Prop Hanger for Stick Fuselages

HOME MADE PROP HANGER

by Bob Kopski

The following method has been successfully applied for motor sticks from 3/32″ X 3/16″ to 1/2″ square. Pictured is a prop hanger for a 1/4″ square fuselage stick. A similar one is shown completed on a Cloud Tramp.

Begin with the subject motor stick and place two pieces of cardstock paper strip as shown. These effectively increase the dimensions of the stick slightly otherwise the resulting hanger will become overly tight on the stick.

Slip on a length of heat shrink tubing as pictured and shrink tight.

Allow it to cool, remove the paper spacers, and verify the tubing will slide off / on the motor stick. Neat, huh?!

Next cut a balsa spacer block as required, taper for down thrust as desired, and spot CA to the heat shrink tubing. Medium CA works well for this but be sure not to get any CA between the hanger and fuselage stick. Move on to making the shaft bearing.

This example uses a 3/32″ OD aluminum tubing 3/4″ long intended for a 0.055″ prop shaft.

The shaft would be a sloppy fit in the tubing so in this case each end of the tubing is necked down a bit using a keyed 3 jaw chuck and tightening it until the sample shaft is just beginning to drag inside the tubing. Note that this technique works just as well with brass tubing and results in a good working shaft and bearing assembly.

Position this tubing bearing on the balsa spacer block setting any desired side thrust in place and apply a spot of thin CA to fix the position.

Carve and sand the spacer block as shown, bind with thread and apply thin CA – keeping it out of the bearing tube of course! Finally trim and clean up your new prop hanger and effect a proud smile!

Some notes. Some small balsa “stop blocks” can be glued to the motor stick behind the hanger to prevent the hanger from being pulled back by a wound motor. Next – a really neat trick: A fully thrust adjustable version of this hanger can be made by assembling it on a stick larger than the motor stick. Clearly this will allow the hanger to fit loosely so now just wedge in some tapered wood shims between the hanger and the fuselage stick to tilt the bearing and tighten the pair. In this example one might use a 5/16″ square forming stick to make a hanger for a 1/4″ sq. fuselage stick. This whole process is harder to describe than to do.

There are many varieties of heat shrink tubing and I cannot assure how CA will work with all, of course.  I can assure the basic idea does work well in general and in my case the tubing illustrated is a 3M product called polyolefin.  I just have this material on hand for electronic applications and I have made several hangers with it.  Also  I have for other reasons used CA with several other (unknown) heat shrink material samples with no problem.
Note that the thread binding around the hanger assembly adds considerable rigidity to the whole assembly when it is CA coated – it becomes somewhat similar to the familiar molded plastic hanger.  I’m now playing with some variations of the technique and depending on results will forward the details.
Regarding the type of shrink tubing used, here’s a link:
I realize this may not be the answer to all but it is at least one product that works very well in this purpose.  I normally buy a variety of these 4’ lengths for electronic purposes such as bundling or insulating wire joints, connectors, etc – such as in the attached example, FYI.
Since the impressions are personal and variable I’d put this material at “flexible” and certainly not “rigid”, but it is not “limp” !  Whew!  Best I can do!
CA (and others) do not adhere well to many plastics, but it works with this tubing (and others I’ve tried).  Folks may simply need to test what they have.
And yes – just slip it off the stick front end and put on another with different thrust angles – I just did that very thing on the field yesterday!
Also here is a new variation of the hanger.  This was formed on a tapered former as shown but with the tubing overhanging in front some.  The subsequent shrink “necked down” the overhang part thus forming a “built in” stop on the very front of the motor stick.  The aft end of the hanger is “larger” to allow tapered shims to set the thrust.

Happy flying!

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