Replies to This Discussion

Permalink Reply by Richard Boyhan on January 7, 2013 at 6:50pm

How tight are you screwing the collet on the adaptor? I use small nail and tighten it till the nail bends.

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3D RoboticsPermalink Reply by Joshua Ott on January 7, 2013 at 8:46pm

Everyone should be using reverse threaded prop mounts for the reverse rotating props.

Such as these

With one hand twist the motor in it's direction of rotation, with your other hold the leading edge of the prop to represent the drag imposed on it by the air. If this action loosens the prop mount nut then you need to put reverse threaded mounts on that motor. 

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Permalink Reply by Rick Prime on January 7, 2013 at 9:09pm

I have used "Lock-Tite"  BLUE.  It works.

I think reverse thread is a MUCH BETTER idea.  

That's the way ALL saw blades are mounted !

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Permalink Reply by Luke Olson on January 7, 2013 at 9:23pm

That helps but a properly attached prop adapter should work fine regardless of direction. I had issues with props coming loose until using a little bit of Loctite on the nut (the blue kind).

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3D RoboticsPermalink Reply by Joshua Ott on January 9, 2013 at 1:54am

I didn't mean to sound so bossy with that first sentence, sorry.

What I meant was-

Everybody should think about trying reverse threaded prop mounts on half of your motors. It will make your life much easier. Just tighten them a reasonable mount, no need to risk over tightening aluminum threads.

Threadlock works, but I like to remove my props all the time.

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Permalink Reply by R. D. Starwalt on January 9, 2013 at 5:45am

A correctly sized collet-based propellor mount, properly installed, should not come off under normal operation (or even a crash).

I think part of the burst in 'loose prop' posts may be due to:

• A bad fit of the adapter and motor shaft (This includes the wrong adapter for the shaft size)
• A poor installation of the adapter to the shaft (Challenge: Find good instructions that help you understand the device)
• A poor quality adapter even if sized properly (Cheap don't mean good all the time)

Using reverse threaded collets will mitigate the rotational forces on the nut BUT will not fix a badly sized (or fabricated) adapter or installation. When installing the device, you are doing two things; compressing the propellor hub and compressing the collet on the motor shaft.

In a few days I will have a cross-sectional graphic of a typical prop adapter finished. I could not find one to reference to so...in true DIY spirit, I am making one to share. I have been tempted to machine one to a cross-section for the show-and-tell as I could not find a picture of one done that way either.

I hope to illustrate where these devices can go wrong and try to raise the understanding of how they are supposed to work.

The basic machine part has been around since before WW2 so... it was around before Rocket Science became a term.

-=Doug

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Permalink Reply by Martin Poller on January 9, 2013 at 6:25am

Agreed R.D. IMHO the only issue here is whether the collet adapter is the correct size for the motor shaft.

If it isn't correct no amount of screwing down, whether reverse threaded or not, will secure the adapter onto the motor shaft. It could even be that using loctite might, in some instances, glue an incorrectly sized adapter onto the shaft without the splined collet actually biting mechanically onto the shaft, hence causing a potential failure.

Just my two pennies worth.

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Permalink Reply by Tim Green on February 11, 2013 at 7:35am

And the DJI motor shafts are no longer than necessary to seat the prop - less chance of prop wobble compared to long motor shafts, where the prop sits 10-20 mm above the rest of the motor.

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ModeratorPermalink Reply by David Anders on January 9, 2013 at 9:53pm

There are a number of options available there for the standard 3dr motors collets, but I wouldn't use super glue.  Nail varnish works a treat for most applications, or use the blue loctite.

However, I have upgraded all my collets/prop adapters and the problems pretty much disappeared.

I'm looking at changing my motors (for a number of reasons) to Tiger - who have CW and CCW nuts.  Check out: http://www.rctigermotor.com/list.php?catid=55

 

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Permalink Reply by steve F11music.com on January 10, 2013 at 7:04am

I use blue locktite and the types of prop adapters that screw onto the motor with a few screws. Impossible to come off.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

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Permalink Reply by Andrew Chapman on January 10, 2013 at 12:08pm

These clamp style prop adapters seem to me an an unnecessary point of failure. Although I haven't had one come off myself in flight yet, they make me incredibly nervous.

I don't disagree that from an engineering perspective it is *possible* to fit and tighten these to a degree where they are mechanically sound, using loctite and CW/CCW threads to help, but your average user is going to have a pretty high likelihood of getting it wrong over time, as it is not self-evident whether you've done it correctly.

One of the reasons I'm looking to move to T-motors is that they feature prop adapters that screw directly on to the outrunner case, which seems like a much more direct and foolproof solution than hoping that two pieces of cheaply manufactured metal (shaft + adapter) are being pushed together with just the right amount of pressure to stop them sliding apart, yet not too much that you strip the thread or bend something when applying the opposing force.

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Permalink Reply by Jason on January 10, 2013 at 12:21pm

I agree completely. As for the thought of super glue vs locktite how do they differ? When I go to the store they seem to be the same. At this point I am stuck with what I have but it does make it stressful.

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