RC Plane Prop Saver

RC Plane Prop Saver: I found this while researching the Super Cub and thought it might be usefull to those of you not flying EasyStars. :From: http://thesmithfam.org/blog/2006/10/17/rc-plane-prop-saver/Direct quote:"Michael Torrie created a really handy tool to save your RC plane’s propellers from a spinning death on impact. It’s called a prop saver and it’s based on the “elastic rules, static drules” principle. Read on for pictures and explanation:The following is a close-up picture of a prop saver:

It bolts on to your propeller shaft just like a normal propeller, with two hex nuts (which are barely visible on the left and right of the black plastic yoke). The black plastic yoke is made from an old propeller, with the blades cut off, and two screws drilled into it and, of course, coated with tape for good measure. The tape provides a little bit of friction when you slide the new prop on the top. You then attach your prop onto the tip of the yoke with a rubber band, securing it to the screws like this:

The prop sits on the tip of the yoke, swallowing it slightly. The rubber band holds it to the yoke and delivers the rotational force to the prop like a normal nut would, except with a bit more elasticity. That way, the prop’s blades don’t take the brunt of a crash, but rather the rubber band, as this picture shows:

That’s one safe prop! You’d have to crash it pretty hard to break it, in which case the prop will be the cheapest repair you’ll make.This approach observes the “elastic rules, static drules” principle by allowing the prop to give a bit, rather than statically absorbing impact forces. This same principle applies to just about every component that break easily."

Hi Robert, even on a fun flyer, an inadapted rubber band, even twisted around several times, is a dangerous setup on a prop saver. The intention is to save the prop when nose landing. In the picture you posted, it is - in my opinion as well as in other's - a danger for the pilot/operator and for the public.
Slow and park flyers now are mostly powered with brushless motors spinning the prop at many 1000 turns per minute (sometimes as much as 11-12'000 RPM with smaller props on inrunner motors). Any bad rubber will be teared apart when throttling up, because the shaft will at first accelerate faster than the prop itself.
That's why one should only use adapted O-Rings in good shape. And even an o-ring which was left tight on the prop saver for 1-2 months might already show cracks and will ultimately break. And a prop ejected at 6000 RPM is a potential danger for pilot, people, and objects.
So prop savers are fine, but should be setup and handled correctly.

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Comments

Robert Drone July 23, 2009 at 7:00am

Reto; thanks for the info I was not personally thinking about using it since the planes I am looking at have cheap replacement parts but I thought it might be usefull for others.............guess not?
Reto July 23, 2009 at 6:00am

Most brushless motors come with prop saver, though not all, especially not the higher quality engines.
Reto July 23, 2009 at 5:59am

Hi Robert, even on a fun flyer, an inadapted rubber band, even twisted around several times, is a dangerous setup on a prop saver. The intention is to save the prop when nose landing. In the picture you posted, it is - in my opinion as well as in other's - a danger for the pilot/operator and for the public.
Slow and park flyers now are mostly powered with brushless motors spinning the prop at many 1000 turns per minute (sometimes as much as 11-12'000 RPM with smaller props on inrunner motors). Any bad rubber will be teared apart when throttling up, because the shaft will at first accelerate faster than the prop itself.
That's why one should only use adapted O-Rings in good shape. And even an o-ring which was left tight on the prop saver for 1-2 months might already show cracks and will ultimately break. And a prop ejected at 6000 RPM is a potential danger for pilot, people, and objects.
So prop savers are fine, but should be setup and handled correctly.
Robert Drone July 23, 2009 at 5:05am

Peter; it was not up to me what the prop saver was made out of I just found this on the 'net. Also I think this is designed to be built out of parts you already have to save money as that was the apparent intent of the project.

-What engine do you have that comes with one?

Michael; I did not think of that but I think he uses this on planes he flies for the fun/thrill of flying.

Greg; Really? Where did you find them at?

bGatti; 'Uber-rubber band' ? The one in the post is a cheap thick rubber-band you might find around the house if you look in the second picture you can see how it is twisted up like only a rubber-band would do. As for vibration I don't think this is intended for serious aircraft -just for fun flying.

-Rd
bGatti July 22, 2009 at 9:23pm

that uber-rubber band is really just a rubber O ring.
Props are cheap, and vibration is a thief (energy).
Peter Meister July 22, 2009 at 8:13pm

Yup that's what I said. Almost every engine I have comes with one by default...why jerry rig it.. .:)
Greg Fletcher July 22, 2009 at 7:58pm

They all ready make these.
Michael Evans July 22, 2009 at 7:10pm

prop savers are not worth it to me. it will kill onboard video, where you need the prop to be perfectly balanced. you also run the risk of it popping off in flight and causing a crash.
Peter Meister July 22, 2009 at 6:44pm

One other note, never ever use regular Rubber bands for a prop saver ( they will break no matter how many you use ). Always use the thick flexible rubber band that is make specifically for a prop saver. Its very thick, and flexible only to a small extent, thus to provide proper shock absorbtion at the same time provide strong solid lock in of the prop to the hub.
Peter Meister July 22, 2009 at 6:41pm

Great Post !!! - But I have a concern. The prop saver should be metal, machined to the hub for perfect alignment. A prop by nature is not perfectly aligned to a engine hub. Also, drilling into the propeller hub only compromises the integrity of the plastic. With the size of those bolts, I would be super hesitant to use such a prop saver as this. It looks very likely to throw a bolt and then throw the prop. Most electric engines come with a proper prop saver when you purchase them now a days. I would recommend using the stock prop saver that matches your engine over a custom one like above. Good idea no doubt, but when you are dealing with a propeller you need to make sure SAFETY and proper design are adhered too. This looks like a jerry rig at best, and IMHO is not safe for use with others around.

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