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Old Feb 04, 2016, 08:08 AM
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How to mount a prop as a pusher?

What are some good ways to mount a prop when used on a pusher type plane? What mounting methods should be avoided? I tend to over think things, but I really don't want a prop to fly off and hurt somebody because I didn't know what I was doing.

My motors have 3 mm shafts.

The recessed area on the front of the prop doesn't accept the adapter rings that came with it that are supposed to center it, so mounting to a prop saver seems like it wouldn't work well. So I thought I would use a collet or set screw type prop adapter, but will that work since the motor would be spinning clockwise? My fear is that if the nut was to become loose it would back off from the motor spinning rather than getting tighter as it would if I had a left hand thread adapter, which I haven't been able to find. Then I thought that I could use the standard collet but with a reverse rotation prop so the motor would be spinning CCW, but the reverse rotation props seem harder to find without as many sizes available.

So what's the best way to use a prop adapter in a pusher set up?

Also, when using a prop saver, does the prop mount on the cone side of the adapter or the flat side?
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Old Feb 04, 2016, 09:25 AM
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A little more info would help. Like what plane, motor, battery, prop size. As dependent on the power a prop saver may not work for your set up.

As for collets, I use standard ones on all my pushers. I just add a drop of blue Loctite to the threads. Never had one come loose.

Oh and with a prop saver you want the cone to fit into the blade's hole. That's what keeps the blade centered.
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Old Feb 04, 2016, 09:58 AM
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I use the collet type prop adapter whether it’s pushing or pulling. Just make sure the nut is tight.
Most of the time the sizing rings that come with the prop will work. If there is a little more slop than you would like a few wraps of tape on the shaft will get it centered.
You can also buy a pusher prop if you want to. Then everything is made to work that way and the motor will be turning in a direction that will keep tightening the nut.
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Old Feb 04, 2016, 02:35 PM
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Quote:
Originally Posted by ooOoo View Post
......................

I tend to over think things,

................................
Always a danger

Look at how you would mount the prop on the front,then use the basic same method at the rear, just make sure the prop is still facing forwards, and rotating the correct way.

If using a standard prop adapter and an APC type prop, the adapter ring still goes in the same hole, it's the only accurate centered one.

If using a prop saver, (not particularly nice things in my opinion), make sure the stepped end does match the prop hole correctly,
And get some good quality prop retaining rubber rings.

Re-a prop flying off, -- don't forget as a pusher the prop is trying to push itself on the shaft. A prop on the front is trying to pull itself off the shaft.

Don't worry so much , but safety is always a good thing.

Ray.
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Old Feb 04, 2016, 04:59 PM
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Quote:
Originally Posted by Glacier Girl View Post
A little more info would help. Like what plane, motor, battery, prop size. As dependent on the power a prop saver may not work for your set up.

As for collets, I use standard ones on all my pushers. I just add a drop of blue Loctite to the threads. Never had one come loose.

Oh and with a prop saver you want the cone to fit into the blade's hole. That's what keeps the blade centered.
The planes are various versions of Dollar Tree Foam Board planes, mostly delta of some sort. The motors are Hextronic 24 gram in 1700kv with a 7x4 prop and a 3000kv with a 4.75x4.75 prop. The battery is a 1300mah 3s.

And thanks to everyone who has replied, I'll order some standard prop adapters and install them with a drop or two of some blue loctite.


.
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Old Feb 05, 2016, 12:31 AM
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There's no need for loctite. A collet adapter is always under tension, when properly done up. That tension is more than enough to keep the nut from coming loose due to vibration or prop spoolup inertia. Even blue loctite might seize up the assembly to the point where you'd risk damaging the airframe in an attempt to remove the prop.

No need for a prop saver either. Their only advantage is that they protect front-mounted (tractor) props in situations where the prop and motor are the first parts of the plane to meet tera firma. A pusher isn't likely to wear the same impact loads.

A suitable collet is perfectly fine.
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Old Feb 05, 2016, 12:39 AM
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Quote:
Originally Posted by H2SO4 View Post
There's no need for loctite. A collet adapter is always under tension, when properly done up. That tension is more than enough to keep the nut from coming loose due to vibration or prop spoolup inertia. Even blue loctite might seize up the assembly to the point where you'd risk damaging the airframe in an attempt to remove the prop.
Thanks for this information. I see what you mean that it would always be under tension since it's keeping the collet tight.
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Old Feb 05, 2016, 12:59 PM
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If you don't want to use Loctite then you can always use a double nut.
Name: Locknuts.JPG
Views: 4
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Description:
A 400W 28/36 (3mm shaft) driving a 10x3.8 prop on my big pusher.
It needs two spanners but with the first nut done up appropriately the second nut can then be tightened to an even higher torque without the risk of straining the prop adapter.
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