer than standard and would engage more threads.  Supposedly full bolt strength (for steel) is achieved with 1 to 1.5 times the root diameter of the bolt... so many of those prop nuts look like jam nuts, seem kinda thin!
Standoff nuts are used in electronics a good bit, and can be found on Amazon.

[roddie]

I didn't know what Medallion and TeeDee were, thanks for that!

Standoff nuts are used in electronics a good bit, and can be found on Amazon.

That's the ".09's" @ 6-32... the .049/.051 Medallions/Tee Dees have the the 5-40 screws.. as do the reed valve variants in that displacement.

I do like stand-off nuts.. but I've never seen one that wasn't metric. Not saying that SAE's don't exist.. but I've never searched for one.

I like the Cox 5-40 threaded spinner-nuts that utilize a 5-40 double-ended stub-shaft. You can really tighten a prop when using one. Incidentally; CEF member Levent Suberk posted recently.. about his using the rubber from "party-balloons" cut into a disc to fit between a TeeDee style AL. spinner and the propeller-hub.. to prevent the loosening of a propeller.. particularly if running a "reedie" with a L/H prop.

[Sponsored content]