Sausagecopter 2 came down :(

[sausageroll]

So today I was flying the big sausagecopter 2 hex, and all was fine, and all of a sudden, it shook, flipped over and fell. The Naza did well, righted it back up and it fell on its legs, stabbing the leg into the ground.

everything is fine apart from the mount the motor broke off, and two of the three legs. The chassis survived and so did the motor.

I do check these screws but not enough. The hex flew 40mins the other day (7km in a grid pattern) and the long flight must have backed out a few of the screws. This happened only a few mins into flight maybe 3mins.

Threadlock does not always work here because the heat from the motor can soften it. Im going to replace the screws for hex headed type bolts and laser cut a plate with four hexagon cut outs and then sit the plate over the screw heads. This will stop the bolts turning. Im going to design a little tab that sticks out of the side of the motor mount and part of the pre flight will be to waggle this tab and if its loose, you dont fly until you do the bolts up.

Anyway, I guess the real message in all of this is make sure your "mission critical" screws cannot come out. Lock wire would be good if they made lockwire bolts small enough, but loctite (222) on the screws at a min, and if its a part that gets warm, like a motor, then some other kind of mechanical positive lock on the screws would be a good idea.


Pete.

[Gaza07]

Sorry to hear about the crash Pete at least it didnt kill it   

[SimonS]

A quick look at the Loctite website reveals that they do twenty different types of threadlock and that 222 is the weakest. I use 243 which is over four times stronger and is available from Halfords.

[sausageroll]

Yeah, im somewhat of a loctite nut. Ive even got the computer controlled dispensing machine haha, I use it a lot in daily work, but I dont trust it so much in this application. The constant heat of the motor and the vibration is enough to loosen it even with loctite.

Ive designed a plate with hexagon cutouts that sits over the top of the hex head nuts and locks them so they cant rotate. I feel thats a safer way of doing it.

Just had to do a bit of inspection on the motor with this cool machine to make sure I got the dimensions right for the lock plate

[macspite]

Ive designed a plate with hexagon cutouts that sits over the top of the hex head nuts and locks them so they cant rotate. I feel thats a safer way of doing it.

Just had a vision of making, packaging and selling little M4 or M6 indicator tags that show if the nut has loosened - like they fit to truck wheels.



Who is up for a set? 

[sausageroll]

hah, yeh its not a bad idea. For these though it wouldn';t help, as the bolts in question are not really visible.

[sausageroll]

This Family friendly diagram shows the anti crash plate to secure the motor bolts. the two 2mm holes at the side align with two holes in the motor mount plate and an M2 bolt and locknut are used to hold it down. The rounded tips of the anti crash plate stick out either side of the mount so you can feel if they are loose before flying. If that is loose, then you need to do the bolts up, but even if its loose it still wont allow the bolts to undo.

Its a good system. Inspired by a locking plate thing on one of Agent Jay Zs videos - http://www.youtube.com/user/AgentJayZ?feature=watch

Sent the drawing to the laser cutters will have them next week sometime.

Exciting.

[Gaza07]

Nice idea 

[sausageroll]

If anyone is wondering, they were 77p each lol.