Are the supplied prop screws fit for purpose?

[Pendolino]

Or is it just me?!

So after doing a bit of lawn mowing and grazing a rock face with a prop tip, I decided to just swap them all out and start afresh now I know what I can and can't get away with, as well utilising my shiny new landing pad!

Old screws out, props off, new props on, no problem. But the pre-loctite'd screws that come with the spare props are just impossible to screw down the final 1/5 or so. And yes, I'm using a proper PH000 screwdriver which isn't slipping on the screw head.

I was worried I'd stripped the thread due to the force I was starting to put onto it, but the old screws went back in and tightened up perfectly, so it's definitely the loctite.

I've tried the heat trick to no avail, the force required just increases exponentially in those final 5/10 turns, to the point where if I apply any more, I think I'll be hearing the cracking of plastic...

Intuitively I want to just go and get my own loctite, but worried about gassing during curing weakening the plastic components.

Surely it's not normal for them to require so much force?

I don't mind being told I'm an idiot, I just want to put my new props on but have left it in situe for now for fear of causing any damage!

Any pointers other than the usual preheating the screwdriver head etc?

 

[rp6]

It sounds to me as if the new screws were treated with excess thread lock. I suggest that you attempt to remove the excess with a tiny brass brush. Or, If there is a solvent that removes the thread lock, soak the screws until it is dissolved. Then apply your thread lock...less is more, IMO.

 

[old man mavic]

@Pendolino it is because if some of the old threadlock is still left in the motor threads then it adds extra resistance to the new threads being put in
i always get a small fine sewing needle and holding the drone upsidedown pick out as much of the old threadlock as possible and then give the motors a good puff with my air blower
be aware of using liquid threadlock or any sort of solvent to clean the threads ,or lubricate the motors ,as you could cause damage to the insulation, or the glue used to attach the magnets to the outer bell of the motor, if you notice the actual dry type threadlock used by DJI is only applied near to the head of the tiny screws and is activated by the slight heat generated when the screw is being turned in, that is why the resistance increases as the last bit of the screw is being tightened down,there is no reason for the screw to come loose , once the head of the screw is friction locked to the post
the threadlock is simply there to act as a dampener, to prevent any micro vibrations,that may come from the motors ,causing the screws to slacken off slightly

 

[Pendolino]

Thank you both.

Yes, I'm very wary of introducing solvents and the like to things I'm not very knowledgeable about, especially when those things cost as much as a used car!

I know that a good, solid torque is more than enough to keep everything together (I check the screws as part of my pre-flight anyway), but if it DID throw a prop and I hadn't threadlocked it, I know I'd be kicking myself for not doing it, and it's just a bit more peace of mind when flying.

I've got some MAS props arriving later today, so I'll have a go with the sewing needle and air duster before installing them and will report back.

 

[Yorkshire_Pud]

How are you judging the "1/5th" that you can not complete?
Is it by the amount that the head protrudes above the top of the blade's hub?
If so, are the heads of the new screws deeper than the heads of the old screws by the same amount?
I have seen a photo that might indicate that new screws have been designed with a deeper head and a chamfered upper edge.
If I remember correctly the screws screw into a boss or pillar on the motor top.
If so, see if a new screw screws down until its head is against the top of the pillar i.e. don't fit a blade to that pillar.
With the other blades, if the screw is not going fully home there should be an increased amount of vertical play at the blade hubs, note at the hub, I am NOT talking about play at the outer tip of the blades.
The screw head limits the vertical travel of the blade hubs and a not-home screw will allow axial movement of the blade's hub.

 

[Droning on and on...]

Work on it without the blade installed until you're happy. Then install the blade. Much easier.

 

[Pendolino]

Thanks everyone.

Yorkshire_Pud, all the screws I've been using have been of the perfectly flush/flat kind, with no additional convergences or quirks that I can see. I think I may have simply acquired a batch of screws that were overly threadlocked, or old man mavic's suggestion worked, or perhaps a combination of the two...

So I needled and blew out the threads (for reference, earring pins also appear to work), and shortly afterwards the MAS props dropped through my letterbox. Within ten minutes I had them all installed using the supplied screws. Most of them went all the way flush with ease, a couple still needed a good torquing and I'm not 100% happy with them in terms of getting a solid friction lock, but they're not going anywhere and are as near as dammit screwed down. No axial movement and a quick, spirited test flight in sport mode revealed perfect behaviour from the drone.

Although I have a good M000 and M00 screwdriver (the M00 gets better purchase, funnily enough), I'm definitely going to invest in the electrician's screwdriver I've seen mentioned on here... The two I didn't get a satisfying clunk on was because of slipping on the screwhead, I think because my drivers flare out to quickly and thus can't get a nice square hold. The crosshead on the MAS screws is very, very shallow indeed.

Thanks for your input everyone, again hopefully this helps anyone who encounters this in the future!

 

[Starz]

This prop screw issue is one of a few reasons I refrain from any DJI product that has this design. I’m sure DJI has their reasons for this design but I think they could have done better. I’ll cross my fingers for all that are contending with the mini screw dilemma.

 

[360 Guy]

RP6 has the best solution..............small brass brush, then try the screws without the props for fit.

 

[Droning on and on...]

This prop screw issue is one of a few reasons I refrain from any DJI product that has this design. I’m sure DJI has their reasons for this design

Weight.

 

[Starz]

Weight.

And the weight of the bag of money they cart to the bank from all those minis tooling around. They sure have the customer base for that lineup.

 

[Droning on and on...]

And the weight of the bag of money they cart to the bank from all those minis tooling around. They sure have the customer base for that lineup.

Yeah, whatever

I was referring to the extra weight of the hub on the single-assembly props on the bigger brothers, which would tip the total weight over 250g defeating the primary value proposition of the mini line.