Mystery Part 1

[Desifinado]

Alright, so I've had this thing for years, and I have no idea what it really is. I was hoping someone here might recognize it.

It's fairly heavy, and based on surface finish my best guess is that it's a stainless steel. I have some recollection of someone saying it was a propeller hub for a large R/C plane, but I can't find anything that looks like it. It is about 80mm tall, and the ring on top has a fairly nice surface finish to it (a bearing surface of some sort?)

(Let me know if I've thrown this in the wrong forum)

Picture

Thanks!

 

[GregLocock]

The grooves look like a ballscrew arrangement.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[TheTick]

Inertial dampener? Flux capacitor? Sonic screwdriver?

 

[MikeHalloran]

Most affordable large R/C planes couldn't even carry that part.

The external thread profile suggests that it's a really short ballscrew.
The cross-bore seems made to accept a precision pin like a crankpin.
The generous radii between the thread on the pinbore suggest that the part is subject to substantial tensile loads and lots of load cycles.
The pointy feature on the left end looks like the sort of self-centering feature you'd find inside a double Cardan joint.

Lacking any knowledge whatsoever of how such devices are actually made, I'm guessing it's part of the hub/blade root assembly for a variable pitch propeller.



Mike Halloran
Pembroke Pines, FL, USA

 

[kingnero]

from another perspective: instead of a ballscrew, could the grooves not be ment for sealing, eg like oil and compression rings in a typical piston?
I do agree it's odd that they are formed in a helical geometry but a similar feature is used for sealing in low-cost devices. This, admittedly, does not look like a low-cost part.

 

[MintJulep]

Looks like part of a short stroke ball screw actuator to me as well.

I'd imagine that it sits inside a pancake stepper motor and is connected to a piston or lever or crank arm.

 

[dhengr]

I agree that the helical grooves appear to be a ball bearing screw arrangement. But, I think the ball bearing cages are held captive in an outer retaining structure of some sort. When that retaining structure moves along the long axis of your widget, it causes your widget to rotate; a max. of about two revolutions so the ball bearings stay retained in the grooves of your widget. This will cause the rod/pin through the hole on the left to sweep two revolutions, and the little tit on the left end is a rotational centering device. Alternatively, rotating the rod/pin/crank handle could position the retaining structure longitudinally along the axis of your widget.

 

[tomwalz]

Might try posting on practicalmachinist.com

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[ivymike]

I agree with the above posts that the threads seem cut for ball bearings, and that it would be a way to convert rotation to linear motion. Maybe 3 of them are used on the corners of something for leveling?