Hello Everyone,

Ok the only crashed I get now are when a prop falls off the quad will in flight.  It has cost me two cameras and a good amount of embarrassment.  It only happens once every 15 flights but I hate it.  So has anyone ever super glued the collet prop ad pater to there motor?  It seems even if the motor goes bad at some point a new motor comes with a new collet adapter.


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Blue locking compound is spec'ed as appropriate for bolts/screws >= 1/4" in diameter. If used for smaller bolts/screws, you may run into problems removing them unless you heat them up.


Not commonly found in stores, but available on Amazon, is Purple Loctite:


This has a lower locking strength, and is intended for bolts/screws smaller than 1/4" in diameter.

The low strength wicking type is very useful all around the craft. Because it wicks itself into the threads you can apply it after assembly. 


It's amazing what 24 hours can do - and maybe a little embarrassment.

I was set for a standard flight this morning, trialing some waypoints etc, when I see a full sized helicopter wanting to land on the oval i'm using.  I wait for the copter to land and the pilot spots the quad before he's left the cockpit and we have a brief chat about it.  Pull out the video cam and record it fly away.  Filled with the 'coolness' of flight, I set up my quad, hit record on the GoPro and take off...  Get about 30 second into the flight and two props fly off. *face palm*  This was AFTER tightening strongly AND using varnish.

Needless to say that it's not acceptable for the hobbiest, let alone what i'm trying to do. 

So, subsequently I ordered my Tiger motors with screw on prop adapter and CW/CCW nuts to replace the stock quad motors that came with my kit.


In the past Ive exclusively used the Turnigy 2217 motors that come with all the part's needed to mount the props any way you want.....But now that I'm running the 3DR 850 motors I have to use a nail (or whatever) rather then a wrench. What have you guys been using to tighten these?

Thread lockers generally are deisgend to polymerize/harden in the absence of air. So when trapped in the threads, the stuff hardens and fills the gaps between the threads. Different types react differently. The blue tends to be relatively easy to break loose but the red is very tough. Superglue is a different material that hardens in the presence of air and moisture and is not designed to come apart again (also puts out very nasty fumes).

~2mm hex wrench works really well.

+1 on the Allen wrench.

My technique is to seat the collect as far onto the motor shaft as it will go. I think that it should be a 'sliding fit' and would not trust a collet that had any giggle or play before tightening. With my 3DR motors (older purple motors) I think the shafts are too long. The 1/4' or so between the collet face and the motor housing serves no purpose except to provide a place for the shaft to bend easier if an impact/blade strike occurs.

When tightening, I hold onto the prop hub and not the motor housing; running the spinner nut up by hand first. This usually sets the collet. The allen wrench is then used until 'firm'. What's that mean? I have not torque spec but maybe that would be a useful tool? (hmmm..another project...)

I am nearly finished with my crosss-section and am taking additional photos of several kinds of prop mounting hardware.  It is concerning that so many have experienced a loose prop episode. Clearly the topic is significant.

Using the 'old school' type of mount (no disrespect) like on fuel motors eliminates the collet issue. To be fair, I have seen fuel motors start backward and send the prop off...usually into the person trying to start the motor!

Rotational forces are amazingly strong. This is a serious safety topic.


Be very careful with the loctite. If it gets on the prop it may cause the plastic to get brittle and you will have props breaking like crazy. I have seen multiple DJI quads that were mysteriously breaking props for no reason. But there was a reason. They were getting loctite on the prop when they were putting on the prop nut and over time it made the props snap.

I learned about this loctite/plastic issue about 5-6 years ago. JR introduced a new servo ( I think it was the 821) and it had a "stronger" gear set. People had helicopters falling out of the sky because the new gears were failing. Turns out it was because people were using loctite on the servo horn screw and it was causing the main gear to just crumble.

We tested it. The next day we moved the servo and the horn just fell of with the splined portion still in the servo horn.

Not sure what all types of plastic props it affects but DJI props don't play nice with it.

Well I have to say I feel a little better that I am not the only one who has seen there quad fall from the sky because a prop flew off. With that said it seems to me the best way to deal with this problem (other than buying all brand new motors) is to use some type of glue to glue the collet directly to the motor shaft. Every time the prop fell off it because the collet came off. When I would go to pick up the collet the prop would still be attached. If the prop breaks for another reason I can still unscrew the cap from the collet to replace the prop.

I think one thing that hasn't been covered yet is that these collets are soft aluminum, if they aren't tightened properly every time they can spin on the shaft and wear out the inside making them loose even when tightened properly in the future.  I'd dare say that if you have a history of losing props when flying and have started tightening the nuts even more to prevent this, then you  might already have this problem.  New collets and tightening them properly from the onset will go an awfully long way to preventing the props from flying off all the time.  

Just on this - one of the first things I did was change from the 3DR supplied prop adapters to e-flite.  The metal was much stronger and I haven't had a problem with the prop adapter coming off.

We just had a meet here in Melbourne and after buying some more blue loctite and placing it on the tip of the motor shaft there were no issues with the collet coming off either.

Good point Jesse. If the motor shaft is not inserted completely into the collet and then tightend, only a portion of the collect contact area is used. If compression of the collet 'flutes' occurs (due to material quality mentioned in D Anders post), the collet now has two different clamp diameters.

+1 on D Anders mention of E-flite. I have a couple of those (in fact use it in some photos of the soon-to-be-post). The material is first rate. The prices are, of course, higher.

Cheap don't mean good, but all too often is accepted as good enough.


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