Props keep flying off, without the model lol!!

[Andy Ritchie]

Hi guys, I have recently returned to the hobby after a very lengthy break and I am totally loving the foamie models, cheap and easy to build which is great but I have recently been plagued with a problem, my props keep flying off from the motor and this has led to a couple of unplanned landings and then ages trying to find the prop and the prop mount. I have been using the ones that are generally supplied with the motors, silver with a dome which has a hole through it so that you can use something to help tighten it up onto the motor shaft, I have tightened these as much as I can but they still come off after a while, can anyone shed any light on the problem or am I being stupid lol!?
I did wonder about just glueing the adaptors on but wanted to know if anyone else had come across this problem and found an easy cure!
Regards,

Andy.

 

[ZoomNBoom]

Are you sure the prop adapter is the right size? Or maybe the propeller isnt the right thickness preventing the adapter from really catching on ? Some pics might be helpful. Glue either wont help, or if it does, it will be a problem if you need to replace the prop.

 

[nic872]

try adding some of the rings that the propeller comes with( im not sure what they are called) if the propeller is too thin like zoom said it could help to tighten the adapter more. also i had the same thing happen to me but that was because i only hand tightened the adapter.

 

[RAM]

You could try some blue loctite to stiffen the threads.

The only other thing I can think of is that the thread direction of the prop mount is matching the direction of motor spin and unscrewing itself.

 

[razor02097]

No you're not being stupid. I'm going to assume you have the prop adapter with a collet style fitting and the adapter with prop attached is what is flying off?

This is a collet adapter


There are two options you can either epoxy the adapter on the motor shaft (there is a serious and obvious drawback of not being able to service or repair the motor ever again). Or you can purchase a prop adapter with set screws instead of the collet style.

This is a set screw style adapter

 

[RAM]

No you're not being stupid. I'm going to assume you have the prop adapter with a collet style fitting and the adapter with prop attached is what is flying off?

This is a collet adapter
View attachment 50838

There are two options you can either epoxy the adapter on the motor shaft (there is a serious and obvious drawback of not being able to service or repair the motor ever again). Or you can purchase a prop adapter with set screws instead of the collet style.

This is a set screw style adapter
View attachment 50839

maybe scuff the motor shaft lightly for better grip

 

[pressalltheknobs]

If you are using the collet style you need to bend the collet jaws in so they are a tight fit before you put them on the shaft. Otherwise they don't tighten down properly.

On other thought if you have a threaded shaft make sure you are running your motor in the direction that will cause the nut to tighten. There are a lot CW (clockwise) and CCW (counter clockwise) threaded motors available because of multi rotors and if you run a CCW motor CW the nut will tend to spin off. CCW threaded motors really need to run CCW with a CCW prop to work properly.

 

[SOOFLY]

Another options for the (press fit style) collet adapters is to lightly scuff the shaft with sand paper and then put a couple drops of blue locktite where the collet and shaft meet. Push the collet onto the shaft as snug as you can and then let the locktite dry. I've been flying for a couple years now using this method and never had a collet come off during flight, crash or prop strikes that break the props.

 

[quorneng]

I wonder if the collet is 3.1mm but on a 3mm motor shaft?
With this combination the collet would appear to pull down tight but its jaws would never grip the motor shaft properly.

 

[PhenomPilot]

Like quorneng mentioned, a 3.17mm collet won't tighten well if it is a 3mm shaft. Both are fairly common sizes. If it is the right size then your options are scuffing the shaft and/or putting a little locktite on the shaft. I have had to do that on one motor.

 

[Craftydan]

DO NOT scruff/scrape/scratch/sand the motor shaft!!!!

Collets are friction fit devices. While common sense would imply making the surface rougher will increase the friction, roughing up the surface decreases the metal-on-metal surface contact dramatically, decreasing the holding force. This is a mistake a machinist beat out of me when I was younger, and engineering classes have reinforced.

No! NO! BAD! Don't do it!!!!


Get the right size collet (or shim to the right size), and Squeeeeeeeze it on TIGHT!!!

All too often people put it on finger tight and think it's enough . . . or hand tight . . . Collets should be VERY tight. If you can still twist the prop on the shaft, the collet isn't tight enough. A properly sized piece of music wire (the same size as the hole on the nut) is often required to get the leverage needed (I've broken screwdrivers before). Even then, the wire will still bend quite a bit -- it takes a LOT of force. When you can hold the bell and not turn the prop, ONLY then you've tightened it enough.

 

[razor02097]

+1 to CraftyDan's comment


Scuffing or sanding the motor shaft should only be done if you intend to glue it on... which I still do not recommend.

 

[aj308win]

... a mistake a machinist beat out of me when I was younger...

Off topic, but as a Journeyman who spent all day working with a very green and disrespectful apprentice, this made me smile.

 

[Andy Ritchie]

Wow, thanks so much guys, too many to thank individually!! It is indeed the collet type that I am using, they are the ones that were supplied with the motors so I assume that they are the correct size for the spindle but you never know, I have been tightening them with a small screwdriver through the hole but perhaps I need something a bit stronger and not be afraid to tighten more! We never had these sorts of problems when I was in the hobby the last time, which was just as electric was coming in, brushed motors etc! us guys who flew nitro, glow and petrol didn't dabble in such savagery, we would laugh at the guys turning up with an electric model lol!
I shall get those collets tightened to within a gnats hair of their life and try again, in regards to the anti-clockwise rotation I do have mosquito that I built which I have the motors turning opposites to help reduce any torque induced roll and I have not had any problems with that one?!
Thanks again guys, I really appreciate you all taking time to help out a returning hobbyist who is trying to catch up with all this new fangled stuff lol!!

Regards,

Andy.