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3mm prop adapter impossible? Prop saver issue?

Old 11-25-2011, 10:23 PM
  #1  
mclarkson
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Default 3mm prop adapter impossible? Prop saver issue?

Fact-filled version:
I'm running an EMAX CF2805 on one of my planes with a GWS 7035.

I've been using 600/610mAh 2S batteries with it but wanted more power.

I got some Turnigy Nano-Tech 800's to try.

I decided to measure the watts they were making (but now I've lost my scrap of paper with the results.) Ran the 610 up to full throttle, switched to the 800, ran it up to full throttle and ... BANG.

Cut the throttle. The prop has flown off, but is undamaged. The prop saver is still in place and tight. The o-ring is still hanging around the prop saver and is undamaged (and pretty new.)

Nothing is broken or damaged but the prop has come loose.

I decide that it must be producing too much thrust for the o-ring, allowing the prop to pull forward off of the prop saver and then fly loose.

(I've flown that same prop, o-ring, etc. 4 times since with the 610 with no problems.)

So I order a prop adapter from HeadsUp to match the 3mm shaft on the motor, thinking that'll solve my problem nicely. But, when it shows up, it's HUGE. Nearly as big as the motor itself and too big for the 7035 props I'm running. That's not gonna work.

Very short version:
Is it possible I'm generating too much thrust for the prop saver?

Is it possible to find a small prop adapter for a small motor with a 3mm shaft?
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Old 11-25-2011, 10:28 PM
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earthsciteach
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I'd guess the rpm's of the motor was so great that centripetal force stretched the o ring to the point that it came off of the bolts on the shaft. Can you get a thicker/stiffer o ring?
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Old 11-25-2011, 11:10 PM
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gramps2361
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First off the prop adapter is the correct one. Second the prop you have is a direct drive prop that won't work with that prop adapter it is meant to go on a direct drive shaft of a motor. In order for that prop adapter to work a prop has to be on the shaft of it and as you tighten down the prop nut it clamps onto the motor shaft. You need a prop like this and you will be all set. Comes with a set of centering hubs so you can pick the correct size for the prop adapter.
http://www.headsuprc.com/servlet/the...-7-x-4E/Detail

One other trick is to take surgical tubing cut a few pieces about 1/8 thick use 2 of these to hold the prop on cheap and you can make hundreds of them. Myself I never did like prop savers tried them and switched over to what you bought.
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Old 11-26-2011, 12:45 AM
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Wildflyer
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I have had to run double o-rings to hold a prop on. They need to be pretty tight if you are pushing a lot of power.

I bought a big blue box of O-rings at Harbor Freight, been using them for years.
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Old 11-26-2011, 01:53 AM
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Hi guys.

As to thicker/tighter O-rings, I don't know. I don't think I could get them on if they were any tighter. I may try 2 at a time, and see if that helps.

Gramps, I actually have some of those props around, but they seem ridiculous hanging off the front of a 0.9oz motor on an 8oz plane. They weigh about 20grams as opposed to <3grams. With the prop adapter, it's weighs over an ounce, which is more than the motor.

Maybe it's just me and that thinking is flawed. :shrug:

I don't follow what you're suggesting with your surgical tubing trick. How would I hold the prop on with two 1/8" pieces of surgical tubing?

I'm planning on pulling this motor and replacing it with a lower kV model soon but, it seems to me, this problem will follow me wherever the motor ends up. If the prop saver won't hold it and the prop adapter is too big, I'm not sure what the heck to do.
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Old 11-26-2011, 02:13 AM
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A little trick.....

The bell flange of these bell type motors make the best propsavers you could want.Just remove the nut on the flange & replace the 2 small grub screws with 2 regular headed screws to hold on your O-rings (I use regular rubberbands doubled up myself).The threaded part of the bellflange has more area to keep the prop from flying off but still allows to come off on not so perfect landings.

http://www.headsuprc.com/servlet/the...for-the/Detail

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Old 11-26-2011, 02:18 AM
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All right surgical tubing is hollow when you cut a piece 1/8 wide you have a o ring just like a prop saver only stronger. You can buy this stuff at the pharmacy, or use the stuff for a wrist rocket sling shot. Some guys even buy the o-rings in the plumbing section of Home Depot.
Maybe the packers in the warehouse pack the from prop adapter cause the ones I have are small and wgt. next to nothing. I would send Jeff a email telling him about it, he's a good egg and I am sure if it is the wrong one he will make it right for you.

I didn't look at the KV of that motor until now that motor is 2800 KV meant for a wing or pusher jet not for a small airplane like you have it on. Switching to a lower KV motor will solve your prop flying off.
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Old 11-26-2011, 02:20 AM
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Originally Posted by Rolling Thunder View Post
A little trick.....

The bell flange of these bell type motors make the best propsavers you could want.Just remove the nut on the flange & replace the 2 small grub screws with 2 regular headed screws to hold on your O-rings (I use regular rubberbands doubled up myself).The threaded part of the bellflange has more area to keep the prop from flying off but still allows to come off on not so perfect landings.

http://www.headsuprc.com/servlet/the...for-the/Detail


.
He can't use that one with the emax motor only good for the bell ones.
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Old 11-26-2011, 02:24 AM
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Originally Posted by gramps2161 View Post
He can't use that one with the emax motor only good for the bell ones.
You're not getting what Im saying,lol.
Just slide it on to your shaft like you would any propsaver.replace the 2 small grub screws with regular headed screws & batta-bing,,,,prop saver magnifico

Last edited by Rolling Thunder; 11-26-2011 at 02:40 AM. Reason: wanted to add the word magnifico
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Old 11-26-2011, 03:18 AM
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Ah ha yes now I get it my head was wrapped around the idea of it screwing into the bell housing.
Ya that would work great with the way you are doing it.
I should of noticed the grub screw to hold it onto the shaft.
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Old 11-26-2011, 04:17 AM
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mclarkson
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Originally Posted by gramps2161 View Post
All right surgical tubing is hollow when you cut a piece 1/8 wide you have a o ring just like a prop saver only stronger.
Oh! I get it now. Thanks.

I agree that this is the wrong motor for my current plane but, as I said, my fear is that whatever the problem is will still be a problem when I put it on a wing, etc.
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Old 11-26-2011, 12:41 PM
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Originally Posted by mclarkson View Post
Fact-filled version:
I'm running an EMAX CF2805 on one of my planes with a GWS 7035.

I've been using 600/610mAh 2S batteries with it but wanted more power.

I got some Turnigy Nano-Tech 800's to try.

I decided to measure the watts they were making (but now I've lost my scrap of paper with the results.) Ran the 610 up to full throttle, switched to the 800, ran it up to full throttle and ... BANG.

Cut the throttle. The prop has flown off, but is undamaged. The prop saver is still in place and tight. The o-ring is still hanging around the prop saver and is undamaged (and pretty new.)

Nothing is broken or damaged but the prop has come loose.

I decide that it must be producing too much thrust for the o-ring, allowing the prop to pull forward off of the prop saver and then fly loose.

(I've flown that same prop, o-ring, etc. 4 times since with the 610 with no problems.)

So I order a prop adapter from HeadsUp to match the 3mm shaft on the motor, thinking that'll solve my problem nicely. But, when it shows up, it's HUGE. Nearly as big as the motor itself and too big for the 7035 props I'm running. That's not gonna work.

Very short version:
Is it possible I'm generating too much thrust for the prop saver?

Is it possible to find a small prop adapter for a small motor with a 3mm shaft?
Heads up Rc sells a small size prop adapter.
http://www.headsuprc.com/servlet/the...r-3.0mm/Detail

and so does HK
http://www.hobbyking.com/hobbyking/s..._Type_3MM.html

try to get away from using the o ring type of prop adapters, they can be danerous, That being said, o rings from the auto parts store work well, i use the green a/c fitting o rings, they seem to hold up better, use 2 O rings if your going to use the o ring type adapters, also when using the collet type adapters, use APC props, hope that helps, Chellie
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Old 11-26-2011, 10:09 PM
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Originally Posted by CHELLIE View Post
Heads up Rc sells a small size prop adapter.
http://www.headsuprc.com/servlet/the...r-3.0mm/Detail
ARGH! How did I miss that?!! Thanks.
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