|Apr 06, 2011, 12:08 PM|
Prop Savers - Fitting, Using, Testing, & Making Thera-Band Bands
Prop savers are often criticized for how well they work, and they are often stated to be inadequate for use at certain power levels. The criticisms are most often undeserved and the problems are due to an improperly fitted or used prop saver or a prop saver band that is inadequate for the intended use.
Prop Saver Fitting - This video shows how to cut a shaft to length and fit a prop saver. The prop saver used there is the Maxx Products ACC366 tapered cone style prop saver. Tools needed are a Dremel tool, a #102 arbor, and a #409 metal cutting disc. I did not do it here but I would normally put the motor in a plastic bag with a hole for the shaft to prevent metallic particles from getting into the magnets or bearings:
The Loctite mentioned in the video is the key to the screws not loosening themselves in use. It is a thread locking compound that comes in different strengths and each strength is a different color. The one I recommend is the Loctite blue or #242 locking compound. The #271 red compound is stronger and it can create some problems in getting the screws loose later. But with any of them, applying some heat will soften and relax the bond, five seconds or so with a small flame (micro torch, cigarette lighter, etc.) will soften it and relax the bond.
OK, we have a prop saver on. Let's put a prop on it! We're going to use a home made tool made from a scrap of piano wire that is too short to be useful for anything on an airplane. And we are going to use The World's Greatest Prop Saver Bands because we work hard and deserve that kind of quality! And besides, these sooo cheap!:
Once you get your prop saver fitted and have a prop on it, a little testing is in order. That is seen here using a GWS RS EP-1170 slow fly prop. I even spun up to a little bit more than it's recommended maximum RPM limits (45,000 / prop dia. in inches or 4,091 RPM) to demonstrate the look and sound of prop flutter but that turned out to be barely audible on the video:
When I fitted the prop to the prop saver I used the World's Greatest Prop Saver Band, the ones I make myself from Thera-Band blue surgical/physical therapy tubing. Here is the demo of how quickly you can make those for costs that range from the alluring "free" to a typical 2 Cents per band:
I'll be glad to answer questions on the thread of course, harsh criticisms of my sanity and/or workmanship just clot up the thread so they can be addressed to me at "jacker at midmaine dot com".
Go forth and fly safe!
8 April 2011 - Adding this image that shows which of the various sizes or prop savers fits which brands of props if you have the saver with a stepped cylinder or the one that has a cone on one side and a cylinder on the other. Usually using the tapered cone side against the prop will let it fit all or nearly all props.
When using APC, Great Planes, and other props that come with an assortment of small bushings for reducing the hole, fit one of those that takes up all the side to side play and/or that places the prop on the tapered cone surface if there is one. I use small drop of CA when I put the adapters in so they are not lost later.
16 April 2011 - A couple have asked where they can get Thera-Band blue easily. There are a number of people selling it on eBay and at prices are cheap as $1.50 a foot including mail shipment. Search for "theraband" or "thera-band".
Will it work at 250 Watts with a 13-14" prop? You bet it will!
And here it is at over 700W with an APC 14x10 Thin Electric on a D4023-850 motor. Three Thera-Band bands for that one, thrust was about 2000g:
13 May 2012 - Added link to the "big prop and high power test" Video.
16 Nov 2013 - Added link to the D4023-850 motor test with an APC 14 x 10 TE prop.
24 Jun 2014 - Added image of the Alltrade 6" Cable cutter I use for cutting bands
|Apr 06, 2011, 02:37 PM|
I viewed your videos.
Then, I viewed some other propsaver videos on youtube.
Yours are the best.
Thanks for the effort you took.
PS your workbench is way too clean....
|Apr 06, 2011, 02:47 PM|
That is the sawhorses with a piece of wood on them, the workbench is behind me and knee deep in tools and stuff.
But thanks for the kind words and thoughts!
|Apr 06, 2011, 03:14 PM|
United States, NV, North Las Vegas
Joined Sep 2009
Thanks for the videos!
About the only thing I do differnt is once I mark where the shaft needs to be cut I use a plastic/ziploc bag and poke the shaft through so that the motor is inside the bag with only the portion of the shaft to be removed poking through...of course I don't run the motor as I'm cutting... by doing it this way I make sure the magnets don't pull any metal dust inside the motor
The tiny particles may not be a problem... still I'd rather NOT let them get inside the motor.
I'm going to try the thera-band next time I get over to the medical supply...I've been using just plain surgical tubing(kinda tan in color) and so far it works very well... ugly in color but hey it's MUCH better than any O-ring I've tried!
|Apr 06, 2011, 03:54 PM|
Thanks for mentioning that, John.
I left the bags off to get a little better video, I'll edit that and mention it though. I've also taped a shop vacuum nozzle down near the cutting and used that too but that adds another noise...
I think you'll find the blue Thera-Band to be a little better, heavier walls or maybe better rubber or something. I've used surgical tubing too and it was just a little thinner but, like you say, it worked very well.
They have Thera-Band in a number of color coded sizes:
Specs and info - http://www.thera-band.com/store/prod...p?ProductID=27
Color - size specs - Product Code (25-Ft) - Product Code (100-Ft)
Tan .062 ID x .031 wall (.125 O.D.) #21010 #21110
Yellow .200 ID x .045 wall (.290 O.D.) #21020 #21120
Red .200 ID x .057 wall (.314 O.D.) #21030 #21130
Green .200 ID x .069 wall (.338 O.D.) #21040 #21140
Blue .200 ID x .085 wall (.370 O.D.) #21050 #21150
Black .200 ID x .098 wall (.396 O.D.) #21060 #21160
Silver .200 ID x .125 wall (.450 O.D.) #21070 #21170
|Apr 06, 2011, 05:03 PM|
First mentioned on RCG in 2001
Good ideas stay around to be discovered over and over again.
|Apr 18, 2011, 02:14 PM|
Joined Oct 2008
Jack was kind enough to send me some samples. After testing, I made the following observations:
The heavy wall eliminates one of the main problems I had encountered with using silicon tubing for prop saver bands in the past: they split at stress risers caused by notches made during cutting. The heavier wall makes those notches spread out, so the stress riser sorta integrates out and doesn't cause splitting.
These silicon bands have all kindsa stretchiness and shape retention. One of the problems with the el cheapo hair bands you get at Sally Beauty Supply is that they have to be removed after every flying session or you risk having them break the next time because they're all stretched out. Okay, so they cost $1.66 per 500 or whatever, but you still need them to work. The silicon stays soft and doesn't stretch over time, so you can leave them in place.
The silicon tubing is really tough stuff. Even though the bands are easier to install than O-rings (they have more stretch) they can take all kinds of twisting and abuse when you land or crash into something. I've already had a few "incidents" that would have either thrown off all the hair bands or broken an O-ring, and the silicon stuff just springs right back into shape.
I have a new favorite prop saver band.
|Apr 18, 2011, 03:04 PM|
Thanks for the interesting and detailed report geek! You are finding them to better for the same reasons I did.
I'm still waiting for your mailing address, if you would like to find out why these are better than the 2001 ones were, shoot a mailing address to me at "jacker at midmaine dot com".
|May 01, 2011, 08:07 AM|
Thanks guys, a couple of people have asked me where to get it so I'll post a link to one of the best deals goingn (and I do not get a cut!).
If you're in the U.S. that will get you a foot of Thera-Band (I recommend the blue color) by mail for $1.50. And with that, a piece of 1/4" dowel, a razor knife, and a few minutes of time you're good to go for making almost 100 prop saver bands.
|May 01, 2011, 02:27 PM|
Cumbria in the U.K
Joined Jan 2008
Thanks for the videos and information Jack.
Having complete faith in you I have splashed out $20 or so to get 6 feet of the blue band sent to the U.K.
Never going to have to buy a prop band ever again, 6ft is a heck of a lot of bands
|May 01, 2011, 02:40 PM|
I'm thinking you give them one sample and then sell them a packet of a dozen or so with they come back for another you'll get your money back. Or are you allowed to sell anything by the dozen in the UK any more? Maybe a packet of 10...
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