Prop Saver Not Holding Props On

[bwmartens]

I've been using the recommended electronics on my FT Flyer and my FT Delta. Specifically the motor is a hexTronik 24gram Brushless Outrunner 1300kv. Lately I've been having trouble with the prop flying off mid-flight. In fact, if I hold the plane in my hand and run the motor all the way up, the prop will usually come off. I even tried this with brand new O-rings and props just to make sure something wasn't stretched or damaged. It still happens. I can't see any vibration in the motor.

Any ideas what's causing this? Should I be able to run the motor all the way up in my hand and have the prop/propsaver stay on?

 

[Tactical Ex]

I got a similar post going on here . I think I know what is happening in your case. What props are you using? The master air screw brand have these sharp plastic edges on the hub and when you apply a lot of pressure (high throttle) the pressure between the motor and the prop stretch it and drag the O-ring across the sharp edge and severs it.

 

[bwmartens]

I'll check again but I haven't seen a sharp edge on the prop. The o-ring doesn't actually get cut. The prop just falls off to one side (with the o-ring still attached.) I saw in your other thread a comment about using multiple O-rings. That sounds like it might help me out. I should be able to run up to full throttle while holding the plane steady, right?

(I did see that thread but didn't want to thread-jack with my first post to this forum. Thanks for the quick reply!)

 

[Tactical Ex]

We are having similar issues, you could have posted this on the thread I started and it would have been fine. Either way it's fine, no worries. If your prop is popping off to the side it's not centered and balanced and its also not being held on tight enough. Multiple O-rings will HELP but making sure you are using the right sized spacer in the hub is more important. The more O-rings, the less "play" is allowed and the friction between the surface of the prop hub and the prop saver is great, thereby reducing opportunity for the prop to slip out of alignment but the spacer will stop the prop from sliding on the prop saver in the first place. If you are unsure of the terminology please let us know so we can link to pictures (I often use the wrong terminology anyway).

You should be able to run the motor at full throttle, hold the plane by the tail (power pod by the rear) and flap your arm completely outstretched up and down and side to side. (WARNING, wear eye protection and only do this outside!!!) If you do this and the prop comes off-center then it will do the same thing in the air. If it happens in the air your thrust gets reduced ALOT and unless you can punch the throttle and go perfectly strait before you hit the ground the prop will rarely reset itself.

 

[crash bandicoot]

If you are still learning how to fly a little, I ended up buying around 20 props and using fixed hubs. I ended up burning through most of them, but it was fun learning how to fly.

 

[rcspaceflight]

A prop saver is a great idea because it saves the motor shaft more than it saves props. Props are cheap, a new motor shaft, or a new motor, isn't.

The O-rings need to be difficult to put on. And the prop needs to be resting on the prop saver without any play. If there is too big of a gap between the prop and the prop saver, adding hot glue works perfectly. Hot glue doesn't really stick to metal so you don't have to worry about the prop being stuck to the prop saver. Just a dab of hot glue on the back of the prop and then holding it onto the prop saver will create a perfect gap filler. If that's the issue. Otherwise I'm guessing that the O-rings aren't tight enough.

 

[bwmartens]

None of the spacers that came with the props fit the motor shaft. I did a test with two O-rings and that did work but there's some play in the fitting. I'll give the hot glue a try. Thanks!

 

[OrangutangSurfer]

None of the spacers that came with the props fit the motor shaft. I did a test with two O-rings and that did work but there's some play in the fitting. I'll give the hot glue a try. Thanks!

find one of the adapters that is almost a fit, but has to be too small for the prop saver, add a dab of superglue then use this to make the hole big enough.

http://www.harborfreight.com/t-handle-reamer-66936.html

I bought some APC props that had a 3mm -ish hole and I used this to get them to fit on my prop adapter, it works great I've used it on quite a few props, I haven't had any problems with balance (yet).

I also took my prop saver and a well fitting prop to home depot and in the plumbing section I found a 10 pack of o-rings that are thicker and much stronger than ones sold for/with prop savers.

I've nose dived my 24g Hextronic motor (HK version of the blue wonder) in the dirt MANY MANY times and it is still going strong. (I'm very surprised).

-Jes

 

[adamd]

yes o-rings need to be difficult to put on! i have had new o-ring and watched the prop stretch forward at full power. i have a large assortment of o-rings so i just went a size down worked great.

 

[DamoRC]

None of the spacers that came with the props fit the motor shaft.

Bwmartens - what kind of props are you using?

I bought the Turnigy 2730 1300Kv motor from Hobbyking (the Hextronic was not available) and what HK call "APC Style" propellers. I had 2 issues trying to get these to work. One, as you said, was that none of the spacers that came with the props fit the prop saver perfectly. One spacer was too tight and the other was a fraction loose. Although I like OrangutangSurfer's approach to modifying the tight spacer, I just use the slightly loose one and have had no issues with balance or props coming off. The second problem with this props was that the screws that hold the propsaver to the motor shaft (and also hold the o-ring in place) interfere with the hub of the prop, so it will not seat properly on the propsaver. I simply filed a slight chamfer to allow the prop to sit well on the saver and I have no problems since.



+1 on the Home Despot 10 pack of rings, cheap and strong.

DamoRC

 

[OrcaSea]

If you can find a small tapered drill (yes, they make them!) it's great for making small adjustments in the plastic prop adaptors, like you would with a prop reamer on a larger prop. I have one and it is great for tweaking hole sizes without re-drilling and possibly elongating the holes.

http://www.traditionalwoodworker.com/Taper-Drills-Countersinks/departments/281/

 

[skymaster]

can you put a prop saver on any brushless motor?

 

[Merv]

can you put a prop saver on any brushless motor?

In theory you can but I would not recommend it. Prop savers are mostly used on smaller motors, like those used on a the "mini" series of planes. With larger planes (larger motors) you want the prop held on more securely. You are also using a larger prop which is less prone to breakage.

 

[skymaster]

thanks for the info