Running brushless motor without the circlip

[jonnyrich]

Hi,

I'm fairly new to multorotors (a few months) but had a career as a military aircraft designer for BAe Systems in the 90s.

My DJI F550 has been modified with RCTimer 800 arms and Sunnysky 4108 4s motors and I've paralled two 4S 6000mAh Turnigy batteries.

See attached pics for the flight test without the camera gimbal attached.

View attachment 17564View attachment 17565

Question is: when I bought my Sunnysky motors, one of them had a missing circlip. I later found it magnetically attached to the motor windings just before I ran the motor. I reattached it.

Today, I found the thrust washer and circlip was missing from another motor.

I only found this after I had run the motor through two flight tests.

Pulling the motor housing off the offending motor requires quite a hefty pull against the magnetic resistance.

So, is the circlip really the only resistance to the housing and prop flying off, or is the circlip just a safety measure and not really required?

Can someone please assist?!

Many thanks,

Jonathan

 

[RTRyder]

You want the circlip on there. While it may take a lot of force to pull the bell off when the motor is static, the weight of the multi pulling downward and the lift from the prop pulling upward is quite sufficient to remove the bell when the motor is spinning under load, DAMHIK...

Ken

 

[jonnyrich]

That's what I suspected!

I'll have to see if I can find a supplier here in the UK. It's looking tricky to try and find one.

 

[PeteDee]

Without the circlip some some motors will let the bearing fall out, happened on a friends quad.

Pete

 

[jonnyrich]

The bearings seem to be interference fit. So that's OK. Just struggling to get a replacement circlip here in the UK.

 

[jes1111]

You DEFINITELY need the circlip AND the shim washer in there - they effectively provide basic (crude) preload to the bearings. The circlips and shims on the cheaper chinese motors are made of cream cheese, so it's worth replacing all of them when you receive new motors.

Circlips and shims: http://www.springfasteners.co.uk/
Bearings: http://www.smbbearings.com/ (no online purchasing but very friendly on the phone)

 

[jonnyrich]

The clip that came off looked like this View attachment 17567

But I guess an e-clip will do from www.springfasteners??

 

[jes1111]

What is the diameter of the shaft? E-clips can be okay - especially if you don't have circlip pliers - but they are usually thicker than circlips (C-clips). Measure the thickness of the shims fitted to your motors - they are usually 0.5mm IME - the total thickness of the new shim and clip should add up to the same as the original fitted items. May be best to stick with regular circlips.

 

[PeterLester]

In North America "Fastenal" is a good supplier of circ-clips..... Don't re-use old circlips, make sure the new ones are not overstressed when put on. After installation, try to pull it off the shaft with your fingernail as a final check. And use a top quality tools to removing and inserting the circ-clip sometimes referred to by other names such as retainer clip etc.