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Almost all of the brushless motors used in hobby-grade multirotors have a single threaded shaft and rely only on friction between the propeller and motor to keep the prop from slipping. This means that the nuts holding the propeller down must be tightened with considerable force.

When I try to do this, however, while I have a good grip on the nut (via a wrench), I can't hold on to the motor itself very well to keep it from spinning together with the nut, and if I try to hold on to the propeller, it cuts me with its sharp edges. What are the available tools and/or techniques that can aid in keeping the motor still while tightening or undoing the prop nut?

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6 Answers 6

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You know those rubber wristbands that are given out at lots of events?

You can wrap one of those around the motor bell to get better purchase on it, and then torque down the prop nut.

There are also specialised tools to hold motor bells, such as the one pictured below which can be found here, on Thingiverse.

enter image description here

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    $\begingroup$ +1 for promoting my design:) $\endgroup$
    – Michał Trybus
    Commented Apr 19, 2020 at 15:54
  • $\begingroup$ @MichałTrybus it’s a great design - thanks for sharing it on Thingiverse! :) $\endgroup$
    – Drones and Whatnot
    Commented Apr 19, 2020 at 15:56
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There are commercially-available tools that are designed to grab around the bell using a rubber band, like this one: The tool The tool in action

However I felt that it's a fair bit too expensive for what it is.

So I made my own, molded specifically for my motors' size: My tool - open My tool - in use It grabs the motor well (especially thanks to the teeth), but it's quite bulky and motor-specific, so I'm still in search of a more compact and universal solution. Also, I'm quite sure there are other tricks that people use to grab their motors that I don't know of.

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You don't need to hold it with a tool, it's enough to pinch it with your fingers. Using a tool to hold it increases the risk of damaging the threads if you are not careful.

But I can understand if you want to use a tool to simplify things, and in that case the other answers are good. Just remember to be careful.

Some examples of how I like to hold: Example 1 Example 2

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  • $\begingroup$ Well, holding the motor with one's fingers is definitely the first thing one would try. However when I tried that with my newly-built 5" quadcopter I found I can't pinch the motor hard enough with my fingers even to just be able to thread the nylock nut onto the shaft, nevermind actually tightening it agains the prop. So while your answer sounds reasonable, for me it doesn't solve the problem. If you know of some special way of grabbing with your fingers that's superior to pinching, though, telling about that would be appreciated. $\endgroup$
    – FlashCactus
    Commented Apr 19, 2020 at 15:14
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    $\begingroup$ @FlashCactus try wrapping your index finger around the bell and pressing in with your thumb, that’s what works for me. $\endgroup$
    – Drones and Whatnot
    Commented Apr 19, 2020 at 15:22
  • $\begingroup$ I've added some examples $\endgroup$
    – Hannes Hultergård
    Commented Apr 19, 2020 at 15:38
  • $\begingroup$ Hey, you're using the same motors and props as mine! Thanks, I'll try holding them that way next time. $\endgroup$
    – FlashCactus
    Commented Apr 19, 2020 at 15:39
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    $\begingroup$ Haha, what a conference! And remember that it gets easier the more you use the nut, since the nylon has to deform the first time. $\endgroup$
    – Hannes Hultergård
    Commented Apr 19, 2020 at 15:43
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There are also motor bell pliers available at many shops in case you don't have a printer. They are like this:

enter image description here

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For field portable answers, shoving an asparagus rubber band either in the back of a prop wrench, or in a kit with whatever you use to hold onto trickier bells. Dedicated tools are nice, but it's the kind of thing that even when racing, I'll seldom use a bell holding wrench, but a rubber band is always with me.

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These beverage openers work perfectly, and are very cheap.

You can get them e.g. from here.

enter image description here
(source)

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