CedarYopantz

Nice Twice Hobbies is a LHS in Las Vegas started by a friend about 14 years ago. He sells hobby items on consignment, this is the way he has been able to compete with the large chain shops (Hobby Shack and hobbytown). It offers a place for the local guys to find oddball stuff we couldn't normally run across except maybe on Ebay. I will probably never find my '59 Corvette covered under a tarp in the back of some barn for $500 (naturally, in my fantasy, it would only have 200 mi on it). But I did find this at Nice Twice Hobbies last Friday.

Packed in a plain,brown box without markings I just had to know what was inside. When the lid came off I saw more brown cardboard with a red spinner tip sticking out from under some clear plastic bubble wrap. I removed more of the cardboard; then I got really excited. It was a completely new, unused, untouched Mk variable-pitch prop unit!

Here are some pictures and a brief description. I'm positive many of you know more about this than me, your input is welcome. I will just put some pictures out on this thread so we can all get an idea of how these units were built, packaged, functioned etc.

Enjoy, Bill Ervin

CedarYopantz

I haven't figured out what the puller is for and I'm not inclined to start chewing up the beautifully machined aluminum parts. My guess is that it might be for pulling the thrust washer off the front of the Webra engine this particular unit was machined for. the only marking on the outside of the box was WEB written with a felt tip marker. Here are more detailed pics of the machine parts inside the cone.

Bill

CedarYopantz

The very rear of the unit has a swashplate made of what appears to be carbon reinforced plastic. similar to the old Kraft-Hayes motor mounts. It slides fore and aft on the prop shaft and is connected in front to the pitch-control arms. The pitch-control arms are machined aluminum and have a counter-weight, the piece connecting the swashplate to the PCA's is that same reinforced plastic material. The whole assembly is spring loaded to go to high pitch. there are two tabs on either side of the swashplate to hook up your pushrod. Weight of the unit is about 5 1/2 oz. it's significant!

Better explain these first two pics. In the second one I'm pushing down with a pencil erasure putting the unit into low-pitch. When released it springs back to high-pitch. the blades appear to be made of fiberglass.

Bill

8178

My Feedback: (17)

Bill,

That is really cool! Is it an 11” prop? There was some discussion about them on the forum awhile back.

CedarYopantz

Near as I can tell it supposed to be mounted in place of the thrust washer. to put it another way you have to remove the thust washer, slide the unit on, then tighten the thing with the supplied adapter nut. The adapter nut is tapped with 1/4-28 threads for the engine and 2.5 mm threads for the spinner tip (the red part). If you look at the front face of the machined portion (the face just forward of the prop blades) you'll see two, small set screws along the circumference. They are not turned in all the way, they protrude up about a 1/16" and are only used to aligned the forward, red plastic part of the spinner. From that same picture you can see two 3/16" holes, just under those holes are two pan-head allen set screws holding the prop hubs on. The prop blade shafts (about 1/4" dia., I'm sure they're metric but I couldn't get my calipers on them) are supported using ball-bearings/ thrust bearings.

The prop has a 11.4 in diameter, the spinner appears to be exactly 2.5" in diameter. According to what little paperwork was included the pitch is adjustable from 0" to 11.5"


If anybody would like more pictures from a specific angle let me know, I'd be happy to put them here for you to see.

Bill

8178

My Feedback: (17)

The Webra engine uses a key in the prop driver assembly.

CedarYopantz

8178, I measured 11 3/8" for the prop diameter the box says 11.4" For some reason this thing would seem so perfect sitting on the front of your Blue Angel. I know the timeline is about 8-10 years off, maybe it's just because they were both designed by the same person, I'm just sentimental that way I guess.

I should add that this unit will never be used. According to the research I did (mostly here in this forum) these Variable pitch hubs were not the most trustworthy things to have spinning at 15k in front of your pride and joy, even when they were brand new. I might , however, make allowances in the nose to install it for pictures! Up until I bought this thing last Friday I had never considered myself a collector, never be able to say that again.

Bill (President, Cedar Yopantz Aircraft Co.)

grotto2

My Feedback: (2)

Steve Helms flew this type of prop extensively on his Auroras. You might consider contacting him for more information.

CedarYopantz

Thanks Ron, I'll do that. Is this the same assembly H. Prettner used in His Magic?

impactiq

My Feedback: (57)

The biggest problem I remember with the MK variable pitch props were the blades would shear in flight due to the material they were made of. One guy I knew flew with one and that was the constant problem he would have at high RPM. IT sure would be tempting to make a new set of blades.... with today's composites materials and put it in the air to see what it is made of. You have a real gem there. Whatever you paid for it.... you got a deal.

CedarYopantz

Thanks Mark, you guys have sure been gentlemanly about it. I'm a little embarrassed for what I paid but since I'm among friends, it was marked $89 plus tax and that's what I paid. Definitely in the category of "something I couldn't live without" and not "something I need". I could have asked my friend (the shop owner) for a break on the price but this time I just couldn't bring myself to it.


Bill

8178

My Feedback: (17)

For $89 it was a small price for owning a piece of history!

I bought a P&G valve gaper tool on *bay just because I remember how cool it was when I used it to adjust the lash on my high performance Corvette engine in the 60s. I don’t have an engine that needs valve lash adjustment anymore but that didn’t mater.

grotto2

My Feedback: (2)

I heard the original street price was around $200, but the reality was that not just anyone would be "allowed" to own one. From what I understand, the least little prop strike required a trip to the machine shop to replace blades and check runout. MK was concerned about the liability of Joe-Shadetree-Patterndoof having it on his Stuntstik. Still, Futaba produced a radio that allowed the programmability of a channel for prop pitch. I was always puzzled by that. What were we supposed to do with that feature if we couldn't buy a prop?

Just my 2 cents worth of hearsay.

-Ron

rainedave

My Feedback: (1)

A bit more info, scroll to third paragraph:

http://findarticles.com/p/articles/m...08/ai_n8864568

Steve25

Hey Cedar, would you be open to lend your prop, for reengineering purposes ?
I guess with all the guys active here, that should be possible, and make it even better, with new stronger materials ?
Would be great, putting these on our Curare's , Magic, and I can imagine a few other, since that timeline

Steven

doxilia

My Feedback: (3)

Bill,

even if you posted this question 5 years ago (!), the answer would be yes. Hanno used this prop on his Magic in '82 - and then never again.

David.