thread locker for Mavic Mini screws.

[jac1957]

I read somewhere that if you want to reuse the prop screws for the Mavic Mini that you should use some medium strength thread locker. Anyone have any suggestions what product would be good? Or would a low strength be good. I know DJI suggest throwing away the screws and i am guessing it is because of the thread locker.

 

[bumper]

I'd be inclined to use Vibra-Tite, rather than Loctite, though if you do decide to use Loctite, then go with low strength purple for small fasteners. Vibra-Tite is reusable, up to a few times without re-coating the fastener, and is supposed to be compatible with plastics. Get the small size, I have a larger container and the cap is a real hassle to get off once it gets the "product" on it.

https://www.amazon.com/Vibra-TITE-VC-3-Threadmate/dp/B0088YEGXM?th=1

 

[old man mavic]

I read somewhere that if you want to reuse the prop screws for the Mavic Mini that you should use some medium strength thread locker. Anyone have any suggestions what product would be good? Or would a low strength be good. I know DJI suggest throwing away the screws and i am guessing it is because of the thread locker.

yes that is correct DJI supply new screws with the thread lock already applied i think there are three reasons for this generosity,
(1)the screws are very small and if you dropped one in the field you would be hard pressed to find it and would be unable to fly
(2)to ensure that thread lock is used to secure the screws, so that they dont get lots of MMs falling from the sky ,because the props fell off during flight
(3)if you applied to much thread lock it could run into the motor and cause damage to the laquer on the windings or get into the bearing causing drag

it is possible to reuse the screws, and it requires you to clean off all old thread lock from both the screw and the hole in the motor, applying a very tiny amount of new thread lock and refitting the prop,this would be a last resort approach if you did not have any more new screws available, a good branded thread lock would be best just dont splash it on all over its not an aftershave

 

[Capt KO]

That tiny bit of thread lock that you see on the new DJI screws is all you need to put on the reused screws again. I use a drop of blue Loctite on a piece of plastic then using a toothpick I will put a tiny speck of it on the lower screw threads, not the bottom.

 

[Funnone]

Permatex® Medium Strength Threadlocker BLUE Gel

OEM specified. Gel formula provides “liquid-reliability” without drips, globs, mess or waste. Available in four convenient sizes, the 10G GEL TWIST™ pin-point applicator, the 5G GEL SQUEEZE™ applicator, the Professional size 35G GEL TUBE, or the single-use pouch puts the Threadlocker right where...

www.permatex.com

 

[old man mavic]

Permatex® Medium Strength Threadlocker BLUE Gel

OEM specified. Gel formula provides “liquid-reliability” without drips, globs, mess or waste. Available in four convenient sizes, the 10G GEL TWIST™ pin-point applicator, the 5G GEL SQUEEZE™ applicator, the Professional size 35G GEL TUBE, or the single-use pouch puts the Threadlocker right where...

www.permatex.com

thats good a gel would be the way to go, similar to the gel version of super glue

 

[rod goslin]

I read somewhere that if you want to reuse the prop screws for the Mavic Mini that you should use some medium strength thread locker. Anyone have any suggestions what product would be good? Or would a low strength be good. I know DJI suggest throwing away the screws and i am guessing it is because of the thread locker.

I read somewhere that if you want to reuse the prop screws for the Mavic Mini that you should use some medium strength thread locker. Anyone have any suggestions what product would be good? Or would a low strength be good. I know DJI suggest throwing away the screws and i am guessing it is because of the thread locker.

 

[rod goslin]

I don't want to get shot down for this, but why do you need a thread locking agent? A screw thread is held tight by frictional forces generated by the tension in the screw, and has sufficed for many, many years. I've had, in the distant past, a fair amount of experience of the stuff, but mainly to correct a hole and shaft relationship which was supposed to be a drive fit, but was manufactured as a slide fit. It (then), had the property of setting solid. I've no idea whether this is still so. In which case, the old solidified adhesive would have to be removed before applying new. The solvent used to be somewhat aggressive, as I remember.Surely a face profile would be far more effective, and simple to provide.

 

[blakamin]

A screw thread is held tight by frictional forces generated by the tension in the screw

In the case of the mini, the screw is holding the prop on by the head, but it doesn't bind the prop to the housing. The prop is able to swing freely around the screw head, therefore there's no actual pressure on the thread to allow it to bind.

 

[rod goslin]

Not so. The tension in the screw shank is applied equally to the thread and the screw head. I used to be a Jig and Tool Design Draughtsman and am well conversant with the clamping abilities of bolts and screws. A half inch bolt, typically exerts a force of about three tons, and pro rata down to the screws holding the props on. I'm a bit surprised that they didn't make the screws left and right hand threaded, so they automatically self tighten. Or do they? I'm not taking my props off to look. From the inception of the bicycle, the pedal spindles have always been left and right hand threaded. I'm sure China has enough bicycles for this to be common knowledge.

 

[old man mavic]

Not so. The tension in the screw shank is applied equally to the thread and the screw head. I used to be a Jig and Tool Design Draughtsman and am well conversant with the clamping abilities of bolts and screws. A half inch bolt, typically exerts a force of about three tons, and pro rata down to the screws holding the props on. I'm a bit surprised that they didn't make the screws left and right hand threaded, so they automatically self tighten. Or do they? I'm not taking my props off to look. From the inception of the bicycle, the pedal spindles have always been left and right hand threaded. I'm sure China has enough bicycles for this to be common knowledge.

you make a good point ,i think they are all the same thread, and like you i will find out when i have need to change them,the problem with the prop screws is they are very small and the amount of friction from the thread and the seat of the mounting screw would not be that great, the other issue is vibration caused by the props themselves which over time could cause them to loosen and i believe the thread lock is on there mainly for that reason

 

[rod goslin]

Again, not quite so. Friction is solely proportional to the force and the coefficient of friction, not to area. In fact, the greatest frictional effect is between the shaft hub and the prop hub, being of larger diameter. Thus the resistance to turning is due more to that, than the screw. Rather than a lock-tite on the screw, you'd do better to have a dab of epoxy resin between the prop and the shaft hub, as far away from the thread as possible. You can always break away the epoxy, after removing the screw, since it's essentially brittle, and not that strong in tension.
Would that be the Australian Contender for the Americas Cup?

 

[rod goslin]

Having said all that, it has occurred to me that a slight change to the prop design might help. A small lateral extension of the hub, lodging against a similar one on the other hub, would each brace the other against reverse rotation, and still allow the blades to fold FORWARDS, for storage.

 

[old man mavic]

the blades need to be able to flex in either direction, as they change their cross section in flight

 

[rod goslin]

Umm. I was rather under a misapprehension as to the function of the screws, but since they are, in fact only the pivots for the blades, there, should be very little force being applied to loosen them. I should have engaged brain before opening mouth. Rather curiously, in a photo of the mini in flight, the blades are shown to be very close to being parallel to each other, rather than radially in line, as you'd expect from centrifugal forces.

 

[bumper]

the blades need to be able to flex in either direction, as they change their cross section in flight

Huh? The blades do flex torsionally, and that changes the blade's angle of attack depending on input power and loading. However, that flexure doesn't have any affect on their cross sectional area. Due to centrifugal force, the blades behave like a fixed prop, they don't pivot or swing back and forth at speed.

 

[old man mavic]

Huh? The blades do flex torsionally, and that changes the blade's angle of attack depending on input power and loading. However, that flexure doesn't have any affect on their cross sectional area. Due to centrifugal force, the blades behave like a fixed prop, they don't pivot or swing back and forth at speed.

you are right i meant angle of attack as they are spinning it is constantly changing, as you say according to the loading being placed on it