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Author Topic: coupling undoes in reverse  (Read 1646 times)

ntg06

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coupling undoes in reverse
« on: September 10, 2009, 09:11:09 am »

Hi,
This is a bit obvious, but not sure how to stop it!?
I have just connected the motor to the prop shaft via a universal joint. The motor end has a grub screw, and so can be locked to the shaft.
The prop end is an M4 right-hand thread. This is fine in forward, but when I switch to reverse to thread undoes (pretty obvious really!).
How do I stop this happening? Do you use thread lock or something? Or maybe I have bought the wrong coupling?
Also, what stops the prop loosening in reverse?
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DickyD

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Re: coupling undoes in reverse
« Reply #1 on: September 10, 2009, 09:22:22 am »

You need a lock nut on the shaft to tighten against the coupling to stop this happening.
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Colin Bishop

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Re: coupling undoes in reverse
« Reply #2 on: September 10, 2009, 09:36:09 am »

Same with the propellor. Position the locknut to give the minimum amount of shaft play within the tube and then firmly screw the prop down onto it.

Colin
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BarryM

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Re: coupling undoes in reverse
« Reply #3 on: September 10, 2009, 09:39:03 am »

A dab of Threadlok on the threads won't go amiss either.

Barry M
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ntg06

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Re: coupling undoes in reverse
« Reply #4 on: September 10, 2009, 10:04:51 am »

OK, thanks for the advice.
Do you use any kind of locking washer with the nut, or just the nut itself?
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andygh

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Re: coupling undoes in reverse
« Reply #5 on: September 10, 2009, 10:19:13 am »

Washer is not needed
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sheerline

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Re: coupling undoes in reverse
« Reply #6 on: September 10, 2009, 11:46:12 am »

Barry M, I concurr, Loctite the threads every time and  props and shaft coupings loosening will be a thing of the past. I actually don't even use a locknut anymore and I swinging 50mm 5 blade props. You will need heat to soften the Loctite when you eventually wish to dismantle.
 Superglue and other like stuff is not a substitute for proper threadlocking fluid so don't be tempted to use these products instead.
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