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Prop adapter causes the motor shaft break on every crash

hb97

New member
#1
Hi,
I made my first plane, (FT simple Storch) Of course I crashed and my engine shaft broke (surprised :confused: ). I changed the motor and it happened again. The new shaft was a bit too long. I am using a prop adapter and it seems that the break point is always right before the prop adaptor. Anyway, since this shaft was too long after the break I could mount the prop adapter again, but after another crash it broke again. None of those crashes were too hard. The prop itself didn't break and is still useable. And the plane itself is fine after the crash, so please tell me what was wrong? Is it because of the adaptor? Am I tightening it too hard? What is the best way to mount the prop?
 

hb97

New member
#3
The first motor was an EMAX XA2212/980kv and the second one is a GWS (a Chinese brand, I guess) 1100kv .
The first one I bought online and the second one I got in a hobby shop.
 

Hai-Lee

Old and Bold RC PILOT
#4
Thank you! Now I see the issue. The motor is strongly built but has its design firmly in the Multicopter arena.

The shaft is a little too long for my liking.

Firstly see if you can locate replacement shafts for the motors, (generally around $1 or $2 if available). Failing that you could see if the shaft from another brand could be fitted or made to fit.

To make your own you need to find a suitable material. I like using S/Steel offcuts from two-way radio S/Steel whip antennas of suitable diameter or if desperate and/or no other material available I will source a 1/8" or 3mm drill bit and use the un-fluted end as my motor shaft.

You will need the ability to cut the material and make the channels etc required.

NOW as for how to make it safer in the future for a new motor. Well I do cut the shaft down so that the prop adapter sits firmly butted up against the motor magnet housing so that there is not shaft visible. In an impact event the forces are passed into the motor and hopefully through the motor into the motor mount. Generally the shaft is safe.

There is a danger in the shorter shaft though and that is when the impact is severe the motor housings and the mount can be deformed which renders the motor useless and irreparable without special tooling and procedures.

Another possibility is that severe impact will damage the internal mounting hole of the prop adapter, (int is only soft aluminium), and of course then the adapter itself will need to be replaced.

Just a few thoughts and what works for me!

Is this what you wanted to know, do you have further questions, or seek another direction?

Have fun!
 
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hb97

New member
#5
Dear Hai-Lee, Thank you for your great answer,. It's really helpful.

As I understood from your answer, there is nothing wrong with the prop adapter itself, it is the shaft that is too long. Am I right?
Since I don't have the tools to cut/make the shaft, I was thinking to use a prop saver instead, which hopefully absorb some of the impact's force and save the shaft and the prop. Would it help?
 

Hai-Lee

Old and Bold RC PILOT
#6
A little bit of help but the real problem is that the prop shaft is weak and unsupported in the event of a ground impact.

A different replacement motor shaft which is a little shorter might allow the adapter to rest against the motor in its bottom face thereby providing some impact resistance.

The other option you have is to purchase a similarly rated motor with either a shorter output shaft or a built in adapter, (direct prop bolt on).

Have fun!
 
#7
To make your own you need to find a suitable material. I like using S/Steel offcuts from two-way radio S/Steel whip antennas of suitable diameter or if desperate and/or no other material available I will source a 1/8" or 3mm drill bit and use the un-fluted end as my motor shaft.
I have found that music wire makes great replacement shafts. Quite a few of the less expensive motors have shafts that are nearly "glass" hard making them somewhat brittle. In any event, I highly recommend making your own replacement shafts. It's one more element that you can create in this hobby.

Best of luck,
Mike