E5: Motor mounting screw snapped. Should I bother replacing?

[jhamel]

I inserted this motor mounting screw on the E5 with a power driver on a high torque setting and the screw head snapped off. I normally use the lowest torque setting, but I made a mistake this time. . I know how to pull the screw stump out and insert a new screw, but this will require pulling the motor out, which will require pulling out the ESC in addition to disrupting the wiring job. I would also have to reset the mesh, which I hate doing. So now I am wondering if inserting that 6th motor mounting screw is absolutely necessary. I mean, there are 2 good motor mounting screws on that side, and 3 screws on the other side in addition to 4 screws holding the pinion support bearing. So the question is fly as is or go through all the trouble to insert a new screw?

[dpelletier]

Purists would say to replace it.
Myself, I would make sure the others are torqued correctly and fly!

[Grimmy]

If it were mine, I'd replace it. You have 9 out of 10 holding it............I just fall in the last 1/10th category, so that's why I'd replace.

You sure you didn't damage the threads? To break the screw and it's only aluminum. Might want to check the fit of a screw and compare it with one of the other holes.

[tonys-heli]

John, just fly it and the next time you have the motor out, prob never, just fix it then.. the e5's are over built, you know that. you would really have to stress the pinion bearing so bad to even notice that broken screw. FLY THAT BAD BOY

[Indokast]

I doubt it is going anywhere! Id fly a few easy flights and see how it holds. I imagine that is fine since you have the two outer screws left.

[Dmaxison]

Did you apply loctite to the screw? If not, you might be able to spin it out using a powerbit or small drill bit in reverse.

That's the OCD side of me.

In reality, that motor isn't going anywhere.

[Rob Cherry]

Fly it. However, I'd recommend not using a power driver on any setting to install bolts. This isn't Nascar! Take your time, to ensure its not cross threading and of course preventing over torqued bolts, stripped threads, etc.

Sent from my XT1254 using Tapatalk

[whitehedr]

I would fly it as it is until you have need to pull the motor. Replace the screw then. You should keep an eye on the other screws. Make them a preflight inspection item.

Rog

[Freeskiken]

Probably will fly fine. But I am a perfectionist so I would take the motor out and fix it. It would bug me otherwise.

[jhamel]

The pinion support bearing is held by 4 screws. The motor mount is held by 6 screws (5 in my case). Yet, the manual states for the motor itself to be fastened by only 2 screws. I'm trying to keep that in perspective.

[Rodney Kirstine]

If Rob says it's good to go, it's good to go. I would trust his opinion as highly as Matt's.

[tonys-heli]

Originally Posted by curmudgeon

The pinion support bearing is held by 4 screws. The motor mount is held by 6 screws (5 in my case). Yet, the manual states for the motor itself to be fastened by only 2 screws. I'm trying to keep that in perspective.

hey john, don't forget the neat thing about the e5 motor mount is you can put 4 bolts into a kde motor from the mount as well.
pretty cool.

[jhamel]

Originally Posted by tonys-heli

... e5 motor mount is you can put 4 bolts into a kde motor from the mount as well...

Definitely. I've done that for all the E5 builds. Two M3 and two M4 bolts. This tiny 600 size motor is held more secured on the E5 than the huge motor on the Synergy 806 with only two M4 screws. Anyway, I maidened it a few days ago; 8 flights under its belt and as expected the pinion to gear mesh remains intact.

[mverhorst]

Originally Posted by curmudgeon

The pinion support bearing is held by 4 screws. The motor mount is held by 6 screws (5 in my case). Yet, the manual states for the motor itself to be fastened by only 2 screws. I'm trying to keep that in perspective.

Just some more perspective... The motor is held in place on its mount by friction, not the bolts. As soon as the bolts take the load, they will break.


It's the friction between the motor mount and the motor that is keeping it there. The bolts are there to firmly press the motor to the mount so that the friction can do its job...


Same goes for the mount the frame attachment. Is the friction between the two carbon plates that keeps the motor mount in its place in the frame.


Just a thought...

[Rob Cherry]

Originally Posted by mverhorst

Just some more perspective... The motor is held in place on its mount by friction, not the bolts. As soon as the bolts take the load, they will break.


It's the friction between the motor mount and the motor that is keeping it there. The bolts are there to firmly press the motor to the mount so that the friction can do its job...


Same goes for the mount the frame attachment. Is the friction between the two carbon plates that keeps the motor mount in its place in the frame.


Just a thought...

We're getting off topic a little, however...

12.9 M4 bolts can handle oodles of shear forces. In comparison, 12.9 M5 head axle bolts can sustain over 2,000lbs centrifugal loading in speed setups, and they attribute to 100% sheer load. M4 bolts can and do contribute quite a bit to the strength necessary to hold the motor in place, if required.

It even takes a lot of sheer force to break an M3 bolt (apparently a powered driver with the torque setting on max). Have you ever tried to break a 12.9 M4 bolt? The question of needing M3 vs M4 should be regarding the strength of the aluminum threads in the motor itself.

[mverhorst]

Originally Posted by Rob Cherry

We're getting off topic a little, however...

12.9 M4 bolts can handle oodles of shear forces. In comparison, 12.9 M5 head axle bolts can sustain over 2,000lbs centrifugal loading in speed setups, and they attribute to 100% sheer load. M4 bolts can and do contribute quite a bit to the strength necessary to hold the motor in place, if required.

It even takes a lot of sheer force to break an M3 bolt (apparently a powered driver with the torque setting on max). Have you ever tried to break a 12.9 M4 bolt? The question of needing M3 vs M4 should be regarding the strength of the aluminum threads in the motor itself.

Hi Rob,


I kindly disagree. The bolts in the head take axial loads and not so much shearing forces. Bolts are very strong axial, but not so much in the shearing direction.


The tensile strenght in the axial direction is indeed very strong for 12.9 bolts and the threads in the bell are the limiting factor.


But its the friction between the motor and mount that protect the bolts from shearing forces.


Enough axial force is needed to make sure the friction takes all the shearing forces.


http://www.boltscience.com/pages/pre...mentcharts.htm


Just my 0.02$... Not meaning any disrespect...

[Rob Cherry]

Originally Posted by mverhorst

Hi Rob,


Just my 0.02$... Not meaning any disrespect...

None taken! I think my post came across incorrectly, I was simply demonstrating that these bolts are quite strong and that (2) M4 bolts are more than adequate to hold down a 600 class motor, and even an 800 class motor for that matter. This is why I mentioned the threads in the aluminum are what we really need to be concerned with.

[mverhorst]

Originally Posted by Rob Cherry

None taken! I think my post came across incorrectly, I was simply demonstrating that these bolts are quite strong and that (2) M4 bolts are more than adequate to hold down a 600 class motor, and even an 800 class motor for that matter. This is why I mentioned the threads in the aluminum are what we really need to be concerned with.

I'm not a native speaker so I could have read that wrong...


All in all, we seem to agree