23 replies to this topic

[sausageroll]

Hi Everyone,

Decided to build a quad rotor, so did my research, designed something pretty, did some lasercutting and stuff and I think what I have made is pretty damn good (even if I do say so myself).

Im using four 880kv motors, an Eagle N6 board for the time being and Gemfan 12x4.5 props.

http://a7.sphotos.ak...071719589_o.jpg

http://a4.sphotos.ak...438891457_o.jpg

Today I sent it up with one of my gopros on there and got some really nice photos.

http://a1.sphotos.ak...032991205_n.jpg


You can probably guess what happened next.



The end result was my hard work and money falling 100 feet to the ground and ending up looking like this:
http://a5.sphotos.ak...114054211_o.jpg



I have to replace one of the carbon arms, one of the motor mounts (very cheap to laser cut and have loads of spares so thats ok) but the killer is the chassis is bent beyond repair and im gonna have to replace both the chassis pieces.


This is very annoying. These propellers and motors should not fail like this.


So, what we need to do before we rebuild and fly again is work out why this happened and how to stop it. The offending propeller fell from the platform in one piece, so it did not break. The cone shaped spinner nut came unscrewed, as it was not on the motor when we picked up the wreckage.

The first time we tested motors on our test rig, the blades flew apart. We realised that if we do the nuts up with only a bit of force, this does not happen, but it seems the end result of this is the nuts coming unscrewed.


Did I not do the nut up tight enough? Am I using the propsaver hub incorrectly? THe hub came with a large flat washer with a chamfer round one edge. I am not using this as it seems too big to fit anywhere, is this the key, should I have used this washer thing?


Would be great if someone could give me some advice into this, as I really cannot afford for my quad to fall from the sky again because of something like this.

The props are Gemfan 12x4.5



Thanks a lot,

Pete.

[kevinv033]

Sorry to hear about your quad. The best bit of advice I can give is put a drop of thread lock on the prop adapters. Just a tiny amount so you can still remove the nut later. This mostly happens on clockwise spinning props.

[Gravity Thief]

Iv made it a habit of mine, to make sure I do pre flight checks before each and every flight.
Make sure everything is tight etc etc.....

[eFinger]

Attaching props is a real pain in the butt. After losing a few props I eventually got to the point where I put the prop on, then a washer, then a normal nut and then the cone on last acting as a sort of lock-nut. The normal nut I put on with a spanner so its a little tighter than finger tight. Its an annoying process but I havent lost a prop since.

[ddavus]

The use of a washer between the propeller and the propeller nut is an excellent idea if you do not use one now. Thread locker (I use purple locktite), should always be used.

The washer prevents any abrasion and cracking of the propeller as the propeller nut is tightened down.

[2400rdr]

Sorry to hear about your quad. The best bit of advice I can give is put a drop of thread lock on the prop adapters. Just a tiny amount so you can still remove the nut later. This mostly happens on clockwise spinning props.

It just occurred to me from what you said that the manufacturers are missing the boat. They should make reverse threaded prop adapters for those clockwise props. I don't really think that's too far-fetched considering all of the other special development that's going on to suck money away from those of us that are cursed with an addiction to multirotors.

[johnnycat500]

Beautiful design, sorry for your loss. I have not used the cone nuts for some time. A ss washer and nylon lock nut is working real good.

Attached Files

•  DSC_8297 1065x704.jpg   360.28K   38 downloads

[nitromethane]

Failing props ... scary stuf, happend to me once

you can also use lock nuts:
 index.jpg   6.37K   2 downloads

Edit: someone was quicker

Edited by nitromethane, 05 August 2012 - 09:42 PM.

[sausageroll]

Hi Everyone,


I feel so stupid. Im an engineer / designer by trade, and im at the local nut and bolt suppliers nearly every day, how the hell did I send this thing up without thinking of locknuts. I think the gods of quadrotery have punished me with this crash for being so blind.

I will go and see Sam the nut and bolt man tomorrow and sort these out.


Thanks,

Pete.

[sausageroll]

*sob*

http://a7.sphotos.ak...363075432_o.jpg

http://a8.sphotos.ak...666411390_n.jpg

[sausageroll]

Hi Everyone,

I went to see sam the screw man, and amazingly he had aluminium locknuts. Very light weight. I have replaced the chassis for a new one and we are going to change the very very strong carbon fibre arms for 20x20mm balsa wood. Sounds stupid, but its strong enough and it should break in a crash and protect the chassis. If all four arms broke, total repair cost is about a fiver, so thats not bad. Would look stupid with wooden arms but I have found some black heat shrink which will black it up and hide the fact its made from a bit of tree.

Was also looking at APC props, but struggling to find the right size that is available as a pusher. The only ones that are available in both push and pull are the slow fly and thin electric only props. Are these OK?

I have also found some Master Airscrew three bladed props but they are 12x5, not 4.5. I assume this would be OK. Are three blade props OK?

http://a4.sphotos.ak...475986392_n.jpg


Any comments on this setup or any advice re props?

[nitromethane]

Wood is good, it has been done before, but I would avoid balsa.

HobbyKing has some APC like props.

3 Blade props are also good, but 2 blade props are less likely to break in a bump with the ground

Hope that helps

[J Regulator]

I second those who use loctite on their prop nuts. It's worked well for me but is no substitute for a solid preflight check.

[eFinger]

I 'like' the idea of using loctite and other 'thread-locking' liquids, but my concern is how hard they are to remove to replace props etc. Do they need, like, Acetone or something to dissolve?

Also, I remember an engineering friend of mine telling me that 'nyloc' style nuts are great for permanent use, that is, they are not designed to be taken off and on constantly because the nylon in the thread forms a groove and stops holding after a few uses. They are cheap enough to accept that they are only good for a few uses I suppose.

With these things in mind, I am only still new to the whole Quadcopter field so I am happy to be proven wrong.

[HelliYea]

If you use blue loktite then you can easily remove them. Don't over tighten or you can damage the prop. If the loktite is tight, use a heat gun first to loosen it up.

Awesome looking quad btw

[sausageroll]

My theory with loctite is the heat from the motor softens it. Im a bit of a loctite expert, I use it every day, and the stuff I used on those cones the first time should have held it. I think the heat from the motor loosens it up a bit.

[Phyonics]

what a shame. Thank you for sharing here though, really useful to find what others do when something goes wrong... I think a pre-flight check is very worth while (Noted in my brain for when I get up and running). I was planning on using loctite on my prop spinners, so I think some careful testing is in order to see if it softens on my motors too.

I've often wondered if you could drill a very small hole through the nut and shaft and then put some wire through it. Thus, stopping the nut coming undone. I guess it would be too small and maybe weaken the shaft and nut...

Edited by Phyonics, 08 August 2012 - 11:57 AM.

[Stigoe]

I've often wondered if you could drill a very small hole through the nut and shaft and then put some wire through it. Thus, stopping the nut coming undone. I guess it would be too small and maybe weaken the shaft and nut...

Another thing is, would you be able to hit the hole the next time you replace a propeller or would you have to make another hole? And another...?

[sausageroll]

Also could put one of these on the thread after the nut

http://uk.rs-online....ollars/6918099/

[z-axis]

Beautiful design, sorry for your loss. I have not used the cone nuts for some time. A ss washer and nylon lock nut is working real good.

+1 for this. I have never used prop thingies. All this fuss and worry about how to keep them on is something I've never had to worry about. It should not be this hard. I think the key is to find motors that have simple prop adapters, use a plain old nut (what I use, AND w/o threadlock) or better a locknut, and use props that don't break when you tighten them down, like APC slow-flys. It takes me about 15 seconds to change them out with a nut driver, no allen wrenches or threadlock or whatever. Berry simple berry easy.

 Io_with_NewGoProMount.JPG   243.43K   13 downloads

Was also looking at APC props, but struggling to find the right size that is available as a pusher. The only ones that are available in both push and pull are the slow fly and thin electric only props. Are these OK?
I have also found some Master Airscrew three bladed props but they are 12x5, not 4.5. I assume this would be OK. Are three blade props OK?
Any comments on this setup or any advice re props?

Yes. APC slow-flys. I use 9x4.7 and 10x4.7, depending on the motor. I don't like three-bladed props because they're a pain in the ass in that they take up more room and you can't keep a nice little bundle of them in a rubber band. And there's balancing three-bladed props. But some people swear by them, especially AP / AV people, because they are very smooth. I just don't care for them obviously.

About your frame, I hate to be the bearer of bad news, but you will crash again, many many times, and it will not be the prop's fault. So if you're having issues with bending and all that, you're doing the right thing in thinking of other materials and/or other designs. I feel your pain cuz I've broken and rebuilt many many times too and it sucks not flying, for sure.